Download Hi-Res ImageDownload to MS-PowerPointCite This:ACS Energy Lett. 2016, 1, 4, 880-887

LetterSeptember 21, 2016

Direct Observation of Dynamic Symmetry Breaking above Room Temperature in Methylammonium Lead Iodide Perovskite
Click to copy article linkArticle link copied!

View Author Information

Open PDF Supporting Information (1)

ACS Energy Letters

Cite this: ACS Energy Lett. 2016, 1, 4, 880–887

Click to copy citationCitation copied!

https://doi.org/10.1021/acsenergylett.6b00381

Published September 21, 2016

Request reuse permissions

Abstract

Click to copy section linkSection link copied!

Lead halide perovskites such as methylammonium lead triiodide (CH₃NH₃PbI₃) have outstanding optical and electronic properties for photovoltaic applications, yet a full understanding of how this solution-processable material works so well is currently missing. Previous research has revealed that CH₃NH₃PbI₃ possesses multiple forms of static disorder regardless of preparation method, which is surprising in light of its excellent performance. Using high energy resolution inelastic X-ray (HERIX) scattering, we measure phonon dispersions in CH₃NH₃PbI₃ and find direct evidence for another form of disorder in single crystals: large-amplitude anharmonic zone edge rotational instabilities of the PbI₆ octahedra that persist to room temperature and above, left over from structural phase transitions that take place tens to hundreds of degrees below. Phonon calculations show that the orientations of the methylammonium (CH₃NH₃⁺) couple strongly and cooperatively to these modes. The result is a noncentrosymmetric, instantaneous local structure, which we observe in atomic pair distribution function (PDF) measurements. This local symmetry breaking is unobservable by Bragg diffraction but can explain key material properties such as the structural phase sequence, ultralow thermal transport, and large minority charge carrier lifetimes despite moderate carrier mobility. From the PDF we estimate the size of the fluctuating symmetry broken domains to be between 1 and 3 nm in diameter.

Subjects

Structural imperfections normally reduce the photovoltaic action of a material by reducing the carrier mobilities and providing nonradiative recombination pathways for the photogenerated carriers. CH₃NH₃PbI₃ exhibits significant nanocrystallinity, (1) defects, (2) and dynamic disorder, (3, 4) characteristics not normally associated with high-efficiency photovoltaic devices. (5) The puzzle with hybrid halide perovskites is how such a defective solution-processed material can have efficiencies rivaling those of high-quality crystalline semiconductors. (6) Two kinds of framework structural instabilities are expected to be present in perovskites: octahedral tilting, (7) which is associated with antiferroelectricity, and cation off-centering, which can sometimes yield a ferroelectrically active distortion. (8) Polarity in the material can affect the optical and electrical properties, (9-12) but the presence of persistent polarity in these materials has not been established and continues to be disputed. (13-16) In CsPbCl₃, octahedral rotational instabilities have been directly observed by INS (17) and more indirectly for CH₃NH₃PbBr₃ and CH₃NH₃PbCl₃. (18-20) However, in CH₃NH₃PbI₃, while the disorder of the organic cation has been extensively investigated, (3, 13, 21-23) only calculations combined with indirect measurements have predicted octahedral rotational instabilities in the cubic phase. (24-26) In this work, we directly observe the lattice dynamics related to these framework distortions and connect them to the physical properties of CH₃NH₃PbI₃.

Inelastic scattering is a standard method to quantify these kinds of dynamics. However, inelastic neutron scattering (INS) experiments require large single crystals and are additionally challenging on hybrid materials such as CH₃NH₃PbI₃ due to the strong incoherent scattering of hydrogen. We circumvent these issues by using X-ray-based HERIX, which has a larger scattering cross section and sensitivity, and better selectivity for motion of the inorganic framework.

Measurements were performed on high-quality single crystals of CH₃NH₃PbI₃ at the Advanced Photon Source at the Argonne National Laboratory. Due to the large absorption cross section of lead and iodine, crystals were polished to about 100 μm and mounted on a copper post (Figure S1A,B). This polishing and mounting preserves the high-quality single crystal, as shown by single-crystal X-ray diffraction (Figure S1C). Measurements were performed at 350 K in the cubic (Pm3M) phase, which gave a reasonable phonon intensity and removed difficulties associated with crystal twinning, which occurs spontaneously upon descending into the lower symmetry phases. Transverse acoustic (TA) and longitudinal acoustic (LA) phonon energies were measured along the three high-symmetry directions of the Brillouin zone, and one transverse optical (TO) branch was also measured. Representative plots of the raw spectra are shown in Figure 1.

Figure 1. Inelastic scattering spectra plotted from the Brillouin zone center to the zone edge. (a–d) M_TA₂ and X_TA illustrate what a typical dependence looks like. The dashed curve is only to guide the eye. In contrast, the M_TA₁ and R_TA at the zone edge have magnitudes larger even than the Bragg tail. (e) Sketch of the motion of the observed anharmonic modes with the idealized A-site cation (CH₃NH₃⁺) position represented in blue, the B-site cation (Pb²⁺) in gray at the center of the octahedra, and the X-site anion (I^–) in purple. Animations of these modes, and several others, are available online at https://dx.doi.org/10.6084/m9.figshare.3408394.

The TA branch in the [00ζ] direction (X) is shown in Figure 1a. Close to the zone center (ζ = 0), the strongest signal is a resolution-limited elastic line coming from the tail of the nearby Bragg peak. Moving across the zone to the zone edge, the elastic Bragg tail quickly dies off in intensity (indicated by the dashed line), and inelastic shoulders coming from the low-energy acoustic modes become well-resolved peaks at higher energy transfer (ℏω). These peaks lie symmetrically on the energy loss (Stokes) and energy gain (anti-Stokes) side of ℏω = 0, corresponding to phonon creation and annihilation, respectively. Approaching the zone edge, the overall intensity of the spectrum is strongly suppressed due to the lower phonon occupancy of high-energy modes, among other effects. This is the expected behavior for the HERIX spectra of well-defined acoustic phonons: dispersing to higher energy and decreasing in intensity with increasing ζ.

However, this behavior is not observed in two of the phonon modes. In the [0ζζ] direction, the two transverse modes are nondegenerate, and we refer to them as M_TA₁ and M_TA₂ (under cubic symmetry, the two TA phonons are degenerate in both the [00ζ] and [ζζζ] directions). The intensity of the M_TA₂ branch behaves normally, similar to the transverse [00ζ] mode (Figure 1b), but the M_TA₁ mode behaves very differently as the zone is crossed from center to edge. Now, approaching the zone edge, a strikingly large broad central peak emerges at ζ = 0.4 and becomes narrower and very intense at ζ = 0.5 (Figure 1c). The large signal intensity results from the low energy, and therefore high-phonon occupation, of these modes. Even more dramatic behavior is seen in the response of the R_TA mode in the [ζζζ] direction, with a resolution-limited ℏω = 0 peak at the R point of intensity 12 times the corresponding peak at ζ = 0.1 (Figure 1d). These two modes are the most important features of our observed lattice dynamics and correspond to rotation of the octahedra along the principal cubic axes, with neighboring octahedra along the rotation axis either rotating together (M_TA₁) or opposite (R_TA) to each other (in-phase and out-of-phase tilting, respectively). These motions are illustrated in Figure 1e. (17)

We have extracted phonon dispersions for the seven nondegenerate acoustic branches and one transverse optic branch (Figure 2). Details of the fitting are presented in the Experimental Section and Figure S2. From the initial slope of the acoustic phonons, we extract elastic constants and the bulk modulus (K = 13 ± 2 GPa), which implies that CH₃NH₃PbI₃ has a softness similar to wood (27) (Table S1). The width (Γ) of the Lorentz oscillator line shape used to fit the modes is related to the phonon lifetime, τ = h/Γ. This analysis yields phonon lifetimes between 0.8 and 20 ps. Interestingly, these lifetimes are comparable to the residence time of CH₃NH₃⁺ in different preferred orientations as measured by quasi-elastic neutron scattering (QENS) at room temperature. (22) Combined with the anharmonic phonon modes, these short phonon lifetimes explain the ultralow thermal conductivity, (28) as in related lead chalcogenides. (29, 30)

Figure 2. Measured and calculated dispersion curves. (a) The X, M, and R LA and TA modes and one TO branch measured by HERIX are plotted. The 1σ uncertainty in ζ and phonon energy (by fitting) are generally less than the size of the marker. The lines (sine fits) are only to guide the eye. At the zone edge of M and R, the phonon energy becomes small and overdamped; therefore, we fit to a Lorentzian peak convoluted with the resolution function and centered at ℏω = 0 meV and plot bars with height equal to the half-width at half-maximum of the Lorentzian. (b) Calculated phonon dispersion curves become imaginary along M_TA₁ and R_TA, as expected for a soft mode.

We now turn to first-principles lattice dynamics calculations of the phonon spectrum. The calculated and measured dispersions along the three directions are in good agreement, as evident in Figure 2. The strong softening of the M_TA₁ and R_TA modes is predicted by the athermal harmonic calculations, where the mode frequencies become imaginary at ζ = 0.3, close to where the onset of mode softening is observed in experiment.

The spread (shaded regions in Figure 2b) in the calculated dispersion curves arises from the anisotropy of the molecule, which breaks the degeneracy of the high-symmetry points in the Brillouin zone. This shows very different restoring forces and mode energies calculated depending on the orientation of the ion in the cage, indicating a strong coupling of the CH₃NH₃⁺ dynamics to the cuboctahedral cage in which it resides. The spread, and therefore the coupling, is largest at the zone edge (Figure 2b) where the modes softened to zero frequency and are found to be highly anharmonic.

