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Application of Voronoi Polyhedra for Analysis of Electronic Dimensionality in Emissive Halide Materials
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Journal of the American Chemical Society

Cite this: J. Am. Chem. Soc. 2024, 146, 51, 35449–35461
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https://doi.org/10.1021/jacs.4c14554
Published December 10, 2024

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Abstract

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The synthesis of new hybrid halide materials is attracting increasing research interest due to their potential optoelectronic applications. However, general design principles that explain and predict their properties are still limited. In this work, we attempted to reveal the role of intermolecular interactions on the optical properties in a series of hybrid halides with an (EtnNH4–n)2Sn1–xTexCl6 (n = 1–4) composition. DFT calculations showed that the dispersions of the bands involving the Te 5s orbital character gradually decrease as the size of the organic cation increases, indicating a reducing orbital overlap between neighboring TeCl62– complexes. We characterized the photoluminescence (PL) of the Sn/Te solid solutions in (EtnNH4–n)2Sn1–xTexCl6 (n = 1–4) phases to correlate the electronic and optical properties. The PL response shows no concentration quenching effects in the (Et4N)2Sn1–xTexCl6 series, which demonstrated electronically isolated TeCl62– complexes. However, the series with smaller organic cations (n = 1–3) and higher electronic dimensionality show concentration quenching effects, which decrease as a function of the Te 5s band dispersions in these compounds. Similar trends can be revealed using a simple semiquantitative electronic dimensionality analysis method by means of Voronoi polyhedra. Since this approach relies only on structural data, it enables rapid characterization of orbital overlap between metal halide complexes in hybrid materials without DFT calculations. The present results allow us to conclude that electronic dimensionality plays an essential role in the photophysical properties of hybrid halide compounds and can be used to fine-tune their properties.

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Introduction

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Compositional tunability and almost limitless structural variations in hybrid organic–inorganic metal halides (OIMHs) have made them one of the most widely studied classes of contemporary materials. Apart from fundamental interest in OIMHs, their remarkable optoelectronic properties, tunable band gaps, broadband photoluminescence, and high photoluminescence quantum yields make them excellent candidates for solar cell, (1−8) light-emitting diode, (9−12) radiation detector, and photodetector applications. (13−21) While hybrid lead halide semiconductors with perovskite and perovskite-related structures remain the benchmark for photovoltaics, other classes of hybrid materials have been studied to circumvent the use of toxic lead and expand the new materials library. (22−28) Particular interest has been paid to cations with an ns2 electron configuration and transition metal ions for the synthesis of air-stable lead-free OIMHs. (29−37)
The tremendous structural diversity of halides with ns2 ions is contributed by various coordination modes of metal cations, different dimensionalities of the structures, and a vast choice of organic cations. Besides the most common MX6 octahedral coordination (M = main group elements, X = halides), cations with stereoactive ns2 lone pairs can form MX3 pyramids, MX4 disphenoids, or MX5 square pyramids. (38) MXn units’ connection defines the structure’s dimensionality: corner-, edge-, and rarely face-sharing MXn polyhedra form 3D frameworks, 2D layers, 1D chains, or 0D mono- and polynuclear anionic units. To balance the negative charge of metal halide units, various organic amines, which can act as structure-directing agents, (39,40) are employed. The dimensionality of the OIMHs defines their properties and practical applications. Extended structure semiconductors favor properties, such as high charge carrier mobility, that are required for photovoltaics and photodetection. (41−43) On the other hand, the extended structures demonstrate lower luminescence quantum yields and are more prone to photon reabsorption due to lower Stokes shifts of their luminescence compared to 1D and 0D materials. (32,34,44) On the contrary, typically broad emission of 1D and 0D materials makes them perfect for luminescence applications.
One general assumption commonly made when studying 0D hybrid compounds is the isolated nature of the metal centers in these materials. Since 0D hybrid halides show no direct M–X–M bonds, this assumption is partially justified. However, the importance of anion interactions in some purely inorganic 0D halide compounds has been realized to contribute to band dispersions, increasing the charge carrier mobilities and enabling the resonant transfer of excitons in these compounds. (45) In some cases, their conductivity is on par with materials that have generally recognized semiconducting properties due to their framework metal halide structures. (46) For example, halide interactions are essential in Cs2SnI6 and Cs2TeI6, which have vacancy-ordered double perovskite structures. (47) From a structural chemistry point of view, both of these compounds are built from isolated [SnI6]2–/[TeI6]2– octahedra and Cs+ cations, representing a typical example of 0D structure. However, their electronic structures consist of highly dispersive bands due to interactions between the halogen atoms, rendering them with high charge carrier mobilities. While the importance of halogen orbital interactions has been realized, their influence on the properties of hybrid materials remains underexplored. (48−52) Moreover, the elucidation of the electronic structures of these compounds requires somewhat costly DFT calculations, especially when it comes to hybrid functionals, which generally are not readily available to chemists. Because the electronic coupling in compounds depends on their crystal structures, information about interactions between the metal halide complexes should be available, at least in some approximation, from crystallographic data. However, no robust and universal tool for such an assessment has been developed so far.
In this report, we aim to develop tools that enable a simple assessment of halogen orbital overlap in hybrid halide materials. As a platform system, a series of tin and tellurium chloride compounds with an A2MCl6 general composition (A = (C2H5)nNH4–n+, n = 1–4, M = Sn or Te) has been selected. This system allows for convenient variation of the interactions between the MCl6 octahedra as a function of the organic cation volume (Figure 1). DFT calculations showed a changing degree of band dispersions in the series, from disperse to flat bands when n changes from 1 to 4. The photoluminescence properties of solid solutions with isomorphous Sn substitution for Te show agreement with the DFT data: PL concertation quenching effects are reduced as n increases. Importantly, we showed that the orbital overlap between the metal halide complexes could not be considered as a function of the metal–metal distance in the structure, and the mutual orientation of the complexes must be taken into account. Finally, the implementation of the Voronoi tessellation method for the analysis of intermolecular interactions between MCl6 complexes showed very promising results by providing semiquantitative data without time-consuming DFT calculations. We expect that further utilization of this method will enable a rational structural description to design highly efficient optoelectronic hybrid materials.

Figure 1

Figure 1. Schematic representation of two major components of energy transfer and photoluminescence quenching in 0D organic–inorganic metal halides.

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Results and Discussion

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Crystal Structures

We used single-crystal X-ray diffraction to characterize four new compounds with the A2TeCl6 general composition (A = EtnNH4–n+, Et = −C2H5, n = 1–4, Tables S1–S22). (EtNH3)2TeCl6 crystallizes with the trigonal space group P3̅m1 with single crystallographically unique Te and Cl atoms occupying 1b and 6i Wyckoff positions. The ethylammonium cations are disordered over a 3-fold rotation axis. Both (Et2NH2)2TeCl6 and the monoclinic polymorph of (Et3NH)2TeCl6 (m-(Et3NH)2TeCl6) crystallize with the same P21/n space group and have similar unit cell parameters and structural unit arrangements (Table S1). A single Te atom occupies the 2a Wyckoff position in both structures, while three independent Cl atoms are in general 4e positions (Table S2). The orthorhombic polymorph of (Et3NH)2TeCl6 (o-(Et3NH)2TeCl6) crystallizes with the Pbca space group. Unlike the other three hybrid halide structures discussed here, this phase has two independent Te atoms in the general 8c Wyckoff position.
In all new structures with an A2TeCl6 composition, each Te4+ cation is coordinated by six Cl– anions in an octahedral manner. The octahedral TeCl62– units are isolated from each other, and their negative charges are balanced by the organic cations (Figure 2). As expected, a hydrogen bonding system is present in the new compounds (Table S23). In the (Et2NH2)2TeCl6 structure, each chlorine in a TeCl62– octahedron participates in hydrogen bonding with diethylammonium cations. As a result, this structure has infinite layers formed by N–H···Cl bonds running parallel to the (101̅) plane (Figure S1). In m- and o-(Et3NH)2TeCl6, hydrogen bonding forms 0D units. In the m phase, the sole TeCl62– octahedron is connected to two Et3NH+ cations, while the o phase shows a distinct hydrogen bonding pattern: only one of two independent TeCl62– anions forms hydrogen bonds with four Et3NH+ cations (Figure S1).

Figure 2

Figure 2. Views on the structures of hybrid tellurium halides of interest: (a) (EtNH3)2TeCl6, (b) (Et2NH2)2TeCl6, (c) m-(Et3NH)2TeCl6, and (d) (Et4N)2TeCl6. (53) The yellow octahedra are TeCl62–, Cl atoms are green, C atoms are gray, N atoms are blue, and H atoms (if located) are light blue.

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Electronic Structures

Recent detailed studies on Cs4PbBr6 and Cs2SnI6 showed that band structure dispersion is a convenient tool to assess noncovalent interactions between neighboring halide complexes. (45−47) Although this approach is somewhat universal, (54) it is rarely discussed in the context of hybrid halide materials, which usually show a greatly reduced degree of orbital overlap compared to 3D halide perovskites. While it is commonly accepted that the dimensionality of hybrid halides with structurally isolated AX6 octahedra is 0D, their electronic dimensionality is strongly affected by the mutual arrangement and interactions between the octahedra. This section begins with a discussion of the molecular orbital (MO) diagrams of the SnCl6 and TeCl6 octahedral complexes. After introducing the MOs, we consider their interactions in a structure by paying close attention to the dispersion of bands formed by the Sn 5s, Te 5s, and Te 5p orbitals.
Schematic molecular orbital diagrams of SnCl6 and TeCl6 complexes are given in Figure 3. (46) In the SnCl6 MO diagram, the Sn 5s and Cl 3p orbitals with A1g symmetry form a pair of bonding and antibonding orbitals. The interaction of the T1u Sn 5p and Cl 3p orbitals results in another pair of bonding and antibonding orbitals at different energy levels. The remaining Cl 3p orbitals form numerous nonbonding states. For Sn4+, both the antibonding A1g and T1u orbitals hold no electrons. Thus, lower-energy A1g orbitals form the conduction band in the Sn4+X6-containing periodic compounds. In contrast, the valence bands are contributed by nonbonding Cl 3p orbitals, making a transition from the HOMO to LUMO (from the valence band to the conduction band in a periodic compound) a nominal ligand-to-metal charge transfer transition. Unlike Sn4+, more electronegative Te4+ retains its 5s2 electrons in the TeCl62– complexes. Due to a large energy difference between Te 5s and Cl 3p orbitals, their overlap causes only a small energy splitting, resulting in antibonding A1g orbitals being slightly higher in energy than nonbonding Cl 3p orbitals. Larger overlap between Te 5p and Cl 3p orbitals leads to greater energy splitting of the resulting bonding and antibonding MOs. Due to this, the LUMO orbitals are contributed by Te 5p and Cl 3p T1u orbitals. Since both the HOMO and LUMO of the Te4+Cl6 complexes are contributed by Te orbitals, 5s for the HOMO and 5p for the LUMO, one can consider an electron excitation as a well-known 5s25p0 → 5s15p1 transition, assuming that there are no orbital interactions between neighboring TeCl6 complexes. In periodic compounds with isolated TeCl62– complexes, MOs mostly retain their individuality, often resulting in flat or nearly flat bands.

Figure 3

Figure 3. (a,f) Schematic molecular orbital diagrams of octahedral SnCl6 and TeCl6 complexes. (b–e) Band structure diagrams of ((C2H5)nNH4–n)2SnCl6 and (g–j) ((C2H5)nNH4–n)2TeCl6 (n = 1–4). A1g MO orbitals (σ bonds formed by Sn/Te 5s and Cl 3p orbitals) are highlighted with blue, and T1u orbitals (σ and π bonds formed by Te 5p and Cl 3p orbitals) are highlighted with orange.

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Although 0D hybrid structures contain structurally distinct octahedral units with no apparent covalent bonds between them, noncovalent interactions can contribute to the corresponding band dispersion. (45) To study this effect in greater detail, we calculated the band structures of all eight compounds in the A2MCl6 (A = EtnNH4–n+, Et = −C2H5, n = 1–4, M = Sn or Te) family (Figure 3). In the case of the bulky cation Et4N+, the band structures consist of almost perfectly flat bands corresponding to the isolated MOs of the SnCl6 or TeCl6 complexes. The lack of band dispersions indicates nearly no orbital interactions between the complexes, which are structurally and electronically isolated by organic cations, thus making (Et4N)2SnCl6 and (Et4N)2TeCl6 truly 0D compounds. As the size of the organic cation decreases, the band dispersion increases. Since the A1g MO in MCl6 complexes consists of Cl 3p orbitals that form σ bonds and extend further away from the complex (Figure 3a), we chose Sn 5s and Te 5s band dispersions to assess the interactions between the complexes (Figure S2). As expected, the most dispersed bands are observed in the (EtNH3)2MCl6 (M = Sn or Te) electronic structures, where the bands with Sn 5s and Te 5s characters have dispersions of 0.486 and 0.368 eV, respectively. These values indicate that the ethylammonium cations’ sizes are insufficient to shield the MCl6 octahedra completely. Increasing the cation size by one ethyl group results in lower band dispersions of 0.401 and 0.314 eV for (Et2NH2)2MCl6, where M = Sn and Te, respectively. Interestingly, in a very similar structure of (Et3NH)2MCl6, the band dispersions are twice as small as those in the diethyl counterpart, 0.202 and 0.127 for Sn and Te, respectively. Although the change in the band dispersion shows a gradual decrease in the orbital overlap between neighboring octahedra, it is not directly proportional to the M···M distance in these structures. This somewhat unexpected trend can be illustrated in the Sn series, where the shortest experimental Sn···Sn distances of 7.27, 8.40, 8.51, and 9.59 Å correspond to the dispersions of 0.486, 0.401, 0.202, and <0.001 eV. Although these values of dispersion are significantly less than the ranges that are typically observed for 3D perovskites (>2 eV) (55,56) or vacancy-ordered double perovskite (∼1 eV), (47) they can be sufficient to promote electronic coupling between the complexes. These energy interactions can be characterized by measuring the optical properties of the A2Sn1–xTexCl6 solid solutions.

Photoluminescence Properties of ((C2H5)nNH4–n)2Sn1–xTexCl6 (n = 1–4) Solid Solutions

Since (EtnNH4–n)2TeCl6 phases are isostructural with (EtnNH4–n)2SnCl6 compounds with the same organic cations (Table S1), (53,57−61) the isomorphous substitution of Sn4+ for Te4+ in all ranges of concentrations is highly favorable. The varying degree of band dispersions makes these solid solutions highly suitable for characterizing energy exchange as a function of Te dopant concentration. Due to this, we synthesized four series of solid solutions and characterized their photoluminescence properties.
In all four series of the hydrothermally prepared (EtnNH4–n)2Sn1–xTexCl6 solid solutions (x = 0.0–1.0), along with selected compounds from the (Et2NH2)2Sn1–xTexCl6 series prepared by solid-state reactions, gradual diffraction peak shifts were observed (Figure 4). Bragg peak splitting is another clear sign of successful solid solution formation. For example, in the pristine (EtNH3)2TeCl6 phase, two peaks corresponding to the (103) and (022) families of crystallographic planes are separated by ≈0.06° 2θ, while in (EtNH3)2SnCl6, this separation is ≈0.6°, which can be easily detected experimentally (Figure 4). Similarly, peak splitting is observed for the (Et2NH2)2MCl6 phases at around 27° (Figure 4). Additionally, we collected EDS data (Figure S3 and Table S24) to confirm Te incorporation in the desired ratios. Raman spectroscopy can also serve as evidence of the solid solution formation. Pristine phases feature two peaks associated with ν1 and ν2 bands of the MCl62– anions in the low-frequency region. (62−65) In comparison, the Raman spectrum of an (Et2NH2)2Te0.5Sn0.5Cl6 sample with three peaks appears as an overlap of the pristine phase spectra (Figure S6).

Figure 4

Figure 4. PXRD patterns of the (EtnNH4–n)2Sn1–xTexCl6 series: (a) (EtNH3)2Sn1–xTexCl6, (b) (Et2NH2)2Sn1–xTexCl6, (c) (Et3NH)2Sn1–xTexCl6, and (d) (Et4N)2Sn1–xTexCl6. Ref. stands for the reference line; (Et4N)2Sn1–xTexCl6 samples were collected with the Ge powder as an internal standard.

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(EtnNH4–n)2Sn1–xTexCl6 samples emit visible light in the orange-red region under UV-light excitation. The corresponding photoluminescence excitation (PLE) and emission (PL) data are listed in Figure 5. Independent of the organic cation, the photoluminescence of all (EtnNH4–n)2Sn1–xTexCl6 samples features a broad asymmetric excitation band and broad emission with one near-Gaussian shape peak. At lower concentrations of Te4+, the PLE spectra have two distinguished regions with maxima at ≈330 and ≈400 nm, while at high Te4+ concentrations, the regions overlap (Figure 5). These two regions are referred to as the A and B bands of ns2 ion in octahedral surroundings. (66,67) The lower-energy A band originates in the spin-forbidden 1S0 → 3P1 transition. The A band is a doublet since the 3P1 level is split in the octahedral field by the dynamic Jahn–Teller effect, so the experimentally observed peak is asymmetric. (66) The singlet B band originates in the forbidden electric dipole 1S0 → 3P2 transition, while the high-intensity and highest-energy C band arises from the spin-allowed 1S0 → 1P1 transition and usually lies in the UV-B region. (67) PL spectra of (EtnNH4–n)2Sn1–xTexCl6 samples feature single broad (fwhm ≈ 110–130 nm, Figure S4) symmetric peaks.

Figure 5

Figure 5. PLE and PL spectra of (EtnNH4–n)2Sn1–xTexCl6 series: (a) (EtNH3)2Sn1–xTexCl6 (x = 0.05–0.80, λex. = 388 nm, and λem. = 620 nm), (b) (Et2NH2)2Sn1–xTexCl6 (x = 0.05–1.00, λex. = 375 nm, and λem. = 600 nm), (c) (Et3NH)2Sn1–xTexCl6 (x = 0.05–0.80, λex. = 405 nm, and λem. = 650 nm), and (d) (Et4N)2Sn1–xTexCl6 (x = 0.1–1.0, λex. = 395 nm, and λem. = 600 nm).

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The peak positions do not change significantly with x in (EtnNH4–n)2Sn1–xTexCl6 but depend on the organic cation. The lowest emission wavelengths (600 nm) are observed in the (Et2NH2)2Sn1–xTexCl6 and (Et4N)2Sn1–xTexCl6 series. (EtNH3)2Sn1–xTexCl6 samples have an emission peak at 620 nm. Finally, the emission of (Et3NH)2Sn1–xTexCl6 samples is redshifted to 650 nm. PL peaks correspond to the 3P1 → 1S0 relaxation of the Te4+ species. (68) All four compounds have similar Stokes shifts of 1.20, 1.24, 1.15, and 1.07 eV for n = 1–4, respectively, indicating a similar spectral overlap among them.
The compounds with smaller organic cations, n = 1–3, show different PL dependence on the Te concentration from the n = 4 series. In the (Et4N)2Sn1–xTexCl6 series, the Te concentration has little effect on the PL intensity, indicating low energy exchange between the Te centers. This observation agrees well with the 0D electronic band structure of the (Et4N)2SnCl6 and (Et4N)2TeCl6 compounds, as evidenced by their nearly flat bands. Reducing the organic cation size in the compounds with n = 1–3 “switches on” the orbital overlap and energy exchange between the complexes. In all three series, the PL intensity increases as the concentration of Te decreases, showing prominent concentration quenching effects. The effect is especially remarkable in the (EtNH3)2Sn1–xTexCl6 series where samples with x ≥ 0.8 appear nonluminous, and Te dilution causes a multifold emission intensity increase. This observation is in excellent agreement with the theoretically calculated highest band dispersion in both (EtNH3)2MCl6 (M = Sn or Te) compounds.
The concentration effects on the PL lifetimes in the series from n = 1 to 4 provide additional experimental evidence for energy exchange reduction (Figure 6 and Table S25). Nearly absent orbital overlap between the octahedral complexes in the (Et4N)2Sn1–xTexCl6 series makes the PL lifetime independent of the Te concentration changes. The small EtNH3+ cation promotes the energy exchange that leads to a strong concentration quenching effect and shorter PL lifetimes at higher Te concentrations. Despite very similar structures and similar shortest Te···Te distances, the two intermediate series (Et2NH2)2Sn1–xTexCl6 and (Et3NH)2Sn1–xTexCl6 behave differently. In (Et2NH2)2Sn1–xTexCl6, which has a relatively strong orbital overlap between the complexes, the PL lifetime rapidly decreases from 36(1) ns for x = 0.05 to 4.0(1) ns for x = 0.8. The (Et3NH)2Sn1–xTexCl6 series that has half of the band dispersion compared to the Et2NH2 analog demonstrates significantly longer PL lifetimes varying from 959(6) to 278(6) ns for x = 0.05 and 0.8, respectively.

Figure 6

Figure 6. Time-resolved PL spectra of (EtnNH4–n)2Sn1–xTexCl6 series, λex. = 372 nm: (a) (EtNH3)2Sn1–xTexCl6 (x = 0.05–0.80), (b) (Et2NH2)2Sn1–xTexCl6 (x = 0.05–1.00), (c) (Et3NH)2Sn1–xTexCl6 (x = 0.05–0.80), and (d) (Et4N)2Sn1–xTexCl6 (x = 0.1–1.0).

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Results of PLQY measurements for the (EtnNH4–n)2Sn1–xTexCl6 series also agree with the calculated energy exchange interactions (Figure 7). Samples with ethyl- and diethylammonium demonstrate low quantum yields (Table S26) below the measurement limit. For the (Et3NH)2Sn1–xTexCl6 series, PLQY values demonstrate significant growth with lowering Te4+ concentration, and the highest η = 20.5% was achieved in the (Et3NH)2Sn0.95Te0.05Cl6 sample. For the (Et4N)2Sn1–xTexCl6 series, no significant changes of PLQY were observed with the change of the Te4+ content: the experimental η values of all samples are close to those of the pristine (Et4N)2TeCl6 phase. Notably, the distortion levels of TeCl62– units cannot be considered as a factor predetermining higher lifetimes or quantum yields of the (EtnNH4–n)2Sn1–xTexCl6 phases. For example (Table S27), (EtNH3)2MCl6 (M = Sn or Te) has the lowest Δd, (69) while (Et2NH2)2SnTeCl6 the lowest Σ, (70) yet both phases have PLQY near the background of the measurement.

Figure 7

Figure 7. Photoluminescence quantum yield (PLQY) as a function of the organic cation and Te concentration.

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Assessment of Orbital Overlap between Halide Complexes in Hybrid Phases

Photoluminescence measurements show that the orbital overlap between the halide complexes plays a central role in the optical properties of these materials. While the lack of orbital overlap in (Et4N)2Sn1–xTexCl6 solid solutions results in independent TeCl6 centers that show no concentration quenching effects, their PLQY is also relatively low, likely because of the absence of energy exchange between the complexes. On the other hand, the presence of the strong orbital overlap in (EtNH3)2Sn1–xTexCl6 and (Et2NH2)2Sn1–xTexCl6 results in the dominant concentration quenching effects and, therefore, low PLQY of the solid solutions even at low Te concentrations. The optimal balance in orbital overlap and Stokes shift is achieved when Et3NH+ serves as an organic cation, which enables the highest among these series PLQY values in diluted (Et3NH)2Sn1–xTexCl6 solid solutions.
Despite the apparent importance of orbital overlap between the isolated octahedral complexes, its influence on the optical properties of hybrid materials remains largely underexplored, although some attempts have been made in recent years. For example, Mao et al. established the influence of interatomic Mn···Mn distances on PLQY of a series of hybrid manganese bromides. (71) Similarly, Sb···Sb distances in hybrid antimony halides play an important role in defining PLQY of these compounds. (72) These examples can be considered as one of the attempts to quantify interactions between halide complexes in optical hybrid materials, which in the case of the Mn hybrids showed that concentration quenching effects become predominant in compounds where Mn···Mn distances are below 9 Å. Although M···M distances seem to be an intuitive measure of interactions between the metal halide complexes, our attempt to implement it to the (EtnNH4–n)2Sn1–xTexCl6 (n = 1–4) series did not provide satisfactory results. For example, the shortest Sn···Sn distances in (Et2NH2)2SnCl6 and (Et3NH)2SnCl6, 8.40 and 8.51 Å, cannot explain a dramatic change in the optical properties of their solid solutions with Te. Moreover, these compounds have the same packing of cations and octahedral complexes in their structures, highlighting the importance of subtle changes in their structures for their optical properties.
To study the effect of mutual orientation of the MCl6 octahedra on exchange interactions, we performed a series of DFT calculations on chains of TeCl6 octahedra with two distinct orientations: in one case, the Cl–Te–Cl···Cl–Te–Cl fragments are linear (vertex to vertex); in the other one, they are rotated by 45° (edge to edge) as shown in Figure 8. The A1g band dispersion plotted as a function of the interatomic Te distance indicates a strong dependence of the orbital overlap on the mutual orientation of the octahedra. As expected, the linear orientation results in much higher band dispersion even at significantly longer Te···Te distances. One apparent reason for this is shorter Cl···Cl distances for the linear configuration (Figure 8b). However, when the band dispersions are plotted as a function of Cl···Cl distances, the interactions become very similar when d(Cl···Cl) > 3.5 Å. The increasing difference in dispersions below 3.5 Å arises due to better orbital overlap in σ vs non-σ bonds and has little effect on noncovalent bonding. For example, the shortest Cl···Cl contact within a TeCl6 complex in (EtNH3)2TeCl6 is 3.50 Å, which can arbitrarily be set as the shortest noncovalent interaction between Cl atoms in real structures. Assuming this shortest bond limit, there is virtually no difference in band dispersions for these two mutual orientations. This allows one to come to a somewhat intuitive conclusion that the main deciding factor in orbital overlap between halide complexes is the shortest distance between halide atoms.

Figure 8

Figure 8. A1g band dispersion energy as a function of (a) Te···Te or (b) Cl···Cl distances in chains of TeCl6 complexes. Two octahedral complex orientations are shown: linear (red plots) and rotated by 45° around the z-axis (blue plots).

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While using simple geometric parameters such as Cl···Cl distances seems to be a straightforward way of assessing interactions between the complexes, this characterization can become tedious for all possible contacts in a structure. Voronoi polyhedra provide a more convenient visual and quantitative characterization of Cl···Cl interatomic contacts that also consider other structural fragments. A Voronoi polyhedron (VP) can be viewed as an atom’s electron density in a crystal structure, where each point of a Voronoi polyhedron is closer to its central atom than to any other atom in the structure (Figure 9a). (73) One can, therefore, conclude the dimensionality and the strength of Cl orbital overlap by assessing the Cl atoms’ Voronoi polyhedra contacts. For example, a fragment of the (EtNH3)2TeCl6 structure is shown in Figure 9b. In this fragment, there are strong interactions between neighboring TeCl6 complexes, which correspond to short 3.77 Å contacts between the Cl atoms. These contacts correspond to relatively large solid angles, 4–5% of the total 2π steradian solid angle, of the Voronoi polyhedron (for comparison, valence bonds correspond to 5–21% solid angles). (73,74) Strong Cl···Cl contacts form dense 2D slabs of overlapping Cl orbitals (Figure 9c). In each TeCl6 complex of the slabs, six Cl atoms form Cl···Cl contacts, corresponding to a total of 51.3% solid angle. These slabs have virtually no overlap since the shortest Cl···Cl contact between them is 5.9 Å long with a negligible total solid angle of 0.02%. This geometric analysis allows one to conclude that (EtNH3)2TeCl6 has a 2D electronic structure with strong orbital overlap between the TeCl6 complexes, which agrees with the DFT calculations (note the flat band in the Γ–Z direction vs disperse bands in the Γ–X and Y–Γ directions in Figure 3g).

Figure 9

Figure 9. Voronoi polyhedra (VP) analysis of intermolecular interactions in (EtnNH4–n)2TeCl6 structures. (a) View on the Te atom VP in a [TeCl6]2– complex. (b,c) Cl atom VPs show a strong interaction between two complexes. (d,e) Decreasing interaction between the octahedral TeCl6 complexes as d(Cl···Cl) and the corresponding solid angle decrease. (f) Electronically isolated TeCl6 complexes in (Et4N)2TeCl6.