Considered alongside QENS measurements (22) that indicate a hopping rotational dynamics of the CH₃NH₃⁺, we conclude that the rotational motions of the cation and the cage dynamics are cooperative with important implications discussed below. Octahedral tilting varies the shape of the perovskite A-site cavity in which the CH₃NH₃⁺ ions reside. As the cavity distorts, it elongates along one direction and is shortened in the perpendicular direction (Figure 3a,b). The above analysis suggests that the CH₃NH₃⁺ ions stay aligned within locally distorted A sites and only fluctuate between different local minima of the distorted cavity, cooperatively, on picosecond time scales. On a time scale important for charge carriers (5 fs carrier scattering time (31)) and at solar-relevant temperatures, the crystal structure is effectively frozen in local metastable symmetry-broken domains.

Figure 3. Local symmetry breaking in CH₃NH₃PbI₃ at 350 K. (a,b) Distortions from cubic symmetry generate anisotropic cavities and couple to motion of the CH₃NH₃⁺ ion, which we represent as off-centered and oriented along the long axis of the cavity. (c) DFT-based lattice dynamic calculations show that the energy minimum at the R point at 350 K is displaced in a double-well potential that causes local symmetry breaking. (d) Comparison of the experimental PDF (purple) to cubic (Pm3M), centrosymmetric (I4/*mcm*), and noncentrosymmetric (I4cm) tetragonal models (blue) shows a superior fit for the low-symmetry models at low r (2–8 Å). However, the models perform oppositely at high r with the high-symmetry cubic structure giving the best agreement to the data in the 12–50 Å region. The residuals (orange) are scaled ×3 for clarity.

The computed potential landscapes of the anharmonic modes are indeed displaced minima of shallow double-well potentials (Figures 3c and S3), consistent with our observation of a central peak in the inelastic spectra. This dynamic symmetry breaking (see animations in the Supporting Information and at https://dx.doi.org/10.6084/m9.figshare.3408394) is also evident in room-temperature ab initio molecular dynamics simulations where persistent octahedral tilting away from the high-symmetry cubic orientation is observed. (32)

Further evidence for this hypothesis is provided by X-ray atomic pair-distribution function (PDF) analysis of these materials. We discover that the low-r region (where r is the interatomic distance) of the PDF is better fit by low-symmetry tetragonal models than the cubic one, even at 350 K (Figure 3d), indicating that the local structure is best described by tilted octahedra. The PDF refinement is further improved at low r when Pb is allowed to displace (0.041 Å) from the high-symmetry position (Figure 3d, bottom row). When we zoom out to the high-r region, we discover that a cubic model gives a better fit (Figure 3d, second column), as expected due to averaging over dynamic differently oriented symmetry-broken domains. By performing PDF fits across different refinement ranges (Figure S4), we estimate the domain size to be 1–3 nm in diameter. Given the off-centering of the Pb and the methylammonium, (33, 34) these domains may be polar.

The anharmonic modes indicate an incipient phase transition to the symmetry-broken phases that emerges at lower temperatures but with diffusive (order–disorder) dynamics persisting many tens to hundreds of Kelvin above the transition temperatures. This is further supported by the intensity of the X_TA, M_TA₁, and R_TA zone edge peaks as a function of temperature. As shown in Figure 4, there is no change in the intensity of the zone edge X_TA, but the intensity of the zone edge R_TA intensity diverges sharply through the 330 K phase transition as a Bragg peak of the new tetragonal (I4/mcm) phase grows in. There is little change in the intensity of the zone edge M_TA₁ at this temperature, suggesting that the M_TA₁ mode is related to the lower-temperature phase transition at 160 K, reversing the sequence observed in CsPbCl₃. (17) Although it was not possible to track this peak to 160 K due to the difficulty of aligning a sample with changing lattice constants, this finding is supported by crystallography (14) where a Bragg peak is observed in the low-temperature phase at the pseudocubic M point of the parent structure.

Figure 4. Temperature dependence of inelastic scattering spectra. (a,b) Intensity as a function of temperature is measured at the X, M, and R points (ΔCounts is equal to the intensity of the measured mode at a given temperature less the intensity of the least intense peak in the temperature series). Scattering at the X point has little temperature dependence, while scattering at the M point slightly increases in intensity with decreasing temperature. In contrast, scattering at the R point responds dramatically, increasing sharply upon approaching the phase transition temperature due to the emergence of a Bragg peak in the tetragonal phase. This response indicates that the phase transition is driven by condensation of the R_TA mode at 330 K.

We now explore implications of the discovery of soft anharmonic motion in CH₃NH₃PbI₃. First, the soft anharmonic modes provide a large bath of acoustic phonons that are available for scattering and thermalizng carriers. The population of low-energy phonons may explain the finding that electrical transport in these materials is phonon-limited. (31) In CH₃NH₃PbI₃, the electronic band extrema are in the vicinity of the R point, though made slightly indirect by the Rashba interaction. (35) As well as local intravalley scattering (by acoustic and optical phonons at Γ), there is the possibility of intervalley scattering from phonon modes at the Brillouin zone boundary. These are low in energy with a large occupancy at room temperature, suggesting that intervalley scattering may be significant. In the material GaP, (36) where the band extrema have multiple valleys, intervalley scattering dominates mobility above 200 K.

Second, these anharmonic modes point to a general model of the structural phase sequence in lead halide perovskites. The cubic-to-tetragonal phase transition arises from condensation of the R_TA mode (antisymmetric octahedral tilts, R₄⁺), while the tetragonal-to-orthorhombic phase transition is driven by condensation of the M_TA₁ mode (concerted octahedral tilts, M₃⁺). (8) In cesium lead halides, the order is reversed, (17) likely due to a different coupling mechanism of Cs⁺ to the M₃⁺ and R₄⁺ modes. The M₃⁺ and R₄⁺ distortions may also explain the anomalously large halide atomic displacement parameters seen in structural analyses of many of these materials. (14, 37)

Last, the observation of an instantaneous symmetry-broken local structure caused by the combined effects of octahedral tilting and CH₃NH₃⁺ and Pb off-centering will have implications for the electronic band structure and, therefore, carrier recombination. For example, the presence of a local electric polarization can result in an indirect band gap (24) or spatial separation of the electron and hole, (9, 10, 12) which will reduce carrier recombination and thus benefit photovoltaic performance. The off-centering and orientation of the CH₃NH₃⁺ ions, coupled to the local symmetry-broken state, can support a quasi-static local polarization that persists over a wide temperature range if the CH₃NH₃⁺ ion displacement and orientation correlate between crystallographic unit cells. This polarization may promote the formation of polarons upon photoexcitation, which can protect carriers from recombination. (11)

Experimental Section

Click to copy section linkSection link copied!

Sample Preparation. Single crystals of CH₃NH₃PbI₃ were grown via vapor diffusion, (38) as reported previously. (39) Crystals with original dimensions on the order of 1 mm were polished down to flakes with a thickness of approximately 90 μm, the X-ray attenuation length of CH₃NH₃PbI₃ for an X-ray energy of 23.7 keV. We performed a single-crystal X-ray diffraction experiment to confirm that samples remained single-crystalline after polishing.

Data Collection. Measurements were performed on the high-energy resolution inelastic X-ray (HERIX) scattering instrument at Sector 30-ID of the Advanced Photon Source at Argonne National Laboratory with an incident beam energy of 23.724 keV (λ = 0.5226 Å) and an overall energy resolution of 1.5 meV. (40, 41) Crystals were mounted on a copper rod using epoxy (Figure S1A,B) and placed inside of a beryllium dome. Temperature control was achieved through use of a cryostat. The horizontally polarized incident beam was focused on the sample using a bimorph KB mirror system with a beam size of 15 × 35 μm² (V × H) full width at half-maximum (fwhm) at the scattering location. Energy scans, typically in the ±8 meV range with a 0.5 meV step and a collection time of 30 s per point, were taken at fixed momentum transfers Q = H + q, where H is the reciprocal lattice vector and q is the phonon wave vector. The scattered beam was analyzed by a system of nine, equally spaced, spherically bent Si(12 12 12) analyzers. The standard momentum transfer resolution of the HERIX instrument is 0.066 Å^–1. For the dispersion measurements, we placed a circular slit in front of the analyzer to increase the momentum transfer resolution to 0.020 Å^–1. The basic principles of such instrumentation are discussed elsewhere. (42, 43)

A small elastic component remains at the center at all positions across the zone, coming from static disorder associated with defects in the material. This disorder scattering increases slowly with time in the beam, indicating the presence of beam damage to the sample (Figure S6). The level of the beam damage is small, containing less intensity than the phonon signals, and was mitigated experimentally by frequently moving the beam to a fresh area of the crystal and realigning the sample.

Analysis of Phonon Spectra. The shape of the incident X-ray energy spectrum was fit using a pseudo-Voigt function. This experimental resolution function R(ℏω) was then convolved with both an elastic and an inelastic scattering component to reproduce the entire spectra as in

(1)where the elastic component was given by a delta function centered on the zero point so that the elastic scattering would be given by the resolution function. To model the inelastic scattering component, a single-phonon scattering model was assumed and is defined as the response function for a damped harmonic oscillator, given by

(2)corrected for temperature-dependent occupation of phonon modes and the relationship between energy gain and energy loss processes using a Bose–Einstein distribution adjusted by the detailed balance factor (44)N(ℏω)

(3)Phonon lifetimes were estimated by τ = h/Γ. For the soft zone edge modes centered at ℏω = 0, these are fit with a Lorentzian centered on zero frequency, convoluted with the resolution function, and plotted in Figure 2 with the bars of height equal to the half-width at half-maximum of the Lorentzian.

The respective phonon velocities were extracted from the initial slope of the seven acoustic phonon branches. These phonon velocities were used to extract elastic constants by minimizing the difference between the measured velocities and those predicted by v(C₁₁, C₁₂, C₄₄). The bulk modulus was calculated from the elastic constants as K = (C₁₁ + 2C₁₂)/3.

Pair Distribution Function Data Collection and Analysis. Total scattering PDF measurements were carried out on beamline 28-ID-2 at the National Synchrotron Light Source II (NSLS-II) at Brookhaven National Laboratory. Data were collected in rapid acquisition mode (45) at an X-ray energy of 67.603 keV (λ = 0.18340 Å) and a temperature of 350 K. A large-area 2D PerkinElmer detector (2048 × 2048 pixels and 200 × 200 μm pixel sizes) was mounted orthogonal to the beam path with a sample-to-detector distance of 207.5270 mm. Calibration was performed using FIT2D (46) on a measurement of nickel. The raw 2D intensity was corrected for experimental effects and azimuthally integrated using FIT2D to obtain the 1D scattering intensity versus the magnitude of the scattering momentum transfer Q (Q = 4π sin θ/λ for a scattering angle of 2θ and X-ray wavelength λ). xPDFsuite (47, 48) was used for data reduction and Fourier transformation of the total scattering structure function S(Q) to obtain the PDF, G(R), by

(4)where the integration limits, Q_min–Q_max, were governed by the experimental setup.

PDF refinements were carried out using the program PDFgui, (49) in which PDFs were simulated from model structures using

(5)summed over all atoms in the model with periodic boundary conditions on the unit cell. N is the number of atoms, f_i and f_j are the X-ray atomic form factors of atoms i and j, respectively, and ρ₀ is the average atom pair density. Models were derived from cubic and tetragonal structures of CH₃NH₃PbI₃ determined by neutron powder diffraction. (33) Unit cell parameters, thermal factors, and symmetry-allowed positions were refined to give the best fit to the experimental data. Experimental resolution parameters Q_damp = 0.0434148 and Q_broad = 0.0164506 were determined through refinements of the PDF of the nickel standard.

Materials Modeling. First-principles calclations were carried out using the pseudopotential plane-wave density functional theory (DFT) code, VASP, (50) in conjunction with the Phonopy lattice dynamics package. (51, 52) The calculations are described in detail elsewhere. (25) Projector augmented wave pseudopotentials (53, 54) were used, which included the Pb semicore 5d electrons in the valence region. A 700 eV kinetic energy cutoff was used for the basis set, and a Γ-centered k-point mesh with 6 × 6 × 6 subdivisions was used to sample the electronic Brillouin zone. A tolerance of 10^–8 eV was applied during the electronic minimizations, and the initial structure was optimized to a force tolerance of 10^–3 eV/A. These tight convergence criteria were found to be necessary for accurate lattice dynamics calculations, in particular, to eliminate spurious imaginary modes.

Force constant matrices (FCMs) were calculated from a 2 × 2 × 2 supercell expansion. Harmonic phonon dispersions were computed along the Γ → X, Γ → M, and Γ → R segments of the phonon Brillouin zone, as measured in the HERIX experiments, and the nature of the anharmonic modes at M and R were investigated by visualizing the phonon mode eigenvectors (see the Supporting Information and https://dx.doi.org/10.6084/m9.figshare.3408394 for animations). Images of the cubic nonequilibrium and local instantaneous structures (Figure 3) were generated with VESTA. (55) In our model, the CH₃NH₃⁺ cation is roughly aligned along the Cartesian x direction, between two faces of the cuboctahedral cavity, which was found in previous work to be the energetically preferred configuration. (56) The fixed cation orientation breaks the cubic symmetry, leading to three inequivalent X and M directions, all three of which were analyzed in the simulated dispersions.

Supporting Information

Click to copy section linkSection link copied!

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsenergylett.6b00381.

Figures showing the crystal of CH₃NH₃PbI₃ used for HERIX measurements, HERIX spectra fitting, calculated potential energy surfaces for ion displacement in CH₃NH₃PbI₃ comparison of PDF refinements, HERIX energy scans as a function of temperature, and evidence of sample instability in the X-ray beam as well as a table of extracted elastic constants (PDF)

nz6b00381_si_001.pdf (3.47 MB)

Terms & Conditions

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

Click to copy section linkSection link copied!

Corresponding Author
- Simon J. L. Billinge - Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027, United States; Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, United States; Email: [email protected]
Authors
- Alexander N. Beecher - Department of Chemistry, Columbia University, New York, New York 10027, United States
- Octavi E. Semonin - Department of Chemistry, Columbia University, New York, New York 10027, United States
- Jonathan M. Skelton - Department of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY, United Kingdom
- Jarvist M. Frost - Department of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY, United Kingdom
- Maxwell W. Terban - Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027, United States
- Haowei Zhai - Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027, United States
- Ahmet Alatas - Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, United States
- Jonathan S. Owen - Department of Chemistry, Columbia University, New York, New York 10027, United States
- Aron Walsh - Department of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY, United Kingdom
Author Contributions
A.N.B. and O.E.S. contributed equally to this work.
Notes
The authors declare no competing financial interest.
Supporting research data (animations of the modes in Figure 1 and several others) for this Letter may be accessed at https://dx.doi.org/10.6084/m9.figshare.3408394.

Acknowledgment

Click to copy section linkSection link copied!

Work in the Billinge group was funded by the U.S. National Science Foundation through Grant DMR-1534910. Growth and characterization of single crystals was supported by the Center for Precision Assembly of Superstratic and Superatomic Solids, an NSF MRSEC (Award Number DMR-1420634). This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. X-ray PDF measurements were conducted on beamline 28-ID-2 of the National Synchrotron Light Source II, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory under Contract No. DE-SC0012704. The work at Bath has been supported by the EPSRC (Grant Nos. EP/L000202, EP/M009580/1, EP/K016288/1, and EP/K004956/1), and Federico Brivio is thanked for preliminary phonon calculations. We are grateful to Soham Banerjee for assistance with PDF measurements and to Bogdan M. Leu, Daniel W. Paley, Ayman Said, John Tranquada, and Omer Yaffe for helpful conversations.

Added in Proof

Click to copy section linkSection link copied!

After this article was accepted for publication, the authors discovered another paper that also includes inelastic X-ray scattering data: Comin, R.; Crawford, M. K.; Said, A. H.; Herron, N.; Guise, W. E.; Wang, X.; Whitfield, P. S.; Jain, A.; Gong, X; McGaughey, A. J. H.; Sargent, E. H. Lattice dynamics and the nature of structural transitions in organolead halide perovskites. Phys. Rev. B: Condens. Matter Mater. Phys.2016, 94, 094301.

References

Click to copy section linkSection link copied!

This article references 56 other publications.