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Simple geometric structure analysis with Voronoi polyhedra also enables an understanding of decreasing orbital overlap interactions in the remaining series. The other end member of the series, (Et4N)2TeCl6, has no short Cl···Cl contacts in its structure. Therefore, the Cl Voronoi polyhedra of the neighboring TeCl6 octahedra share no common faces (Figure 9f). This TeCl6 octahedra isolation results in a 0D electronic structure, which agrees well with the results of DFT calculations and optical properties measurements. The two intermediate cases, (Et2NH2)2TeCl6 and (Et3NH)2TeCl6, offer a convenient way of probing the effect of slight changes in the outer sphere cation on the nonvalent interactions between the TeCl6 complexes. Both compounds have a 2D net of Cl···Cl contacts between TeCl6 octahedra (Figure 9d,e), which arrange them in a square net motif. In the case of the smaller Et2NH2+ cation, each TeCl6 complex forms four Cl···Cl contacts, which are 3.76 Å apart, with the corresponding Voronoi polyhedron solid angle of 3.59%. The total solid angle of the interacting Cl atoms is 14.36%. The addition of one more ethyl group to the organic cation does not alter the packing of structural units, and similar square layers of interacting TeCl6 octahedra form in the structure of (Et3NH)2TeCl6. Moreover, the Te···Te distance demonstrates only a marginal increase from 8.52 to 8.58 Å. Despite this seemingly subtle difference, TeCl6 undergoes a slight reorientation that results in Cl···Cl distance elongation from 3.76 to 4.19 Å. This more apparent change leads to a double reduction in the solid angles, from 3.59 to 1.79% (or from a total of 14.36 to 7.16%), which is also associated with reducing the band dispersion of the A1g bands from 0.314 to 0.127 eV for A = Et2NH2+ and Et3NH+, respectively. This example shows that two nominally electronically 2D structures can have a significantly different degree of orbital overlap, which requires quantification for assessing the properties of the compounds.
Notably, the orbital overlap (i.e., electron coupling) is one of the two components necessary for enabling energy transfer between complexes in hybrid halide compounds, which leads to luminescence quenching. The other requirement is the presence of sufficient spectral overlap according to the Dexter equation. (75,76) Since spectral overlap is roughly similar in the (EtnNH4–n)2Sn1–xTexCl6 series due to close Stokes shifts, most of the changes in concentration quenching are due to electron coupling between the metal halide complexes. However, it is important to take into account spectral overlap effects when comparing series with sufficiently different Stokes shifts due to its competing role in luminescence quenching. This interdependence can be illustrated by temperature-dependent PL effects in compounds with high electron coupling. For example, Cs2TeCl6 exhibits thermal quenching at 200–300 K that occurs as spectral overlap increases with temperature due to exciton–phonon coupling. (77) At low temperatures, however, there is no significant spectral overlap, thus leading to a “turning off” of PL quenching. On the other hand, PL quenching can be suppressed by strongly diluting Te in a Cs2HfCl6 matrix, which results in an efficient emission in Cs2Hf0.99Te0.01Cl6 at room temperature. (68)

Conclusions

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This report illustrates the difference between electronic and structural dimensionalities and their influence on the optical properties of hybrid halide compounds. Using the (EtnNH4–n)2Sn1–xTexCl6 series as an example, we showed that interactions between the TeCl62– complexes are strongly dependent on the organic cations. The bulkiest cation, Et4N+, almost completely shields the complexes from each other, resulting in the lack of an orbital overlap between them as shown by nearly flat bands corresponding to TeCl6 A1g orbitals. The near absence of exchange interactions between the complexes results in no concentration quenching effects in the (Et4N)2Sn1–xTexCl6 solid solutions. On the other hand, the small cation EtNH3+ offers little shielding and promotes strong interactions between closely arranged TeCl6 complexes, leading to a rapid PL concentration quenching in the corresponding Sn/Te solid solutions. The intermediate examples, Et2NH2+ and Et3NH+, show a decreasing degree of orbital overlap as the cation size increases. Interestingly, the highest PL quantum yields of ∼20% were observed for highly Te-diluted compounds in the (Et3NH)2Sn1–xTexCl6 series. Since this PLQY value is significantly higher than that in the (Et4N)2Sn1–xTexCl6 solid solutions, ∼ 4%, the orbital overlap may play a positive role in quantum yields, although further analysis is required to establish this trend unambiguously.
We also demonstrated the application of a simple geometric approach for crystal structure analysis, Voronoi tessellation, for semiquantitative characterization of orbital overlap (and, therefore, band dispersions) in structurally 0D hybrid halide compounds. This automated method allows one to visualize interactions among the isolated complexes and determine their dimensionality and strength. As an example, we demonstrated the correlation between the Cl atoms’ Voronoi polyhedra parameters and optical properties. This method is universal and can be readily extended to other hybrid structures for quick characterization of energy transfer between structurally isolated metal halide complexes. Since many properties of hybrid solid-state materials depend on the degree of the orbital overlap between the isolated complexes, this method offers a fast and simple insight into the properties of the previously synthesized or new materials.

Experimental Methods

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Synthesis of (EtnNH4–n)2TeCl 6(n = 1–3) and (Et3NH)2Te2Cl10 Single Crystals for X-ray Diffraction (XRD)

For the synthesis of all compounds, TeO2 (99.995%) was completely dissolved in excess of concentrated HCl (≥36.5 wt %) on stirring and moderate heating on a hot plate. After dissolution, EtnNH3–n (99%) was slowly added to the solution. In all cases, a stoichiometric ratio TeO2:EtnNH3–n of 1:2 was used. Yellow crystals of (EtNH3)2TeCl6 and (Et3NH)2TeCl6 formed upon slow evaporation of solutions at room temperature within several days, while (Et2NH2)2TeCl6 crystals formed almost immediately. Two polymorphic modifications of the (Et3NH)2TeCl6 phase, monoclinic and orthorhombic, were found to crystallize simultaneously. Variations in starting molar ratios yielded identical products when ethylamine and diethylamine were used. However, using a 1:1 TeO2:Et3NH ratio yields a different composition, (Et3NH)2Te2Cl10 (Table S28).

Synthesis of (EtnNH4–n)2Sn1–xTexCl6 Solid Solutions for Optical Characterization

Four series of (EtnNH4–n)2Sn1–xTexCl6 (n = 1–4) solid solutions with isomorphous substitutions of Sn4+ for Te4+ were prepared to study the effect of the substitution on the photoluminescent properties. To ensure the starting reagents' complete dissolution (especially sparsely soluble at room temperature SnO2) and homogenization, we employed a hydrothermal reaction: (1 – x)SnO2 + xTeO2 + 2(Et)3NH3–n/Et4NCl → (EtnNH4–n)2Sn1–xTexCl6 at 190 °C for 3 h in excess of concentrated HCl (Table S28). The reactions yielded crystalline target phases. For Et3NH+, the hydrothermal reactions yielded transparent solutions, and the target products crystallized after partial solution evaporation. Since the solid-state synthesis route provides more control over the composition, we synthesized several (Et2NH2)2Sn1–xTexCl6 phases via solid-state reactions for comparison with the hydrothermal products. Three (Et2NH2)2Te1–xSnxCl6 phases with x = 0.5, 0.1, and 0.05 were prepared by mixing and grounding of (Et2NH2)2SnCl6 and (Et2NH2)TeCl6 powders in the corresponding molar ratios. Mixed powders were pressed into pellets using steel dies and annealed for 12 h at 120 °C in a sealed silica tube. After slow cooling (10°/h) to room temperature, pellets were reground and annealed for another 12 h.

Single-Crystal XRD

Single-crystal X-ray diffraction experiments (Mo Kα radiation) were performed on a Bruker D8 QUEST diffractometer equipped with a PHOTON 100 CMOS area detector at room temperature. Data integration was performed via SAINT-Plus software; (78) absorption correction was done with the SADABS program. (79) Structures of new tellurium hybrid chlorides were solved by the intrinsic phasing method (SHELXT (80) and Olex2 (81)) and refined by the full-matrix least-squares method against F2 in an anisotropic approximation (SHELXL (82)). Hydrogen atoms were placed in geometrically calculated positions if no disorder was presented. Tables S1 and S2 contain crystallographic data on the new hybrid tellurium chlorides with no matches on CCDC. (83) Note that the structure of (Et4N)2TeCl6 phase was reported earlier. (53)

Powder XRD

Powder X-ray diffraction patterns for (EtnNH4–n)2Sn1–xTexCl6 (n = 1–4, x = 0–1) polycrystalline samples were collected on a Bruker D2 PHASER diffractometer featuring a LYNXEYE XE-T energy-discriminating detector (Cu Kα radiation) over a 5–65° 2θ range.

Photoluminescence Measurements

Photoluminescence excitation and emission spectra, time-resolved photoluminescence data, and photoluminescence quantum yields were collected at room temperature on an Edinburgh Instruments FS5 spectrofluorometer featuring a 150 W CW ozone-free xenon arc lamp and EPL-375 ps pulsed diode laser excitation sources.

UV–Vis and Raman Spectroscopy

Diffuse reflectance spectra were collected at room temperature using a Shimadzu UV-2450 (Kyoto, Japan) spectrometer in a wavelength range of 200–800 nm. BaSO4 was employed as a nonabsorbing reflectance reference for calibration. Experimental reflection data were transformed into absorption spectra based on the Kubelka–Munk theory, and optical band gaps were extracted. The surface-enhanced Raman spectra were collected using a Renishaw inVia confocal Raman microscope system with a 785 nm laser and with a 9.5 mW laser power (Figure S6).

Thermogravimetric (TGA) and Differential Thermal Analysis (DTA)

Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were performed on powder samples of pristine (Et2NH2)2TeCl6 and (Et2NH2)SnCl6 by using an SDT Q600 thermogravimetric analyzer. Samples were heated from room temperature to 600 °C at a rate of 10 °C/min under a nitrogen flow (100 mL/min) (Figure S6).

Energy-Dispersive Spectroscopy (EDS)

The elemental analysis of the (EtnNH4–n)2Sn1–xTexCl6 (n = 3 and 4) phases was performed on a Thermo Fisher Scientific Teneo field-emission scanning electron microscope at the Georgia Electron Microscopy facility.

DFT Calculations

First-principles calculations were performed using density functional theory (DFT) with the Vienna ab initio simulation package (VASP) planewave code, (84,85) generalized gradient approximation of Perdew, Burke, and Ernzerhof (PBE), (86) and projector-augmented wave (PAW) method. (87,88) The initial unit cells were converted to a primitive cell using VESTA software before geometry optimization. (89) The ground-state geometries at 0 K were optimized by relaxing the cell volume, atomic positions, and cell symmetry until the maximum force on each atom is less than 0.01 eV/Å. Nonspin-polarized calculations were performed, with a 520 eV cutoff energy for the plane wave basis set and 10–5 eV energy convergence criteria. The k-paths for band structure calculations were generated using the VASPKIT package. (90) Band structure visualization was performed using the Sumo package. (91)

Geometric Analysis of Crystal Structures Using Voronoi Tessellation

Crystal structure analysis was performed using the TOPOS 4.0 and ToposPro software packages. (92,94) The method of intersecting spheres was employed for coordination number determination using the AutoCN program. (74,92−94) Dirichlet and ADS programs were employed for Voronoi polyhedra construction and topological analysis, respectively.

Supporting Information

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The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/jacs.4c14554.

  • Selected crystallographic data and XRD experiment parameters, atomic displacement parameters, bond lengths, bond angles, characteristics of N–H···Cl hydrogen bonds, EDS results and SEM images, average PL lifetimes, PLQYs, parameters of TeCl62– octahedra distortion, synthesis details, Tauc plots, TGA/DTA, and Raman spectra (Tables S1–S28 and Figures S1–S6) (PDF)

Accession Codes

CCDC 2391291–2391295 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by emailing [email protected], or by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: + 44 1223 336033.

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Most electronic Supporting Information files are available without a subscription to ACS Web Editions. Such files may be downloaded by article for research use (if there is a public use license linked to the relevant article, that license may permit other uses). Permission may be obtained from ACS for other uses through requests via the RightsLink permission system: http://pubs.acs.org/page/copyright/permissions.html.

Author Information

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  • Corresponding Author
  • Authors
    • Sergei A. Novikov - Department of Chemistry, University of Georgia, Athens, Georgia 30602, United States;  Orcidhttps://orcid.org/0000-0003-2007-3162
    • Hope A. Long - Department of Chemistry, University of Georgia, Athens, Georgia 30602, United States
    • Aleksandra D. Valueva - Department of Chemistry, University of Georgia, Athens, Georgia 30602, United States
  • Author Contributions

    The manuscript was written with the contributions of all authors. All authors have approved the final version of the manuscript.

  • Notes
    The authors declare no competing financial interest.

Acknowledgments

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This work was supported by the University of Georgia Department of Chemistry, Franklin College of Arts and Sciences, and the Office of Provost. The computational study was supported in part by resources and technical expertise from the Georgia Advanced Computing Resource Center, a partnership between the University of Georgia’s Office of the Vice President for Research and the Office of the Vice President for Information Technology. The authors thank Dr. Alevtina A. Maksimova (University of South Carolina) and Dr. Yanjun Yang (University of Georgia) for their assistance with DTA/TGA and Raman spectroscopy data collection.