1
Choi, J. J.; Yang, X.; Norman, Z. M.; Billinge, S. J. L.; Owen, J. S. Structure of Methylammonium Lead Iodide Within Mesoporous Titanium Dioxide: Active Material in High-Performance Perovskite Solar Cells Nano Lett. 2014, 14, 127– 133 DOI: 10.1021/nl403514x
Google Scholar
1
Structure of Methylammonium Lead Iodide Within Mesoporous Titanium Dioxide: Active Material in High-Performance Perovskite Solar Cells
Choi, Joshua J.; Yang, Xiaohao; Norman, Zachariah M.; Billinge, Simon J. L.; Owen, Jonathan S.
Nano Letters (2014), 14 (1), 127-133CODEN: NALEFD; ISSN:1530-6984. (American Chemical Society)
The authors report the structure of methylammonium Pb-(II) iodide perovskite in mesoporous TiO2, as used in high-performance solar cells. Pair distribution function anal. of x-ray scattering reveals a 2. component nanostructure: one component with medium range cryst. order (30 atom %) and another with only local structural coherence (70 atom %). The nanostructuring correlates with a blueshift of the absorption onset and increases the photoluminescence. The findings underscore the importance of fully characterizing and controlling the structure for improved solar cell efficiency.
2
Walsh, A.; Scanlon, D. O.; Chen, S.; Gong, X. G.; Wei, S.-H. Self-Regulation Mechanism for Charged Point Defects in Hybrid Halide Perovskites Angew. Chem., Int. Ed. 2015, 54, 1791– 1794 DOI: 10.1002/anie.201409740
Google Scholar
2
Self-regulation mechanism for charged point defects in hybrid halide perovskites
Walsh, Aron; Scanlon, David O.; Chen, Shiyou; Gong, X. G.; Wei, Su-Huai
Angewandte Chemie, International Edition (2015), 54 (6), 1791-1794CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
Hybrid halide perovskites such as methylammonium lead iodide (CH3NH3PbI3) exhibit unusually low free-carrier concns. despite being processed at low-temps. from soln. We demonstrate, through quantum mech. calcns., that an origin of this phenomenon is a prevalence of ionic over electronic disorder in stoichiometric materials. Schottky defect formation provides a mechanism to self-regulate the concn. of charge carriers through ionic compensation of charged point defects. The equil. charged vacancy concn. is predicted to exceed 0.4 % at room temp. This behavior, which goes against established defect conventions for inorg. semiconductors, has implications for photovoltaic performance.
3
Poglitsch, A.; Weber, D. Dynamic disorder in methylammoniumtrihalogenoplumbates (II) observed by millimeter-wave spectroscopy J. Chem. Phys. 1987, 87, 6373– 6378 DOI: 10.1063/1.453467
Google Scholar
3
Dynamic disorder in methylammonium trihaloplumbates(II) observed by millimeter-wave spectroscopy
Poglitsch, A.; Weber, D.
Journal of Chemical Physics (1987), 87 (11), 6373-8CODEN: JCPSA6; ISSN:0021-9606.
The temp.-dependent structure of cryst. methylammonium trihaloplumbates(II) CH3NH3+PbX3- (X = Cl, Br, I) as detd. by x-ray diffraction, was compared with measurements of the temp.-dependent complex permittivity at frequencies of 50-150 GHz. The dielec. measurements reveal a ps relaxation process which corresponds to a dynamic disorder of the methylammonium group in the high-temp. phases of the trihaloplumbates.
4
Yaffe, O. The nature of dynamic disorder in lead halide perovskite crystals. arXiv:1604.08107 [cond-mat] 2016.
Google Scholar
There is no corresponding record for this reference.
5
Stranks, S. D.; Snaith, H. J. Metal-halide perovskites for photovoltaic and light-emitting devices Nat. Nanotechnol. 2015, 10, 391– 402 DOI: 10.1038/nnano.2015.90
Google Scholar
5
Metal-halide perovskites for photovoltaic and light-emitting devices
Stranks, Samuel D.; Snaith, Henry J.
Nature Nanotechnology (2015), 10 (5), 391-402CODEN: NNAABX; ISSN:1748-3387. (Nature Publishing Group)
A review. Metal-halide perovskites are cryst. materials originally developed out of scientific curiosity. Unexpectedly, solar cells incorporating these perovskites are rapidly emerging as serious contenders to rival the leading photovoltaic technologies. Power conversion efficiencies have jumped from 3% to over 20% in just four years of academic research. Here, we review the rapid progress in perovskite solar cells, as well as their promising use in light-emitting devices. In particular, we describe the broad tunability and fabrication methods of these materials, the current understanding of the operation of state-of-the-art solar cells and we highlight the properties that have delivered light-emitting diodes and lasers. We discuss key thermal and operational stability challenges facing perovskites, and give an outlook of future research avenues that might bring perovskite technol. to commercialization.
6
Green, M. A.; Emery, K.; Hishikawa, Y.; Warta, W.; Dunlop, E. D. Solar cell efficiency tables (version 47) Prog. Photovoltaics 2016, 24, 3– 11 DOI: 10.1002/pip.2728
Google Scholar
There is no corresponding record for this reference.
7
Glazer, A. M. Simple ways of determining perovskite structures Acta Crystallogr., Sect. A: Cryst. Phys., Diffr., Theor. Gen. Crystallogr. 1975, 31, 756– 762 DOI: 10.1107/S0567739475001635
Google Scholar
There is no corresponding record for this reference.
8
Benedek, N. A.; Fennie, C. J. Why Are There So Few Perovskite Ferroelectrics? J. Phys. Chem. C 2013, 117, 13339– 13349 DOI: 10.1021/jp402046t
Google Scholar
8
Why Are There So Few Perovskite Ferroelectrics?
Benedek, Nicole A.; Fennie, Craig J.
Journal of Physical Chemistry C (2013), 117 (26), 13339-13349CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)
The authors use a combination of symmetry arguments and 1st-principles calcns. to explore the connection between structural distortions and ferroelectricity in the perovskite family of materials. The authors explain the role of octahedral rotations in suppressing ferroelectricity in these materials and show that, as the tolerance factor decreases, rotations alone cannot fully suppress ferroelectricity. The results show that it is cation displacements (hidden in Glazer notation) that accompany the rotations, rather than the rotations themselves, that play the decisive role in suppressing ferroelectricity in these cases. The authors use the knowledge gained in the anal. of this problem to explain the origin of ferroelectricity in R3c materials such as FeTiO3 and ZnSnO3 and to suggest strategies for the design and synthesis of new perovskite ferroelecs. The results have implications not only for the fundamental crystal chem. of the perovskites but also for the discovery of new functional materials.
9
Frost, J. M.; Butler, K. T.; Brivio, F.; Hendon, C. H.; van Schilfgaarde, M.; Walsh, A. Atomistic Origins of High-Performance in Hybrid Halide Perovskite Solar Cells Nano Lett. 2014, 14, 2584– 2590 DOI: 10.1021/nl500390f
Google Scholar
9
Atomistic Origins of High-Performance in Hybrid Halide Perovskite Solar Cells
Frost, Jarvist M.; Butler, Keith T.; Brivio, Federico; Hendon, Christopher H.; van Schilfgaarde, Mark; Walsh, Aron
Nano Letters (2014), 14 (5), 2584-2590CODEN: NALEFD; ISSN:1530-6984. (American Chemical Society)
The performance of organometallic perovskite solar cells has rapidly surpassed that of both conventional dye-sensitized and org. photovoltaics. High-power conversion efficiency can be realized in both mesoporous and thin-film device architectures. The authors address the origin of this success in the context of the materials chem. and physics of the bulk perovskite as described by electronic structure calcns. In addn. to the basic optoelectronic properties essential for an efficient photovoltaic device (spectrally suitable band gap, high optical absorption, low carrier effective masses), the materials are structurally and compositionally flexible. As the authors show, hybrid perovskites exhibit spontaneous elec. polarization; the authors also suggest ways in which this can be tuned through judicious choice of the org. cation. The presence of ferroelec. domains will result in internal junctions that may aid sepn. of photoexcited electron and hole pairs, and redn. of recombination through segregation of charge carriers. The combination of high dielec. const. and low effective mass promotes both Wannier-Mott exciton sepn. and effective ionization of donor and acceptor defects. The photoferroic effect could be exploited in nanostructured films to generate a higher open circuit voltage and may contribute to the current-voltage hysteresis obsd. in perovskite solar cells.
10
Ma, J.; Wang, L.-W. Nanoscale Charge Localization Induced by Random Orientations of Organic Molecules in Hybrid Perovskite CH 3NH 3PbI 3 Nano Lett. 2015, 15, 248– 253 DOI: 10.1021/nl503494y
Google Scholar
There is no corresponding record for this reference.
11
Zhu, X. Y.; Podzorov, V. Charge Carriers in Hybrid Organic-Inorganic Lead Halide Perovskites Might Be Protected as Large Polarons J. Phys. Chem. Lett. 2015, 6, 4758– 4761 DOI: 10.1021/acs.jpclett.5b02462
Google Scholar
11
Charge Carriers in Hybrid Organic-Inorganic Lead Halide Perovskites Might Be Protected as Large Polarons
Zhu, X.-Y.; Podzorov, V.
Journal of Physical Chemistry Letters (2015), 6 (23), 4758-4761CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
Large polaron that provides the protection of charge carrier is explained in terms of carrier diffusion length,electron hole recombination rates, charge carrier and Hall mobility and low carrier scattering rate.
12
Liu, S.; Zheng, F.; Koocher, N. Z.; Takenaka, H.; Wang, F.; Rappe, A. M. Ferroelectric Domain Wall Induced Band Gap Reduction and Charge Separation in Organometal Halide Perovskites J. Phys. Chem. Lett. 2015, 6, 693– 699 DOI: 10.1021/jz502666j
Google Scholar
12
Ferroelectric domain wall induced band gap reduction and charge separation in organometal halide perovskites
Liu, Shi; Zheng, Fan; Koocher, Nathan Z.; Takenaka, Hiroyuki; Wang, Fenggong; Rappe, Andrew M.
Journal of Physical Chemistry Letters (2015), 6 (4), 693-699CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
Organometal halide perovskites have been intensely studied in the past 5 years, inspired by their certified high photovoltaic power conversion efficiency. Some of these materials are room-temp. ferroelecs. The presence of switchable ferroelec. domains in methylammonium lead triiodide, CH3NH3PbI3, has recently been obsd. via piezoresponse force microscopy. Here, we focus on the structural and electronic properties of ferroelec. domain walls in CH3NH3PbX3 (X = Cl, Br, I). We find that organometal halide perovskites can form both charged and uncharged domain walls due to the flexible orientational order of the org. mols. The electronic band gaps for domain structures possessing 180 and 90° walls are estd. with d. functional theory. It is found that the presence of charged domain walls will significantly reduce the band gap by 20-40%, while the presence of uncharged domain walls has no substantial impact on the band gap. We demonstrate that charged domain walls can serve as segregated channels for the motions of charge carriers. These results highlight the importance of ferroelec. domain walls in hybrid perovskites for photovoltaic applications and suggest a possible avenue for device optimization through domain patterning.
13
Stoumpos, C. C.; Malliakas, C. D.; Kanatzidis, M. G. Semiconducting tin and lead iodide perovskites with organic cations: phase transitions, high mobilities, and near-infrared photoluminescent properties Inorg. Chem. 2013, 52, 9019– 9038 DOI: 10.1021/ic401215x
Google Scholar
13
Semiconducting Tin and Lead Iodide Perovskites with Organic Cations: Phase Transitions, High Mobilities, and Near-Infrared Photoluminescent Properties
Stoumpos, Constantinos C.; Malliakas, Christos D.; Kanatzidis, Mercouri G.
Inorganic Chemistry (2013), 52 (15), 9019-9038CODEN: INOCAJ; ISSN:0020-1669. (American Chemical Society)
A broad org.-inorg. series of hybrid metal iodide perovskites AMI3, where A is the methylammonium (MeNH3+) or formamidinium (HC(NH2)2+) cation and M is Sn (1 and 2) or Pb (3 and 4) are reported. The compds. were prepd. through a variety of synthetic approaches, and the nature of the resulting materials is discussed in terms of their thermal stability and optical and electronic properties. The chem. and phys. properties of these materials strongly depend on the prepn. method. Single crystal x-ray diffraction anal. of 1-4 classifies the compds. in the perovskite structural family. Structural phase transitions were obsd. and studied by temp.-dependent single crystal x-ray diffraction in the 100-400 K range. The charge transport properties of the materials are discussed in conjunction with diffuse reflectance studies in the mid-IR region that display characteristic absorption features. Temp.-dependent studies show a strong dependence of the resistivity as a function of the crystal structure. Optical absorption measurements indicate that 1-4 behave as direct-gap semiconductors with energy band gaps distributed at 1.25-1.75 eV. The compds. exhibit an intense near-IR luminescence (PL) emission in the 700-1000 nm range (1.1-1.7 eV) at room temp. Solid solns. between the Sn and Pb compds. are readily accessible throughout the compn. range. The optical properties such as energy band gap, emission intensity, and wavelength can be readily controlled for the isostructural series of solid solns. MeNH3Sn1-xPbxI3 (5). The charge transport type in these materials was characterized by Seebeck coeff. and Hall-effect measurements. The compds. behave as p- or n-type semiconductors depending on the prepn. method. The samples with the lowest carrier concn. are prepd. from soln. and are n-type; p-type samples can be obtained through solid state reactions exposed in air in a controllable manner. In the case of Sn compds., there is a facile tendency toward oxidn. which causes the materials to be doped with Sn4+ and thus behave as p-type semiconductors displaying metal-like cond. The compds. appear to possess very high estd. electron and hole mobilities that exceed 2000 cm2/(V s) and 300 cm2/(V s), resp., as shown in the case of MeNH3SnI3 (1). The authors also compare the properties of the title hybrid materials with those of the all-inorg. CsSnI3 and CsPbI3 prepd. using identical synthetic methods.
14
Baikie, T.; Barrow, N. S.; Fang, Y.; Keenan, P. J.; Slater, P. R.; Piltz, R. O.; Gutmann, M.; Mhaisalkar, S. G.; White, T. J. A combined single crystal neutron/X-ray diffraction and solid-state nuclear magnetic resonance study of the hybrid perovskites CH 3NH 3PbX 3(X = I, Br and Cl) J. Mater. Chem. A 2015, 3, 9298– 9307 DOI: 10.1039/C5TA01125F
Google Scholar
14
A combined single crystal neutron/X-ray diffraction and solid-state nuclear magnetic resonance study of the hybrid perovskites CH3NH3PbX3 (X = I, Br and Cl)
Baikie, Tom; Barrow, Nathan S.; Fang, Yanan; Keenan, Philip J.; Slater, Peter R.; Piltz, Ross O.; Gutmann, Matthias; Mhaisalkar, Subodh G.; White, Tim J.
Journal of Materials Chemistry A: Materials for Energy and Sustainability (2015), 3 (17), 9298-9307CODEN: JMCAET; ISSN:2050-7496. (Royal Society of Chemistry)
The 1H and 13C NMR spectra in methylammonium lead halide perovskites, CH3NH3PbX3 (X = I, Br and Cl) show that the CH3NH3+ units undergo dynamic reorientation, as the org. component tumbles in the perovskite cage. In addn., the differences in the anomalously long relaxation times of the protons assocd. with the CH3 and not the NH3 groups indicate that only the amine end of the CH3NH3+ group is interacting with the inorg. network. Using this information, we have refined some single crystal X-ray and neutron diffraction data to probe their unusual structures in more detail. Furthermore, impedance spectroscopy has been used to monitor the high-temp. phase transition of CH3NH3PbI3, which confirms a significant increase in cond., when it is in its high temp. and higher symmetry structural regime. The optical band-gaps of each halide perovskite were detd. using UV-visible spectroscopy and are consistent with previous reports.
15
Stroppa, A.; Quarti, C.; De Angelis, F.; Picozzi, S. Ferroelectric Polarization of CH3NH3PbI3: A Detailed Study Based on Density Functional Theory and Symmetry Mode Analysis J. Phys. Chem. Lett. 2015, 6, 2223– 2231 DOI: 10.1021/acs.jpclett.5b00542
Google Scholar
15
Ferroelectric Polarization of CH3NH3PbI3: A Detailed Study Based on Density Functional Theory and Symmetry Mode Analysis
Stroppa, Alessandro; Quarti, Claudio; De Angelis, Filippo; Picozzi, Silvia
Journal of Physical Chemistry Letters (2015), 6 (12), 2223-2231CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
Ferroelectricity in halide perovskites currently represents a crucial issue, as it may have an important role for the enhancement of solar cells efficiency. Simulations of ferroelec. properties based on d. functional theory are conceptually more demanding compared with conventional inorg. ferroelecs. due to the presence of both org. and inorg. components in the same compd. Here the authors present a detailed study focused on the prototypical CH3NH3PbI3 perovskite. By using d. functional theory combined with symmetry mode anal., the authors disentangle the contributions of the methylammonium cations and the role of the inorg. framework, therefore suggesting possible routes to enhance the polarization in this compd. The authors' est. of the polarization for the tetragonal phase at low temp. is ∼4.42 μC/cm2, which is substantially lower than that of traditional perovskite oxides.
16
Beilsten-Edmands, J.; Eperon, G. E.; Johnson, R. D.; Snaith, H. J.; Radaelli, P. G. Non-ferroelectric nature of the conductance hysteresis in CH3NH3PbI3 perovskite-based photovoltaic devices Appl. Phys. Lett. 2015, 106, 173502 DOI: 10.1063/1.4919109
Google Scholar
16
Non-ferroelectric nature of the conductance hysteresis in CH3NH3PbI3 perovskite-based photovoltaic devices
Beilsten-Edmands, J.; Eperon, G. E.; Johnson, R. D.; Snaith, H. J.; Radaelli, P. G.
Applied Physics Letters (2015), 106 (17), 173502/1-173502/5CODEN: APPLAB; ISSN:0003-6951. (American Institute of Physics)
We present measurements of conductance hysteresis on CH3NH3PbI3 perovskite thin films, performed using the double-wave method, in order to investigate the possibility of a ferroelec. response. A strong frequency dependence of the hysteresis is obsd. in the range of 0.1-150 Hz, with a hysteretic charge d. in excess of 1000 μC cm-2 at frequencies below 0.4 Hz, a behavior uncharacteristic of a ferroelec. response. We show that the obsd. hysteretic conductance, as well as the presence of a double arc in the impedance spectroscopy, can be fully explained by the migration of mobile ions under bias on a timescale of seconds. Our measurements place an upper limit of ≈ 1 μC cm-2 on any intrinsic frequency-independent polarization, ruling out ferroelectricity as the main cause of current-voltage hysteresis and providing further evidence of the importance of ionic migration in modifying the efficiency of CH3NH3PbI3 devices. (c) 2015 American Institute of Physics.
17
Fujii, Y.; Hoshino, S.; Yamada, Y.; Shirane, G. Neutron-scattering study on phase transitions of CsPb Cl3 Phys. Rev. B 1974, 9, 4549– 4559 DOI: 10.1103/PhysRevB.9.4549
Google Scholar
There is no corresponding record for this reference.
18
Swainson, I. P.; Hammond, R. P.; Soullière, C.; Knop, O.; Massa, W. Phase transitions in the perovskite methylammonium lead bromide, CH3ND3PbBr3 J. Solid State Chem. 2003, 176, 97– 104 DOI: 10.1016/S0022-4596(03)00352-9
Google Scholar
18
Phase transitions in the perovskite methylammonium lead bromide, CH3ND3PbBr3
Swainson, I. P.; Hammond, R. P.; Soulliere, C.; Knop, O.; Massa, W.
Journal of Solid State Chemistry (2003), 176 (1), 97-104CODEN: JSSCBI; ISSN:0022-4596. (Elsevier Science)
The structure of phase IV of methylammonium lead bromide, CH3ND3PbBr3, is shown from Rietveld refinement of neutron powder diffraction data to be centrosym., with space group Pnma: Z = 4; a 7.9434(4), b 11.8499(5), c 8.5918(4) Å at 11 K; Rwp = 2.34% Rp = 1.81%. This corresponds to one of the pure tilt transitions, a-b+a-, commonly obsd. in perovskites. Addnl. distortions not required by pure tilting are found in the PbBr6 octahedra, and apparently the structure optimizes the H bonding between the methylammonium cation and the framework. It is likely that the lowest temp. phase of the corresponding iodide also has this structure. The structure is compared to the available data for that of other Pnma perovskites. A brief comparison to the higher temp. phases in which the methylammonium ion is disordered is given.
19
Chi, L.; Swainson, I.; Cranswick, L.; Her, J.-H.; Stephens, P.; Knop, O. The ordered phase of methylammonium lead chloride CH3ND3PbCl3 J. Solid State Chem. 2005, 178, 1376– 1385 DOI: 10.1016/j.jssc.2004.12.037