References

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    Cortecchia, Daniele; Yin, Jun; Petrozza, Annamaria; Soci, Cesare
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    Low-dimensional perovskites are rapidly emerging due to their distinctive emission properties, consisting of ultrabroad and highly Stokes shifted luminescence with pure white light chromaticity, which makes them very attractive for soln.-processed light-emitting devices and scintillators. To foster the design of new materials and their device applications, it is timely to review the relation between perovskite structural properties and the photophys. phenomena underlying their unique light emission characteristics. From a no. of recent studies, it has emerged that broadband emission properties in metal halide frameworks are very common, stemming from the self-localization of small polaron species at specific sites of the inorg. lattice, with a wide energy distribution. This review aims to provide an account of the current understanding of the photophys. processes underpinning luminescence broadening and highly efficient emission in various classes of low-dimensional metal-halide frameworks, and to highlight their potential for soln.-processed optoelectronic device applications. The discussion will addnl. establish a wider perspective on the role of intrinsic and extrinsic self-trapping, formation of polarons and their effect on charge generation and transport in low-dimensional perovskites.
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  11. 11
    Zhou, G.; Su, B.; Huang, J.; Zhang, Q.; Xia, Z. Broad-Band Emission in Metal Halide Perovskites: Mechanism, Materials, and Applications. Materials Science and Engineering: R: Reports 2020, 141, 100548  DOI: 10.1016/j.mser.2020.100548
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    Spanopoulos, I.; Hadar, I.; Ke, W.; Guo, P.; Mozur, E. M.; Morgan, E.; Wang, S.; Zheng, D.; Padgaonkar, S.; Manjunatha Reddy, G. N.; Weiss, E. A.; Hersam, M. C.; Seshadri, R.; Schaller, R. D.; Kanatzidis, M. G. Tunable Broad Light Emission from 3D “Hollow” Bromide Perovskites through Defect Engineering. J. Am. Chem. Soc. 2021, 143 (18), 7069– 7080,  DOI: 10.1021/jacs.1c01727
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    12
    Tunable Broad Light Emission from 3D "Hollow" Bromide Perovskites through Defect Engineering
    Spanopoulos, Ioannis; Hadar, Ido; Ke, Weijun; Guo, Peijun; Mozur, Eve M.; Morgan, Emily; Wang, Shuxin; Zheng, Ding; Padgaonkar, Suyog; Manjunatha Reddy, G. N.; Weiss, Emily A.; Hersam, Mark C.; Seshadri, Ram; Schaller, Richard D.; Kanatzidis, Mercouri G.
    Journal of the American Chemical Society (2021), 143 (18), 7069-7080CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    Hybrid halide perovskites consisting of corner-sharing metal halide octahedra and small cuboctahedral cages filled with counter cations have proven to be prominent candidates for many high-performance optoelectronic devices. The stability limits of their three-dimensional perovskite framework are defined by the size range of the cations present in the cages of the structure. In some cases, the stability of the perovskite-type structure can be extended even when the counterions violate the size and shape requirements, as is the case in the so-called "hollow" perovskites. In this work, we engineered a new family of 3D highly defective yet cryst. "hollow" bromide perovskites with general formula (FA)1-x(en)x(Pb)1-0.7x(Br)3-0.4x (FA = formamidinium (FA+), en = ethylenediammonium (en2+), x = 0-0.44). Pair distribution function anal. shed light on the local structural coherence, revealing a wide distribution of Pb-Pb distances in the crystal structure as a consequence of the Pb/Br-deficient nature and en inclusion in the lattice. By manipulating the no. of Pb/Br vacancies, we finely tune the optical properties of the pristine FAPbBr3 by blue shifting the band gap from 2.20 to 2.60 eV for the x = 0.42 en sample. A most unexpected outcome was that at x> 0.33 en incorporation, the material exhibits strong broad light emission (1% photoluminescence quantum yield (PLQY)) that is maintained after exposure to air for more than a year. This is the first example of strong broad light emission from a 3D hybrid halide perovskite, demonstrating that meticulous defect engineering is an excellent tool for customizing the optical properties of these semiconductors.
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  13. 13
    Dou, L.; Yang, Y.; You, J.; Hong, Z.; Chang, W. H.; Li, G.; Yang, Y. Solution-Processed Hybrid Perovskite Photodetectors with High Detectivity. Nat. Commun. 2014, 5 (1), 5404,  DOI: 10.1038/ncomms6404
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    Solution-processed hybrid perovskite photodetectors with high detectivity
    Dou, Letian; Yang, Yang; You, Jingbi; Hong, Ziruo; Chang, Wei-Hsuan; Li, Gang; Yang, Yang
    Nature Communications (2014), 5 (), 5404CODEN: NCAOBW; ISSN:2041-1723. (Nature Publishing Group)
    Photodetectors capture optical signals with a wide range of incident photon flux d. and convert them to elec. signals instantaneously. They have many important applications including imaging, optical communication, remote control, chem./biol. sensing and so on. Currently, GaN, Si and InGaAs photodetectors are used in com. available products. Here we demonstrate a novel soln.-processed photodetector based on an org.-inorg. hybrid perovskite material. Operating at room temp., the photodetectors exhibit a large detectivity (the ability to detect weak signals) approaching 1014 Jones, a linear dynamic range over 100 decibels (dB) and a fast photoresponse with 3-dB bandwidth up to 3 MHz. The performance is significantly better than most of the org., quantum dot and hybrid photodetectors reported so far; and is comparable, or even better than, the traditional inorg. semiconductor-based photodetectors. Our results indicate that with proper device interface design, perovskite materials are promising candidates for low-cost, high-performance photodetectors.
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  14. 14
    Birowosuto, M. D.; Cortecchia, D.; Drozdowski, W.; Brylew, K.; Lachmanski, W.; Bruno, A.; Soci, C. X-Ray Scintillation in Lead Halide Perovskite Crystals. Sci. Rep 2016, 6 (1), 37254,  DOI: 10.1038/srep37254
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    14
    X-ray Scintillation in Lead Halide Perovskite Crystals
    Birowosuto, M. D.; Cortecchia, D.; Drozdowski, W.; Brylew, K.; Lachmanski, W.; Bruno, A.; Soci, C.
    Scientific Reports (2016), 6 (), 37254CODEN: SRCEC3; ISSN:2045-2322. (Nature Publishing Group)
    Current technologies for X-ray detection rely on scintillation from expensive inorg. crystals grown at high-temp., which so far has hindered the development of large-area scintillator arrays. Thanks to the presence of heavy atoms, soln.-grown hybrid lead halide perovskite single crystals exhibit short X-ray absorption length and excellent detection efficiency. Here we compare X-ray scintillator characteristics of three-dimensional (3D) MAPbI3 and MAPbBr3 and two-dimensional (2D) (EDBE)PbCl4 hybrid perovskite crystals. X-ray excited thermoluminescence measurements indicate the absence of deep traps and a very small d. of shallow trap states, which lessens after-glow effects. All perovskite single crystals exhibit high X-ray excited luminescence yields of >120,000 photons/MeV at low temp. Although thermal quenching is significant at room temp., the large exciton binding energy of 2D (EDBE)PbCl4 significantly reduces thermal effects compared to 3D perovskites, and moderate light yield of 9,000 photons/MeV can be achieved even at room temp. This highlights the potential of 2D metal halide perovskites for large-area and low-cost scintillator devices for medical, security and scientific applications.
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  15. 15
    Zhao, Y.; Zhu, K. Organic–Inorganic Hybrid Lead Halide Perovskites for Optoelectronic and Electronic Applications. Chem. Soc. Rev. 2016, 45 (3), 655– 689,  DOI: 10.1039/C4CS00458B
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    15
    Organic-inorganic hybrid lead halide perovskites for optoelectronic and electronic applications
    Zhao, Yixin; Zhu, Kai
    Chemical Society Reviews (2016), 45 (3), 655-689CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)
    Org. and inorg. hybrid perovskites (e.g., CH3NH3PbI3), with advantages of facile processing, tunable bandgaps, and superior charge-transfer properties, have emerged as a new class of revolutionary optoelectronic semiconductors promising for various applications. Perovskite solar cells constructed with a variety of configurations have demonstrated unprecedented progress in efficiency, reaching about 20% from multiple groups after only several years of active research. A key to this success is the development of various soln.-synthesis and film-deposition techniques for controlling the morphol. and compn. of hybrid perovskites. The rapid progress in material synthesis and device fabrication has also promoted the development of other optoelectronic applications including light-emitting diodes, photodetectors, and transistors. Both exptl. and theor. investigations on org.-inorg. hybrid perovskites have enabled some crit. fundamental understandings of this material system. Recent studies have also demonstrated progress in addressing the potential stability issue, which has been identified as a main challenge for future research on halide perovskites. Here, we review recent progress on hybrid perovskites including basic chem. and crystal structures, chem. synthesis of bulk/nanocrystals and thin films with their chem. and phys. properties, device configurations, operation principles for various optoelectronic applications (with a focus on solar cells), and photophysics of charge-carrier dynamics. We also discuss the importance of further understanding of the fundamental properties of hybrid perovskites, esp. those related to chem. and structural stabilities.
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  16. 16
    García de Arquer, F. P.; Armin, A.; Meredith, P.; Sargent, E. H. Solution-Processed Semiconductors for next-Generation Photodetectors. Nat. Rev. Mater. 2017, 2 (3), 1– 17,  DOI: 10.1038/natrevmats.2016.100
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    He, Y.; Ke, W.; Alexander, G. C. B.; McCall, K. M.; Chica, D. G.; Liu, Z.; Hadar, I.; Stoumpos, C. C.; Wessels, B. W.; Kanatzidis, M. G. Resolving the Energy of γ-Ray Photons with MAPbI3 Single Crystals. ACS Photonics 2018, 5 (10), 4132– 4138,  DOI: 10.1021/acsphotonics.8b00873
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    17
    Resolving the Energy of γ-Ray Photons with MAPbI3 Single Crystals
    He, Yihui; Ke, Weijun; Alexander, Grant C. B.; McCall, Kyle M.; Chica, Daniel G.; Liu, Zhifu; Hadar, Ido; Stoumpos, Constantinos C.; Wessels, Bruce W.; Kanatzidis, Mercouri G.
    ACS Photonics (2018), 5 (10), 4132-4138CODEN: APCHD5; ISSN:2330-4022. (American Chemical Society)
    Halide perovskites exhibit remarkably high-performance as semiconductors compared to conventional materials because of an unusually favorable combination of optoelectronic properties. Soln.-grown single-crystals of org.-inorg. hybrid perovskite MeNH3PbI3 (MAPbI3), implemented in a Schottky-type device design, can produce outstanding hard radiation detectors with high spectral response and low dark current. Schottky-type MAPbI3 detector achieves an excellent energy resoln. of 6.8% for 57Co 122 keV gamma ray. The high detector performance is achieved due to the balanced charge collection efficiency for both electrons and holes, reflected in the high mobility-lifetime (μτ) products of both carriers (∼0.8 × 10-3 cm2/V). MAPbI3 demonstrates remarkably long electron and hole lifetimes (τe = 10 μs and τh = 17 μs) and impressive operational stability over time. Dual-source detection of α particle (5.5 MeV) and γ-ray (59.5 keV) from the 241Am radiation source is achieved simultaneously by Schottky-type MAPbI3 detector. These results reveal the great potential of MAPbI3 as a high-performance, low-cost radiation detection material.
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  18. 18
    Mozur, E. M.; Trowbridge, J. C.; Maughan, A. E.; Gorman, M. J.; Brown, C. M.; Prisk, T. R.; Neilson, J. R. Dynamical Phase Transitions and Cation Orientation-Dependent Photoconductivity in CH(NH2)2PbBr3. ACS Materials Lett. 2019, 1 (2), 260– 264,  DOI: 10.1021/acsmaterialslett.9b00209
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    Kakavelakis, G.; Gedda, M.; Panagiotopoulos, A.; Kymakis, E.; Anthopoulos, T. D.; Petridis, K. Metal Halide Perovskites for High-Energy Radiation Detection. Advanced Science 2020, 7 (22), 2002098  DOI: 10.1002/advs.202002098
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    Metal Halide Perovskites for High-Energy Radiation Detection
    Kakavelakis, George; Gedda, Murali; Panagiotopoulos, Apostolis; Kymakis, Emmanuel; Anthopoulos, Thomas D.; Petridis, Konstantinos
    Advanced Science (Weinheim, Germany) (2020), 7 (22), 2002098CODEN: ASDCCF; ISSN:2198-3844. (Wiley-VCH Verlag GmbH & Co. KGaA)
    Metal halide perovskites (MHPs) have emerged as a frontrunner semiconductor technol. for application in third generation photovoltaics while simultaneously making significant strides in other areas of optoelectronics. Photodetectors are one of the latest addns. in an expanding list of applications of this fascinating family of materials. The extensive range of possible inorg. and hybrid perovskites coupled with their processing versatility and ability to convert external stimuli into easily measurable optical/elec. signals makes them an auspicious sensing element even for the high-energy domain of the electromagnetic spectrum. Key to this is the ability of MHPs to accommodate heavy elements while being able to form large, high-quality crystals and polycryst. layers, making them one of the most promising emerging X-ray and γ-ray detector technologies. Here, the fundamental principles of high-energy radiation detection are reviewed with emphasis on recent progress in the emerging and fascinating field of metal halide perovskite-based X-ray and γ-ray detectors. The review starts with a discussion of the basic principles of high-energy radiation detection with focus on key performance metrics followed by a comprehensive summary of the recent progress in the field of perovskite-based detectors. The article concludes with a discussion of the remaining challenges and future perspectives.
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  20. 20
    Xu, L.-J.; Lin, X.; He, Q.; Worku, M.; Ma, B. Highly Efficient Eco-Friendly X-Ray Scintillators Based on an Organic Manganese Halide. Nat. Commun. 2020, 11 (1), 4329,  DOI: 10.1038/s41467-020-18119-y
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    20
    Highly efficient eco-friendly X-ray scintillators based on an organic manganese halide
    Xu, Liang-Jin; Lin, Xinsong; He, Qingquan; Worku, Michael; Ma, Biwu
    Nature Communications (2020), 11 (1), 4329CODEN: NCAOBW; ISSN:2041-1723. (Nature Research)
    Scintillation based X-ray detection has received great attention for its application in a wide range of areas from security to healthcare. Here, we report highly efficient X-ray scintillators with state-of-the-art performance based on an org. metal halide, ethylenebis-triphenylphosphonium manganese (II) bromide ((C38H34P2)MnBr4), which can be prepd. using a facile soln. growth method at room temp. to form inch sized single crystals. This zero-dimensional org. metal halide hybrid exhibits green emission peaked at 517 nm with a photoluminescence quantum efficiency of ∼ 95%. Its X-ray scintillation properties are characterized with an excellent linear response to X-ray dose rate, a high light yield of ∼ 80,000 photon MeV-1, and a low detection limit of 72.8 nGy s-1. X-ray imaging tests show that scintillators based on (C38H34P2)MnBr4 powders provide an excellent visualization tool for X-ray radiog., and high resoln. flexible scintillators can be fabricated by blending (C38H34P2)MnBr4 powders with polydimethylsiloxane.
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  21. 21
    Liu, R.; Li, F.; Zeng, F.; Zhao, R.; Zheng, R. Halide Perovskite X-Ray Detectors: Fundamentals, Progress, and Outlook. Applied Physics Reviews 2024, 11 (2), 021327  DOI: 10.1063/5.0198695
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    Gao, P.; Grätzel, M.; Nazeeruddin, M. K. Organohalide Lead Perovskites for Photovoltaic Applications. Energy Environ. Sci. 2014, 7 (8), 2448– 2463,  DOI: 10.1039/C4EE00942H
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    Organohalide lead perovskites for photovoltaic applications
    Gao, Peng; Gratzel, Michael; Nazeeruddin, Mohammad K.
    Energy & Environmental Science (2014), 7 (8), 2448-2463CODEN: EESNBY; ISSN:1754-5706. (Royal Society of Chemistry)
    There are only few semiconducting materials that have been shaping the progress of third generation photovoltaic cells as much as perovskites. Although they are deceivingly simple in structure, the archetypal AMX3-type perovskites have built-in potential for complex and surprising discoveries. Since 2009, a small and somewhat exotic class of perovskites, which are quite different from the common rock-solid oxide perovskite, have turned over a new leaf in solar cell research. Highlighted as one of the major scientific breakthroughs of the year 2013, the power conversion efficiency of the title compd. hybrid org.-inorg. perovskite has now exceeded 18%, making it competitive with thin-film PV technol. In this mini-review, a brief history of perovskite materials for photovoltaic applications is reported, the current state-of-the-art is distd. and the basic working mechanisms have been discussed. By analyzing the attainable photocurrent and photovoltage, realizing perovskite solar cells with 20% efficiency for a single junction, and 30% for a tandem configuration on a c-Si solar cell would be realistic.
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    Brenner, T. M.; Egger, D. A.; Kronik, L.; Hodes, G.; Cahen, D. Hybrid Organic─Inorganic Perovskites: Low-Cost Semiconductors with Intriguing Charge-Transport Properties. Nat. Rev. Mater. 2016, 1 (1), 1– 16,  DOI: 10.1038/natrevmats.2015.7
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    Saparov, B.; Mitzi, D. B. Organic–Inorganic Perovskites: Structural Versatility for Functional Materials Design. Chem. Rev. 2016, 116 (7), 4558– 4596,  DOI: 10.1021/acs.chemrev.5b00715
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    Organic-inorganic perovskites: structural versatility for functional materials design
    Saparov, Bayrammurad; Mitzi, David B.
    Chemical Reviews (Washington, DC, United States) (2016), 116 (7), 4558-4596CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
    A review. Although known since the late 19th century, org.-inorg. perovskites have recently received extraordinary research community attention because of their unique phys. properties, which make them promising candidates for application in photovoltaic and related optoelectronic devices. This review explores beyond the current focus on 3-dimensional lead(II) halide perovskites, to highlight the great chem. flexibility and outstanding potential of the broader class of 3-dimensional and lower dimensional org.-based perovskite family for electronic, optical and energy-based applications as well as fundamental research. The concept of a multifunctional org.-inorg. hybrid, in which the org. and inorg. structural components provide intentional, unique, and hopefully synergistic features to the compd., represents an important contemporary target.
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  25. 25
    Spanopoulos, I.; Hadar, I.; Ke, W.; Tu, Q.; Chen, M.; Tsai, H.; He, Y.; Shekhawat, G.; Dravid, V. P.; Wasielewski, M. R.; Mohite, A. D.; Stoumpos, C. C.; Kanatzidis, M. G. Uniaxial Expansion of the 2D Ruddlesden–Popper Perovskite Family for Improved Environmental Stability. J. Am. Chem. Soc. 2019, 141 (13), 5518– 5534,  DOI: 10.1021/jacs.9b01327
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    25
    Uniaxial Expansion of the 2D Ruddlesden-Popper Perovskite Family for Improved Environmental Stability
    Spanopoulos, Ioannis; Hadar, Ido; Ke, Weijun; Tu, Qing; Chen, Michelle; Tsai, Hsinhan; He, Yihui; Shekhawat, Gajendra; Dravid, Vinayak P.; Wasielewski, Michael R.; Mohite, Aditya D.; Stoumpos, Constantinos C.; Kanatzidis, Mercouri G.
    Journal of the American Chemical Society (2019), 141 (13), 5518-5534CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    The unique hybrid nature of 2D Ruddlesden-Popper (R-P) perovskites has bestowed upon them not only tunability of their electronic properties but also high-performance electronic devices with improved environmental stability as compared to their 3D analogs. However, there is limited information about their inherent heat, light, and air stability and how different parameters such as the inorg. layer no. and length of org. spacer mol. affect stability. To gain deeper understanding on the matter we have expanded the family of 2D R-P perovskites, by utilizing pentylamine (PA)2(MA)n-1PbnI3n+1 (n = 1-5, PA = CH3(CH2)4NH3+, C5) and hexylamine (HA)2(MA)n-1PbnI3n+1 (n = 1-4, HA = CH3(CH2)5NH3+, C6) as the org. spacer mols. between the inorg. slabs, creating two new series of layered materials, for up to n = 5 and 4 layers, resp. The resulting compds. were extensively characterized through a combination of phys. and spectroscopic methods, including single crystal X-ray anal. High resoln. powder X-ray diffraction studies using synchrotron radiation shed light for the first time to the phase transitions of the higher layer 2D R-P perovskites. The increase in the length of the org. spacer mols. did not affect their optical properties; however, it has a pronounced effect on the air, heat, and light stability of the fabricated thin films. An extensive study of heat, light, and air stability with and without encapsulation revealed that specific compds. can be air stable (relative humidity (RH) = 20-80% ± 5%) for more than 450 days, while heat and light stability in air can be exponentially increased by encapsulating the corresponding films. Evaluation of the out-of-plane mech. properties of the corresponding materials showed that their soft and flexible nature can be compared to current com. available polymer substrates (e.g., PMMA), rendering them suitable for fabricating flexible and wearable electronic devices.
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  26. 26
    Ke, W.; Mao, L.; Stoumpos, C. C.; Hoffman, J.; Spanopoulos, I.; Mohite, A. D.; Kanatzidis, M. G. Compositional and Solvent Engineering in Dion–Jacobson 2D Perovskites Boosts Solar Cell Efficiency and Stability. Adv. Energy Mater. 2019, 9 (10), 1803384  DOI: 10.1002/aenm.201803384
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    Spanopoulos, I.; Ke, W.; Stoumpos, C. C.; Schueller, E. C.; Kontsevoi, O. Y.; Seshadri, R.; Kanatzidis, M. G. Unraveling the Chemical Nature of the 3D “Hollow” Hybrid Halide Perovskites. J. Am. Chem. Soc. 2018, 140 (17), 5728– 5742,  DOI: 10.1021/jacs.8b01034
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    27
    Unraveling the Chemical Nature of the 3D "Hollow" Hybrid Halide Perovskites
    Spanopoulos, Ioannis; Ke, Weijun; Stoumpos, Constantinos C.; Schueller, Emily C.; Kontsevoi, Oleg Y.; Seshadri, Ram; Kanatzidis, Mercouri G.
    Journal of the American Chemical Society (2018), 140 (17), 5728-5742CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    The newly introduced class of 3D halide perovskites, termed "hollow" perovskites, has been recently demonstrated as light absorbing semiconductor materials for fabricating lead-free perovskite solar cells with enhanced efficiency and superior stability. Hollow perovskites derive from three-dimensional (3D) AMX3 perovskites (A = methylammonium (MA), formamidinium (FA); M = Sn, Pb; X = Cl, Br, I), where small mols. such as ethylenediammonium cations (en) can be incorporated as the dication without altering the structure dimensionality. We present in this work the inherent structural properties of the hollow perovskites and expand this class of materials to the Pb-based analogs. Through a combination of phys. and spectroscopic methods (XRD, gas pycnometry, 1H NMR, TGA, SEM/EDX), we have assigned the general formula (A)1-x(en)x(M)1-0.7x(X)3-0.4x to the hollow perovskites. The incorporation of en in the 3D perovskite structure leads to massive M and X vacancies in the 3D [MX3] framework, thus the term hollow. The resulting materials are semiconductors with significantly blue-shifted direct band gaps from 1.25 to 1.51 eV for Sn-based perovskites and from 1.53 to 2.1 eV for the Pb-based analogs. The increased structural disorder and hollow nature were validated by single crystal X-ray diffraction anal. as well as pair distribution function (PDF) anal. D. functional theory (DFT) calcns. support the exptl. trends and suggest that the obsd. widening of the band gap is attributed to the massive M and X vacancies, which create a less connected 3D hollow structure. The resulting materials have superior air stability, where in the case of Sn-based hollow perovskites it exceeds two orders of temporal magnitude compared to the conventional full perovskites of MASnI3 and FASnI3. The hollow perovskite compds. pose as a new platform of promising light absorbers that can be utilized in single junction or tandem solar cells.
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  28. 28
    Mozur, E. M.; Hope, M. A.; Trowbridge, J. C.; Halat, D. M.; Daemen, L. L.; Maughan, A. E.; Prisk, T. R.; Grey, C. P.; Neilson, J. R. Cesium Substitution Disrupts Concerted Cation Dynamics in Formamidinium Hybrid Perovskites. Chem. Mater. 2020, 32 (14), 6266– 6277,  DOI: 10.1021/acs.chemmater.0c01862
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    Cesium substitution disrupts concerted cation dynamics in formamidinium hybrid perovskites
    Mozur, Eve M.; Hope, Michael A.; Trowbridge, Julia C.; Halat, David M.; Daemen, Luke L.; Maughan, Annalise E.; Prisk, Timothy R.; Grey, Clare P.; Neilson, James R.
    Chemistry of Materials (2020), 32 (14), 6266-6277CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)
    Although initial studies on hybrid perovskites for photovoltaic applications focused on simple compns., the most technol. relevant perovskites are heavily substituted. The influence of chem. substitution on the general phase behavior and specific phys. properties remains ambiguous. The hybrid perovskite formamidinium lead bromide, CH(NH2)2PbBr3, exhibits complex phase behavior manifesting in a series of crystallog. unresolvable phase transitions assocd. with changes in the cation dynamics. Here, we characterize the mol. and lattice dynamics of CH(NH2)2PbBr3 as a function of temp. and their evolution upon chem. substitution of CH(NH2)2+ for cesium (Cs+) with crystallog., neutron scattering, 1H and 14N NMR spectroscopy, and 79Br nuclear quadrupolar spectroscopy. Cs+ substitution suppresses the four low-temp. phase transitions of CH(NH2)2PbBr3, which propagate through concerted changes in the dynamic degrees of freedom of the org. sublattice and local or long-range distortions of the octahedral framework. We propose that cesium substitution suppresses the phase transitions through the relief of geometric frustration assocd. with the orientations of CH(NH2)2+ mols., which retain their local dynamical degrees of freedom.
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  29. 29
    Kontos, A. G.; Kaltzoglou, A.; Arfanis, M. K.; McCall, K. M.; Stoumpos, C. C.; Wessels, B. W.; Falaras, P.; Kanatzidis, M. G. Dynamic Disorder, Band Gap Widening, and Persistent Near-IR Photoluminescence up to At Least 523 K in ASnI3 Perovskites (A = Cs+, CH3NH3+ and NH2–CH═NH2+). J. Phys. Chem. C 2018, 122 (46), 26353– 26361,  DOI: 10.1021/acs.jpcc.8b10218
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  30. 30
    Jana, A.; Zhumagali, S.; Ba, Q.; Nissimagoudar, A. S.; Kim, K. S. Direct Emission from Quartet Excited States Triggered by Upconversion Phenomena in Solid-Phase Synthesized Fluorescent Lead-Free Organic–Inorganic Hybrid Compounds. J. Mater. Chem. A 2019, 7 (46), 26504– 26512,  DOI: 10.1039/C9TA08268A
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    30
    Direct emission from quartet excited states triggered by upconversion phenomena in solid-phase synthesized fluorescent lead-free organic-inorganic hybrid compounds
    Jana, Atanu; Zhumagali, Shynggys; Ba, Qiankai; Nissimagoudar, Arun S.; Kim, Kwang S.
    Journal of Materials Chemistry A: Materials for Energy and Sustainability (2019), 7 (46), 26504-26512CODEN: JMCAET; ISSN:2050-7496. (Royal Society of Chemistry)
    We report, for the first time, the solid-phase gram-scale synthesis of two lead-free, zero-dimensional (0D) fluorescent org.-inorg. hybrid compds., [Bu4N]2[MnBr4] (1) and [Ph4P]2[MnBr4] (2), achieved by grinding the org. and inorg. precursor salts. The solid-phase synthetic route has several advantages for modulating mol. dimensionalities. During grinding, org. cations and Mn2+ cations are co-crystd. together in the solid-state, forming a 0D assembly at the mol. level where each individual metal center is surrounded by org. cations. Both compds. exhibit an emission peak at 520 nm and a photoluminescence (PL) quantum yield (QY) of 47%. Here, we also report, for the first time, the upconversion phenomena which trigger different emission energies occurring in different quartet states of Mn, 4T1(4G), 4T2(4G), 4A1(4G), 4E(4G), 4T2(4D), 4E(4D), and 4T1(4P). These optical properties are unusual phenomena which break Kasha's rule of emission. Single particle imaging and low-temp. PL measurement are performed to obtain a deeper insight into these ground products. These results pave a new path to develop highly fluorescent non-toxic hybrid compds. with remarkable optical properties.
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  31. 31
    Fattal, H.; Creason, T. D.; Delzer, C. J.; Yangui, A.; Hayward, J. P.; Ross, B. J.; Du, M.-H.; Glatzhofer, D. T.; Saparov, B. Zero-Dimensional Hybrid Organic–Inorganic Indium Bromide with Blue Emission. Inorg. Chem. 2021, 60 (2), 1045– 1054,  DOI: 10.1021/acs.inorgchem.0c03164
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    31
    Zero-Dimensional Hybrid Organic-Inorganic Indium Bromide with Blue Emission
    Fattal, Hadiah; Creason, Tielyr D.; Delzer, Cordell J.; Yangui, Aymen; Hayward, Jason P.; Ross, Bradley J.; Du, Mao-Hua; Glatzhofer, Daniel T.; Saparov, Bayrammurad
    Inorganic Chemistry (2021), 60 (2), 1045-1054CODEN: INOCAJ; ISSN:0020-1669. (American Chemical Society)
    Low-dimensional hybrid org.-inorg. metal halides have received increased attention because of their outstanding optical and electronic properties. However, the most studied hybrid compds. contain lead and have long-term stability issues, which must be addressed for their use in practical applications. Here, we report a new zero-dimensional hybrid org.-inorg. halide, RInBr4, featuring photoemissive trimethyl(4-stilbenyl)methylammonium (R+) cations and nonemissive InBr4- tetrahedral anions. The crystal structure of RInBr4 is composed of alternating layers of inorg. anions and org. cations along the crystallog. a axis. The resultant hybrid demonstrates bright-blue emission with Commission Internationale de l'Eclairage color coordinates of (0.19, 0.20) and a high photoluminescence quantum yield (PLQY) of 16.36% at room temp., a 2-fold increase compared to the PLQY of 8.15% measured for the precursor org. salt RBr. On the basis of our optical spectroscopy and computational work, the org. component is responsible for the obsd. blue emission of the hybrid material. In addn. to the enhanced light emission efficiency, the novel hybrid indium bromide demonstrates significantly improved environmental stability. These findings may pave the way for the consideration of hybrid org. In(III) halides for light emission applications. The prepn. and optical properties of a novel hybrid org.-inorg. halide, RInBr4 [R = trimethyl(4-stilbenyl)methylammonium cation], are reported. The zero-dimensional crystal structure of RInBr4 features alternating layers of isolated InBr4- tetrahedra sepd. by layers of org. cations R+. RInBr4 shows high-efficiency blue emission with a quantum yield of 16.36% originating from the org. cation R+. Importantly, the novel hybrid indium bromide shows significantly improved air and thermal stability and photostability compared to the precursor org. salt.
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  32. 32
    Morad, V.; Yakunin, S.; Benin, B. M.; Shynkarenko, Y.; Grotevent, M. J.; Shorubalko, I.; Boehme, S. C.; Kovalenko, M. V. Hybrid 0D Antimony Halides as Air-Stable Luminophores for High-Spatial-Resolution Remote Thermography. Adv. Mater. 2021, 33 (9), 2007355  DOI: 10.1002/adma.202007355
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    32
    Hybrid 0D Antimony Halides as Air-Stable Luminophores for High-Spatial-Resolution Remote Thermography
    Morad, Viktoriia; Yakunin, Sergii; Benin, Bogdan M.; Shynkarenko, Yevhen; Grotevent, Matthias J.; Shorubalko, Ivan; Boehme, Simon C.; Kovalenko, Maksym V.
    Advanced Materials (Weinheim, Germany) (2021), 33 (9), 2007355CODEN: ADVMEW; ISSN:0935-9648. (Wiley-VCH Verlag GmbH & Co. KGaA)
    Luminescent org.-inorg. low-dimensional ns2 metal halides are of rising interest as thermog. phosphors. The intrinsic nature of the excitonic self-trapping provides for reliable temp. sensing due to the existence of a temp. range, typically 50-100 K wide, in which the luminescence lifetimes (and quantum yields) are steeply temp.-dependent. This sensitivity range can be adjusted from cryogenic temps. to above room temp. by structural engineering, thus enabling diverse thermometric and thermog. applications ranging from protein crystallog. to diagnostics in microelectronics. Owing to the stable oxidn. state of Sb3+, Sb(III)-based halides are far more attractive than all major non-heavy-metal alternatives (Sn-, Ge-, Bi-based halides). In this work, the relationship between the luminescence characteristics and crystal structure and microstructure of TPP2SbBr5 (TPP = tetraphenylphosphonium) is established, and then its potential is showcased as environmentally stable and robust phosphor for remote thermog. The material is easily processable into thin films, which is highly beneficial for high-spatial-resoln. remote thermog. In particular, a compelling combination of high spatial resoln. (1μm) and high thermometric precision (high specific sensitivities of 0.03-0.04 K-1) is demonstrated by fluorescence-lifetime imaging of a heated resistive pattern on a flat substrate, covered with a soln.-spun film of TPP2SbBr5.
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  33. 33
    Creason, T. D.; Fattal, H.; Gilley, I. W.; Evans, B. N.; Jiang, J.; Pachter, R.; Glatzhofer, D. T.; Saparov, B. Stabilized Photoemission from Organic Molecules in Zero-Dimensional Hybrid Zn and Cd Halides. Inorg. Chem. Front. 2022, 9 (23), 6202– 6210,  DOI: 10.1039/D2QI01293F
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  34. 34
    McWhorter, T. M.; Zhang, Z.; Creason, T. D.; Thomas, L.; Du, M.-H.; Saparov, B. (C7H11N2)2MBr4 (M = Cu, Zn): X-Ray Sensitive 0D Hybrid Metal Halides with Tunable Broadband Emission. Eur. J. Inorg. Chem. 2022, 2022 (10), e202100954  DOI: 10.1002/ejic.202100954
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    34
    (C7H11N2)2MBr4 (M=Cu, Zn): X-Ray Sensitive 0D Hybrid Metal Halides with Tunable Broadband Emission
    McWhorter, Timothy M.; Zhang, Zheng; Creason, Tielyr D.; Thomas, Leonard; Du, Mao-Hua; Saparov, Bayram
    European Journal of Inorganic Chemistry (2022), 2022 (10), e202100954CODEN: EJICFO; ISSN:1434-1948. (Wiley-VCH Verlag GmbH & Co. KGaA)
    Herein, a new family of hybrid metal halides, (DMAP)2MBr4 (M = Cu, Zn), featuring zero-dimensional (0D), pseudo-layered crystal structures contg. isolated mol. 4-dimethylaminopyridinium (DMAP, C7H11N2+) cations and MBr42- tetrahedral anions are reported. (DMAP)2MBr4 show remarkable long-term stability, with no signs of degrdn. after one year of ambient air exposure. The reported soln. synthesis affords large crystals measuring up to 1 cm, which showed significant response to soft 8 keV X-ray photons when implemented into X-ray detectors. Furthermore, (DMAP)2ZnBr4 demonstrates tunable color light emission properties, which is attributed to the org. mol. units based on our combined exptl. and computational results. The measured photoluminescence quantum yield (PLQY) for (DMAP)2ZnBr4 is 7.35 %, a remarkable enhancement of emission efficiency as compared to a weak emission from the org. precursor. The inexpensive and earth-abundant chem. compns. and ease of prepn. of the new hybrid metal halides make them promising candidates for optical and electronic applications.
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    Vishnoi, P.; Zuo, J. L.; Li, X.; Binwal, D. C.; Wyckoff, K. E.; Mao, L.; Kautzsch, L.; Wu, G.; Wilson, S. D.; Kanatzidis, M. G.; Seshadri, R.; Cheetham, A. K. Hybrid Layered Double Perovskite Halides of Transition Metals. J. Am. Chem. Soc. 2022, 144 (15), 6661– 6666,  DOI: 10.1021/jacs.1c12760
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    Hybrid Layered Double Perovskite Halides of Transition Metals
    Vishnoi, Pratap; Zuo, Julia L.; Li, Xiaotong; Binwal, Devesh Chandra; Wyckoff, Kira E.; Mao, Lingling; Kautzsch, Linus; Wu, Guang; Wilson, Stephen D.; Kanatzidis, Mercouri G.; Seshadri, Ram; Cheetham, Anthony K.
    Journal of the American Chemical Society (2022), 144 (15), 6661-6666CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    Hybrid layered double perovskite (HLDP) halides comprise hexacoordinated 1+ and 3+ metals in the octahedral sites within a perovskite layer and org. amine cations between the layers. Progress on such materials has hitherto been limited to compds. contg. main Group 3+ ions isoelectronic with PbII (such as SbIII and BiIII). Here, the authors report eight HLDP halides from the A2MIMIIIX8 family, where A = para-phenylenediammonium (PPDA), 1,4-butanediammonium (1,4-BDA), or 1,3-propanediammonium (1,3-PDA); MI = Cu or Ag; MIII = Ru or Mo; X = Cl or Br. The optical band gaps, which lie in the range 1.55 to 2.05 eV, are tunable according to the layer compn., but are largely independent of the spacer. Magnetic measurements carried out for (PPDA)2AgIRuIIICl8 and (PPDA)2AgIMoIIICl8 show no obvious evidence of a magnetic ordering transition. While the t2g3 MoIII compd. displays Curie-Weiss behavior for a spin-only d3 ion, the t2g5 RuIII compd. displays marked deviations from the Kotani theory.
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  36. 36
    Wang, S.; Morgan, E. E.; Panuganti, S.; Mao, L.; Vishnoi, P.; Wu, G.; Liu, Q.; Kanatzidis, M. G.; Schaller, R. D.; Seshadri, R. Ligand Control of Structural Diversity in Luminescent Hybrid Copper(I) Iodides. Chem. Mater. 2022, 34 (7), 3206– 3216,  DOI: 10.1021/acs.chemmater.1c04408
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    Ligand Control of Structural Diversity in Luminescent Hybrid Copper(I) Iodides
    Wang, Shuxin; Morgan, Emily E.; Panuganti, Shobhana; Mao, Lingling; Vishnoi, Pratap; Wu, Guang; Liu, Quanlin; Kanatzidis, Mercouri G.; Schaller, Richard D.; Seshadri, Ram
    Chemistry of Materials (2022), 34 (7), 3206-3216CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)
    Copper(I) iodide hybrids are of interest for next-generation lighting technologies because of their efficient luminescence in the absence of rare-earth elements. Here, the authors report 10 structurally diverse hybrid copper(I) iodides that emit in the green-red region with quantum yields reaching 67%. The compds. display a diversity of structures including ones with one-dimensional (1D) Cu-1 chains, Cu2I2 rhomboid dimers, and structures with two different arrangements of Cu4I4 tetramers. The compds. with Cu2I2 rhomboid dimers or Cu4I4 cubane tetramers have higher photoluminescence quantum yields than those with Cu-I 1D chains and octahedral Cu4I4 tetramers, owing to the optimal degree of condensation of the inorg. motifs, which suppresses nonradiative processes. Electronic structure calcns. on these compds. point out the crit. influence of the inorg. motif and org. ligand on the nature of the band gaps and thus the excitation characteristics. Temp.-dependent photoluminescence spectra are presented to better understand the nature of luminescence in compds. with different inorg. motifs. The emerging understanding of compn.-structure-property correlations in this family provides inspiration for the rational design of hybrid phosphors for general lighting applications.
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  37. 37
    Morgan, E. E.; Kent, G. T.; Zohar, A.; O’Dea, A.; Wu, G.; Cheetham, A. K.; Seshadri, R. Hybrid and Inorganic Vacancy-Ordered Double Perovskites A2WCl6. Chem. Mater. 2023, 35 (17), 7032– 7038,  DOI: 10.1021/acs.chemmater.3c01300
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    Hybrid and Inorganic Vacancy-Ordered Double Perovskites A2WCl6
    Morgan, Emily E.; Kent, Greggory T.; Zohar, Arava; O.bxsolid.Dea, Anthony; Wu, Guang; Cheetham, Anthony K.; Seshadri, Ram
    Chemistry of Materials (2023), 35 (17), 7032-7038CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)
    We report hybrid and all-inorg., vacancy-ordered double perovskites of d2 W4+ with the formula A2WCl6 (A = CH3NH3+, Rb+, and Cs+). These compds., which are reddish in color, can be distinguished from structurally similar compds. obtained by hydrothermal methods on the basis of structure, spectroscopic, and magnetic properties. The latter are green and incorporate oxygen, with the actual formula Cs2WOxCl6-x and distinct optical absorption and emission behavior. The local-moment magnetism of the pure-red d2 compds. reported here does not correspond to the appropriate Kotani model, suggesting as-yet undiscovered physics in these systems.
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  38. 38
    McCall, K. M.; Morad, V.; Benin, B. M.; Kovalenko, M. V. Efficient Lone-Pair-Driven Luminescence: Structure–Property Relationships in Emissive 5s2 Metal Halides. ACS Materials Lett. 2020, 2 (9), 1218– 1232,  DOI: 10.1021/acsmaterialslett.0c00211
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    38
    Efficient Lone-Pair-Driven Luminescence: Structure-Property Relationships in Emissive 5s2 Metal Halides
    McCall, Kyle M.; Morad, Viktoriia; Benin, Bogdan M.; Kovalenko, Maksym V.
    ACS Materials Letters (2020), 2 (9), 1218-1232CODEN: AMLCEF; ISSN:2639-4979. (American Chemical Society)
    Low-dimensional metal halides have been the focus of intense investigations in recent years following the success of hybrid lead halide perovskites as optoelectronic materials. In particular, the light emission of low-dimensional halides based on the 5s2 cations Sn2+ and Sb3+ has found utility in a variety of applications complementary to those of the three-dimensional halide perovskites because of its unusual properties such as broadband character and highly temp.-dependent lifetime. These properties derive from the exceptional chem. of the 5s2 lone pair, but the terminol. and explanations given for such emission vary widely, hampering efforts to build a cohesive understanding of these materials that would lead to the development of efficient optoelectronic devices. In this Perspective, we provide a structural overview of these materials with a focus on the dynamics driven by the stereoactivity of the 5s2 lone pair to identify the structural features that enable strong emission. We unite the different theor. models that have been able to explain the success of these bright 5s2 emission centers into a cohesive framework, which is then applied to the array of compds. recently developed by our group and other researchers, demonstrating its utility and generating a holistic picture of the field from the point of view of a materials chemist. We highlight those state-of-the-art materials and applications that demonstrate the unique capabilities of these versatile emissive centers and identify promising future directions in the field of low-dimensional 5s2 metal halides.
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    Lyu, R.; Moore, C. E.; Liu, T.; Yu, Y.; Wu, Y. Predictive Design Model for Low-Dimensional Organic–Inorganic Halide Perovskites Assisted by Machine Learning. J. Am. Chem. Soc. 2021, 143 (32), 12766– 12776,  DOI: 10.1021/jacs.1c05441
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    39
    Predictive Design Model for Low-Dimensional Organic-Inorganic Halide Perovskites Assisted by Machine Learning
    Lyu, Ruiyang; Moore, Curtis E.; Liu, Tianyu; Yu, Yongze; Wu, Yiying
    Journal of the American Chemical Society (2021), 143 (32), 12766-12776CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    Low-dimensional org.-inorg. halide perovskites have attracted interest for their properties in exciton dynamics, broad-band emission, magnetic spin selectivity. However, there is no quant. model for predicting the structure-directing effect of org. cations on the dimensionality of these low-dimensional perovskites. Here, we report a machine learning (ML)-assisted approach to predict the dimensionality of lead iodide-based perovskites. A literature review reveals 86 reported amines that are classified into "2D"-forming and "non-2D"-forming based on the dimensionality of their perovskites. Machining learning models were trained and tested based on the classification and descriptor features of these ammonium cations. Four structural features, including steric effect index, eccentricity, largest ring size, and hydrogen-bond donor, have been identified as the key controlling factors. On the basis of these features, a quantified equation is created to calc. the probability of forming 2D perovskite for a selected amine. To further illustrate its predicting capability, the built model is applied to several untested amines, and the predicted dimensionality is verified by growing single crystals of perovskites from these amines. This work represents a step toward predicting the crystal structures of low dimensional hybrid halide perovskites using ML as a tool.
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  40. 40
    Feng, W.; Tan, Y.; Yang, M.; Jiang, Y.; Lei, B.-X.; Wang, L.; Wu, W.-Q. Small Amines Bring Big Benefits to Perovskite-Based Solar Cells and Light-Emitting Diodes. Chem. 2022, 8 (2), 351– 383,  DOI: 10.1016/j.chempr.2021.11.010
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    Lee, J.-W.; Kim, D.-H.; Kim, H.-S.; Seo, S.-W.; Cho, S. M.; Park, N.-G. Formamidinium and Cesium Hybridization for Photo- and Moisture-Stable Perovskite Solar Cell. Adv. Energy Mater. 2015, 5 (20), 1501310  DOI: 10.1002/aenm.201501310
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    Stoumpos, C. C.; Cao, D. H.; Clark, D. J.; Young, J.; Rondinelli, J. M.; Jang, J. I.; Hupp, J. T.; Kanatzidis, M. G. Ruddlesden–Popper Hybrid Lead Iodide Perovskite 2D Homologous Semiconductors. Chem. Mater. 2016, 28 (8), 2852– 2867,  DOI: 10.1021/acs.chemmater.6b00847
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    42
    Ruddlesden-Popper Hybrid Lead Iodide Perovskite 2D Homologous Semiconductors
    Stoumpos, Constantinos C.; Cao, Duyen H.; Clark, Daniel J.; Young, Joshua; Rondinelli, James M.; Jang, Joon I.; Hupp, Joseph T.; Kanatzidis, Mercouri G.
    Chemistry of Materials (2016), 28 (8), 2852-2867CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)