Google Scholar
19
The ordered phase of methylammonium lead chloride CH3ND3PbCl3
Chi, Lisheng; Swainson, Ian; Cranswick, Lachlan; Her, Jae-Hyuk; Stephens, Peter; Knop, Osvald
Journal of Solid State Chemistry (2005), 178 (5), 1376-1385CODEN: JSSCBI; ISSN:0022-4596. (Elsevier)
The perovskite-structured compd. methylammonium lead chloride orders into a low-temp. phase of space group Pnma, in which at 80 K each of the orthorhombic axes a 11.1747(2), b 11.3552(1) and c 11.2820(1) Å is doubled with respect to the room temp. disordered cubic phase (a 5.669 Å). Crystallog. data and at. coordinates are given. The structure was solved by ab initio methods using the programs EXPO and FOX. This unusual cell basis for space group Pnma is not that of a std. tilt system. This phase, in which the methylammonium ions, are ordered shows distorted octahedra. The octahedra possess a bond angle variance of 60.663°2 and a quadratic elongation of 1.018, and are more distorted than those in the ordered phase of methylammonium lead bromide. There is also an alternating long and short Pb-Cl bond along a, due to an off-center displacement of Pb within the octahedron. Probably the most rigid unit is actually the methylammonium cation, rather than the PbCl6 octahedra, in agreement with existing spectroscopic data.
20
Swainson, I. P.; Stock, C.; Parker, S. F.; Van Eijck, L.; Russina, M.; Taylor, J. W. From soft harmonic phonons to fast relaxational dynamics in CH3NH3PbBr3 Phys. Rev. B: Condens. Matter Mater. Phys. 2015, 92, 100303 DOI: 10.1103/PhysRevB.92.100303
Google Scholar
20
From soft harmonic phonons to fast relaxational dynamics in CH3NH3PbBr3
Swainson, I. P.; Stock, C.; Parker, S. F.; Van Eijck, L.; Russina, M.; Taylor, J. W.
Physical Review B: Condensed Matter and Materials Physics (2015), 92 (10), 100303/1-100303/5CODEN: PRBMDO; ISSN:1098-0121. (American Physical Society)
The lead-halide perovskites, including CH3NH3PbBr3, are components in cost effective, highly efficient photovoltaics, where the interactions of the mol. cations with the inorg. framework are suggested to influence the electronic and ferroelec. properties. CH3NH3PbBr3 undergoes a series of structural transitions assocd. with orientational order of the CH3NH3 (methylammonium) mol. cation and tilting of the PbBr3 host framework. We apply high-resoln. neutron scattering to study the soft harmonic phonons assocd. with these transitions, and find a strong coupling between the PbBr3 framework and the quasistatic CH3NH3 dynamics at low energy transfers. At higher energy transfers, we observe a PbBr6 octahedra soft mode driving a transition at 150 K from bound mol. excitations at low temps. to relatively fast relaxational excitations that extend up to ∼50-100 meV. We suggest that these temporally overdamped dynamics enables possible indirect band gap processes in these materials that are related to the enhanced photovoltaic properties.
21
Wasylishen, R. E.; Knop, O.; Macdonald, J. B. Cation rotation in methylammonium lead halides Solid State Commun. 1985, 56, 581– 582 DOI: 10.1016/0038-1098(85)90959-7
Google Scholar
21
Cation rotation in methylammonium lead halides
Wasylishen, R. E.; Knop, Osvald; Macdonald, J. B.
Solid State Communications (1985), 56 (7), 581-2CODEN: SSCOA4; ISSN:0038-1098.
2H and 14N NMR spectra of the simple perovskites MeNH3PbX3 (X = Cl, Br, I) reveal the existence of several phases. In the high-temp. phase I the long spin-lattice relaxation times T1 of both nuclei and the absence of quadrupole splitting indicate extremely rapid overall reorientation of the C-N axis of the cation in a potential of cubic symmetry. In phase II of the bromide and iodide, both T1 and the small quadrupole splitting show unusual variation with temp. In the lowest-temp. phase, rotations of the C-N axis are restricted.
22
Leguy, A. M. A.; Frost, J. M.; McMahon, A. P.; Sakai, V. G.; Kochelmann, W.; Law, C.; Li, X.; Foglia, F.; Walsh, A.; O’Regan, B. C.; Nelson, J.; Cabral, J. T.; Barnes, P. R. F. The dynamics of methylammonium ions in hybrid organic-inorganic perovskite solar cells Nat. Commun. 2015, 6, 7124 DOI: 10.1038/ncomms8124
Google Scholar
22
The dynamics of methylammonium ions in hybrid organic-inorganic perovskite solar cells
Leguy Aurelien M A; McMahon Andrew P; Nelson Jenny; Barnes Piers R F; Frost Jarvist Moore; Walsh Aron; Sakai Victoria Garcia; Kochelmann W; Law ChunHung; Li Xiaoe; O'Regan Brian C; Foglia Fabrizia; Cabral Joao T
Nature communications (2015), 6 (), 7124 ISSN:.
Methylammonium lead iodide perovskite can make high-efficiency solar cells, which also show an unexplained photocurrent hysteresis dependent on the device-poling history. Here we report quasielastic neutron scattering measurements showing that dipolar CH3NH3(+) ions reorientate between the faces, corners or edges of the pseudo-cubic lattice cages in CH3NH3PbI3 crystals with a room temperature residence time of ∼14 ps. Free rotation, π-flips and ionic diffusion are ruled out within a 1-200-ps time window. Monte Carlo simulations of interacting CH3NH3(+) dipoles realigning within a 3D lattice suggest that the scattering measurements may be explained by the stabilization of CH3NH3(+) in either antiferroelectric or ferroelectric domains. Collective realignment of CH3NH3(+) to screen a device's built-in potential could reduce photovoltaic performance. However, we estimate the timescale for a domain wall to traverse a typical device to be ∼0.1-1 ms, faster than most observed hysteresis.
23
Chen, T.; Foley, B. J.; Ipek, B.; Tyagi, M.; Copley, J. R. D.; Brown, C. M.; Choi, J. J.; Lee, S.-H. Rotational dynamics of organic cations in the CH 3 NH 3 PbI 3 perovskite Phys. Chem. Chem. Phys. 2015, 17, 31278– 31286 DOI: 10.1039/C5CP05348J
Google Scholar
There is no corresponding record for this reference.
24
Quarti, C.; Mosconi, E.; De Angelis, F. Interplay of Orientational Order and Electronic Structure in Methylammonium Lead Iodide: Implications for Solar Cell Operation Chem. Mater. 2014, 26, 6557– 6569 DOI: 10.1021/cm5032046
Google Scholar
24
Interplay of Orientational Order and Electronic Structure in Methylammonium Lead Iodide: Implications for Solar Cell
Quarti, Claudio; Mosconi, Edoardo; De Angelis, Filippo
Chemistry of Materials (2014), 26 (22), 6557-6569CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)
The ab initio electronic structure and Car-Parrinello mol. dynamics simulations are reported for several structural models of the prototype MAPbI3 perovskite for solar cells applications. Both configurations having a preferred orientation are considered of the MA cations, giving rise to a net dipole alignment, and configurations with an isotropic distribution of the MA cations, resp. representative of polar (ferroelec.) and apolar (antiferroelec.) structures. The calcns. demonstrate the preferred stability of a set of polar structures over apolar ones, with an energy difference within 0.1 eV and a conversion barrier within 0.2 eV per unit cell (four MAPbI3), thus possibly accessible at room temp. Ferroelec.-like orientations lead to a quasi I4cm structure for the inorg. component, characterized by lack of inversion symmetry, while the antiferroelec.-like orientations are assocd. to a quasi I4/mcm structure. Ab initio mol. dynamics simulations on the polar structures show no mol. rotations in the investigated time-scale, while several MA rotations are obsd. in the same time scale for the considered apolar structure, which is thus characterized by a higher disorder. The I4cm and I4/mcm types of structure have markedly different band structures, despite showing a relatively small band gap variation. Simulations carried out on finite surface slabs demonstrate that a net orientation of the MA cations gives rise to a strong bending in the valence and conduction bands, which could definitely assist charge sepn. and reduce carrier recombination, provided one is able to effectively stabilize polar compared to apolar structures. The results could contribute an important step toward an in-depth comprehension of the basic properties of organohalide perovskites, assisting a further optimization of their photovoltaic response.
25
Brivio, F.; Frost, J. M.; Skelton, J. M.; Jackson, A. J.; Weber, O. J.; Weller, M. T.; Goñi, A. R.; Leguy, A. M. A.; Barnes, P. R. F.; Walsh, A. Lattice dynamics and vibrational spectra of the orthorhombic, tetragonal, and cubic phases of methylammonium lead iodide Phys. Rev. B: Condens. Matter Mater. Phys. 2015, 92, 144308 DOI: 10.1103/PhysRevB.92.144308
Google Scholar
25
Lattice dynamics and vibrational spectra of the orthorhombic, tetragonal, and cubic phases of methylammonium lead iodide
Brivio, Federico; Frost, Jarvist M.; Skelton, Jonathan M.; Jackson, Adam J.; Weber, Oliver J.; Weller, Mark T.; Goni, Alejandro R.; Leguy, Aurelien M. A.; Barnes, Piers R. F.; Walsh, Aron
Physical Review B: Condensed Matter and Materials Physics (2015), 92 (14), 144308/1-144308/8CODEN: PRBMDO; ISSN:1098-0121. (American Physical Society)
The hybrid halide perovskite CH3NH3PbI3 exhibits a complex structural behavior, with successive transitions between orthorhombic, tetragonal, and cubic polymorphs around 165 and 327 K. Herein we report first-principles lattice dynamics (phonon spectrum) for each phase of CH3NH3PbI3. The equil. structures compare well to solns. of temp.-dependent powder neutron diffraction. By following the normal modes, we calc. IR and Raman intensities of the vibrations, and compare them to the measurement of a single crystal where the Raman laser is controlled to avoid degrdn. of the sample. Despite a clear sepn. in energy between low-frequency modes assocd. with the inorg. (PbI3-)n network and high-frequency modes of the org. CH3NH3+ cation, significant coupling between them is found, which emphasizes the interplay between mol. orientation and the corner-sharing octahedral networks in the structural transformations. Soft modes are found at the boundary of the Brillouin zone of the cubic phase, consistent with displacive instabilities and anharmonicity involving tilting of the PbI6 octahedra around room temp.
26