    The hybrid two-dimensional (2D) halide perovskites have recently drawn significant interest because they can serve as excellent photoabsorbers in perovskite solar cells. The large scale synthesis, crystal structure, and optical characterization are presented of the 2D (CH3(CH2)3NH3)2(CH3NH3)n-1PbnI3n+1 (n = 1, 2, 3, 4, ∞) perovskites, a family of layered compds. with tunable semiconductor characteristics. These materials consist of well-defined inorg. perovskite layers intercalated with bulky butylammonium cations that act as spacers between these fragments, adopting the crystal structure of the Ruddlesden-Popper type. It is found that the perovskite thickness (n) can be synthetically controlled by adjusting the ratio between the spacer cation and the small org. cation, thus allowing the isolation of compds. in pure form and large scale. The orthorhombic crystal structures of (CH3(CH2)3NH3)2(CH3NH3)Pb2I7 (n = 2, Cc2m; a = 8.9470(4), b = 39.347(2) Å, c = 8.8589(6)), (CH3(CH2)3NH3)2(CH3NH3)2Pb3I10 (n = 3, C2cb; a = 8.9275(6), b = 51.959(4) Å, c = 8.8777(6)), and (CH3(CH2)3NH3)2(CH3NH3)3Pb4I13 (n = 4, Cc2m; a = 8.9274(4), b = 64.383(4) Å, c = 8.8816(4)) have been solved by single-crystal X-ray diffraction and are reported here for the first time. The compds. are noncentrosym., as supported by measurements of the nonlinear optical properties of the compds. and d. functional theory (DFT) calcns. The band gaps of the series change progressively between 2.43 eV for the n = 1 member to 1.50 eV for the n = ∞ adopting intermediate values of 2.17 eV (n = 2), 2.03 eV (n = 3), and 1.91 eV (n = 4) for those between the two compositional extrema. DFT calcns. confirm this exptl. trend and predict a direct band gap for all the members of the Ruddlesden-Popper series. The estd. effective masses have values of mh = 0.14 m0 and me = 0.08 m0 for holes and electrons, resp., and are found to be nearly compn. independent. The band gaps of higher n members indicate that these compds. can be used as efficient light absorbers in solar cells, which offer better soln. processability and good environmental stability. The compds. exhibit intense room-temp. photoluminescence with emission wavelengths consistent with their energy gaps, 2.35 eV (n = 1), 2.12 eV (n = 2), 2.01 eV (n = 3), and 1.90 eV (n = 4) and point to their potential use in light-emitting diodes. In addn., owing to the low dimensionality and the difference in dielec. properties between the org. spacers and the inorg. perovskite layers, these compds. are naturally occurring multiple quantum well structures, which give rise to stable excitons at room temp.
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    Thouin, F.; Valverde-Chávez, D. A.; Quarti, C.; Cortecchia, D.; Bargigia, I.; Beljonne, D.; Petrozza, A.; Silva, C.; Srimath Kandada, A. R. Phonon Coherences Reveal the Polaronic Character of Excitons in Two-Dimensional Lead Halide Perovskites. Nat. Mater. 2019, 18 (4), 349– 356,  DOI: 10.1038/s41563-018-0262-7
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    Phonon coherences reveal the polaronic character of excitons in two-dimensional lead halide perovskites
    Thouin, Felix; Valverde-Chavez, David A.; Quarti, Claudio; Cortecchia, Daniele; Bargigia, Ilaria; Beljonne, David; Petrozza, Annamaria; Silva, Carlos; Srimath Kandada, Ajay Ram
    Nature Materials (2019), 18 (4), 349-356CODEN: NMAACR; ISSN:1476-1122. (Nature Research)
    Hybrid org.-inorg. semiconductors feature complex lattice dynamics due to the ionic character of the crystal and the softness arising from non-covalent bonds between mol. moieties and the inorg. network. Here we establish that such dynamic structural complexity in a prototypical two-dimensional lead iodide perovskite gives rise to the coexistence of diverse excitonic resonances, each with a distinct degree of polaronic character. By means of high-resoln. resonant impulsive stimulated Raman spectroscopy, we identify vibrational wavepacket dynamics that evolve along different configurational coordinates for distinct excitons and photocarriers. Employing d. functional theory calcns., we assign the obsd. coherent vibrational modes to various low-frequency (.ltorsim.50 cm-1) optical phonons involving motion in the lead iodide layers. We thus conclude that different excitons induce specific lattice reorganizations, which are signatures of polaronic binding. This insight into the energetic/configurational landscape involving globally neutral primary photoexcitations may be relevant to a broader class of emerging hybrid semiconductor materials.
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  44. 44
    Mao, L.; Chen, J.; Vishnoi, P.; Cheetham, A. K. The Renaissance of Functional Hybrid Transition-Metal Halides. Acc. Mater. Res. 2022, 3 (4), 439– 448,  DOI: 10.1021/accountsmr.1c00270
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    The Renaissance of Functional Hybrid Transition-Metal Halides
    Mao, Lingling; Chen, Jian; Vishnoi, Pratap; Cheetham, Anthony K.
    Accounts of Materials Research (2022), 3 (4), 439-448CODEN: AMRCDA; ISSN:2643-6728. (American Chemical Society)
    A review. There is an extensive history of research on both inorg. and hybrid metal halides, with the latter being first reported in the 1960s. Although work on hybrid systems has progressed steadily over the last 60 years, it has enjoyed a major renaissance during the last 5 years. This has arisen as a consequence of the 2009 discovery of the outstanding optoelectronic properties of hybrid lead halides, such as (MA)PbI3 (MA = methylammonium), and the recognition that there are many opportunities for equally exciting discoveries with compds. of the transition metals. Some of the early work on hybrid transition-metal halides put more emphasis on crystal structures but less on properties. In the modern era, we aim to grasp both the structure and properties, with a new twist. In this Account, we shall explore the recent developments in hybrid transition-metal halides with a focus on work in four main areas: magnetism, photoluminescence, semicond., and spintronics. Our work on magnetism centers on the Ru-based hybrid halides, where the structural types are diversely composed of vacancy-ordered double perovskite, as well as chain-like one-dimensional structures and layered double perovskite (LDP) when paired with a (1+) metal. We explore their magnetic properties and find that their spin-orbit coupling (SOC) behavior can be tuned through changing the A cation and the halide. In the luminescence section, we focus on our recent works on hybrid tetrahedral Mn(II) bromides and Cu(I) and Ag(I) iodides. We correlated our newly discovered 0D AmMnBr4 (A = org. cation, m = 1 or 2) compds. with previous reports, and generated a trend where the photoluminescence quantum yield (PLQY) increases with larger Mn-Mn distances. The flexible org. cation becomes the most important tool here to tune the structure-PLQY relations. Cu(I) and Ag(I) iodides coordinated with iodides and org. ligands produce new crystal structures with intense PL. For the semiconducting properties, we explore the Pt-based vacancy-ordered double perovskite and hybrid bismuth and indium-based LDPs to show the structural evolution with different choices for the org. cation, the metal and the halide; these have a strong influence on the optical properties. The LDPs specifically exhibit high structure tunability, with a wide range of (1+) and (3+) metal choices, and are exempt from some of the limitations of 3D double perovskite. In the last section, we introduce the recent progress on hybrid transition-metal-based ferroelecs. and spintronic materials. We successfully demonstrate the utilization of chiral Cu(II) chlorides for circularly polarized light (CPL) detection, showing the high anisotropy of the photoresponsivity. We also highlight the work that the authors have contributed in these areas and suggest several exciting opportunities for future developments.
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  45. 45
    Han, D.; Shi, H.; Ming, W.; Zhou, C.; Ma, B.; Saparov, B.; Ma, Y.-Z.; Chen, S.; Du, M.-H. Unraveling Luminescence Mechanisms in Zero-Dimensional Halide Perovskites. J. Mater. Chem. C 2018, 6 (24), 6398– 6405,  DOI: 10.1039/C8TC01291A
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    Unraveling luminescence mechanisms in zero-dimensional halide perovskites
    Han, Dan; Shi, Hongliang; Ming, Wenmei; Zhou, Chenkun; Ma, Biwu; Saparov, Bayrammurad; Ma, Ying-Zhong; Chen, Shiyou; Du, Mao-Hua
    Journal of Materials Chemistry C: Materials for Optical and Electronic Devices (2018), 6 (24), 6398-6405CODEN: JMCCCX; ISSN:2050-7534. (Royal Society of Chemistry)
    Zero-dimensional (0D) halides perovskites, in which anionic metal-halide octahedra (MX6)4- are sepd. by org. or inorg. countercations, have recently shown promise as excellent luminescent materials. However, the origin of the photoluminescence (PL) and, in particular, the different photophys. properties in hybrid org.-inorg. and all inorg. halides are still poorly understood. In this work, first-principles calcns. were performed to study the excitons and intrinsic defects in 0D hybrid org.-inorg. halides (C4N2H14X)4SnX6 (X = Br, I), which exhibit a high photoluminescence quantum efficiency (PLQE) at room temp. (RT), and also in the 0D inorg. halide Cs4PbBr6, which suffers from strong thermal quenching when T > 100 K. We show that the excitons in all three 0D halides are strongly bound and cannot be detrapped or dissocd. at RT, which leads to immobile excitons in (C4N2H14X)4SnX6. However, the excitons in Cs4PbBr6 can still migrate by tunneling, enabled by the resonant transfer of excitation energy (Dexter energy transfer). The exciton migration in Cs4PbBr6 leads to a higher probability of trapping and nonradiative recombination at the intrinsic defects. We show that a large Stokes shift and the negligible electronic coupling between luminescent centers are important for suppressing exciton migration; thereby, enhancing the photoluminescence quantum efficiency. Our results also suggest that the frequently obsd. bright green emission in Cs4PbBr6 is not due to the exciton or defect-induced emission in Cs4PbBr6 but rather the result of exciton emission from CsPbBr3 inclusions trapped in Cs4PbBr6.
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    Maughan, A. E.; Ganose, A. M.; Scanlon, D. O.; Neilson, J. R. Perspectives and Design Principles of Vacancy-Ordered Double Perovskite Halide Semiconductors. Chem. Mater. 2019, 31 (4), 1184– 1195,  DOI: 10.1021/acs.chemmater.8b05036
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    Perspectives and design principles of vacancy-ordered double perovskite halide semiconductors
    Maughan, Annalise E.; Ganose, Alex M.; Scanlon, David O.; Neilson, James R.
    Chemistry of Materials (2019), 31 (4), 1184-1195CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)
    A review. Here, the authors focus upon the structure-dynamics-property relations in vacancy-ordered double perovskite semiconductors as they pertain to applications in photovoltaics, and they propose avenues of future study within the context of the broader perovskite halide literature. They describe the compositional and structural motifs that dictate the optical gaps and charge transport behavior and discuss the implications of charge ordering, lattice dynamics, and org.-inorg. coupling upon the properties of these materials. The design principles they elucidate here represent an important step toward extending the understanding of perovskite functionality to defect-ordered perovskites.
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    Maughan, A. E.; Ganose, A. M.; Bordelon, M. M.; Miller, E. M.; Scanlon, D. O.; Neilson, J. R. Defect Tolerance to Intolerance in the Vacancy-Ordered Double Perovskite Semiconductors Cs2SnI6 and Cs2TeI6. J. Am. Chem. Soc. 2016, 138 (27), 8453– 8464,  DOI: 10.1021/jacs.6b03207
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    Defect Tolerance to Intolerance in the Vacancy-Ordered Double Perovskite Semiconductors Cs2SnI6 and Cs2TeI6
    Maughan, Annalise E.; Ganose, Alex M.; Bordelon, Mitchell M.; Miller, Elisa M.; Scanlon, David O.; Neilson, James R.
    Journal of the American Chemical Society (2016), 138 (27), 8453-8464CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    Vacancy-ordered double perovskites of the general formula A2BX6 are a family of perovskite derivs. composed of a face-centered lattice of nearly isolated [BX6] units with A-site cations occupying the cuboctahedral voids. Despite the presence of isolated octahedral units, the close-packed iodide lattice provides significant electronic dispersion, such that Cs2SnI6 has recently been explored for applications in photovoltaic devices. To elucidate the structure-property relationships of these materials, we have synthesized solid-soln. Cs2Sn1-xTexI6. However, even though tellurium substitution increases electronic dispersion via closer I-I contact distances, the substitution exptl. yields insulating behavior from a significant decrease in carrier concn. and mobility. D. functional calcns. of native defects in Cs2SnI6 reveal that iodine vacancies exhibit a low enthalpy of formation, and that the defect energy level is a shallow donor to the conduction band rendering the material tolerant to these defect states. The increased covalency of Te-I bonding renders the formation of iodine vacancy states unfavorable and is responsible for the redn. in cond. upon Te substitution. Addnl., Cs2TeI6 is intolerant to the formation of these defects, because the defect level occurs deep within the band gap and thus localizes potential mobile charge carriers. In these vacancy-ordered double perovskites, the close-packed lattice of iodine provides significant electronic dispersion, while the interaction of the B- and X-site ions dictates the properties as they pertain to electronic structure and defect tolerance. This simplified perspective based on extensive exptl. and theor. anal. provides a platform from which to understand structure-property relationships in functional perovskite halides.
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    Lee, J. H.; Lee, J.-H.; Kong, E.-H.; Jang, H. M. The Nature of Hydrogen-Bonding Interaction in the Prototypic Hybrid Halide Perovskite, Tetragonal CH3NH3PbI3. Sci. Rep 2016, 6 (1), 21687,  DOI: 10.1038/srep21687
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    The nature of hydrogen-bonding interaction in the prototypic hybrid halide perovskite, tetragonal CH3NH3PbI3
    Lee, June Ho; Lee, Jung-Hoon; Kong, Eui-Hyun; Jang, Hyun Myung
    Scientific Reports (2016), 6 (), 21687CODEN: SRCEC3; ISSN:2045-2322. (Nature Publishing Group)
    In spite of the key role of hydrogen bonding in the structural stabilization of the prototypic hybrid halide perovskite, CH3NH3PbI3 (MAPbI3), little progress has been made in our in-depth understanding of the hydrogen-bonding interaction between the MA+-ion and the iodide ions in the PbI6-octahedron network. Herein, we show that there exist two distinct types of the hydrogen-bonding interaction, naming α- and β-modes, in the tetragonal MAPbI3 on the basis of symmetry argument and d.-functional theory calcns. The computed Kohn-Sham (K-S) energy difference between these two interaction modes is 45.14 meV per MA-site with the α-interaction mode being responsible for the stable hydrogen-bonding network. The computed bandgap (Eg) is also affected by the hydrogen-bonding mode, with Eg of the α-interaction mode (1.73 eV) being significantly narrower than that of the β-interaction mode (2.03 eV). We have further estd. the individual bonding strength for the ten relevant hydrogen bonds having a bond crit. point.
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    Egger, D. A. Intermediate Bands in Zero-Dimensional Antimony Halide Perovskites. J. Phys. Chem. Lett. 2018, 9 (16), 4652– 4656,  DOI: 10.1021/acs.jpclett.8b01730
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    Intermediate Bands in Zero-Dimensional Antimony Halide Perovskites
    Egger, David A.
    Journal of Physical Chemistry Letters (2018), 9 (16), 4652-4656CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
    Using d. functional theory, the structural and electronic-structure properties of a recently discovered, zero-dimensional antimony halide perovskite were studied. The herein considered material EtPySbBr6 exhibits very promising electronic-structure properties: a direct band gap close to the peak of the solar spectrum and effective masses allowing for efficient carrier transport of electrons in particular. These results are rationalized by anal. of the electronic structure, which reveals the formation of intermediate bands due to orbital-hybridization effects of the Sb s-states. The formation of intermediate bands can lead to highly favorable electronic-structure properties of zero-dimensional perovskites and discusses the possibility of fabricating lead-free halide perovskites with promising optoelectronic properties by targeted substitution of ions and emergence of intermediate bands. These insights are important when understanding and further enhancing the capabilities of antimony and other promising lead-free compds.
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    Nicholas, A. D.; Halli, R. N.; Garman, L. C.; Cahill, C. L. Low-Dimensional Hybrid Indium/Antimony Halide Perovskites: Supramolecular Assembly and Electronic Properties. J. Phys. Chem. C 2020, 124 (47), 25686– 25700,  DOI: 10.1021/acs.jpcc.0c07268
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    Low-Dimensional Hybrid Indium/Antimony Halide Perovskites: Supramolecular Assembly and Electronic Properties
    Nicholas, Aaron D.; Halli, Ryan N.; Garman, Leah C.; Cahill, Christopher L.
    Journal of Physical Chemistry C (2020), 124 (47), 25686-25700CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)
    The phenomenon of quantum confinement in hybrid low-dimensional lead-free perovskite derivs. continues to hinder the development of these materials for electron carrier devices such as next-generation solar cells. Spatial sepn. of metal-halide octahedra within crystal structures yields materials with greater moisture and photodegrdn. resistance, but at the expense of desired photophys. properties such as small band gaps. We report the synthesis and characterization of an unexplored isomorphic series of perovskite derivs. consisting of isolated dimeric metal-halide M2X104- (M = In, Sb; X = Cl, Br) anions charge-balanced with halopyridinium cations. Assembly of these species results in a supramol. network via extensive noncovalent interactions and may be described as a pseudo-zero-dimensional arrangement. Despite the low dimensionality, these materials display semiconductive optical band-gap energies owing to the appearance of an intermediate band due to hybridization of metal-halide at. and MOs. Low-temp. luminescence measurements provide evidence of electron delocalization where photoexcited metal/halide electrons are captured by org. cations via energetically accessible π* MOs, sepg. electron/hole pairs. Natural bonding orbital (NBO) calcns. reveal that metal hybridization is more pronounced in compds. contg. Sb3+ and can be influenced by noncovalent interactions between anionic and cationic building units.
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    Nicholas, A. D.; Walusiak, B. W.; Garman, L. C.; Huda, M. N.; Cahill, C. L. Impact of Noncovalent Interactions on Structural and Photophysical Properties of Zero-Dimensional Tellurium(IV) Perovskites. J. Mater. Chem. C 2021, 9 (9), 3271– 3286,  DOI: 10.1039/D0TC06000C
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    Nicholas, A. D.; Garman, L. C.; Albano, N.; Cahill, C. L. Insight on Noncovalent Interactions and Orbital Constructs in Low-Dimensional Antimony Halide Perovskites. Phys. Chem. Chem. Phys. 2022, 24 (25), 15305– 15320,  DOI: 10.1039/D2CP01996E
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    Bukvetskii, B. V.; Sedakova, T. V.; Mirochnik, A. G. Crystal Structure, Luminescent and Thermochromic Properties of Bis(Tetraethylammonium) Hexachlorotellurate(IV). Russ J. Coord Chem. 2010, 36 (9), 651– 656,  DOI: 10.1134/S1070328410090034
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    Li, Z.; Park, J.-S.; Ganose, A. M.; Walsh, A. From Cubic to Hexagonal: Electronic Trends across Metal Halide Perovskite Polytypes. J. Phys. Chem. C 2023, 127 (26), 12695– 12701,  DOI: 10.1021/acs.jpcc.3c01232
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    Ghaithan, H. M.; Alahmed, Z. A.; Qaid, S. M. H.; Hezam, M.; Aldwayyan, A. S. Density Functional Study of Cubic, Tetragonal, and Orthorhombic CsPbBr3 Perovskite. ACS Omega 2020, 5 (13), 7468– 7480,  DOI: 10.1021/acsomega.0c00197
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    Density Functional Study of Cubic, Tetragonal, and Orthorhombic CsPbBr3 Perovskite
    Ghaithan, Hamid M.; Alahmed, Zeyad A.; Qaid, Saif M. H.; Hezam, Mahmoud; Aldwayyan, Abdullah S.
    ACS Omega (2020), 5 (13), 7468-7480CODEN: ACSODF; ISSN:2470-1343. (American Chemical Society)
    Cesium lead bromide (CsPbBr3) perovskite has recently gained significance owing to its rapidly increasing performance when used for light-emitting devices. In this study, we used d. functional theory to det. the structural, electronic, and optical properties of the cubic, tetragonal, and orthorhombic temp.-dependent phases of CsPbBr3 perovskite using the full-potential linear APW method. The electronic properties of CsPbBr3 perovskite have been investigated by evaluating their changes upon exerting spin-orbit coupling (SOC). The following exchange potentials were used: the local d. approxn. (LDA), Perdew-Burke-Ernzerhof generalized gradient approxn. (PBE-GGA), Engel-Vosko GGA (EV-GGA), Perdew-Burke-Ernzerhof GGA revised for solids (PBEsol-GGA), modified Becke-Johnson GGA (mBJ-GGA), new modified Becke-Johnson GGA (nmBJ-GGA), and unmodified Becke-Johnson GGA (umBJ-GGA). Our band structure results indicated that the cubic, tetragonal, and orthorhombic phases have direct energy bandgaps. By including the SOC effect in the calcns., the bandgaps computed with mBJ-GGA and nmBJ-GGA were found to be in good agreement with the exptl. results. Addnl., despite the large variations in their lattice consts., the three CsPbBr3 phases possessed similar optical properties. These results demonstrate a wide temp. range of operation for CsPbBr3.
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    Hussain, M.; Rashid, M.; Saeed, F.; Bhatti, A. S. Spin–Orbit Coupling Effect on Energy Level Splitting and Band Structure Inversion in CsPbBr3. J. Mater. Sci. 2021, 56 (1), 528– 542,  DOI: 10.1007/s10853-020-05298-8
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    The absorption and emission spectra of GeCl3-, SnCl3-, PbCl3-, and PbCl42- in acetonitrile were recorded. In addn., emission quantum yields and lifetimes were detd. The emitting excited states are of the metal-centered sp type and originate from the 3P state of the free s2 ions. It is suggested that the complex ions which have trigonal-pyramidal C3v (MCl3-) and seesaw C2v (PbCl42-) structures in the ground state rearrange toward trigonal-planar D3h and tetrahedral Td geometries, resp., in their sp excited states.
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    Ackerman, J. F. Preparation and Luminescence of Some [K2PtCl6] Materials. Mater. Res. Bull. 1984, 19 (6), 783– 791,  DOI: 10.1016/0025-5408(84)90036-9
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    Materials Research Bulletin (1984), 19 (6), 783-91CODEN: MRBUAC; ISSN:0025-5408.
    The prepn. of Cs2TaOCl5 and Cs2TaSCl5, new materials with the [K2PtCl6] structure, is described. Lattice parameters and indexed diffraction patterns are reported for 8 materials with space group Fm3m, including the newly prepd. compds. Luminescence was measured for these materials and electronic transition assignments were made.
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    McCusker, J. K.; Rheingold, A. L.; Hendrickson, D. N. Variable-Temperature Studies of Laser-Initiated 5T2 → 1A1 Intersystem Crossing in Spin-Crossover Complexes: Empirical Correlations between Activation Parameters and Ligand Structure in a Series of Polypyridyl Ferrous Complexes. Inorg. Chem. 1996, 35 (7), 2100– 2112,  DOI: 10.1021/ic9507880
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    Variable-Temperature Studies of Laser-Initiated 5T2 → 1A1 Intersystem Crossing in Spin-Crossover Complexes: Empirical Correlations between Activation Parameters and Ligand Structure in a Series of Polypyridyl Ferrous Complexes
    McCusker, James K.; Rheingold, Arnold L.; Hendrickson, David N.
    Inorganic Chemistry (1996), 35 (7), 2100-12CODEN: INOCAJ; ISSN:0020-1669. (American Chemical Society)
    Results are presented from a variable-temp. soln.-phase laser photolysis study of the 5T2 → 1A1 intersystem crossing in a series of related complexes: [Fe(tpen)](ClO4)2, [Fe(tppn)](ClO4)2, [Fe(tptn)](ClO4)2, [Fe(t-tpchxn)](ClO4)2, and [Fe(dpa)2](ClO4)2. The hexadentate ligands are formed with four 2-pyridylmethyl arms attached to ethylenediamine (tpen), 1,2-diaminopropylene (tppn), 1,3-diaminopropylene (tptn), or trans-1,2-diaminocyclohexane (t-tpchxn). The dpa ligand is a tridentate analog of these ligands, namely, bis(2-pyridylmethyl)amine. The complex [Fe(mtpen)](ClO4)2·2/3H2O, where mtpen is the same as tpen except one of the pyridyl rings has a 6-Me substituent, crystallizes in the space group C2/c, which at 173 K has a unit cell with a = 41.390(13) Å, b = 9.5239(16) Å, c = 24.016(6) Å, β = 108.24(3)°, and Z = 12. Refinement with 2844 obsd. [F > 5.0σ(F)] reflections gave R = 0.075 and Rw = 0.076. The complex [Fe(tppn)](ClO4)2·H2O crystallizes in the space group P21/n, which at 296 K has a unit cell with a = 12.979(4) Å, b = 12.624(4) Å, c = 19.475(6) Å, β = 108.17(2)°, and Z = 4. Refinement with 2357 obsd. [F > 5.0σ(F)] reflections gave R = 0.1198 and Rw = 0.1141. The mtpen complex is a high-spin FeII complex at all temps. (4.2-400 K), whereas the hydrated tpen complex is a spin-crossover complex with the temp. where there are 50% high-spin complexes as T1/2 ≃ 385 K, the hydrated tppn complex is also spin-crossover with a higher T1/2 value, and the hydrated tptn complex is low spin up to 400 K. The present crystallog. results, together with previously reported structural results for the tpen complex at two temps., are used to show that the conversion from low spin to high spin leads to an increase in the trigonal twist of these distorted octahedral complexes. The influence of this variation in trigonal twist on the rate of 5T2 → 1A1 intersystem crossing is examd. with variable-temp. laser-flash photolysis. Data collected for the tpen complex in MeOH in the 190-294 K range give a linear Arrhenius plot with an activation energy of Ea = 767 ± 22 cm-1 and a preexponential term of A = (1.35 ± 0.2) × 109 s-1. The tppn complex gives similar results of Ea = 771 ± 17 cm-1 and A = (1.45 ± 0.2) × 109 s-1. At 294 K the rate (k-1) for the 5T2 → 1A1 intersystem crossing is 2.87 × 107 s-1 for the tpen complex, and 3.21 × 107 s-1 for the tppn complex. On the other hand the tptn complex has k-1 = 6.25 × 108 s-1 at 295 K as measured with a picosecond spectrometer, and together with nanosecond data measured in the 186-210 K range gives an Arrhenius activation energy of Ea = 777 ± 50 cm-1 with A = (2.6 ± 0.8) × 1010 s-1. The bis(tridentate) complex [Fe(dpa)2](ClO4)2 in MeOH is found to give k-1 = 4.59 × 107 s-1 at 282 K and with the 191-282 K data gives Arrhenius values of Ea = 339 ± 13 cm-1 and A = (2.5 ± 0.25) × 108 s-1. The terpyridine complex [Fe(terpy)2](ClO4)2 is found to have k-1 = 1.0 × 108 s-1 in MeOH at 239 K, and the anal. of 190-239 K data gives Ea = 532 ± 36 cm-1 and A = (2.4 ± 0.4) × 109 s-1. Previous studies have shown that the greater the trigonal twist, the lower in energy is the 3T1 state which facilitates the spin-orbit interaction between the 5T2 high-spin and 1A1 low-spin states. It is suggested that the trigonal twist is a vibrational coordinate strongly coupled to the 5T2 → 1A1 intersystem crossing. It is addnl. shown that the data are consistent with a model wherein the "intrinsic" rate of 5T2 → 1A1 intersystem crossing, as gauged by the preexponential term, is a function of how far along the reaction coordinate a complex proceeds.
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    Mao, L.; Guo, P.; Wang, S.; Cheetham, A. K.; Seshadri, R. Design Principles for Enhancing Photoluminescence Quantum Yield in Hybrid Manganese Bromides. J. Am. Chem. Soc. 2020, 142 (31), 13582– 13589,  DOI: 10.1021/jacs.0c06039
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    Design Principles for Enhancing Photoluminescence Quantum Yield in Hybrid Manganese Bromides
    Mao, Lingling; Guo, Peijun; Wang, Shuxin; Cheetham, Anthony K.; Seshadri, Ram
    Journal of the American Chemical Society (2020), 142 (31), 13582-13589CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    Hybrid manganese halides have attracted widespread attention because of their highly emissive optical properties. To understand the underlying structural factors that dictate the photoluminescence quantum yield (PLQY) of these materials, we report five new hybrid manganese bromides with the general formula AmMnBr4 [m = 1 or 2, A = dimethylammonium (DMA), 3-methylpiperidinium (3MP), 3-aminomethylpiperidinium (3AMP), heptamethylenimine (HEP), and trimethylphenylammonium (TMPEA)]. By studying the crystal structures and optical properties of these materials and combining our results with the findings from previously reported analogs, we have found a direct correlation between Mn···Mn distance and the PLQY, where high PLQYs are assocd. with long Mn···Mn distances. This effect can be viewed as a manifestation of the concn.-quenching effect, except these are in stoichiometric compds. with precise interat. distances rather than random alloys. To gain better sepn. of the Mn centers and prevent energy transfer, a bulky singly protonated cation that avoids H-bonding is ideal. We have demonstrated this principle in one of our newly reported material, (TMPEA)2MnBr4, where a PLQY of 70.8% for a powder sample and 98% for a large single crystal sample is achieved. Our study reveals a generalized method for improving PLQYs in hybrid manganese bromides and is readily extended to designing all varieties of highly emissive hybrid materials.
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    Theory of concentration quenching in inorganic phosphors
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    Journal of Chemical Physics (1954), 22 (), 1063-70CODEN: JCPSA6; ISSN:0021-9606.
    cf. C.A. 47, 7900i. A theory is presented for concn. quenching in solid systems, based on the migration of excitation energy from one activator center to another and eventually to an imperfection which may act as an energy sink. Calcns. are made on the dependence of the fluorescence yield on concn., and to indicate typical activator concns. at which appreciable quenching may be expected to occur. If the transition in the activator is of the elec. dipole or elec. quadrupole type, appreciable quenching may arise when the activator concn. is 10-3 to 10-2; if it is a magnetic dipole transition, transfer will occur by exchange rather than by overlapping of magnetic dipole fields, and the crit. concn. will be of the order of a few percent. The implications of transfer phenomena upon the observed absence of luminescence in most pure inorg. crystals are discussed, and it is concluded that transfer rates are so high in strongly absorbing crystals that the energy can migrate easily to a very few sinks dispersed throughout the lattice.
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    Blasse, G.; Dirksen, G. J.; Abriel, W. The Influence of Distortion of the Te(IV) Coordination Octahedron on Its Luminescence. Chem. Phys. Lett. 1987, 136 (5), 460– 464,  DOI: 10.1016/0009-2614(87)80287-7
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    The influence of distortion of the tellurium(IV) coordination octahedron on its luminescence
    Blasse, G.; Dirksen, G. J.; Abriel, W.
    Chemical Physics Letters (1987), 136 (5), 460-4CODEN: CHPLBC; ISSN:0009-2614.
    The luminescence of the following compds. is reported: Cs2TeCl6 and Rb2TeBr6, both with undistorted TeX62- octahedra (X = Cl, Br) and (1,3-propanediamine)TeCl6 and Ca(H2O)7TeBr6, both with distorted TeX62- octahedra. In agreement with results obtained earlier for other ions with the s2 configuration, the distortion results in an increase of the Stokes shift and a decrease of the thermal quenching temp.
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    Sheldrick, G. M. SHELXT – Integrated Space-Group and Crystal-Structure Determination. Acta Cryst. A 2015, 71 (1), 3– 8,  DOI: 10.1107/S2053273314026370
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    SHELXT - Integrated space-group and crystal-structure determination
    Sheldrick, George M.
    Acta Crystallographica, Section A: Foundations and Advances (2015), 71 (1), 3-8CODEN: ACSAD7; ISSN:2053-2733. (International Union of Crystallography)
    The new computer program SHELXT employs a novel dual-space algorithm to solve the phase problem for single-crystal reflection data expanded to the space group P1. Missing data are taken into account and the resoln. extended if necessary. All space groups in the specified Laue group are tested to find which are consistent with the P1 phases. After applying the resulting origin shifts and space-group symmetry, the solns. are subject to further dual-space recycling followed by a peak search and summation of the electron d. around each peak. Elements are assigned to give the best fit to the integrated peak densities and if necessary addnl. elements are considered. An isotropic refinement is followed for non-centrosym. space groups by the calcn. of a Flack parameter and, if appropriate, inversion of the structure. The structure is assembled to maximize its connectivity and centered optimally in the unit cell. SHELXT has already solved many thousand structures with a high success rate, and is optimized for multiprocessor computers. It is, however, unsuitable for severely disordered and twinned structures because it is based on the assumption that the structure consists of atoms.
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    Dolomanov, O. V.; Bourhis, L. J.; Gildea, R. J.; Howard, J. a. K.; Puschmann, H. OLEX2: A Complete Structure Solution, Refinement and Analysis Program. J. Appl. Crystallogr. 2009, 42 (2), 339– 341,  DOI: 10.1107/S0021889808042726
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    OLEX2: a complete structure solution, refinement and analysis program
    Dolomanov, Oleg V.; Bourhis, Luc J.; Gildea, Richard J.; Howard, Judith A. K.; Puschmann, Horst
    Journal of Applied Crystallography (2009), 42 (2), 339-341CODEN: JACGAR; ISSN:0021-8898. (International Union of Crystallography)
    New software, OLEX2, was developed for the detn., visualization and anal. of mol. crystal structures. The software has a portable mouse-driven workflow-oriented and fully comprehensive graphical user interface for structure soln., refinement and report generation, as well as novel tools for structure anal. OLEX2 seamlessly links all aspects of the structure soln., refinement and publication process and presents them in a single workflow-driven package, with the ultimate goal of producing an application which will be useful to both chemists and crystallographers.
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    Sheldrick, G. M. Crystal Structure Refinement with SHELXL. Acta Cryst. C 2015, 71 (1), 3– 8,  DOI: 10.1107/S2053229614024218
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    Crystal structure refinement with SHELXL
    Sheldrick, George M.
    Acta Crystallographica, Section C: Structural Chemistry (2015), 71 (1), 3-8CODEN: ACSCGG; ISSN:2053-2296. (International Union of Crystallography)
    The improvements in the crystal structure refinement program SHELXL have been closely coupled with the development and increasing importance of the CIF (Crystallog. Information Framework) format for validating and archiving crystal structures. An important simplification is that now only one file in CIF format (for convenience, referred to simply as 'a CIF') contg. embedded reflection data and SHELXL instructions is needed for a complete structure archive; the program SHREDCIF can be used to ext. the and files required for further refinement with SHELXL. Recent developments in SHELXL facilitate refinement against neutron diffraction data, the treatment of H atoms, the detn. of abs. structure, the input of partial structure factors and the refinement of twinned and disordered structures. SHELXL is available free to academics for the Windows, Linux and Mac OS X operating systems, and is particularly suitable for multiple-core processors.
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    Cambridge Structural Database System; Cambridge Crystallographic Data Centre., 2024.
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    Kresse, G.; Furthmüller, J. Efficiency of Ab-Initio Total Energy Calculations for Metals and Semiconductors Using a Plane-Wave Basis Set. Comput. Mater. Sci. 1996, 6 (1), 15– 50,  DOI: 10.1016/0927-0256(96)00008-0
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    Efficiency of ab-initio total energy calculations for metals and semiconductors using a plane-wave basis set
    Kresse, G.; Furthmuller, J.
    Computational Materials Science (1996), 6 (1), 15-50CODEN: CMMSEM; ISSN:0927-0256. (Elsevier)
    The authors present a detailed description and comparison of algorithms for performing ab-initio quantum-mech. calcns. using pseudopotentials and a plane-wave basis set. The authors will discuss: (a) partial occupancies within the framework of the linear tetrahedron method and the finite temp. d.-functional theory, (b) iterative methods for the diagonalization of the Kohn-Sham Hamiltonian and a discussion of an efficient iterative method based on the ideas of Pulay's residual minimization, which is close to an order N2atoms scaling even for relatively large systems, (c) efficient Broyden-like and Pulay-like mixing methods for the charge d. including a new special preconditioning optimized for a plane-wave basis set, (d) conjugate gradient methods for minimizing the electronic free energy with respect to all degrees of freedom simultaneously. The authors have implemented these algorithms within a powerful package called VAMP (Vienna ab-initio mol.-dynamics package). The program and the techniques have been used successfully for a large no. of different systems (liq. and amorphous semiconductors, liq. simple and transition metals, metallic and semi-conducting surfaces, phonons in simple metals, transition metals and semiconductors) and turned out to be very reliable.
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    Kresse, G.; Furthmüller, J. Efficient Iterative Schemes for Ab Initio Total-Energy Calculations Using a Plane-Wave Basis Set. Phys. Rev. B 1996, 54 (16), 11169– 11186,  DOI: 10.1103/PhysRevB.54.11169
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    Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set
    Kresse, G.; Furthmueller, J.
    Physical Review B: Condensed Matter (1996), 54 (16), 11169-11186CODEN: PRBMDO; ISSN:0163-1829. (American Physical Society)
    The authors present an efficient scheme for calcg. the Kohn-Sham ground state of metallic systems using pseudopotentials and a plane-wave basis set. In the first part the application of Pulay's DIIS method (direct inversion in the iterative subspace) to the iterative diagonalization of large matrixes will be discussed. This approach is stable, reliable, and minimizes the no. of order Natoms3 operations. In the second part, we will discuss an efficient mixing scheme also based on Pulay's scheme. A special "metric" and a special "preconditioning" optimized for a plane-wave basis set will be introduced. Scaling of the method will be discussed in detail for non-self-consistent and self-consistent calcns. It will be shown that the no. of iterations required to obtain a specific precision is almost independent of the system size. Altogether an order Natoms2 scaling is found for systems contg. up to 1000 electrons. If we take into account that the no. of k points can be decreased linearly with the system size, the overall scaling can approach Natoms. They have implemented these algorithms within a powerful package called VASP (Vienna ab initio simulation package). The program and the techniques have been used successfully for a large no. of different systems (liq. and amorphous semiconductors, liq. simple and transition metals, metallic and semiconducting surfaces, phonons in simple metals, transition metals, and semiconductors) and turned out to be very reliable.
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    Perdew, J. P.; Burke, K.; Ernzerhof, M. Generalized Gradient Approximation Made Simple. Phys. Rev. Lett. 1996, 77 (18), 3865– 3868,  DOI: 10.1103/PhysRevLett.77.3865
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    Generalized gradient approximation made simple
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    Physical Review Letters (1996), 77 (18), 3865-3868CODEN: PRLTAO; ISSN:0031-9007. (American Physical Society)
    Generalized gradient approxns. (GGA's) for the exchange-correlation energy improve upon the local spin d. (LSD) description of atoms, mols., and solids. We present a simple derivation of a simple GGA, in which all parameters (other than those in LSD) are fundamental consts. Only general features of the detailed construction underlying the Perdew-Wang 1991 (PW91) GGA are invoked. Improvements over PW91 include an accurate description of the linear response of the uniform electron gas, correct behavior under uniform scaling, and a smoother potential.
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    Projector augmented-wave method
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    Kresse, G.; Joubert, D. From Ultrasoft Pseudopotentials to the Projector Augmented-Wave Method. Phys. Rev. B 1999, 59 (3), 1758– 1775,  DOI: 10.1103/PhysRevB.59.1758
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    From ultrasoft pseudopotentials to the projector augmented-wave method
    Kresse, G.; Joubert, D.
    Physical Review B: Condensed Matter and Materials Physics (1999), 59 (3), 1758-1775CODEN: PRBMDO; ISSN:0163-1829. (American Physical Society)
    The formal relationship between ultrasoft (US) Vanderbilt-type pseudopotentials and Blochl's projector augmented wave (PAW) method is derived. The total energy functional for US pseudopotentials can be obtained by linearization of two terms in a slightly modified PAW total energy functional. The Hamilton operator, the forces, and the stress tensor are derived for this modified PAW functional. A simple way to implement the PAW method in existing plane-wave codes supporting US pseudopotentials is pointed out. In addn., crit. tests are presented to compare the accuracy and efficiency of the PAW and the US pseudopotential method with relaxed-core all-electron methods. These tests include small mols. (H2, H2O, Li2, N2, F2, BF3, SiF4) and several bulk systems (diamond, Si, V, Li, Ca, CaF2, Fe, Co, Ni). Particular attention is paid to the bulk properties and magnetic energies of Fe, Co, and Ni.
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    Momma, K.; Izumi, F. VESTA 3 for Three-Dimensional Visualization of Crystal, Volumetric and Morphology Data. J. Appl. Crystallogr. 2011, 44 (6), 1272– 1276,  DOI: 10.1107/S0021889811038970
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    VESTA 3 for three-dimensional visualization of crystal, volumetric and morphology data
    Momma, Koichi; Izumi, Fujio
    Journal of Applied Crystallography (2011), 44 (6), 1272-1276CODEN: JACGAR; ISSN:0021-8898. (International Union of Crystallography)
    VESTA is a 3D visualization system for crystallog. studies and electronic state calcns. It was upgraded to the latest version, VESTA 3, implementing new features including drawing the external morphpol. of crysals; superimposing multiple structural models, volumetric data and crystal faces; calcn. of electron and nuclear densities from structure parameters; calcn. of Patterson functions from the structure parameters or volumetric data; integration of electron and nuclear densities by Voronoi tessellation; visualization of isosurfaces with multiple levels, detn. of the best plane for selected atoms; an extended bond-search algorithm to enable more sophisticated searches in complex mols. and cage-like structures; undo and redo is graphical user interface operations; and significant performance improvements in rendering isosurfaces and calcg. slices.
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    Wang, V.; Xu, N.; Liu, J.-C.; Tang, G.; Geng, W.-T. VASPKIT: A User-Friendly Interface Facilitating High-Throughput Computing and Analysis Using VASP Code. Comput. Phys. Commun. 2021, 267, 108033  DOI: 10.1016/j.cpc.2021.108033
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    VASPKIT: A user-friendly interface facilitating high-throughput computing and analysis using VASP code
    Wang, Vei; Xu, Nan; Liu, Jin-Cheng; Tang, Gang; Geng, Wen-Tong
    Computer Physics Communications (2021), 267 (), 108033CODEN: CPHCBZ; ISSN:0010-4655. (Elsevier B.V.)
    A review. We present the VASPKIT, a command-line program that aims at providing a robust and user-friendly interface to perform high-throughput anal. of a variety of material properties from the raw data produced by the VASP code. It consists of mainly the pre- and post-processing modules. The former module is designed to prep. and manipulate input files such as the necessary input files generation, symmetry anal., supercell transformation, k-path generation for a given crystal structure. The latter module is designed to ext. and analyze the raw data about elastic mechanics, electronic structure, charge d., electrostatic potential, linear optical coeffs., wave function plots in real space, etc. This program can run conveniently in either interactive user interface or command line mode. The command-line options allow the user to perform high-throughput calcns. together with bash scripts. This article gives an overview of the program structure and presents illustrative examples for some of its usages. The program can run on Linux, macOS, and Windows platforms. The executable versions of VASPKIT and the related examples and tutorials are available on its official website vaspkit .com.
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    M Ganose, A.; J Jackson, A.; O Scanlon, D. Sumo: Command-Line Tools for Plotting and Analysis of Periodic *ab Initio* Calculations. J. Open Source Software 2018, 3 (28), 717,  DOI: 10.21105/joss.00717
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    Blatov, V. A.; Shevchenko, A. P.; Serezhkin, V. N. TOPOS3.2: A New Version of the Program Package for Multipurpose Crystal-Chemical Analysis. J. Appl. Crystallogr. 2000, 33 (4), 1193– 1193,  DOI: 10.1107/S0021889800007202
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    TOPOS3.2: a new version of the program package for multipurpose crystal-chemical analysis
    Blatov, V. A.; Shevchenko, A. P.; Serezhkin, V. N.
    Journal of Applied Crystallography (2000), 33 (4), 1193CODEN: JACGAR; ISSN:0021-8898. (Munksgaard International Publishers Ltd.)
    There is no expanded citation for this reference.
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  • Abstract

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    Figure 1

    Figure 1. Schematic representation of two major components of energy transfer and photoluminescence quenching in 0D organic–inorganic metal halides.

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    Figure 2

    Figure 2. Views on the structures of hybrid tellurium halides of interest: (a) (EtNH3)2TeCl6, (b) (Et2NH2)2TeCl6, (c) m-(Et3NH)2TeCl6, and (d) (Et4N)2TeCl6. (53) The yellow octahedra are TeCl62–, Cl atoms are green, C atoms are gray, N atoms are blue, and H atoms (if located) are light blue.

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    Figure 3

    Figure 3. (a,f) Schematic molecular orbital diagrams of octahedral SnCl6 and TeCl6 complexes. (b–e) Band structure diagrams of ((C2H5)nNH4–n)2SnCl6 and (g–j) ((C2H5)nNH4–n)2TeCl6 (n = 1–4). A1g MO orbitals (σ bonds formed by Sn/Te 5s and Cl 3p orbitals) are highlighted with blue, and T1u orbitals (σ and π bonds formed by Te 5p and Cl 3p orbitals) are highlighted with orange.

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    Figure 4

    Figure 4. PXRD patterns of the (EtnNH4–n)2Sn1–xTexCl6 series: (a) (EtNH3)2Sn1–xTexCl6, (b) (Et2NH2)2Sn1–xTexCl6, (c) (Et3NH)2Sn1–xTexCl6, and (d) (Et4N)2Sn1–xTexCl6. Ref. stands for the reference line; (Et4N)2Sn1–xTexCl6 samples were collected with the Ge powder as an internal standard.

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    Figure 5

    Figure 5. PLE and PL spectra of (EtnNH4–n)2Sn1–xTexCl6 series: (a) (EtNH3)2Sn1–xTexCl6 (x = 0.05–0.80, λex. = 388 nm, and λem. = 620 nm), (b) (Et2NH2)2Sn1–xTexCl6 (x = 0.05–1.00, λex. = 375 nm, and λem. = 600 nm), (c) (Et3NH)2Sn1–xTexCl6 (x = 0.05–0.80, λex. = 405 nm, and λem. = 650 nm), and (d) (Et4N)2Sn1–xTexCl6 (x = 0.1–1.0, λex. = 395 nm, and λem. = 600 nm).

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    Figure 6

    Figure 6. Time-resolved PL spectra of (EtnNH4–n)2Sn1–xTexCl6 series, λex. = 372 nm: (a) (EtNH3)2Sn1–xTexCl6 (x = 0.05–0.80), (b) (Et2NH2)2Sn1–xTexCl6 (x = 0.05–1.00), (c) (Et3NH)2Sn1–xTexCl6 (x = 0.05–0.80), and (d) (Et4N)2Sn1–xTexCl6 (x = 0.1–1.0).

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    Figure 7

    Figure 7. Photoluminescence quantum yield (PLQY) as a function of the organic cation and Te concentration.

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    Figure 8

    Figure 8. A1g band dispersion energy as a function of (a) Te···Te or (b) Cl···Cl distances in chains of TeCl6 complexes. Two octahedral complex orientations are shown: linear (red plots) and rotated by 45° around the z-axis (blue plots).

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    Figure 9

    Figure 9. Voronoi polyhedra (VP) analysis of intermolecular interactions in (EtnNH4–n)2TeCl6 structures. (a) View on the Te atom VP in a [TeCl6]2– complex. (b,c) Cl atom VPs show a strong interaction between two complexes. (d,e) Decreasing interaction between the octahedral TeCl6 complexes as d(Cl···Cl) and the corresponding solid angle decrease. (f) Electronically isolated TeCl6 complexes in (Et4N)2TeCl6.