Quarti, C.; Mosconi, E.; Ball, J. M.; D’Innocenzo, V.; Tao, C.; Pathak, S.; Snaith, H. J.; Petrozza, A.; De Angelis, F. Structural and optical properties of methylammonium lead iodide across the tetragonal to cubic phase transition: implications for perovskite solar cells Energy Environ. Sci. 2016, 9, 155– 163 DOI: 10.1039/C5EE02925B
Google Scholar
26
Structural and optical properties of methylammonium lead iodide across the tetragonal to cubic phase transition: implications for perovskite solar cells
Quarti, Claudio; Mosconi, Edoardo; Ball, James M.; D'Innocenzo, Valerio; Tao, Chen; Pathak, Sandeep; Snaith, Henry J.; Petrozza, Annamaria; De Angelis, Filippo
Energy & Environmental Science (2016), 9 (1), 155-163CODEN: EESNBY; ISSN:1754-5706. (Royal Society of Chemistry)
We report temp. resolved UV-vis absorption and spectral photocurrent response measurements of MAPbI3 thin films and solar cells, together with ab initio simulations, to investigate the changes in material properties occurring across the tetragonal to cubic phase transition. We find that the MAPbI3 band-gap does not abruptly change when exceeding the tetragonal to cubic transition temp., but it rather monotonically blue-shifts following the same temp. evolution obsd. within the tetragonal phase. Car-Parrinello mol. dynamics simulations demonstrate that the high temp. phase corresponds on av. to the expected sym. cubic structure assigned from XRD measurements, but that the system strongly deviates from such a structure in the sub-picosecond time scale. Thus, on the time scale of electronic transitions, the material seldom experiences a cubic environment, rather an increasingly distorted tetragonal one. This result explains the absence of dramatic changes in the optical of MAPbI3 across the explored temp. range of 270-420 K, which could have important consequences for the practical uptake of perovskite solar cells.
27
Gindl, W.; Gupta, H. S. Cell-wall hardness and Young’s modulus of melamine-modified spruce wood by nano-indentation Composites, Part A 2002, 33, 1141– 1145 DOI: 10.1016/S1359-835X(02)00080-5
Google Scholar
27
Cell-wall hardness and Young's modulus of melamine-modified spruce wood by nano-indentation
Gindl, W.; Gupta, H. S.
Composites, Part A: Applied Science and Manufacturing (2002), 33A (8), 1141-1145CODEN: CASMFJ; ISSN:1359-835X. (Elsevier Science Ltd.)
Samples of spruce wood were infiltrated with a melamine-HCHO resin. After curing of the resin, a melamine concn. of 24% (vol./vol.) was measured in the secondary cell walls of melamine resin-treated wood. Nano-indentation tests revealed an av. Young's modulus of 16.1 GPa and a hardness of 0.24 GPa for untreated secondary cell walls. In the melamine resin-treated cell walls, an increase in the Young's modulus of 33% to 21.4 GPa was obsd. With 115%, i.e. 0.52 GPa, the increase in longitudinal hardness because of melamine-HCHO resin treatment was even more pronounced. This proves clearly that melamine resin treatment of wood improves mech. properties of cell walls. Thus, treatment of wood with melamine-HCHO resin shows a considerable potential to improve mech. properties, as desired for applications where large stresses normal to grain arise.
28
Pisoni, A.; Jaćimović, J.; Barišić, O. S.; Spina, M.; Gaal, R.; Forró, L.; Horváth, E. Ultra-Low Thermal Conductivity in Organic-Inorganic Hybrid Perovskite CH 3NH 3PbI 3 J. Phys. Chem. Lett. 2014, 5, 2488– 2492 DOI: 10.1021/jz5012109
Google Scholar
28
Ultra-Low Thermal Conductivity in Organic-Inorganic Hybrid Perovskite CH3NH3PbI3
Pisoni, Andrea; Jacimovic, Jacim; Barisic, Osor S.; Spina, Massimo; Gaal, Richard; Forro, Laszlo; Horvath, Endre
Journal of Physical Chemistry Letters (2014), 5 (14), 2488-2492CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
The authors report on the temp. dependence of thermal cond. of single cryst. and polycryst. organometallic perovskite CH3NH3PbI3. The comparable abs. values and temp. dependence of the two samples' morphologies indicate the minor role of the grain boundaries on the heat transport. Theor. modeling demonstrates the importance of the resonant scattering in both specimens. The interaction between phonon waves and rotational degrees of freedom of CH3NH3+ sublattice emerges as the dominant mechanism for attenuation of heat transport and for ultralow thermal cond. of 0.5 W/(Km) at room temp.
29
Delaire, O.; Ma, J.; Marty, K.; May, A. F.; McGuire, M. A.; Du, M.-H.; Singh, D. J.; Podlesnyak, A.; Ehlers, G.; Lumsden, M. D.; Sales, B. C. Giant anharmonic phonon scattering in PbTe Nat. Mater. 2011, 10, 614– 619 DOI: 10.1038/nmat3035
Google Scholar
29
Giant anharmonic phonon scattering in PbTe
Delaire, O.; Ma, J.; Marty, K.; May, A. F.; McGuire, M. A.; Du, M-H.; Singh, D. J.; Podlesnyak, A.; Ehlers, G.; Lumsden, M. D.; Sales, B. C.
Nature Materials (2011), 10 (8), 614-619CODEN: NMAACR; ISSN:1476-1122. (Nature Publishing Group)
Understanding the microscopic processes affecting the bulk thermal cond. is crucial to develop more efficient thermoelec. materials. PbTe is currently one of the leading thermoelec. materials, largely thanks to its low thermal cond. However, the origin of this low thermal cond. in a simple rocksalt structure has so far been elusive. Using a combination of inelastic neutron scattering measurements and first-principles computations of the phonons, we identify a strong anharmonic coupling between the ferroelec. transverse optic mode and the longitudinal acoustic modes in PbTe. This interaction extends over a large portion of reciprocal space, and directly affects the heat-carrying longitudinal acoustic phonons. The longitudinal acoustic-transverse optic anharmonic coupling is likely to play a central role in explaining the low thermal cond. of PbTe. The present results provide a microscopic picture of why many good thermoelec. materials are found near a lattice instability of the ferroelec. type.
30
Li, C. W.; Hong, J.; May, A. F.; Bansal, D.; Chi, S.; Hong, T.; Ehlers, G.; Delaire, O. Orbitally driven giant phonon anharmonicity in SnSe Nat. Phys. 2015, 11, 1063– 1069 DOI: 10.1038/nphys3492
Google Scholar
30
Orbitally driven giant phonon anharmonicity in SnSe
Li, C. W.; Hong, J.; May, A. F.; Bansal, D.; Chi, S.; Hong, T.; Ehlers, G.; Delaire, O.
Nature Physics (2015), 11 (12), 1063-1069CODEN: NPAHAX; ISSN:1745-2473. (Nature Publishing Group)
Understanding elementary excitations and their couplings in condensed matter systems is crit. for developing better energy-conversion devices. In thermoelec. materials, the heat-to-electricity conversion efficiency is directly improved by suppressing the propagation of phonon quasiparticles responsible for macroscopic thermal transport. The current record material for thermoelec. conversion efficiency, SnSe, has an ultralow thermal cond., but the mechanism behind the strong phonon scattering remains largely unknown. From inelastic neutron scattering measurements and first-principles simulations, we mapped the four-dimensional phonon dispersion surfaces of SnSe, and found the origin of the ionic-potential anharmonicity responsible for the unique properties of SnSe. We show that the giant phonon scattering arises from an unstable electronic structure, with orbital interactions leading to a ferroelec.-like lattice instability. The present results provide a microscopic picture connecting electronic structure and phonon anharmonicity in SnSe, and offers new insights on how electron-phonon and phonon-phonon interactions may lead to the realization of ultralow thermal cond.
31
Karakus, M.; Jensen, S. A.; D’Angelo, F.; Turchinovich, D.; Bonn, M.; Cánovas, E. Phonon-Electron Scattering Limits Free Charge Mobility in Methylammonium Lead Iodide Perovskites J. Phys. Chem. Lett. 2015, 6, 4991– 4996 DOI: 10.1021/acs.jpclett.5b02485
Google Scholar
31
Phonon-Electron Scattering Limits Free Charge Mobility in Methylammonium Lead Iodide Perovskites
Karakus, Melike; Jensen, Soeren A.; D'Angelo, Francesco; Turchinovich, Dmitry; Bonn, Mischa; Canovas, Enrique
Journal of Physical Chemistry Letters (2015), 6 (24), 4991-4996CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
The nature of the photocond. in soln.-processed films of methylammonium lead iodide perovskite was studied by detg. the variation of the photoconductive response with temp. Ultrabroadband terahertz (THz) photocond. spectra in the 0.3-10 THz range can be reproduced well by a simple Drude-like response at room temp., where free charge carrier motion was characterized by an av. scattering time. The scattering time detd. from Drude fits in the 0.3-2THz region increases from ∼4 fs at 300 K (tetragonal phase; mobility of ∼27 cm2 V-1 s-1) to almost ∼25 fs at 77 K (orthorhombic phase, mobility of ∼150 cm2 V-1 s-1). For the tetragonal phase (temp. range 150 < T < 300 K) the scattering time shows a approx. T-3/2 dependence, approaching the theor. limit for pure acoustic phonon (deformation potential) scattering. Hence, electron-phonon, rather than impurity scattering, sets the upper limit on free charge transport for this perovskite.
32
Frost, J. M.; Walsh, A. What Is Moving in Hybrid Halide Perovskite Solar Cells? Acc. Chem. Res. 2016, 49, 528– 535 DOI: 10.1021/acs.accounts.5b00431
Google Scholar
32
What Is Moving in Hybrid Halide Perovskite Solar Cells?
Frost, Jarvist M.; Walsh, Aron
Accounts of Chemical Research (2016), 49 (3), 528-535CODEN: ACHRE4; ISSN:0001-4842. (American Chemical Society)