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  • References

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      Nature Communications (2015), 6 (), 7497CODEN: NCAOBW; ISSN:2041-1723. (Nature Publishing Group)
      Solar cells based on org.-inorg. halide perovskites have recently shown rapidly rising power conversion efficiencies, but exhibit unusual behavior such as current-voltage hysteresis and a low-frequency giant dielec. response. Ionic transport has been suggested to be an important factor contributing to these effects; however, the chem. origin of this transport and the mobile species are unclear. Here, the activation energies for ionic migration in methylammonium lead iodide (CH3NH3PbI3) are derived from first principles, and are compared with kinetic data extd. from the current-voltage response of a perovskite-based solar cell. We identify the microscopic transport mechanisms, and find facile vacancy-assisted migration of iodide ions with an activation energy of 0.6 eV, in good agreement with the kinetic measurements. The results of this combined computational and exptl. study suggest that hybrid halide perovskites are mixed ionic-electronic conductors, a finding that has major implications for solar cell device architectures.
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      A review. A new chapter in the long and distinguished history of perovskites is being written with the breakthrough success of metal halide perovskites (MHPs) as soln.-processed photovoltaic (PV) absorbers. The current surge in MHP research has largely arisen out of their rapid progress in PV devices; however, these materials are potentially suitable for a diverse array of optoelectronic applications. Like oxide perovskites, MHPs have ABX3 stoichiometry, where A and B are cations and X is a halide anion. Here, the underlying phys. and photophys. properties of inorg. (A = inorg.) and hybrid org.-inorg. (A = org.) MHPs are reviewed with an eye toward their potential application in emerging optoelectronic technologies. Significant attention is given to the prototypical compd. methylammonium lead iodide (CH3NH3PbI3) due to the preponderance of exptl. and theor. studies surrounding this material. We also discuss other salient MHP systems, including 2-dimensional compds., where relevant. More specifically, this review is a crit. account of the interrelation between MHP electronic structure, absorption, emission, carrier dynamics and transport, and other relevant photophys. processes that have propelled these materials to the forefront of modern optoelectronics research.
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      Mao, L.; Stoumpos, C. C.; Kanatzidis, M. G. Two-Dimensional Hybrid Halide Perovskites: Principles and Promises. J. Am. Chem. Soc. 2019, 141 (3), 1171– 1190,  DOI: 10.1021/jacs.8b10851
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      Two-Dimensional Hybrid Halide Perovskites: Principles and Promises
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      Hybrid halide perovskites have become the "next big thing" in emerging semiconductor materials, as the past decade witnessed their successful application in high-performance photovoltaics. This resurgence has encompassed enormous and widespread development of the three-dimensional (3D) perovskites, spearheaded by CH3NH3PbI3. The next generation of halide perovskites, however, is characterized by reduced dimensionality perovskites, emphasizing the two-dimensional (2D) perovskite derivs. which expand the field into a more diverse subgroup of semiconducting hybrids that possesses even higher tunability and excellent photophys. properties. In this perspective, a historical flashback is given to early reports before the "perovskite fever", and followed this original work to its fruition in the present day, where 2D halide perovskites are in the spotlight of current research, offering characteristics desirable in high-performance optoelectronics. The evolution approached of 2D halide perovskites from a structural perspective, providing a way to classify the diverse structure types of the materials, which largely dictate the unusual phys. properties obsd. The 2D hybrid halide perovskites are sorted on the basis of two key components: the inorg. layers and their modification, and the org. cation diversity. As these two heterogeneous components blend, either by synthetic manipulation (shuffling the org. cations or inorg. elements) or by application of external stimuli (temp. and pressure), the modular perovskite structure evolves to construct crystallog. defined quantum wells (QWs). The complex electronic structure that arises is sensitive to the structural features that could be in turn used as a knob to control the dielec. and optical properties the QWs. The perspective is concluded with the most notable achievements in optoelectronic devices that have been demonstrated to date, with an eye toward future material discovery and potential technol. developments.
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      Halide Perovskite Photovoltaics: Background, Status, and Future Prospects
      Jena, Ajay Kumar; Kulkarni, Ashish; Miyasaka, Tsutomu
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      The photovoltaics of org.-inorg. lead halide perovskite materials have shown rapid improvements in solar cell performance, surpassing the top efficiency of semiconductor compds. such as CdTe and CIGS (copper indium gallium selenide) used in solar cells in just about a decade. Perovskite prepn. via simple and inexpensive soln. processes demonstrates the immense potential of this thin-film solar cell technol. to become a low-cost alternative to the presently com. available photovoltaic technologies. Significant developments in almost all aspects of perovskite solar cells and discoveries of some fascinating properties of such hybrid perovskites have been made recently. This Review describes the fundamentals, recent research progress, present status, and our views on future prospects of perovskite-based photovoltaics, with discussions focused on strategies to improve both intrinsic and extrinsic (environmental) stabilities of high-efficiency devices. Strategies and challenges regarding compositional engineering of the hybrid perovskite structure are discussed, including potentials for developing all-inorg. and lead-free perovskite materials. Looking at the latest cutting-edge research, the prospects for perovskite-based photovoltaic and optoelectronic devices, including non-photovoltaic applications such as X-ray detectors and image sensing devices in industrialization, are described. In addn. to the aforementioned major topics, we also review, as a background, our encounter with perovskite materials for the first solar cell application, which should inspire young researchers in chem. and physics to identify and work on challenging interdisciplinary research problems through exchanges between academia and industry.
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      Bibi, A.; Lee, I.; Nah, Y.; Allam, O.; Kim, H.; Quan, L. N.; Tang, J.; Walsh, A.; Jang, S. S.; Sargent, E. H.; Kim, D. H. Lead-Free Halide Double Perovskites: Toward Stable and Sustainable Optoelectronic Devices. Mater. Today 2021, 49, 123– 144,  DOI: 10.1016/j.mattod.2020.11.026
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      Lead-free halide double perovskites: Toward stable and sustainable optoelectronic devices
      Bibi, Asia; Lee, Ilgeum; Nah, Yoonseo; Allam, Omar; Kim, Heejun; Quan, Li Na; Tang, Jiang; Walsh, Aron; Jang, Seung Soon; Sargent, Edward H.; Kim, Dong Ha
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      A review. In recent years, metal halide perovskites (MHPs) have attracted attention as semiconductors that achieve desirable properties for optoelectronic devices. However, two challenges-instability and the regulated nature of Pb -remain to be addressed with com. applications. The development of Pb-free halide double perovskite (HDP) materials has gained interest and attention as a result. This family offers potential in the field of optoelectronic devices through flexible material designs and compositional adjustments. We highlight recent progress and development in halide double perovskites and encompass the synthesis, optoelectronic properties, and engineering of the electronic structures of these materials along with their applications in optoelectronic devices. Computational and data-driven statistical methods can also be used to explore mechanisms and discover promising candidate double perovskites.
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    9. 9
      Song, Z.; Zhao, J.; Liu, Q. Luminescent Perovskites: Recent Advances in Theory and Experiments. Inorg. Chem. Front. 2019, 6 (11), 2969– 3011,  DOI: 10.1039/C9QI00777F
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      Luminescent perovskites: recent advances in theory and experiments
      Song, Zhen; Zhao, Jing; Liu, Quanlin
      Inorganic Chemistry Frontiers (2019), 6 (11), 2969-3011CODEN: ICFNAW; ISSN:2052-1553. (Royal Society of Chemistry)
      Perovskites form an important and enormous class of inorg. compds. Recently, perovskite materials have attracted extensive research interest owing to their excellent optoelectronic properties. Deep insights into the relationships between the crystal structure, electronic structure and properties play an important role in the development of new functional materials and high-performance devices. In this review, after a brief introduction, we first discuss the crystal structure and crystal chem. of perovskites according to their three classes: std. perovskites, low-dimensional perovskites and perovskite-like halides. Next, the electronic structure and luminescence from different phys. origins are presented. Then, we present a survey on the design, synthesis and luminescence properties of different perovskites, including halide perovskites, oxide perovskites, and lanthanide- or transition metal-doped perovskites, also including dimension-different perovskites (3D, 2D, 1D and quantum dots). We also summarize the strategies for improving the photoluminescence quantum yield (PLQY) and chem. stability, including by surface passivation, encapsulation and doping. Finally, we review their applications and give a brief outlook.
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    10. 10
      Cortecchia, D.; Yin, J.; Petrozza, A.; Soci, C. White Light Emission in Low-Dimensional Perovskites. J. Mater. Chem. C 2019, 7 (17), 4956– 4969,  DOI: 10.1039/C9TC01036J
      10
      White light emission in low-dimensional perovskites
      Cortecchia, Daniele; Yin, Jun; Petrozza, Annamaria; Soci, Cesare
      Journal of Materials Chemistry C: Materials for Optical and Electronic Devices (2019), 7 (17), 4956-4969CODEN: JMCCCX; ISSN:2050-7534. (Royal Society of Chemistry)
      Low-dimensional perovskites are rapidly emerging due to their distinctive emission properties, consisting of ultrabroad and highly Stokes shifted luminescence with pure white light chromaticity, which makes them very attractive for soln.-processed light-emitting devices and scintillators. To foster the design of new materials and their device applications, it is timely to review the relation between perovskite structural properties and the photophys. phenomena underlying their unique light emission characteristics. From a no. of recent studies, it has emerged that broadband emission properties in metal halide frameworks are very common, stemming from the self-localization of small polaron species at specific sites of the inorg. lattice, with a wide energy distribution. This review aims to provide an account of the current understanding of the photophys. processes underpinning luminescence broadening and highly efficient emission in various classes of low-dimensional metal-halide frameworks, and to highlight their potential for soln.-processed optoelectronic device applications. The discussion will addnl. establish a wider perspective on the role of intrinsic and extrinsic self-trapping, formation of polarons and their effect on charge generation and transport in low-dimensional perovskites.
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    11. 11
      Zhou, G.; Su, B.; Huang, J.; Zhang, Q.; Xia, Z. Broad-Band Emission in Metal Halide Perovskites: Mechanism, Materials, and Applications. Materials Science and Engineering: R: Reports 2020, 141, 100548  DOI: 10.1016/j.mser.2020.100548
      There is no corresponding record for this reference.
    12. 12
      Spanopoulos, I.; Hadar, I.; Ke, W.; Guo, P.; Mozur, E. M.; Morgan, E.; Wang, S.; Zheng, D.; Padgaonkar, S.; Manjunatha Reddy, G. N.; Weiss, E. A.; Hersam, M. C.; Seshadri, R.; Schaller, R. D.; Kanatzidis, M. G. Tunable Broad Light Emission from 3D “Hollow” Bromide Perovskites through Defect Engineering. J. Am. Chem. Soc. 2021, 143 (18), 7069– 7080,  DOI: 10.1021/jacs.1c01727
      12
      Tunable Broad Light Emission from 3D "Hollow" Bromide Perovskites through Defect Engineering
      Spanopoulos, Ioannis; Hadar, Ido; Ke, Weijun; Guo, Peijun; Mozur, Eve M.; Morgan, Emily; Wang, Shuxin; Zheng, Ding; Padgaonkar, Suyog; Manjunatha Reddy, G. N.; Weiss, Emily A.; Hersam, Mark C.; Seshadri, Ram; Schaller, Richard D.; Kanatzidis, Mercouri G.
      Journal of the American Chemical Society (2021), 143 (18), 7069-7080CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      Hybrid halide perovskites consisting of corner-sharing metal halide octahedra and small cuboctahedral cages filled with counter cations have proven to be prominent candidates for many high-performance optoelectronic devices. The stability limits of their three-dimensional perovskite framework are defined by the size range of the cations present in the cages of the structure. In some cases, the stability of the perovskite-type structure can be extended even when the counterions violate the size and shape requirements, as is the case in the so-called "hollow" perovskites. In this work, we engineered a new family of 3D highly defective yet cryst. "hollow" bromide perovskites with general formula (FA)1-x(en)x(Pb)1-0.7x(Br)3-0.4x (FA = formamidinium (FA+), en = ethylenediammonium (en2+), x = 0-0.44). Pair distribution function anal. shed light on the local structural coherence, revealing a wide distribution of Pb-Pb distances in the crystal structure as a consequence of the Pb/Br-deficient nature and en inclusion in the lattice. By manipulating the no. of Pb/Br vacancies, we finely tune the optical properties of the pristine FAPbBr3 by blue shifting the band gap from 2.20 to 2.60 eV for the x = 0.42 en sample. A most unexpected outcome was that at x> 0.33 en incorporation, the material exhibits strong broad light emission (1% photoluminescence quantum yield (PLQY)) that is maintained after exposure to air for more than a year. This is the first example of strong broad light emission from a 3D hybrid halide perovskite, demonstrating that meticulous defect engineering is an excellent tool for customizing the optical properties of these semiconductors.
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    13. 13
      Dou, L.; Yang, Y.; You, J.; Hong, Z.; Chang, W. H.; Li, G.; Yang, Y. Solution-Processed Hybrid Perovskite Photodetectors with High Detectivity. Nat. Commun. 2014, 5 (1), 5404,  DOI: 10.1038/ncomms6404
      13
      Solution-processed hybrid perovskite photodetectors with high detectivity
      Dou, Letian; Yang, Yang; You, Jingbi; Hong, Ziruo; Chang, Wei-Hsuan; Li, Gang; Yang, Yang
      Nature Communications (2014), 5 (), 5404CODEN: NCAOBW; ISSN:2041-1723. (Nature Publishing Group)
      Photodetectors capture optical signals with a wide range of incident photon flux d. and convert them to elec. signals instantaneously. They have many important applications including imaging, optical communication, remote control, chem./biol. sensing and so on. Currently, GaN, Si and InGaAs photodetectors are used in com. available products. Here we demonstrate a novel soln.-processed photodetector based on an org.-inorg. hybrid perovskite material. Operating at room temp., the photodetectors exhibit a large detectivity (the ability to detect weak signals) approaching 1014 Jones, a linear dynamic range over 100 decibels (dB) and a fast photoresponse with 3-dB bandwidth up to 3 MHz. The performance is significantly better than most of the org., quantum dot and hybrid photodetectors reported so far; and is comparable, or even better than, the traditional inorg. semiconductor-based photodetectors. Our results indicate that with proper device interface design, perovskite materials are promising candidates for low-cost, high-performance photodetectors.
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    14. 14
      Birowosuto, M. D.; Cortecchia, D.; Drozdowski, W.; Brylew, K.; Lachmanski, W.; Bruno, A.; Soci, C. X-Ray Scintillation in Lead Halide Perovskite Crystals. Sci. Rep 2016, 6 (1), 37254,  DOI: 10.1038/srep37254
      14
      X-ray Scintillation in Lead Halide Perovskite Crystals
      Birowosuto, M. D.; Cortecchia, D.; Drozdowski, W.; Brylew, K.; Lachmanski, W.; Bruno, A.; Soci, C.
      Scientific Reports (2016), 6 (), 37254CODEN: SRCEC3; ISSN:2045-2322. (Nature Publishing Group)
      Current technologies for X-ray detection rely on scintillation from expensive inorg. crystals grown at high-temp., which so far has hindered the development of large-area scintillator arrays. Thanks to the presence of heavy atoms, soln.-grown hybrid lead halide perovskite single crystals exhibit short X-ray absorption length and excellent detection efficiency. Here we compare X-ray scintillator characteristics of three-dimensional (3D) MAPbI3 and MAPbBr3 and two-dimensional (2D) (EDBE)PbCl4 hybrid perovskite crystals. X-ray excited thermoluminescence measurements indicate the absence of deep traps and a very small d. of shallow trap states, which lessens after-glow effects. All perovskite single crystals exhibit high X-ray excited luminescence yields of >120,000 photons/MeV at low temp. Although thermal quenching is significant at room temp., the large exciton binding energy of 2D (EDBE)PbCl4 significantly reduces thermal effects compared to 3D perovskites, and moderate light yield of 9,000 photons/MeV can be achieved even at room temp. This highlights the potential of 2D metal halide perovskites for large-area and low-cost scintillator devices for medical, security and scientific applications.
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    15. 15
      Zhao, Y.; Zhu, K. Organic–Inorganic Hybrid Lead Halide Perovskites for Optoelectronic and Electronic Applications. Chem. Soc. Rev. 2016, 45 (3), 655– 689,  DOI: 10.1039/C4CS00458B
      15
      Organic-inorganic hybrid lead halide perovskites for optoelectronic and electronic applications
      Zhao, Yixin; Zhu, Kai
      Chemical Society Reviews (2016), 45 (3), 655-689CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)
      Org. and inorg. hybrid perovskites (e.g., CH3NH3PbI3), with advantages of facile processing, tunable bandgaps, and superior charge-transfer properties, have emerged as a new class of revolutionary optoelectronic semiconductors promising for various applications. Perovskite solar cells constructed with a variety of configurations have demonstrated unprecedented progress in efficiency, reaching about 20% from multiple groups after only several years of active research. A key to this success is the development of various soln.-synthesis and film-deposition techniques for controlling the morphol. and compn. of hybrid perovskites. The rapid progress in material synthesis and device fabrication has also promoted the development of other optoelectronic applications including light-emitting diodes, photodetectors, and transistors. Both exptl. and theor. investigations on org.-inorg. hybrid perovskites have enabled some crit. fundamental understandings of this material system. Recent studies have also demonstrated progress in addressing the potential stability issue, which has been identified as a main challenge for future research on halide perovskites. Here, we review recent progress on hybrid perovskites including basic chem. and crystal structures, chem. synthesis of bulk/nanocrystals and thin films with their chem. and phys. properties, device configurations, operation principles for various optoelectronic applications (with a focus on solar cells), and photophysics of charge-carrier dynamics. We also discuss the importance of further understanding of the fundamental properties of hybrid perovskites, esp. those related to chem. and structural stabilities.
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    16. 16
      García de Arquer, F. P.; Armin, A.; Meredith, P.; Sargent, E. H. Solution-Processed Semiconductors for next-Generation Photodetectors. Nat. Rev. Mater. 2017, 2 (3), 1– 17,  DOI: 10.1038/natrevmats.2016.100
      There is no corresponding record for this reference.
    17. 17
      He, Y.; Ke, W.; Alexander, G. C. B.; McCall, K. M.; Chica, D. G.; Liu, Z.; Hadar, I.; Stoumpos, C. C.; Wessels, B. W.; Kanatzidis, M. G. Resolving the Energy of γ-Ray Photons with MAPbI3 Single Crystals. ACS Photonics 2018, 5 (10), 4132– 4138,  DOI: 10.1021/acsphotonics.8b00873
      17
      Resolving the Energy of γ-Ray Photons with MAPbI3 Single Crystals
      He, Yihui; Ke, Weijun; Alexander, Grant C. B.; McCall, Kyle M.; Chica, Daniel G.; Liu, Zhifu; Hadar, Ido; Stoumpos, Constantinos C.; Wessels, Bruce W.; Kanatzidis, Mercouri G.
      ACS Photonics (2018), 5 (10), 4132-4138CODEN: APCHD5; ISSN:2330-4022. (American Chemical Society)
      Halide perovskites exhibit remarkably high-performance as semiconductors compared to conventional materials because of an unusually favorable combination of optoelectronic properties. Soln.-grown single-crystals of org.-inorg. hybrid perovskite MeNH3PbI3 (MAPbI3), implemented in a Schottky-type device design, can produce outstanding hard radiation detectors with high spectral response and low dark current. Schottky-type MAPbI3 detector achieves an excellent energy resoln. of 6.8% for 57Co 122 keV gamma ray. The high detector performance is achieved due to the balanced charge collection efficiency for both electrons and holes, reflected in the high mobility-lifetime (μτ) products of both carriers (∼0.8 × 10-3 cm2/V). MAPbI3 demonstrates remarkably long electron and hole lifetimes (τe = 10 μs and τh = 17 μs) and impressive operational stability over time. Dual-source detection of α particle (5.5 MeV) and γ-ray (59.5 keV) from the 241Am radiation source is achieved simultaneously by Schottky-type MAPbI3 detector. These results reveal the great potential of MAPbI3 as a high-performance, low-cost radiation detection material.
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    18. 18
      Mozur, E. M.; Trowbridge, J. C.; Maughan, A. E.; Gorman, M. J.; Brown, C. M.; Prisk, T. R.; Neilson, J. R. Dynamical Phase Transitions and Cation Orientation-Dependent Photoconductivity in CH(NH2)2PbBr3. ACS Materials Lett. 2019, 1 (2), 260– 264,  DOI: 10.1021/acsmaterialslett.9b00209
      There is no corresponding record for this reference.
    19. 19
      Kakavelakis, G.; Gedda, M.; Panagiotopoulos, A.; Kymakis, E.; Anthopoulos, T. D.; Petridis, K. Metal Halide Perovskites for High-Energy Radiation Detection. Advanced Science 2020, 7 (22), 2002098  DOI: 10.1002/advs.202002098
      19
      Metal Halide Perovskites for High-Energy Radiation Detection
      Kakavelakis, George; Gedda, Murali; Panagiotopoulos, Apostolis; Kymakis, Emmanuel; Anthopoulos, Thomas D.; Petridis, Konstantinos
      Advanced Science (Weinheim, Germany) (2020), 7 (22), 2002098CODEN: ASDCCF; ISSN:2198-3844. (Wiley-VCH Verlag GmbH & Co. KGaA)
      Metal halide perovskites (MHPs) have emerged as a frontrunner semiconductor technol. for application in third generation photovoltaics while simultaneously making significant strides in other areas of optoelectronics. Photodetectors are one of the latest addns. in an expanding list of applications of this fascinating family of materials. The extensive range of possible inorg. and hybrid perovskites coupled with their processing versatility and ability to convert external stimuli into easily measurable optical/elec. signals makes them an auspicious sensing element even for the high-energy domain of the electromagnetic spectrum. Key to this is the ability of MHPs to accommodate heavy elements while being able to form large, high-quality crystals and polycryst. layers, making them one of the most promising emerging X-ray and γ-ray detector technologies. Here, the fundamental principles of high-energy radiation detection are reviewed with emphasis on recent progress in the emerging and fascinating field of metal halide perovskite-based X-ray and γ-ray detectors. The review starts with a discussion of the basic principles of high-energy radiation detection with focus on key performance metrics followed by a comprehensive summary of the recent progress in the field of perovskite-based detectors. The article concludes with a discussion of the remaining challenges and future perspectives.
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    20. 20
      Xu, L.-J.; Lin, X.; He, Q.; Worku, M.; Ma, B. Highly Efficient Eco-Friendly X-Ray Scintillators Based on an Organic Manganese Halide. Nat. Commun. 2020, 11 (1), 4329,  DOI: 10.1038/s41467-020-18119-y
      20
      Highly efficient eco-friendly X-ray scintillators based on an organic manganese halide
      Xu, Liang-Jin; Lin, Xinsong; He, Qingquan; Worku, Michael; Ma, Biwu
      Nature Communications (2020), 11 (1), 4329CODEN: NCAOBW; ISSN:2041-1723. (Nature Research)
      Scintillation based X-ray detection has received great attention for its application in a wide range of areas from security to healthcare. Here, we report highly efficient X-ray scintillators with state-of-the-art performance based on an org. metal halide, ethylenebis-triphenylphosphonium manganese (II) bromide ((C38H34P2)MnBr4), which can be prepd. using a facile soln. growth method at room temp. to form inch sized single crystals. This zero-dimensional org. metal halide hybrid exhibits green emission peaked at 517 nm with a photoluminescence quantum efficiency of ∼ 95%. Its X-ray scintillation properties are characterized with an excellent linear response to X-ray dose rate, a high light yield of ∼ 80,000 photon MeV-1, and a low detection limit of 72.8 nGy s-1. X-ray imaging tests show that scintillators based on (C38H34P2)MnBr4 powders provide an excellent visualization tool for X-ray radiog., and high resoln. flexible scintillators can be fabricated by blending (C38H34P2)MnBr4 powders with polydimethylsiloxane.
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    21. 21
      Liu, R.; Li, F.; Zeng, F.; Zhao, R.; Zheng, R. Halide Perovskite X-Ray Detectors: Fundamentals, Progress, and Outlook. Applied Physics Reviews 2024, 11 (2), 021327  DOI: 10.1063/5.0198695
      There is no corresponding record for this reference.
    22. 22
      Gao, P.; Grätzel, M.; Nazeeruddin, M. K. Organohalide Lead Perovskites for Photovoltaic Applications. Energy Environ. Sci. 2014, 7 (8), 2448– 2463,  DOI: 10.1039/C4EE00942H
      22
      Organohalide lead perovskites for photovoltaic applications
      Gao, Peng; Gratzel, Michael; Nazeeruddin, Mohammad K.
      Energy & Environmental Science (2014), 7 (8), 2448-2463CODEN: EESNBY; ISSN:1754-5706. (Royal Society of Chemistry)
      There are only few semiconducting materials that have been shaping the progress of third generation photovoltaic cells as much as perovskites. Although they are deceivingly simple in structure, the archetypal AMX3-type perovskites have built-in potential for complex and surprising discoveries. Since 2009, a small and somewhat exotic class of perovskites, which are quite different from the common rock-solid oxide perovskite, have turned over a new leaf in solar cell research. Highlighted as one of the major scientific breakthroughs of the year 2013, the power conversion efficiency of the title compd. hybrid org.-inorg. perovskite has now exceeded 18%, making it competitive with thin-film PV technol. In this mini-review, a brief history of perovskite materials for photovoltaic applications is reported, the current state-of-the-art is distd. and the basic working mechanisms have been discussed. By analyzing the attainable photocurrent and photovoltage, realizing perovskite solar cells with 20% efficiency for a single junction, and 30% for a tandem configuration on a c-Si solar cell would be realistic.
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    23. 23
      Brenner, T. M.; Egger, D. A.; Kronik, L.; Hodes, G.; Cahen, D. Hybrid Organic─Inorganic Perovskites: Low-Cost Semiconductors with Intriguing Charge-Transport Properties. Nat. Rev. Mater. 2016, 1 (1), 1– 16,  DOI: 10.1038/natrevmats.2015.7
      There is no corresponding record for this reference.
    24. 24
      Saparov, B.; Mitzi, D. B. Organic–Inorganic Perovskites: Structural Versatility for Functional Materials Design. Chem. Rev. 2016, 116 (7), 4558– 4596,  DOI: 10.1021/acs.chemrev.5b00715
      24
      Organic-inorganic perovskites: structural versatility for functional materials design
      Saparov, Bayrammurad; Mitzi, David B.
      Chemical Reviews (Washington, DC, United States) (2016), 116 (7), 4558-4596CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
      A review. Although known since the late 19th century, org.-inorg. perovskites have recently received extraordinary research community attention because of their unique phys. properties, which make them promising candidates for application in photovoltaic and related optoelectronic devices. This review explores beyond the current focus on 3-dimensional lead(II) halide perovskites, to highlight the great chem. flexibility and outstanding potential of the broader class of 3-dimensional and lower dimensional org.-based perovskite family for electronic, optical and energy-based applications as well as fundamental research. The concept of a multifunctional org.-inorg. hybrid, in which the org. and inorg. structural components provide intentional, unique, and hopefully synergistic features to the compd., represents an important contemporary target.
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    25. 25
      Spanopoulos, I.; Hadar, I.; Ke, W.; Tu, Q.; Chen, M.; Tsai, H.; He, Y.; Shekhawat, G.; Dravid, V. P.; Wasielewski, M. R.; Mohite, A. D.; Stoumpos, C. C.; Kanatzidis, M. G. Uniaxial Expansion of the 2D Ruddlesden–Popper Perovskite Family for Improved Environmental Stability. J. Am. Chem. Soc. 2019, 141 (13), 5518– 5534,  DOI: 10.1021/jacs.9b01327
      25
      Uniaxial Expansion of the 2D Ruddlesden-Popper Perovskite Family for Improved Environmental Stability
      Spanopoulos, Ioannis; Hadar, Ido; Ke, Weijun; Tu, Qing; Chen, Michelle; Tsai, Hsinhan; He, Yihui; Shekhawat, Gajendra; Dravid, Vinayak P.; Wasielewski, Michael R.; Mohite, Aditya D.; Stoumpos, Constantinos C.; Kanatzidis, Mercouri G.
      Journal of the American Chemical Society (2019), 141 (13), 5518-5534CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      The unique hybrid nature of 2D Ruddlesden-Popper (R-P) perovskites has bestowed upon them not only tunability of their electronic properties but also high-performance electronic devices with improved environmental stability as compared to their 3D analogs. However, there is limited information about their inherent heat, light, and air stability and how different parameters such as the inorg. layer no. and length of org. spacer mol. affect stability. To gain deeper understanding on the matter we have expanded the family of 2D R-P perovskites, by utilizing pentylamine (PA)2(MA)n-1PbnI3n+1 (n = 1-5, PA = CH3(CH2)4NH3+, C5) and hexylamine (HA)2(MA)n-1PbnI3n+1 (n = 1-4, HA = CH3(CH2)5NH3+, C6) as the org. spacer mols. between the inorg. slabs, creating two new series of layered materials, for up to n = 5 and 4 layers, resp. The resulting compds. were extensively characterized through a combination of phys. and spectroscopic methods, including single crystal X-ray anal. High resoln. powder X-ray diffraction studies using synchrotron radiation shed light for the first time to the phase transitions of the higher layer 2D R-P perovskites. The increase in the length of the org. spacer mols. did not affect their optical properties; however, it has a pronounced effect on the air, heat, and light stability of the fabricated thin films. An extensive study of heat, light, and air stability with and without encapsulation revealed that specific compds. can be air stable (relative humidity (RH) = 20-80% ± 5%) for more than 450 days, while heat and light stability in air can be exponentially increased by encapsulating the corresponding films. Evaluation of the out-of-plane mech. properties of the corresponding materials showed that their soft and flexible nature can be compared to current com. available polymer substrates (e.g., PMMA), rendering them suitable for fabricating flexible and wearable electronic devices.
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    26. 26
      Ke, W.; Mao, L.; Stoumpos, C. C.; Hoffman, J.; Spanopoulos, I.; Mohite, A. D.; Kanatzidis, M. G. Compositional and Solvent Engineering in Dion–Jacobson 2D Perovskites Boosts Solar Cell Efficiency and Stability. Adv. Energy Mater. 2019, 9 (10), 1803384  DOI: 10.1002/aenm.201803384
      There is no corresponding record for this reference.
    27. 27
      Spanopoulos, I.; Ke, W.; Stoumpos, C. C.; Schueller, E. C.; Kontsevoi, O. Y.; Seshadri, R.; Kanatzidis, M. G. Unraveling the Chemical Nature of the 3D “Hollow” Hybrid Halide Perovskites. J. Am. Chem. Soc. 2018, 140 (17), 5728– 5742,  DOI: 10.1021/jacs.8b01034
      27
      Unraveling the Chemical Nature of the 3D "Hollow" Hybrid Halide Perovskites
      Spanopoulos, Ioannis; Ke, Weijun; Stoumpos, Constantinos C.; Schueller, Emily C.; Kontsevoi, Oleg Y.; Seshadri, Ram; Kanatzidis, Mercouri G.
      Journal of the American Chemical Society (2018), 140 (17), 5728-5742CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      The newly introduced class of 3D halide perovskites, termed "hollow" perovskites, has been recently demonstrated as light absorbing semiconductor materials for fabricating lead-free perovskite solar cells with enhanced efficiency and superior stability. Hollow perovskites derive from three-dimensional (3D) AMX3 perovskites (A = methylammonium (MA), formamidinium (FA); M = Sn, Pb; X = Cl, Br, I), where small mols. such as ethylenediammonium cations (en) can be incorporated as the dication without altering the structure dimensionality. We present in this work the inherent structural properties of the hollow perovskites and expand this class of materials to the Pb-based analogs. Through a combination of phys. and spectroscopic methods (XRD, gas pycnometry, 1H NMR, TGA, SEM/EDX), we have assigned the general formula (A)1-x(en)x(M)1-0.7x(X)3-0.4x to the hollow perovskites. The incorporation of en in the 3D perovskite structure leads to massive M and X vacancies in the 3D [MX3] framework, thus the term hollow. The resulting materials are semiconductors with significantly blue-shifted direct band gaps from 1.25 to 1.51 eV for Sn-based perovskites and from 1.53 to 2.1 eV for the Pb-based analogs. The increased structural disorder and hollow nature were validated by single crystal X-ray diffraction anal. as well as pair distribution function (PDF) anal. D. functional theory (DFT) calcns. support the exptl. trends and suggest that the obsd. widening of the band gap is attributed to the massive M and X vacancies, which create a less connected 3D hollow structure. The resulting materials have superior air stability, where in the case of Sn-based hollow perovskites it exceeds two orders of temporal magnitude compared to the conventional full perovskites of MASnI3 and FASnI3. The hollow perovskite compds. pose as a new platform of promising light absorbers that can be utilized in single junction or tandem solar cells.
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    28. 28
      Mozur, E. M.; Hope, M. A.; Trowbridge, J. C.; Halat, D. M.; Daemen, L. L.; Maughan, A. E.; Prisk, T. R.; Grey, C. P.; Neilson, J. R. Cesium Substitution Disrupts Concerted Cation Dynamics in Formamidinium Hybrid Perovskites. Chem. Mater. 2020, 32 (14), 6266– 6277,  DOI: 10.1021/acs.chemmater.0c01862
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      Cesium substitution disrupts concerted cation dynamics in formamidinium hybrid perovskites
      Mozur, Eve M.; Hope, Michael A.; Trowbridge, Julia C.; Halat, David M.; Daemen, Luke L.; Maughan, Annalise E.; Prisk, Timothy R.; Grey, Clare P.; Neilson, James R.
      Chemistry of Materials (2020), 32 (14), 6266-6277CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)
      Although initial studies on hybrid perovskites for photovoltaic applications focused on simple compns., the most technol. relevant perovskites are heavily substituted. The influence of chem. substitution on the general phase behavior and specific phys. properties remains ambiguous. The hybrid perovskite formamidinium lead bromide, CH(NH2)2PbBr3, exhibits complex phase behavior manifesting in a series of crystallog. unresolvable phase transitions assocd. with changes in the cation dynamics. Here, we characterize the mol. and lattice dynamics of CH(NH2)2PbBr3 as a function of temp. and their evolution upon chem. substitution of CH(NH2)2+ for cesium (Cs+) with crystallog., neutron scattering, 1H and 14N NMR spectroscopy, and 79Br nuclear quadrupolar spectroscopy. Cs+ substitution suppresses the four low-temp. phase transitions of CH(NH2)2PbBr3, which propagate through concerted changes in the dynamic degrees of freedom of the org. sublattice and local or long-range distortions of the octahedral framework. We propose that cesium substitution suppresses the phase transitions through the relief of geometric frustration assocd. with the orientations of CH(NH2)2+ mols., which retain their local dynamical degrees of freedom.
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    29. 29
      Kontos, A. G.; Kaltzoglou, A.; Arfanis, M. K.; McCall, K. M.; Stoumpos, C. C.; Wessels, B. W.; Falaras, P.; Kanatzidis, M. G. Dynamic Disorder, Band Gap Widening, and Persistent Near-IR Photoluminescence up to At Least 523 K in ASnI3 Perovskites (A = Cs+, CH3NH3+ and NH2–CH═NH2+). J. Phys. Chem. C 2018, 122 (46), 26353– 26361,  DOI: 10.1021/acs.jpcc.8b10218
      There is no corresponding record for this reference.
    30. 30
      Jana, A.; Zhumagali, S.; Ba, Q.; Nissimagoudar, A. S.; Kim, K. S. Direct Emission from Quartet Excited States Triggered by Upconversion Phenomena in Solid-Phase Synthesized Fluorescent Lead-Free Organic–Inorganic Hybrid Compounds. J. Mater. Chem. A 2019, 7 (46), 26504– 26512,  DOI: 10.1039/C9TA08268A
      30
      Direct emission from quartet excited states triggered by upconversion phenomena in solid-phase synthesized fluorescent lead-free organic-inorganic hybrid compounds
      Jana, Atanu; Zhumagali, Shynggys; Ba, Qiankai; Nissimagoudar, Arun S.; Kim, Kwang S.
      Journal of Materials Chemistry A: Materials for Energy and Sustainability (2019), 7 (46), 26504-26512CODEN: JMCAET; ISSN:2050-7496. (Royal Society of Chemistry)
      We report, for the first time, the solid-phase gram-scale synthesis of two lead-free, zero-dimensional (0D) fluorescent org.-inorg. hybrid compds., [Bu4N]2[MnBr4] (1) and [Ph4P]2[MnBr4] (2), achieved by grinding the org. and inorg. precursor salts. The solid-phase synthetic route has several advantages for modulating mol. dimensionalities. During grinding, org. cations and Mn2+ cations are co-crystd. together in the solid-state, forming a 0D assembly at the mol. level where each individual metal center is surrounded by org. cations. Both compds. exhibit an emission peak at 520 nm and a photoluminescence (PL) quantum yield (QY) of 47%. Here, we also report, for the first time, the upconversion phenomena which trigger different emission energies occurring in different quartet states of Mn, 4T1(4G), 4T2(4G), 4A1(4G), 4E(4G), 4T2(4D), 4E(4D), and 4T1(4P). These optical properties are unusual phenomena which break Kasha's rule of emission. Single particle imaging and low-temp. PL measurement are performed to obtain a deeper insight into these ground products. These results pave a new path to develop highly fluorescent non-toxic hybrid compds. with remarkable optical properties.
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    31. 31
      Fattal, H.; Creason, T. D.; Delzer, C. J.; Yangui, A.; Hayward, J. P.; Ross, B. J.; Du, M.-H.; Glatzhofer, D. T.; Saparov, B. Zero-Dimensional Hybrid Organic–Inorganic Indium Bromide with Blue Emission. Inorg. Chem. 2021, 60 (2), 1045– 1054,  DOI: 10.1021/acs.inorgchem.0c03164
      31
      Zero-Dimensional Hybrid Organic-Inorganic Indium Bromide with Blue Emission
      Fattal, Hadiah; Creason, Tielyr D.; Delzer, Cordell J.; Yangui, Aymen; Hayward, Jason P.; Ross, Bradley J.; Du, Mao-Hua; Glatzhofer, Daniel T.; Saparov, Bayrammurad
      Inorganic Chemistry (2021), 60 (2), 1045-1054CODEN: INOCAJ; ISSN:0020-1669. (American Chemical Society)
      Low-dimensional hybrid org.-inorg. metal halides have received increased attention because of their outstanding optical and electronic properties. However, the most studied hybrid compds. contain lead and have long-term stability issues, which must be addressed for their use in practical applications. Here, we report a new zero-dimensional hybrid org.-inorg. halide, RInBr4, featuring photoemissive trimethyl(4-stilbenyl)methylammonium (R+) cations and nonemissive InBr4- tetrahedral anions. The crystal structure of RInBr4 is composed of alternating layers of inorg. anions and org. cations along the crystallog. a axis. The resultant hybrid demonstrates bright-blue emission with Commission Internationale de l'Eclairage color coordinates of (0.19, 0.20) and a high photoluminescence quantum yield (PLQY) of 16.36% at room temp., a 2-fold increase compared to the PLQY of 8.15% measured for the precursor org. salt RBr. On the basis of our optical spectroscopy and computational work, the org. component is responsible for the obsd. blue emission of the hybrid material. In addn. to the enhanced light emission efficiency, the novel hybrid indium bromide demonstrates significantly improved environmental stability. These findings may pave the way for the consideration of hybrid org. In(III) halides for light emission applications. The prepn. and optical properties of a novel hybrid org.-inorg. halide, RInBr4 [R = trimethyl(4-stilbenyl)methylammonium cation], are reported. The zero-dimensional crystal structure of RInBr4 features alternating layers of isolated InBr4- tetrahedra sepd. by layers of org. cations R+. RInBr4 shows high-efficiency blue emission with a quantum yield of 16.36% originating from the org. cation R+. Importantly, the novel hybrid indium bromide shows significantly improved air and thermal stability and photostability compared to the precursor org. salt.
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    32. 32
      Morad, V.; Yakunin, S.; Benin, B. M.; Shynkarenko, Y.; Grotevent, M. J.; Shorubalko, I.; Boehme, S. C.; Kovalenko, M. V. Hybrid 0D Antimony Halides as Air-Stable Luminophores for High-Spatial-Resolution Remote Thermography. Adv. Mater. 2021, 33 (9), 2007355  DOI: 10.1002/adma.202007355
      32
      Hybrid 0D Antimony Halides as Air-Stable Luminophores for High-Spatial-Resolution Remote Thermography
      Morad, Viktoriia; Yakunin, Sergii; Benin, Bogdan M.; Shynkarenko, Yevhen; Grotevent, Matthias J.; Shorubalko, Ivan; Boehme, Simon C.; Kovalenko, Maksym V.
      Advanced Materials (Weinheim, Germany) (2021), 33 (9), 2007355CODEN: ADVMEW; ISSN:0935-9648. (Wiley-VCH Verlag GmbH & Co. KGaA)
      Luminescent org.-inorg. low-dimensional ns2 metal halides are of rising interest as thermog. phosphors. The intrinsic nature of the excitonic self-trapping provides for reliable temp. sensing due to the existence of a temp. range, typically 50-100 K wide, in which the luminescence lifetimes (and quantum yields) are steeply temp.-dependent. This sensitivity range can be adjusted from cryogenic temps. to above room temp. by structural engineering, thus enabling diverse thermometric and thermog. applications ranging from protein crystallog. to diagnostics in microelectronics. Owing to the stable oxidn. state of Sb3+, Sb(III)-based halides are far more attractive than all major non-heavy-metal alternatives (Sn-, Ge-, Bi-based halides). In this work, the relationship between the luminescence characteristics and crystal structure and microstructure of TPP2SbBr5 (TPP = tetraphenylphosphonium) is established, and then its potential is showcased as environmentally stable and robust phosphor for remote thermog. The material is easily processable into thin films, which is highly beneficial for high-spatial-resoln. remote thermog. In particular, a compelling combination of high spatial resoln. (1μm) and high thermometric precision (high specific sensitivities of 0.03-0.04 K-1) is demonstrated by fluorescence-lifetime imaging of a heated resistive pattern on a flat substrate, covered with a soln.-spun film of TPP2SbBr5.
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    33. 33
      Creason, T. D.; Fattal, H.; Gilley, I. W.; Evans, B. N.; Jiang, J.; Pachter, R.; Glatzhofer, D. T.; Saparov, B. Stabilized Photoemission from Organic Molecules in Zero-Dimensional Hybrid Zn and Cd Halides. Inorg. Chem. Front. 2022, 9 (23), 6202– 6210,  DOI: 10.1039/D2QI01293F
      There is no corresponding record for this reference.
    34. 34
      McWhorter, T. M.; Zhang, Z.; Creason, T. D.; Thomas, L.; Du, M.-H.; Saparov, B. (C7H11N2)2MBr4 (M = Cu, Zn): X-Ray Sensitive 0D Hybrid Metal Halides with Tunable Broadband Emission. Eur. J. Inorg. Chem. 2022, 2022 (10), e202100954  DOI: 10.1002/ejic.202100954
      34
      (C7H11N2)2MBr4 (M=Cu, Zn): X-Ray Sensitive 0D Hybrid Metal Halides with Tunable Broadband Emission
      McWhorter, Timothy M.; Zhang, Zheng; Creason, Tielyr D.; Thomas, Leonard; Du, Mao-Hua; Saparov, Bayram
      European Journal of Inorganic Chemistry (2022), 2022 (10), e202100954CODEN: EJICFO; ISSN:1434-1948. (Wiley-VCH Verlag GmbH & Co. KGaA)
      Herein, a new family of hybrid metal halides, (DMAP)2MBr4 (M = Cu, Zn), featuring zero-dimensional (0D), pseudo-layered crystal structures contg. isolated mol. 4-dimethylaminopyridinium (DMAP, C7H11N2+) cations and MBr42- tetrahedral anions are reported. (DMAP)2MBr4 show remarkable long-term stability, with no signs of degrdn. after one year of ambient air exposure. The reported soln. synthesis affords large crystals measuring up to 1 cm, which showed significant response to soft 8 keV X-ray photons when implemented into X-ray detectors. Furthermore, (DMAP)2ZnBr4 demonstrates tunable color light emission properties, which is attributed to the org. mol. units based on our combined exptl. and computational results. The measured photoluminescence quantum yield (PLQY) for (DMAP)2ZnBr4 is 7.35 %, a remarkable enhancement of emission efficiency as compared to a weak emission from the org. precursor. The inexpensive and earth-abundant chem. compns. and ease of prepn. of the new hybrid metal halides make them promising candidates for optical and electronic applications.
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    35. 35
      Vishnoi, P.; Zuo, J. L.; Li, X.; Binwal, D. C.; Wyckoff, K. E.; Mao, L.; Kautzsch, L.; Wu, G.; Wilson, S. D.; Kanatzidis, M. G.; Seshadri, R.; Cheetham, A. K. Hybrid Layered Double Perovskite Halides of Transition Metals. J. Am. Chem. Soc. 2022, 144 (15), 6661– 6666,  DOI: 10.1021/jacs.1c12760
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      Hybrid Layered Double Perovskite Halides of Transition Metals
      Vishnoi, Pratap; Zuo, Julia L.; Li, Xiaotong; Binwal, Devesh Chandra; Wyckoff, Kira E.; Mao, Lingling; Kautzsch, Linus; Wu, Guang; Wilson, Stephen D.; Kanatzidis, Mercouri G.; Seshadri, Ram; Cheetham, Anthony K.
      Journal of the American Chemical Society (2022), 144 (15), 6661-6666CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      Hybrid layered double perovskite (HLDP) halides comprise hexacoordinated 1+ and 3+ metals in the octahedral sites within a perovskite layer and org. amine cations between the layers. Progress on such materials has hitherto been limited to compds. contg. main Group 3+ ions isoelectronic with PbII (such as SbIII and BiIII). Here, the authors report eight HLDP halides from the A2MIMIIIX8 family, where A = para-phenylenediammonium (PPDA), 1,4-butanediammonium (1,4-BDA), or 1,3-propanediammonium (1,3-PDA); MI = Cu or Ag; MIII = Ru or Mo; X = Cl or Br. The optical band gaps, which lie in the range 1.55 to 2.05 eV, are tunable according to the layer compn., but are largely independent of the spacer. Magnetic measurements carried out for (PPDA)2AgIRuIIICl8 and (PPDA)2AgIMoIIICl8 show no obvious evidence of a magnetic ordering transition. While the t2g3 MoIII compd. displays Curie-Weiss behavior for a spin-only d3 ion, the t2g5 RuIII compd. displays marked deviations from the Kotani theory.
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    36. 36
      Wang, S.; Morgan, E. E.; Panuganti, S.; Mao, L.; Vishnoi, P.; Wu, G.; Liu, Q.; Kanatzidis, M. G.; Schaller, R. D.; Seshadri, R. Ligand Control of Structural Diversity in Luminescent Hybrid Copper(I) Iodides. Chem. Mater. 2022, 34 (7), 3206– 3216,  DOI: 10.1021/acs.chemmater.1c04408
      36
      Ligand Control of Structural Diversity in Luminescent Hybrid Copper(I) Iodides
      Wang, Shuxin; Morgan, Emily E.; Panuganti, Shobhana; Mao, Lingling; Vishnoi, Pratap; Wu, Guang; Liu, Quanlin; Kanatzidis, Mercouri G.; Schaller, Richard D.; Seshadri, Ram
      Chemistry of Materials (2022), 34 (7), 3206-3216CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)
      Copper(I) iodide hybrids are of interest for next-generation lighting technologies because of their efficient luminescence in the absence of rare-earth elements. Here, the authors report 10 structurally diverse hybrid copper(I) iodides that emit in the green-red region with quantum yields reaching 67%. The compds. display a diversity of structures including ones with one-dimensional (1D) Cu-1 chains, Cu2I2 rhomboid dimers, and structures with two different arrangements of Cu4I4 tetramers. The compds. with Cu2I2 rhomboid dimers or Cu4I4 cubane tetramers have higher photoluminescence quantum yields than those with Cu-I 1D chains and octahedral Cu4I4 tetramers, owing to the optimal degree of condensation of the inorg. motifs, which suppresses nonradiative processes. Electronic structure calcns. on these compds. point out the crit. influence of the inorg. motif and org. ligand on the nature of the band gaps and thus the excitation characteristics. Temp.-dependent photoluminescence spectra are presented to better understand the nature of luminescence in compds. with different inorg. motifs. The emerging understanding of compn.-structure-property correlations in this family provides inspiration for the rational design of hybrid phosphors for general lighting applications.
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    37. 37
      Morgan, E. E.; Kent, G. T.; Zohar, A.; O’Dea, A.; Wu, G.; Cheetham, A. K.; Seshadri, R. Hybrid and Inorganic Vacancy-Ordered Double Perovskites A2WCl6. Chem. Mater. 2023, 35 (17), 7032– 7038,  DOI: 10.1021/acs.chemmater.3c01300
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      Hybrid and Inorganic Vacancy-Ordered Double Perovskites A2WCl6
      Morgan, Emily E.; Kent, Greggory T.; Zohar, Arava; O.bxsolid.Dea, Anthony; Wu, Guang; Cheetham, Anthony K.; Seshadri, Ram
      Chemistry of Materials (2023), 35 (17), 7032-7038CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)
      We report hybrid and all-inorg., vacancy-ordered double perovskites of d2 W4+ with the formula A2WCl6 (A = CH3NH3+, Rb+, and Cs+). These compds., which are reddish in color, can be distinguished from structurally similar compds. obtained by hydrothermal methods on the basis of structure, spectroscopic, and magnetic properties. The latter are green and incorporate oxygen, with the actual formula Cs2WOxCl6-x and distinct optical absorption and emission behavior. The local-moment magnetism of the pure-red d2 compds. reported here does not correspond to the appropriate Kotani model, suggesting as-yet undiscovered physics in these systems.
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    38. 38
      McCall, K. M.; Morad, V.; Benin, B. M.; Kovalenko, M. V. Efficient Lone-Pair-Driven Luminescence: Structure–Property Relationships in Emissive 5s2 Metal Halides. ACS Materials Lett. 2020, 2 (9), 1218– 1232,  DOI: 10.1021/acsmaterialslett.0c00211
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      Efficient Lone-Pair-Driven Luminescence: Structure-Property Relationships in Emissive 5s2 Metal Halides
      McCall, Kyle M.; Morad, Viktoriia; Benin, Bogdan M.; Kovalenko, Maksym V.
      ACS Materials Letters (2020), 2 (9), 1218-1232CODEN: AMLCEF; ISSN:2639-4979. (American Chemical Society)
      Low-dimensional metal halides have been the focus of intense investigations in recent years following the success of hybrid lead halide perovskites as optoelectronic materials. In particular, the light emission of low-dimensional halides based on the 5s2 cations Sn2+ and Sb3+ has found utility in a variety of applications complementary to those of the three-dimensional halide perovskites because of its unusual properties such as broadband character and highly temp.-dependent lifetime. These properties derive from the exceptional chem. of the 5s2 lone pair, but the terminol. and explanations given for such emission vary widely, hampering efforts to build a cohesive understanding of these materials that would lead to the development of efficient optoelectronic devices. In this Perspective, we provide a structural overview of these materials with a focus on the dynamics driven by the stereoactivity of the 5s2 lone pair to identify the structural features that enable strong emission. We unite the different theor. models that have been able to explain the success of these bright 5s2 emission centers into a cohesive framework, which is then applied to the array of compds. recently developed by our group and other researchers, demonstrating its utility and generating a holistic picture of the field from the point of view of a materials chemist. We highlight those state-of-the-art materials and applications that demonstrate the unique capabilities of these versatile emissive centers and identify promising future directions in the field of low-dimensional 5s2 metal halides.
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    39. 39
      Lyu, R.; Moore, C. E.; Liu, T.; Yu, Y.; Wu, Y. Predictive Design Model for Low-Dimensional Organic–Inorganic Halide Perovskites Assisted by Machine Learning. J. Am. Chem. Soc. 2021, 143 (32), 12766– 12776,  DOI: 10.1021/jacs.1c05441
      39
      Predictive Design Model for Low-Dimensional Organic-Inorganic Halide Perovskites Assisted by Machine Learning
      Lyu, Ruiyang; Moore, Curtis E.; Liu, Tianyu; Yu, Yongze; Wu, Yiying
      Journal of the American Chemical Society (2021), 143 (32), 12766-12776CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      Low-dimensional org.-inorg. halide perovskites have attracted interest for their properties in exciton dynamics, broad-band emission, magnetic spin selectivity. However, there is no quant. model for predicting the structure-directing effect of org. cations on the dimensionality of these low-dimensional perovskites. Here, we report a machine learning (ML)-assisted approach to predict the dimensionality of lead iodide-based perovskites. A literature review reveals 86 reported amines that are classified into "2D"-forming and "non-2D"-forming based on the dimensionality of their perovskites. Machining learning models were trained and tested based on the classification and descriptor features of these ammonium cations. Four structural features, including steric effect index, eccentricity, largest ring size, and hydrogen-bond donor, have been identified as the key controlling factors. On the basis of these features, a quantified equation is created to calc. the probability of forming 2D perovskite for a selected amine. To further illustrate its predicting capability, the built model is applied to several untested amines, and the predicted dimensionality is verified by growing single crystals of perovskites from these amines. This work represents a step toward predicting the crystal structures of low dimensional hybrid halide perovskites using ML as a tool.
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    40. 40
      Feng, W.; Tan, Y.; Yang, M.; Jiang, Y.; Lei, B.-X.; Wang, L.; Wu, W.-Q. Small Amines Bring Big Benefits to Perovskite-Based Solar Cells and Light-Emitting Diodes. Chem. 2022, 8 (2), 351– 383,  DOI: 10.1016/j.chempr.2021.11.010
      There is no corresponding record for this reference.
    41. 41
      Lee, J.-W.; Kim, D.-H.; Kim, H.-S.; Seo, S.-W.; Cho, S. M.; Park, N.-G. Formamidinium and Cesium Hybridization for Photo- and Moisture-Stable Perovskite Solar Cell. Adv. Energy Mater. 2015, 5 (20), 1501310  DOI: 10.1002/aenm.201501310
      There is no corresponding record for this reference.
    42. 42
      Stoumpos, C. C.; Cao, D. H.; Clark, D. J.; Young, J.; Rondinelli, J. M.; Jang, J. I.; Hupp, J. T.; Kanatzidis, M. G. Ruddlesden–Popper Hybrid Lead Iodide Perovskite 2D Homologous Semiconductors. Chem. Mater. 2016, 28 (8), 2852– 2867,  DOI: 10.1021/acs.chemmater.6b00847
      42
      Ruddlesden-Popper Hybrid Lead Iodide Perovskite 2D Homologous Semiconductors
      Stoumpos, Constantinos C.; Cao, Duyen H.; Clark, Daniel J.; Young, Joshua; Rondinelli, James M.; Jang, Joon I.; Hupp, Joseph T.; Kanatzidis, Mercouri G.
      Chemistry of Materials (2016), 28 (8), 2852-2867CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)
      The hybrid two-dimensional (2D) halide perovskites have recently drawn significant interest because they can serve as excellent photoabsorbers in perovskite solar cells. The large scale synthesis, crystal structure, and optical characterization are presented of the 2D (CH3(CH2)3NH3)2(CH3NH3)n-1PbnI3n+1 (n = 1, 2, 3, 4, ∞) perovskites, a family of layered compds. with tunable semiconductor characteristics. These materials consist of well-defined inorg. perovskite layers intercalated with bulky butylammonium cations that act as spacers between these fragments, adopting the crystal structure of the Ruddlesden-Popper type. It is found that the perovskite thickness (n) can be synthetically controlled by adjusting the ratio between the spacer cation and the small org. cation, thus allowing the isolation of compds. in pure form and large scale. The orthorhombic crystal structures of (CH3(CH2)3NH3)2(CH3NH3)Pb2I7 (n = 2, Cc2m; a = 8.9470(4), b = 39.347(2) Å, c = 8.8589(6)), (CH3(CH2)3NH3)2(CH3NH3)2Pb3I10 (n = 3, C2cb; a = 8.9275(6), b = 51.959(4) Å, c = 8.8777(6)), and (CH3(CH2)3NH3)2(CH3NH3)3Pb4I13 (n = 4, Cc2m; a = 8.9274(4), b = 64.383(4) Å, c = 8.8816(4)) have been solved by single-crystal X-ray diffraction and are reported here for the first time. The compds. are noncentrosym., as supported by measurements of the nonlinear optical properties of the compds. and d. functional theory (DFT) calcns. The band gaps of the series change progressively between 2.43 eV for the n = 1 member to 1.50 eV for the n = ∞ adopting intermediate values of 2.17 eV (n = 2), 2.03 eV (n = 3), and 1.91 eV (n = 4) for those between the two compositional extrema. DFT calcns. confirm this exptl. trend and predict a direct band gap for all the members of the Ruddlesden-Popper series. The estd. effective masses have values of mh = 0.14 m0 and me = 0.08 m0 for holes and electrons, resp., and are found to be nearly compn. independent. The band gaps of higher n members indicate that these compds. can be used as efficient light absorbers in solar cells, which offer better soln. processability and good environmental stability. The compds. exhibit intense room-temp. photoluminescence with emission wavelengths consistent with their energy gaps, 2.35 eV (n = 1), 2.12 eV (n = 2), 2.01 eV (n = 3), and 1.90 eV (n = 4) and point to their potential use in light-emitting diodes. In addn., owing to the low dimensionality and the difference in dielec. properties between the org. spacers and the inorg. perovskite layers, these compds. are naturally occurring multiple quantum well structures, which give rise to stable excitons at room temp.
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    43. 43
      Thouin, F.; Valverde-Chávez, D. A.; Quarti, C.; Cortecchia, D.; Bargigia, I.; Beljonne, D.; Petrozza, A.; Silva, C.; Srimath Kandada, A. R. Phonon Coherences Reveal the Polaronic Character of Excitons in Two-Dimensional Lead Halide Perovskites. Nat. Mater. 2019, 18 (4), 349– 356,  DOI: 10.1038/s41563-018-0262-7
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      Phonon coherences reveal the polaronic character of excitons in two-dimensional lead halide perovskites
      Thouin, Felix; Valverde-Chavez, David A.; Quarti, Claudio; Cortecchia, Daniele; Bargigia, Ilaria; Beljonne, David; Petrozza, Annamaria; Silva, Carlos; Srimath Kandada, Ajay Ram
      Nature Materials (2019), 18 (4), 349-356CODEN: NMAACR; ISSN:1476-1122. (Nature Research)
      Hybrid org.-inorg. semiconductors feature complex lattice dynamics due to the ionic character of the crystal and the softness arising from non-covalent bonds between mol. moieties and the inorg. network. Here we establish that such dynamic structural complexity in a prototypical two-dimensional lead iodide perovskite gives rise to the coexistence of diverse excitonic resonances, each with a distinct degree of polaronic character. By means of high-resoln. resonant impulsive stimulated Raman spectroscopy, we identify vibrational wavepacket dynamics that evolve along different configurational coordinates for distinct excitons and photocarriers. Employing d. functional theory calcns., we assign the obsd. coherent vibrational modes to various low-frequency (.ltorsim.50 cm-1) optical phonons involving motion in the lead iodide layers. We thus conclude that different excitons induce specific lattice reorganizations, which are signatures of polaronic binding. This insight into the energetic/configurational landscape involving globally neutral primary photoexcitations may be relevant to a broader class of emerging hybrid semiconductor materials.
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    44. 44
      Mao, L.; Chen, J.; Vishnoi, P.; Cheetham, A. K. The Renaissance of Functional Hybrid Transition-Metal Halides. Acc. Mater. Res. 2022, 3 (4), 439– 448,  DOI: 10.1021/accountsmr.1c00270
      44
      The Renaissance of Functional Hybrid Transition-Metal Halides
      Mao, Lingling; Chen, Jian; Vishnoi, Pratap; Cheetham, Anthony K.
      Accounts of Materials Research (2022), 3 (4), 439-448CODEN: AMRCDA; ISSN:2643-6728. (American Chemical Society)
      A review. There is an extensive history of research on both inorg. and hybrid metal halides, with the latter being first reported in the 1960s. Although work on hybrid systems has progressed steadily over the last 60 years, it has enjoyed a major renaissance during the last 5 years. This has arisen as a consequence of the 2009 discovery of the outstanding optoelectronic properties of hybrid lead halides, such as (MA)PbI3 (MA = methylammonium), and the recognition that there are many opportunities for equally exciting discoveries with compds. of the transition metals. Some of the early work on hybrid transition-metal halides put more emphasis on crystal structures but less on properties. In the modern era, we aim to grasp both the structure and properties, with a new twist. In this Account, we shall explore the recent developments in hybrid transition-metal halides with a focus on work in four main areas: magnetism, photoluminescence, semicond., and spintronics. Our work on magnetism centers on the Ru-based hybrid halides, where the structural types are diversely composed of vacancy-ordered double perovskite, as well as chain-like one-dimensional structures and layered double perovskite (LDP) when paired with a (1+) metal. We explore their magnetic properties and find that their spin-orbit coupling (SOC) behavior can be tuned through changing the A cation and the halide. In the luminescence section, we focus on our recent works on hybrid tetrahedral Mn(II) bromides and Cu(I) and Ag(I) iodides. We correlated our newly discovered 0D AmMnBr4 (A = org. cation, m = 1 or 2) compds. with previous reports, and generated a trend where the photoluminescence quantum yield (PLQY) increases with larger Mn-Mn distances. The flexible org. cation becomes the most important tool here to tune the structure-PLQY relations. Cu(I) and Ag(I) iodides coordinated with iodides and org. ligands produce new crystal structures with intense PL. For the semiconducting properties, we explore the Pt-based vacancy-ordered double perovskite and hybrid bismuth and indium-based LDPs to show the structural evolution with different choices for the org. cation, the metal and the halide; these have a strong influence on the optical properties. The LDPs specifically exhibit high structure tunability, with a wide range of (1+) and (3+) metal choices, and are exempt from some of the limitations of 3D double perovskite. In the last section, we introduce the recent progress on hybrid transition-metal-based ferroelecs. and spintronic materials. We successfully demonstrate the utilization of chiral Cu(II) chlorides for circularly polarized light (CPL) detection, showing the high anisotropy of the photoresponsivity. We also highlight the work that the authors have contributed in these areas and suggest several exciting opportunities for future developments.
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    45. 45
      Han, D.; Shi, H.; Ming, W.; Zhou, C.; Ma, B.; Saparov, B.; Ma, Y.-Z.; Chen, S.; Du, M.-H. Unraveling Luminescence Mechanisms in Zero-Dimensional Halide Perovskites. J. Mater. Chem. C 2018, 6 (24), 6398– 6405,  DOI: 10.1039/C8TC01291A
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      Unraveling luminescence mechanisms in zero-dimensional halide perovskites
      Han, Dan; Shi, Hongliang; Ming, Wenmei; Zhou, Chenkun; Ma, Biwu; Saparov, Bayrammurad; Ma, Ying-Zhong; Chen, Shiyou; Du, Mao-Hua
      Journal of Materials Chemistry C: Materials for Optical and Electronic Devices (2018), 6 (24), 6398-6405CODEN: JMCCCX; ISSN:2050-7534. (Royal Society of Chemistry)
      Zero-dimensional (0D) halides perovskites, in which anionic metal-halide octahedra (MX6)4- are sepd. by org. or inorg. countercations, have recently shown promise as excellent luminescent materials. However, the origin of the photoluminescence (PL) and, in particular, the different photophys. properties in hybrid org.-inorg. and all inorg. halides are still poorly understood. In this work, first-principles calcns. were performed to study the excitons and intrinsic defects in 0D hybrid org.-inorg. halides (C4N2H14X)4SnX6 (X = Br, I), which exhibit a high photoluminescence quantum efficiency (PLQE) at room temp. (RT), and also in the 0D inorg. halide Cs4PbBr6, which suffers from strong thermal quenching when T > 100 K. We show that the excitons in all three 0D halides are strongly bound and cannot be detrapped or dissocd. at RT, which leads to immobile excitons in (C4N2H14X)4SnX6. However, the excitons in Cs4PbBr6 can still migrate by tunneling, enabled by the resonant transfer of excitation energy (Dexter energy transfer). The exciton migration in Cs4PbBr6 leads to a higher probability of trapping and nonradiative recombination at the intrinsic defects. We show that a large Stokes shift and the negligible electronic coupling between luminescent centers are important for suppressing exciton migration; thereby, enhancing the photoluminescence quantum efficiency. Our results also suggest that the frequently obsd. bright green emission in Cs4PbBr6 is not due to the exciton or defect-induced emission in Cs4PbBr6 but rather the result of exciton emission from CsPbBr3 inclusions trapped in Cs4PbBr6.
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    46. 46
      Maughan, A. E.; Ganose, A. M.; Scanlon, D. O.; Neilson, J. R. Perspectives and Design Principles of Vacancy-Ordered Double Perovskite Halide Semiconductors. Chem. Mater. 2019, 31 (4), 1184– 1195,  DOI: 10.1021/acs.chemmater.8b05036
      46
      Perspectives and design principles of vacancy-ordered double perovskite halide semiconductors
      Maughan, Annalise E.; Ganose, Alex M.; Scanlon, David O.; Neilson, James R.
      Chemistry of Materials (2019), 31 (4), 1184-1195CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)
      A review. Here, the authors focus upon the structure-dynamics-property relations in vacancy-ordered double perovskite semiconductors as they pertain to applications in photovoltaics, and they propose avenues of future study within the context of the broader perovskite halide literature. They describe the compositional and structural motifs that dictate the optical gaps and charge transport behavior and discuss the implications of charge ordering, lattice dynamics, and org.-inorg. coupling upon the properties of these materials. The design principles they elucidate here represent an important step toward extending the understanding of perovskite functionality to defect-ordered perovskites.
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    47. 47
      Maughan, A. E.; Ganose, A. M.; Bordelon, M. M.; Miller, E. M.; Scanlon, D. O.; Neilson, J. R. Defect Tolerance to Intolerance in the Vacancy-Ordered Double Perovskite Semiconductors Cs2SnI6 and Cs2TeI6. J. Am. Chem. Soc. 2016, 138 (27), 8453– 8464,  DOI: 10.1021/jacs.6b03207
      47
      Defect Tolerance to Intolerance in the Vacancy-Ordered Double Perovskite Semiconductors Cs2SnI6 and Cs2TeI6
      Maughan, Annalise E.; Ganose, Alex M.; Bordelon, Mitchell M.; Miller, Elisa M.; Scanlon, David O.; Neilson, James R.
      Journal of the American Chemical Society (2016), 138 (27), 8453-8464CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      Vacancy-ordered double perovskites of the general formula A2BX6 are a family of perovskite derivs. composed of a face-centered lattice of nearly isolated [BX6] units with A-site cations occupying the cuboctahedral voids. Despite the presence of isolated octahedral units, the close-packed iodide lattice provides significant electronic dispersion, such that Cs2SnI6 has recently been explored for applications in photovoltaic devices. To elucidate the structure-property relationships of these materials, we have synthesized solid-soln. Cs2Sn1-xTexI6. However, even though tellurium substitution increases electronic dispersion via closer I-I contact distances, the substitution exptl. yields insulating behavior from a significant decrease in carrier concn. and mobility. D. functional calcns. of native defects in Cs2SnI6 reveal that iodine vacancies exhibit a low enthalpy of formation, and that the defect energy level is a shallow donor to the conduction band rendering the material tolerant to these defect states. The increased covalency of Te-I bonding renders the formation of iodine vacancy states unfavorable and is responsible for the redn. in cond. upon Te substitution. Addnl., Cs2TeI6 is intolerant to the formation of these defects, because the defect level occurs deep within the band gap and thus localizes potential mobile charge carriers. In these vacancy-ordered double perovskites, the close-packed lattice of iodine provides significant electronic dispersion, while the interaction of the B- and X-site ions dictates the properties as they pertain to electronic structure and defect tolerance. This simplified perspective based on extensive exptl. and theor. anal. provides a platform from which to understand structure-property relationships in functional perovskite halides.
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    48. 48
      Lee, J. H.; Lee, J.-H.; Kong, E.-H.; Jang, H. M. The Nature of Hydrogen-Bonding Interaction in the Prototypic Hybrid Halide Perovskite, Tetragonal CH3NH3PbI3. Sci. Rep 2016, 6 (1), 21687,  DOI: 10.1038/srep21687
      48
      The nature of hydrogen-bonding interaction in the prototypic hybrid halide perovskite, tetragonal CH3NH3PbI3
      Lee, June Ho; Lee, Jung-Hoon; Kong, Eui-Hyun; Jang, Hyun Myung
      Scientific Reports (2016), 6 (), 21687CODEN: SRCEC3; ISSN:2045-2322. (Nature Publishing Group)
      In spite of the key role of hydrogen bonding in the structural stabilization of the prototypic hybrid halide perovskite, CH3NH3PbI3 (MAPbI3), little progress has been made in our in-depth understanding of the hydrogen-bonding interaction between the MA+-ion and the iodide ions in the PbI6-octahedron network. Herein, we show that there exist two distinct types of the hydrogen-bonding interaction, naming α- and β-modes, in the tetragonal MAPbI3 on the basis of symmetry argument and d.-functional theory calcns. The computed Kohn-Sham (K-S) energy difference between these two interaction modes is 45.14 meV per MA-site with the α-interaction mode being responsible for the stable hydrogen-bonding network. The computed bandgap (Eg) is also affected by the hydrogen-bonding mode, with Eg of the α-interaction mode (1.73 eV) being significantly narrower than that of the β-interaction mode (2.03 eV). We have further estd. the individual bonding strength for the ten relevant hydrogen bonds having a bond crit. point.
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    49. 49
      Egger, D. A. Intermediate Bands in Zero-Dimensional Antimony Halide Perovskites. J. Phys. Chem. Lett. 2018, 9 (16), 4652– 4656,  DOI: 10.1021/acs.jpclett.8b01730
      49
      Intermediate Bands in Zero-Dimensional Antimony Halide Perovskites
      Egger, David A.
      Journal of Physical Chemistry Letters (2018), 9 (16), 4652-4656CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
      Using d. functional theory, the structural and electronic-structure properties of a recently discovered, zero-dimensional antimony halide perovskite were studied. The herein considered material EtPySbBr6 exhibits very promising electronic-structure properties: a direct band gap close to the peak of the solar spectrum and effective masses allowing for efficient carrier transport of electrons in particular. These results are rationalized by anal. of the electronic structure, which reveals the formation of intermediate bands due to orbital-hybridization effects of the Sb s-states. The formation of intermediate bands can lead to highly favorable electronic-structure properties of zero-dimensional perovskites and discusses the possibility of fabricating lead-free halide perovskites with promising optoelectronic properties by targeted substitution of ions and emergence of intermediate bands. These insights are important when understanding and further enhancing the capabilities of antimony and other promising lead-free compds.
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    50. 50
      Nicholas, A. D.; Halli, R. N.; Garman, L. C.; Cahill, C. L. Low-Dimensional Hybrid Indium/Antimony Halide Perovskites: Supramolecular Assembly and Electronic Properties. J. Phys. Chem. C 2020, 124 (47), 25686– 25700,  DOI: 10.1021/acs.jpcc.0c07268
      50
      Low-Dimensional Hybrid Indium/Antimony Halide Perovskites: Supramolecular Assembly and Electronic Properties
      Nicholas, Aaron D.; Halli, Ryan N.; Garman, Leah C.; Cahill, Christopher L.
      Journal of Physical Chemistry C (2020), 124 (47), 25686-25700CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)
      The phenomenon of quantum confinement in hybrid low-dimensional lead-free perovskite derivs. continues to hinder the development of these materials for electron carrier devices such as next-generation solar cells. Spatial sepn. of metal-halide octahedra within crystal structures yields materials with greater moisture and photodegrdn. resistance, but at the expense of desired photophys. properties such as small band gaps. We report the synthesis and characterization of an unexplored isomorphic series of perovskite derivs. consisting of isolated dimeric metal-halide M2X104- (M = In, Sb; X = Cl, Br) anions charge-balanced with halopyridinium cations. Assembly of these species results in a supramol. network via extensive noncovalent interactions and may be described as a pseudo-zero-dimensional arrangement. Despite the low dimensionality, these materials display semiconductive optical band-gap energies owing to the appearance of an intermediate band due to hybridization of metal-halide at. and MOs. Low-temp. luminescence measurements provide evidence of electron delocalization where photoexcited metal/halide electrons are captured by org. cations via energetically accessible π* MOs, sepg. electron/hole pairs. Natural bonding orbital (NBO) calcns. reveal that metal hybridization is more pronounced in compds. contg. Sb3+ and can be influenced by noncovalent interactions between anionic and cationic building units.
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    51. 51
      Nicholas, A. D.; Walusiak, B. W.; Garman, L. C.; Huda, M. N.; Cahill, C. L. Impact of Noncovalent Interactions on Structural and Photophysical Properties of Zero-Dimensional Tellurium(IV) Perovskites. J. Mater. Chem. C 2021, 9 (9), 3271– 3286,  DOI: 10.1039/D0TC06000C
      There is no corresponding record for this reference.
    52. 52
      Nicholas, A. D.; Garman, L. C.; Albano, N.; Cahill, C. L. Insight on Noncovalent Interactions and Orbital Constructs in Low-Dimensional Antimony Halide Perovskites. Phys. Chem. Chem. Phys. 2022, 24 (25), 15305– 15320,  DOI: 10.1039/D2CP01996E
      There is no corresponding record for this reference.
    53. 53
      Bukvetskii, B. V.; Sedakova, T. V.; Mirochnik, A. G. Crystal Structure, Luminescent and Thermochromic Properties of Bis(Tetraethylammonium) Hexachlorotellurate(IV). Russ J. Coord Chem. 2010, 36 (9), 651– 656,  DOI: 10.1134/S1070328410090034
      There is no corresponding record for this reference.
    54. 54
      Li, Z.; Park, J.-S.; Ganose, A. M.; Walsh, A. From Cubic to Hexagonal: Electronic Trends across Metal Halide Perovskite Polytypes. J. Phys. Chem. C 2023, 127 (26), 12695– 12701,  DOI: 10.1021/acs.jpcc.3c01232
      There is no corresponding record for this reference.
    55. 55
      Ghaithan, H. M.; Alahmed, Z. A.; Qaid, S. M. H.; Hezam, M.; Aldwayyan, A. S. Density Functional Study of Cubic, Tetragonal, and Orthorhombic CsPbBr3 Perovskite. ACS Omega 2020, 5 (13), 7468– 7480,  DOI: 10.1021/acsomega.0c00197
      55
      Density Functional Study of Cubic, Tetragonal, and Orthorhombic CsPbBr3 Perovskite
      Ghaithan, Hamid M.; Alahmed, Zeyad A.; Qaid, Saif M. H.; Hezam, Mahmoud; Aldwayyan, Abdullah S.
      ACS Omega (2020), 5 (13), 7468-7480CODEN: ACSODF; ISSN:2470-1343. (American Chemical Society)
      Cesium lead bromide (CsPbBr3) perovskite has recently gained significance owing to its rapidly increasing performance when used for light-emitting devices. In this study, we used d. functional theory to det. the structural, electronic, and optical properties of the cubic, tetragonal, and orthorhombic temp.-dependent phases of CsPbBr3 perovskite using the full-potential linear APW method. The electronic properties of CsPbBr3 perovskite have been investigated by evaluating their changes upon exerting spin-orbit coupling (SOC). The following exchange potentials were used: the local d. approxn. (LDA), Perdew-Burke-Ernzerhof generalized gradient approxn. (PBE-GGA), Engel-Vosko GGA (EV-GGA), Perdew-Burke-Ernzerhof GGA revised for solids (PBEsol-GGA), modified Becke-Johnson GGA (mBJ-GGA), new modified Becke-Johnson GGA (nmBJ-GGA), and unmodified Becke-Johnson GGA (umBJ-GGA). Our band structure results indicated that the cubic, tetragonal, and orthorhombic phases have direct energy bandgaps. By including the SOC effect in the calcns., the bandgaps computed with mBJ-GGA and nmBJ-GGA were found to be in good agreement with the exptl. results. Addnl., despite the large variations in their lattice consts., the three CsPbBr3 phases possessed similar optical properties. These results demonstrate a wide temp. range of operation for CsPbBr3.
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    56. 56
      Hussain, M.; Rashid, M.; Saeed, F.; Bhatti, A. S. Spin–Orbit Coupling Effect on Energy Level Splitting and Band Structure Inversion in CsPbBr3. J. Mater. Sci. 2021, 56 (1), 528– 542,  DOI: 10.1007/s10853-020-05298-8
      There is no corresponding record for this reference.
    57. 57
      Knop, O.; Cameron, T. S.; James, M. A.; Falk, M. Bis(Triethylammonium) Hexachlorostannate (IV): Crystal Structure and Hydrogen Bonding. Can. J. Chem. 1981, 59 (16), 2550– 2555,  DOI: 10.1139/v81-367
      There is no corresponding record for this reference.
    58. 58
      Knop, O.; Cameron, T. S.; James, M. A.; Falk, M. Alkylammonium Hexachlorostannates(IV), (RnNH4–n)2SnCl6: Crystal Structure, Infrared Spectrum, and Hydrogen Bonding. Can. J. Chem. 1983, 61 (7), 1620– 1646,  DOI: 10.1139/v83-281
      There is no corresponding record for this reference.
    59. 59
      Cameron, T. S.; James, M. A.; Knop, O.; Falk, M. Bis(Diethylammonium) Hexachlorostannate(IV), (Et2NH2)2SnCl6, and Tris-(Di-n-Propylammonium) Hexachlorostannate(IV) Chloride, (n-Pr2NH2)3(SnCl6)Cl: Crystal Structure and Hydrogen Bonding. Can. J. Chem. 1983, 61 (9), 2192– 2198,  DOI: 10.1139/v83-382
      There is no corresponding record for this reference.
    60. 60
      Grigoryeva, T. F.; Samsonova, T. I.; Baidina, I. A.; Ivanov, E. Yu. Thermal Decomposition of [RnNH4-n]TeCl6 in the Solid State. Izvestiya Sibirskogo otdeleniya Akademii nauk SSSR. Seriya khimicheskikh nauk 1985, 29 (5), 29– 34
      There is no corresponding record for this reference.
    61. 61
      Sedakova, T. V.; Mirochnik, A. G. Structure and Luminescent Properties of Complex Compounds of Tellurium(IV) with Ammonium Bases. Opt. Spectrosc. 2015, 119 (1), 54– 58,  DOI: 10.1134/S0030400X15070267
      There is no corresponding record for this reference.
    62. 62
      Stufkens, D. J. Dynamic Jahn-Teller Effect in the Excited States of SeCl62–, SeBr62–, TeCl62– and TeBr62–: Interpretation of Electronic Absorption and Raman Spectra. Recueil des Travaux Chimiques des Pays-Bas 1970, 89 (11), 1185– 1201,  DOI: 10.1002/recl.19700891109
      There is no corresponding record for this reference.
    63. 63
      Ozin, G. A.; Voet, A. V. The Gas Phase Raman Spectrum and Molecular Structure of Dichlorodibromotellurium(IV) TeCl2Br2. Novel Penta- and Hexa-Co-Ordinate Mixed Halide Anions of Tellurium(IV). Synthesis and Infrared and Raman Spectra of [Et4N]TeCl2Br3 and [Et4N]2TeCl2Br4. Can. J. Chem. 1971, 49 (5), 704– 708,  DOI: 10.1139/v71-118
      There is no corresponding record for this reference.
    64. 64
      Clark, R. J. H.; Stead, M. J. Raman Spectroscopy of the [TeX6]2– Ions (X = Cl or Br) at Resonance with Their Lowest 3T1u and 1T1u States: Evidence for Tetragonal Distortion in These Excited States. Chem. Phys. 1984, 91 (1), 113– 118,  DOI: 10.1016/0301-0104(84)80047-6
      There is no corresponding record for this reference.
    65. 65
      Ouasri, A.; Elyoubi, M. S. D.; Guedira, T.; Rhandour, A.; Mhiri, T.; Daoud, A. Synthesis, DTA, IR and Raman Spectra of Penthylenediammonium Hexachlorostannate NH3(CH2)5NH3SnCl6. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 2001, 57 (13), 2593– 2598,  DOI: 10.1016/S1386-1425(01)00431-0
      There is no corresponding record for this reference.
    66. 66
      Drummen, P. J. H.; Donker, H.; Smit, W. M. A.; Blasse, G. Jahn-Teller Distortion in the Excited State of Tellurium(IV) in Cs2MCl6 (M = Zr, Sn). Chem. Phys. Lett. 1988, 144 (5), 460– 462,  DOI: 10.1016/0009-2614(88)87296-8
      There is no corresponding record for this reference.
    67. 67
      Nikol, H.; Becht, A.; Vogler, A. Photoluminescence of Germanium(II), Tin(II), and Lead(II) Chloride Complexes in Solution. Inorg. Chem. 1992, 31 (15), 3277– 3279,  DOI: 10.1021/ic00041a021
      67
      Photoluminescence of germanium(II), tin(II), and lead(II) chloride complexes in solution
      Nikol, Hans; Becht, Alexander; Vogler, Arnd
      Inorganic Chemistry (1992), 31 (15), 3277-9CODEN: INOCAJ; ISSN:0020-1669.
      The absorption and emission spectra of GeCl3-, SnCl3-, PbCl3-, and PbCl42- in acetonitrile were recorded. In addn., emission quantum yields and lifetimes were detd. The emitting excited states are of the metal-centered sp type and originate from the 3P state of the free s2 ions. It is suggested that the complex ions which have trigonal-pyramidal C3v (MCl3-) and seesaw C2v (PbCl42-) structures in the ground state rearrange toward trigonal-planar D3h and tetrahedral Td geometries, resp., in their sp excited states.
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    68. 68
      Ackerman, J. F. Preparation and Luminescence of Some [K2PtCl6] Materials. Mater. Res. Bull. 1984, 19 (6), 783– 791,  DOI: 10.1016/0025-5408(84)90036-9
      68
      Preparation and luminescence of some potassium hexachloroplatinate(IV) materials
      Ackerman, John F.
      Materials Research Bulletin (1984), 19 (6), 783-91CODEN: MRBUAC; ISSN:0025-5408.
      The prepn. of Cs2TaOCl5 and Cs2TaSCl5, new materials with the [K2PtCl6] structure, is described. Lattice parameters and indexed diffraction patterns are reported for 8 materials with space group Fm3m, including the newly prepd. compds. Luminescence was measured for these materials and electronic transition assignments were made.
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    69. 69
      Lufaso, M. W.; Woodward, P. M. Jahn–Teller Distortions, Cation Ordering and Octahedral Tilting in Perovskites. Acta Cryst. B 2004, 60 (1), 10– 20,  DOI: 10.1107/S0108768103026661
      There is no corresponding record for this reference.
    70. 70
      McCusker, J. K.; Rheingold, A. L.; Hendrickson, D. N. Variable-Temperature Studies of Laser-Initiated 5T2 → 1A1 Intersystem Crossing in Spin-Crossover Complexes: Empirical Correlations between Activation Parameters and Ligand Structure in a Series of Polypyridyl Ferrous Complexes. Inorg. Chem. 1996, 35 (7), 2100– 2112,  DOI: 10.1021/ic9507880
      70
      Variable-Temperature Studies of Laser-Initiated 5T2 → 1A1 Intersystem Crossing in Spin-Crossover Complexes: Empirical Correlations between Activation Parameters and Ligand Structure in a Series of Polypyridyl Ferrous Complexes
      McCusker, James K.; Rheingold, Arnold L.; Hendrickson, David N.
      Inorganic Chemistry (1996), 35 (7), 2100-12CODEN: INOCAJ; ISSN:0020-1669. (American Chemical Society)
      Results are presented from a variable-temp. soln.-phase laser photolysis study of the 5T2 → 1A1 intersystem crossing in a series of related complexes: [Fe(tpen)](ClO4)2, [Fe(tppn)](ClO4)2, [Fe(tptn)](ClO4)2, [Fe(t-tpchxn)](ClO4)2, and [Fe(dpa)2](ClO4)2. The hexadentate ligands are formed with four 2-pyridylmethyl arms attached to ethylenediamine (tpen), 1,2-diaminopropylene (tppn), 1,3-diaminopropylene (tptn), or trans-1,2-diaminocyclohexane (t-tpchxn). The dpa ligand is a tridentate analog of these ligands, namely, bis(2-pyridylmethyl)amine. The complex [Fe(mtpen)](ClO4)2·2/3H2O, where mtpen is the same as tpen except one of the pyridyl rings has a 6-Me substituent, crystallizes in the space group C2/c, which at 173 K has a unit cell with a = 41.390(13) Å, b = 9.5239(16) Å, c = 24.016(6) Å, β = 108.24(3)°, and Z = 12. Refinement with 2844 obsd. [F > 5.0σ(F)] reflections gave R = 0.075 and Rw = 0.076. The complex [Fe(tppn)](ClO4)2·H2O crystallizes in the space group P21/n, which at 296 K has a unit cell with a = 12.979(4) Å, b = 12.624(4) Å, c = 19.475(6) Å, β = 108.17(2)°, and Z = 4. Refinement with 2357 obsd. [F > 5.0σ(F)] reflections gave R = 0.1198 and Rw = 0.1141. The mtpen complex is a high-spin FeII complex at all temps. (4.2-400 K), whereas the hydrated tpen complex is a spin-crossover complex with the temp. where there are 50% high-spin complexes as T1/2 ≃ 385 K, the hydrated tppn complex is also spin-crossover with a higher T1/2 value, and the hydrated tptn complex is low spin up to 400 K. The present crystallog. results, together with previously reported structural results for the tpen complex at two temps., are used to show that the conversion from low spin to high spin leads to an increase in the trigonal twist of these distorted octahedral complexes. The influence of this variation in trigonal twist on the rate of 5T2 → 1A1 intersystem crossing is examd. with variable-temp. laser-flash photolysis. Data collected for the tpen complex in MeOH in the 190-294 K range give a linear Arrhenius plot with an activation energy of Ea = 767 ± 22 cm-1 and a preexponential term of A = (1.35 ± 0.2) × 109 s-1. The tppn complex gives similar results of Ea = 771 ± 17 cm-1 and A = (1.45 ± 0.2) × 109 s-1. At 294 K the rate (k-1) for the 5T2 → 1A1 intersystem crossing is 2.87 × 107 s-1 for the tpen complex, and 3.21 × 107 s-1 for the tppn complex. On the other hand the tptn complex has k-1 = 6.25 × 108 s-1 at 295 K as measured with a picosecond spectrometer, and together with nanosecond data measured in the 186-210 K range gives an Arrhenius activation energy of Ea = 777 ± 50 cm-1 with A = (2.6 ± 0.8) × 1010 s-1. The bis(tridentate) complex [Fe(dpa)2](ClO4)2 in MeOH is found to give k-1 = 4.59 × 107 s-1 at 282 K and with the 191-282 K data gives Arrhenius values of Ea = 339 ± 13 cm-1 and A = (2.5 ± 0.25) × 108 s-1. The terpyridine complex [Fe(terpy)2](ClO4)2 is found to have k-1 = 1.0 × 108 s-1 in MeOH at 239 K, and the anal. of 190-239 K data gives Ea = 532 ± 36 cm-1 and A = (2.4 ± 0.4) × 109 s-1. Previous studies have shown that the greater the trigonal twist, the lower in energy is the 3T1 state which facilitates the spin-orbit interaction between the 5T2 high-spin and 1A1 low-spin states. It is suggested that the trigonal twist is a vibrational coordinate strongly coupled to the 5T2 → 1A1 intersystem crossing. It is addnl. shown that the data are consistent with a model wherein the "intrinsic" rate of 5T2 → 1A1 intersystem crossing, as gauged by the preexponential term, is a function of how far along the reaction coordinate a complex proceeds.
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    71. 71
      Mao, L.; Guo, P.; Wang, S.; Cheetham, A. K.; Seshadri, R. Design Principles for Enhancing Photoluminescence Quantum Yield in Hybrid Manganese Bromides. J. Am. Chem. Soc. 2020, 142 (31), 13582– 13589,  DOI: 10.1021/jacs.0c06039
      71
      Design Principles for Enhancing Photoluminescence Quantum Yield in Hybrid Manganese Bromides
      Mao, Lingling; Guo, Peijun; Wang, Shuxin; Cheetham, Anthony K.; Seshadri, Ram
      Journal of the American Chemical Society (2020), 142 (31), 13582-13589CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      Hybrid manganese halides have attracted widespread attention because of their highly emissive optical properties. To understand the underlying structural factors that dictate the photoluminescence quantum yield (PLQY) of these materials, we report five new hybrid manganese bromides with the general formula AmMnBr4 [m = 1 or 2, A = dimethylammonium (DMA), 3-methylpiperidinium (3MP), 3-aminomethylpiperidinium (3AMP), heptamethylenimine (HEP), and trimethylphenylammonium (TMPEA)]. By studying the crystal structures and optical properties of these materials and combining our results with the findings from previously reported analogs, we have found a direct correlation between Mn···Mn distance and the PLQY, where high PLQYs are assocd. with long Mn···Mn distances. This effect can be viewed as a manifestation of the concn.-quenching effect, except these are in stoichiometric compds. with precise interat. distances rather than random alloys. To gain better sepn. of the Mn centers and prevent energy transfer, a bulky singly protonated cation that avoids H-bonding is ideal. We have demonstrated this principle in one of our newly reported material, (TMPEA)2MnBr4, where a PLQY of 70.8% for a powder sample and 98% for a large single crystal sample is achieved. Our study reveals a generalized method for improving PLQYs in hybrid manganese bromides and is readily extended to designing all varieties of highly emissive hybrid materials.
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      Theory of concentration quenching in inorganic phosphors
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      cf. C.A. 47, 7900i. A theory is presented for concn. quenching in solid systems, based on the migration of excitation energy from one activator center to another and eventually to an imperfection which may act as an energy sink. Calcns. are made on the dependence of the fluorescence yield on concn., and to indicate typical activator concns. at which appreciable quenching may be expected to occur. If the transition in the activator is of the elec. dipole or elec. quadrupole type, appreciable quenching may arise when the activator concn. is 10-3 to 10-2; if it is a magnetic dipole transition, transfer will occur by exchange rather than by overlapping of magnetic dipole fields, and the crit. concn. will be of the order of a few percent. The implications of transfer phenomena upon the observed absence of luminescence in most pure inorg. crystals are discussed, and it is concluded that transfer rates are so high in strongly absorbing crystals that the energy can migrate easily to a very few sinks dispersed throughout the lattice.
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      The luminescence of the following compds. is reported: Cs2TeCl6 and Rb2TeBr6, both with undistorted TeX62- octahedra (X = Cl, Br) and (1,3-propanediamine)TeCl6 and Ca(H2O)7TeBr6, both with distorted TeX62- octahedra. In agreement with results obtained earlier for other ions with the s2 configuration, the distortion results in an increase of the Stokes shift and a decrease of the thermal quenching temp.
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      Sheldrick, G. M. SHELXT – Integrated Space-Group and Crystal-Structure Determination. Acta Cryst. A 2015, 71 (1), 3– 8,  DOI: 10.1107/S2053273314026370
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      SHELXT - Integrated space-group and crystal-structure determination
      Sheldrick, George M.
      Acta Crystallographica, Section A: Foundations and Advances (2015), 71 (1), 3-8CODEN: ACSAD7; ISSN:2053-2733. (International Union of Crystallography)
      The new computer program SHELXT employs a novel dual-space algorithm to solve the phase problem for single-crystal reflection data expanded to the space group P1. Missing data are taken into account and the resoln. extended if necessary. All space groups in the specified Laue group are tested to find which are consistent with the P1 phases. After applying the resulting origin shifts and space-group symmetry, the solns. are subject to further dual-space recycling followed by a peak search and summation of the electron d. around each peak. Elements are assigned to give the best fit to the integrated peak densities and if necessary addnl. elements are considered. An isotropic refinement is followed for non-centrosym. space groups by the calcn. of a Flack parameter and, if appropriate, inversion of the structure. The structure is assembled to maximize its connectivity and centered optimally in the unit cell. SHELXT has already solved many thousand structures with a high success rate, and is optimized for multiprocessor computers. It is, however, unsuitable for severely disordered and twinned structures because it is based on the assumption that the structure consists of atoms.
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      Dolomanov, O. V.; Bourhis, L. J.; Gildea, R. J.; Howard, J. a. K.; Puschmann, H. OLEX2: A Complete Structure Solution, Refinement and Analysis Program. J. Appl. Crystallogr. 2009, 42 (2), 339– 341,  DOI: 10.1107/S0021889808042726
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      OLEX2: a complete structure solution, refinement and analysis program
      Dolomanov, Oleg V.; Bourhis, Luc J.; Gildea, Richard J.; Howard, Judith A. K.; Puschmann, Horst
      Journal of Applied Crystallography (2009), 42 (2), 339-341CODEN: JACGAR; ISSN:0021-8898. (International Union of Crystallography)
      New software, OLEX2, was developed for the detn., visualization and anal. of mol. crystal structures. The software has a portable mouse-driven workflow-oriented and fully comprehensive graphical user interface for structure soln., refinement and report generation, as well as novel tools for structure anal. OLEX2 seamlessly links all aspects of the structure soln., refinement and publication process and presents them in a single workflow-driven package, with the ultimate goal of producing an application which will be useful to both chemists and crystallographers.
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      Sheldrick, G. M. Crystal Structure Refinement with SHELXL. Acta Cryst. C 2015, 71 (1), 3– 8,  DOI: 10.1107/S2053229614024218
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      Crystal structure refinement with SHELXL
      Sheldrick, George M.
      Acta Crystallographica, Section C: Structural Chemistry (2015), 71 (1), 3-8CODEN: ACSCGG; ISSN:2053-2296. (International Union of Crystallography)
      The improvements in the crystal structure refinement program SHELXL have been closely coupled with the development and increasing importance of the CIF (Crystallog. Information Framework) format for validating and archiving crystal structures. An important simplification is that now only one file in CIF format (for convenience, referred to simply as 'a CIF') contg. embedded reflection data and SHELXL instructions is needed for a complete structure archive; the program SHREDCIF can be used to ext. the and files required for further refinement with SHELXL. Recent developments in SHELXL facilitate refinement against neutron diffraction data, the treatment of H atoms, the detn. of abs. structure, the input of partial structure factors and the refinement of twinned and disordered structures. SHELXL is available free to academics for the Windows, Linux and Mac OS X operating systems, and is particularly suitable for multiple-core processors.
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      Cambridge Structural Database System; Cambridge Crystallographic Data Centre., 2024.
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      Kresse, G.; Furthmüller, J. Efficiency of Ab-Initio Total Energy Calculations for Metals and Semiconductors Using a Plane-Wave Basis Set. Comput. Mater. Sci. 1996, 6 (1), 15– 50,  DOI: 10.1016/0927-0256(96)00008-0
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      Efficiency of ab-initio total energy calculations for metals and semiconductors using a plane-wave basis set
      Kresse, G.; Furthmuller, J.
      Computational Materials Science (1996), 6 (1), 15-50CODEN: CMMSEM; ISSN:0927-0256. (Elsevier)
      The authors present a detailed description and comparison of algorithms for performing ab-initio quantum-mech. calcns. using pseudopotentials and a plane-wave basis set. The authors will discuss: (a) partial occupancies within the framework of the linear tetrahedron method and the finite temp. d.-functional theory, (b) iterative methods for the diagonalization of the Kohn-Sham Hamiltonian and a discussion of an efficient iterative method based on the ideas of Pulay's residual minimization, which is close to an order N2atoms scaling even for relatively large systems, (c) efficient Broyden-like and Pulay-like mixing methods for the charge d. including a new special preconditioning optimized for a plane-wave basis set, (d) conjugate gradient methods for minimizing the electronic free energy with respect to all degrees of freedom simultaneously. The authors have implemented these algorithms within a powerful package called VAMP (Vienna ab-initio mol.-dynamics package). The program and the techniques have been used successfully for a large no. of different systems (liq. and amorphous semiconductors, liq. simple and transition metals, metallic and semi-conducting surfaces, phonons in simple metals, transition metals and semiconductors) and turned out to be very reliable.
      >> More from SciFinder ®
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      Kresse, G.; Furthmüller, J. Efficient Iterative Schemes for Ab Initio Total-Energy Calculations Using a Plane-Wave Basis Set. Phys. Rev. B 1996, 54 (16), 11169– 11186,  DOI: 10.1103/PhysRevB.54.11169
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      Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set
      Kresse, G.; Furthmueller, J.
      Physical Review B: Condensed Matter (1996), 54 (16), 11169-11186CODEN: PRBMDO; ISSN:0163-1829. (American Physical Society)
      The authors present an efficient scheme for calcg. the Kohn-Sham ground state of metallic systems using pseudopotentials and a plane-wave basis set. In the first part the application of Pulay's DIIS method (direct inversion in the iterative subspace) to the iterative diagonalization of large matrixes will be discussed. This approach is stable, reliable, and minimizes the no. of order Natoms3 operations. In the second part, we will discuss an efficient mixing scheme also based on Pulay's scheme. A special "metric" and a special "preconditioning" optimized for a plane-wave basis set will be introduced. Scaling of the method will be discussed in detail for non-self-consistent and self-consistent calcns. It will be shown that the no. of iterations required to obtain a specific precision is almost independent of the system size. Altogether an order Natoms2 scaling is found for systems contg. up to 1000 electrons. If we take into account that the no. of k points can be decreased linearly with the system size, the overall scaling can approach Natoms. They have implemented these algorithms within a powerful package called VASP (Vienna ab initio simulation package). The program and the techniques have been used successfully for a large no. of different systems (liq. and amorphous semiconductors, liq. simple and transition metals, metallic and semiconducting surfaces, phonons in simple metals, transition metals, and semiconductors) and turned out to be very reliable.
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      Perdew, J. P.; Burke, K.; Ernzerhof, M. Generalized Gradient Approximation Made Simple. Phys. Rev. Lett. 1996, 77 (18), 3865– 3868,  DOI: 10.1103/PhysRevLett.77.3865
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      Perdew, John P.; Burke, Kieron; Ernzerhof, Matthias
      Physical Review Letters (1996), 77 (18), 3865-3868CODEN: PRLTAO; ISSN:0031-9007. (American Physical Society)
      Generalized gradient approxns. (GGA's) for the exchange-correlation energy improve upon the local spin d. (LSD) description of atoms, mols., and solids. We present a simple derivation of a simple GGA, in which all parameters (other than those in LSD) are fundamental consts. Only general features of the detailed construction underlying the Perdew-Wang 1991 (PW91) GGA are invoked. Improvements over PW91 include an accurate description of the linear response of the uniform electron gas, correct behavior under uniform scaling, and a smoother potential.
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      Blöchl, P. E. Projector Augmented-Wave Method. Phys. Rev. B 1994, 50 (24), 17953– 17979,  DOI: 10.1103/PhysRevB.50.17953
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      Blochl
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      There is no expanded citation for this reference.
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      Kresse, G.; Joubert, D. From Ultrasoft Pseudopotentials to the Projector Augmented-Wave Method. Phys. Rev. B 1999, 59 (3), 1758– 1775,  DOI: 10.1103/PhysRevB.59.1758
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      From ultrasoft pseudopotentials to the projector augmented-wave method
      Kresse, G.; Joubert, D.
      Physical Review B: Condensed Matter and Materials Physics (1999), 59 (3), 1758-1775CODEN: PRBMDO; ISSN:0163-1829. (American Physical Society)
      The formal relationship between ultrasoft (US) Vanderbilt-type pseudopotentials and Blochl's projector augmented wave (PAW) method is derived. The total energy functional for US pseudopotentials can be obtained by linearization of two terms in a slightly modified PAW total energy functional. The Hamilton operator, the forces, and the stress tensor are derived for this modified PAW functional. A simple way to implement the PAW method in existing plane-wave codes supporting US pseudopotentials is pointed out. In addn., crit. tests are presented to compare the accuracy and efficiency of the PAW and the US pseudopotential method with relaxed-core all-electron methods. These tests include small mols. (H2, H2O, Li2, N2, F2, BF3, SiF4) and several bulk systems (diamond, Si, V, Li, Ca, CaF2, Fe, Co, Ni). Particular attention is paid to the bulk properties and magnetic energies of Fe, Co, and Ni.
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      Momma, K.; Izumi, F. VESTA 3 for Three-Dimensional Visualization of Crystal, Volumetric and Morphology Data. J. Appl. Crystallogr. 2011, 44 (6), 1272– 1276,  DOI: 10.1107/S0021889811038970
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      VESTA 3 for three-dimensional visualization of crystal, volumetric and morphology data
      Momma, Koichi; Izumi, Fujio
      Journal of Applied Crystallography (2011), 44 (6), 1272-1276CODEN: JACGAR; ISSN:0021-8898. (International Union of Crystallography)
      VESTA is a 3D visualization system for crystallog. studies and electronic state calcns. It was upgraded to the latest version, VESTA 3, implementing new features including drawing the external morphpol. of crysals; superimposing multiple structural models, volumetric data and crystal faces; calcn. of electron and nuclear densities from structure parameters; calcn. of Patterson functions from the structure parameters or volumetric data; integration of electron and nuclear densities by Voronoi tessellation; visualization of isosurfaces with multiple levels, detn. of the best plane for selected atoms; an extended bond-search algorithm to enable more sophisticated searches in complex mols. and cage-like structures; undo and redo is graphical user interface operations; and significant performance improvements in rendering isosurfaces and calcg. slices.
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      Wang, V.; Xu, N.; Liu, J.-C.; Tang, G.; Geng, W.-T. VASPKIT: A User-Friendly Interface Facilitating High-Throughput Computing and Analysis Using VASP Code. Comput. Phys. Commun. 2021, 267, 108033  DOI: 10.1016/j.cpc.2021.108033
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      VASPKIT: A user-friendly interface facilitating high-throughput computing and analysis using VASP code
      Wang, Vei; Xu, Nan; Liu, Jin-Cheng; Tang, Gang; Geng, Wen-Tong
      Computer Physics Communications (2021), 267 (), 108033CODEN: CPHCBZ; ISSN:0010-4655. (Elsevier B.V.)
      A review. We present the VASPKIT, a command-line program that aims at providing a robust and user-friendly interface to perform high-throughput anal. of a variety of material properties from the raw data produced by the VASP code. It consists of mainly the pre- and post-processing modules. The former module is designed to prep. and manipulate input files such as the necessary input files generation, symmetry anal., supercell transformation, k-path generation for a given crystal structure. The latter module is designed to ext. and analyze the raw data about elastic mechanics, electronic structure, charge d., electrostatic potential, linear optical coeffs., wave function plots in real space, etc. This program can run conveniently in either interactive user interface or command line mode. The command-line options allow the user to perform high-throughput calcns. together with bash scripts. This article gives an overview of the program structure and presents illustrative examples for some of its usages. The program can run on Linux, macOS, and Windows platforms. The executable versions of VASPKIT and the related examples and tutorials are available on its official website vaspkit .com.
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      M Ganose, A.; J Jackson, A.; O Scanlon, D. Sumo: Command-Line Tools for Plotting and Analysis of Periodic *ab Initio* Calculations. J. Open Source Software 2018, 3 (28), 717,  DOI: 10.21105/joss.00717
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      Blatov, V. A.; Shevchenko, A. P.; Serezhkin, V. N. TOPOS3.2: A New Version of the Program Package for Multipurpose Crystal-Chemical Analysis. J. Appl. Crystallogr. 2000, 33 (4), 1193– 1193,  DOI: 10.1107/S0021889800007202
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      TOPOS3.2: a new version of the program package for multipurpose crystal-chemical analysis
      Blatov, V. A.; Shevchenko, A. P.; Serezhkin, V. N.
      Journal of Applied Crystallography (2000), 33 (4), 1193CODEN: JACGAR; ISSN:0021-8898. (Munksgaard International Publishers Ltd.)
      There is no expanded citation for this reference.
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      Blatov, V. A. Nanocluster Analysis of Intermetallic Structures with the Program Package TOPOS. Struct. Chem. 2012, 23, 955– 963,  DOI: 10.1007/s11224-012-0013-3
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      Nanocluster analysis of intermetallic structures with the program package TOPOS
      Blatov, V. A.
      Structural Chemistry (2012), 23 (4), 955-963CODEN: STCHES; ISSN:1040-0400. (Springer)
      General principles of the anal. of intermetallic compds. with the program package TOPOS are considered. The nanocluster method is described in detail, which lies in the base of the TOPOS "Nanoclustering" procedure. The applications of the nanocluster method to intermetallic compds. as well as to porous materials are comprehensively overviewed. The perspectives of extending the nanocluster model to other classes of inorg. compds. are outlined.
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      Blatov, V. A.; Shevchenko, A. P.; Proserpio, D. M. Applied Topological Analysis of Crystal Structures with the Program Package ToposPro. Cryst. Growth Des. 2014, 14 (7), 3576– 3586,  DOI: 10.1021/cg500498k
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      Applied Topological Analysis of Crystal Structures with the Program Package ToposPro
      Blatov, Vladislav A.; Shevchenko, Alexander P.; Proserpio, Davide M.
      Crystal Growth & Design (2014), 14 (7), 3576-3586CODEN: CGDEFU; ISSN:1528-7483. (American Chemical Society)
      Basic concepts of computer topol. anal. of crystal structures realized in the current version of the program package ToposPro are considered. Applications of the ToposPro methods to various classes of chem. compds.-coordination polymers, mol. crystals, supramol. ensembles, inorg. ionic compds., intermetallics, fast-ion conductors, microporous materials-are illustrated by many examples. Chem. and crystallog. different structures can be automatically treated in a similar way with the ToposPro approaches.
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  • Supporting Information

    Supporting Information

    The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/jacs.4c14554.

    • Selected crystallographic data and XRD experiment parameters, atomic displacement parameters, bond lengths, bond angles, characteristics of N–H···Cl hydrogen bonds, EDS results and SEM images, average PL lifetimes, PLQYs, parameters of TeCl62– octahedra distortion, synthesis details, Tauc plots, TGA/DTA, and Raman spectra (Tables S1–S28 and Figures S1–S6) (PDF)

    Accession Codes

    CCDC 2391291–2391295 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by emailing [email protected], or by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: + 44 1223 336033.


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