Org.-inorg. semiconductors, which adopt the perovskite crystal structure, have perturbed the landscape of contemporary photovoltaics research. High-efficiency solar cells can be produced with soln.-processed active layers. The materials are earth abundant, and the simple processing required suggests that high-throughput and low-cost manuf. at scale should be possible.While these materials bear considerable similarity to traditional inorg. semiconductors, there are notable differences in their optoelectronic behavior. A key distinction of these materials is that they are phys. soft, leading to considerable thermally activated motion.In this Account, we discuss the internal motion of methylammonium lead iodide (CH3NH3PbI3) and formamidinium lead iodide ([CH(NH2)2]PbI3), covering: (i) mol. rotation-libration in the cuboctahedral cavity; (ii) drift and diffusion of large electron and hole polarons; (iii) transport of charged ionic defects. These processes give rise to a range of properties that are unconventional for photovoltaic materials, including frequency-dependent permittivity, low electron-hole recombination rates, and current-voltage hysteresis. Multiscale simulations, drawing from electronic structure, ab initio mol. dynamic and Monte Carlo computational techniques, have been combined with neutron diffraction measurements, quasi-elastic neutron scattering, and ultrafast vibrational spectroscopy to qualify the nature and time scales of the motions. Electron and hole motion occurs on a femtosecond time scale. Mol. libration is a sub-picosecond process. Mol. rotations occur with a time const. of several picoseconds depending on the cation. Recent exptl. evidence and theor. models for simultaneous electron and ion transport in these materials has been presented, suggesting they are mixed-mode conductors with similarities to fast-ion conducting metal oxide perovskites developed for battery and fuel cell applications. We expound on the implications of these effects for the photovoltaic action.The temporal behavior displayed by hybrid perovskites introduces a sensitivity in materials characterization to the time and length scale of the measurement, as well as the history of each sample. It also poses significant challenges for accurate materials modeling and device simulations. There are large differences between the av. and local crystal structures, and the nature of charge transport is too complex to be described by common one-dimensional drift-diffusion models. Herein, we critically discuss the atomistic origin of the dynamic processes and the assocd. chem. disorder intrinsic to cryst. hybrid perovskite semiconductors.
33
Weller, M. T.; Weber, O. J.; Henry, P. F.; Di Pumpo, A. M.; Hansen, T. C. Complete structure and cation orientation in the perovskite photovoltaic methylammonium lead iodide between 100 and 352 K Chem. Commun. 2015, 51, 4180– 4183 DOI: 10.1039/C4CC09944C
Google Scholar
33
Complete structure and cation orientation in the perovskite photovoltaic methylammonium lead iodide between 100 and 352 K
Weller, Mark T.; Weber, Oliver J.; Henry, Paul F.; Di Pumpo, Antonietta M.; Hansen, Thomas C.
Chemical Communications (Cambridge, United Kingdom) (2015), 51 (20), 4180-4183CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)
The methylammonium cation in [CH3NH3]PbI3 demonstrates increasing positional disorder on heating from 100 K to 352 K. In the tetragonal phase, stable between 165 K and 327 K, the cation is disordered over four sites directed toward the faces of the distorted cubic [PbI3]- framework and migrates towards the cavity center with increasing temp. Crystallog. data and at. coordinates are given.
34
Ren, Y.; Oswald, I. W. H.; Wang, X.; McCandless, G. T.; Chan, J. Y. Orientation of Organic Cations in Hybrid Inorganic-Organic Perovskite CH₃NH₃PbI₃ from Subatomic Resolution Single Crystal Neutron Diffraction Structural Studies Cryst. Growth Des. 2016, 16, 2945– 2951 DOI: 10.1021/acs.cgd.6b00297
Google Scholar
34
Orientation of Organic Cations in Hybrid Inorganic-Organic Perovskite CH3NH3PbI3 from Subatomic Resolution Single Crystal Neutron Diffraction Structural Studies
Ren, Yixin; Oswald, Iain W. H.; Wang, Xiaoping; McCandless, Gregory T.; Chan, Julia Y.
Crystal Growth & Design (2016), 16 (5), 2945-2951CODEN: CGDEFU; ISSN:1528-7483. (American Chemical Society)
The authors report the crystal growth of well-faceted single crystals of methylammonium lead iodide, MeNH3PbI3, and detailed single crystal neutron diffraction structural studies aimed at elucidating the orientation of the methylammonium (MeNH3+) cation in the tetragonal and cubic phases of the hybrid inorg.-org. perovskite. Room temp. expts. reveal a tetragonal structure where the protonated amine substituent (-NH3+) of the cation is disordered in 4 positions, each preferentially located near the neighboring I of the [PbI6] octahedra, while the Me substituent (-Me) is disordered in 8 positions located near the body position of the unit cell. High temp. expts. show a cubic structure where the cation aligns along the [011] (edge), the [111] (diagonal), and the [100] (face) directions of the unit cell. The resulting site occupancy ratio suggests the MeNH3+ cation resides primarily along the [011] direction, in agreement with reported DFT calcns. One important feature that was obsd. for both tetragonal and cubic structures measured at 295 and 350 K, resp., is the middle point of the C-N bond being located off-center from the high symmetry sites in the crystal structure, induced by the formation of H bond-like interactions between the -NH3+ substituent of the org. cation and the I atoms of [PbI6] octahedra.
35
Brivio, F.; Butler, K. T.; Walsh, A.; van Schilfgaarde, M. Relativistic quasiparticle self-consistent electronic structure of hybrid halide perovskite photovoltaic absorbers Phys. Rev. B: Condens. Matter Mater. Phys. 2014, 89, 155204 DOI: 10.1103/PhysRevB.89.155204
Google Scholar
35
Relativistic quasiparticle self-consistent electronic structure of hybrid halide perovskite photovoltaic absorbers
Brivio, Federico; Butler, Keith T.; Walsh, Aron; van Schilfgaarde, Mark
Physical Review B: Condensed Matter and Materials Physics (2014), 89 (15), 155204/1-155204/6CODEN: PRBMDO; ISSN:1098-0121. (American Physical Society)
Solar cells based on a light absorbing layer of the organometal halide perovskite CH3NH3PbI3 have recently surpassed 15% conversion efficiency, though how these materials work remains largely unknown. We analyze the electronic structure and optical properties within the quasiparticle self-consistent GW approxn. While this compd. bears some similarity to conventional sp semiconductors, it also displays unique features. Quasiparticle self-consistency is essential for an accurate description of the band structure: Band gaps are much larger than what is predicted by the local-d. approxn. (LDA) or GW based on the LDA. Valence band dispersions are modified in a very unusual manner. In addn., spin-orbit coupling strongly modifies the band structure and gives rise to unconventional dispersion relations and a Dresselhaus splitting at the band edges. The av. hole mass is small, which partially accounts for the long diffusion lengths obsd. The surface ionization potential (work function) is calcd. to be 5.7 eV with respect to the vacuum level, explaining efficient carrier transfer to TiO2 and Au elec. contacts.
36
Kocsis, S. Lattice scattering mobility of electrons in GaP Phys. Status Solidi A 1975, 28, 133– 138 DOI: 10.1002/pssa.2210280113
Google Scholar
There is no corresponding record for this reference.
37
Worhatch, R. J.; Kim, H.; Swainson, I. P.; Yonkeu, A. L.; Billinge, S. J. L. Study of Local Structure in Selected Organic-Inorganic Perovskites in the Pm3m Phase Chem. Mater. 2008, 20, 1272– 1277 DOI: 10.1021/cm702668d
Google Scholar
There is no corresponding record for this reference.
38
Spingler, B.; Schnidrig, S.; Todorova, T.; Wild, F. Some thoughts about the single crystal growth of small molecules CrystEngComm 2012, 14, 751– 757 DOI: 10.1039/C1CE05624G
Google Scholar
38
Some thoughts about the single crystal growth of small molecules
Spingler, Bernhard; Schnidrig, Stephan; Todorova, Tonya; Wild, Ferdinand
CrystEngComm (2012), 14 (3), 751-757CODEN: CRECF4; ISSN:1466-8033. (Royal Society of Chemistry)
This highlight critically compares various techniques to grow single crystals when only a few milligrams are available of the compd. of interest. The authors describe vapor diffusion, evapn., cooling, and layering techniques, as well as crystn. in gels. A table of successfully applied solvent/antisolvent combinations for initial screening is given. Addnl., a comprehensive table of 107 solvents with their b.ps., densities and dielec. consts. helps to optimize the crystal growth.
39
Glaser, T.; Müller, C.; Sendner, M.; Krekeler, C.; Semonin, O. E.; Hull, T. D.; Yaffe, O.; Owen, J. S.; Kowalsky, W.; Pucci, A.; Lovrinčić, R. Infrared Spectroscopic Study of Vibrational Modes in Methylammonium Lead Halide Perovskites J. Phys. Chem. Lett. 2015, 6, 2913– 2918 DOI: 10.1021/acs.jpclett.5b01309
Google Scholar
39
Infrared Spectroscopic Study of Vibrational Modes in Methylammonium Lead Halide Perovskites
Glaser, Tobias; Mueller, Christian; Sendner, Michael; Krekeler, Christian; Semonin, Octavi E.; Hull, Trevor D.; Yaffe, Omer; Owen, Jonathan S.; Kowalsky, Wolfgang; Pucci, Annemarie; Lovrincic, Robert
Journal of Physical Chemistry Letters (2015), 6 (15), 2913-2918CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
The org. cation and its interplay with the inorg. lattice underlie the exceptional optoelectronic properties of organo-metallic halide perovskites. Herein the authors report high-quality IR spectroscopic measurements of methylammonium lead halide perovskite (CH3NH3Pb(I/Br/Cl)3) films and single crystals at room temp., from which the dielec. function in the studied spectral range is derived. Comparison with electronic structure calcns. in vacuum of the free methylammonium cation allows for a detailed peak assignment. The authors analyze the shifts of the vibrational peak positions between the different halides and infer the extent of interaction between org. moiety and the surrounding inorg. cage. The positions of the NH3+ stretching vibrations point to significant hydrogen bonding between the methylammonium and the halides for all three perovskites.
40
Toellner, T. S.; Alatas, A.; Said, A. H. Six-reflection meV-monochromator for synchrotron radiation J. Synchrotron Radiat. 2011, 18, 605– 611 DOI: 10.1107/S0909049511017535
Google Scholar
40
Six-reflection meV-monochromator for synchrotron radiation
Toellner T S; Alatas A; Said A H
Journal of synchrotron radiation (2011), 18 (Pt 4), 605-11 ISSN:.
An in-line monochromatization scheme suitable for 10-40 keV synchrotron radiation is presented based on the use of six crystal reflections that achieves meV and sub-meV bandwidths with high efficiency. The theoretical spectral efficiency surpasses all previous multicrystal designs and approaches that of single room-temperature back-reflecting crystals. This article presents the designs of two such devices along with their theoretical and measured performances.
41
Said, A. H.; Sinn, H.; Divan, R. New developments in fabrication of high-energy-resolution analyzers for inelastic X-ray spectroscopy J. Synchrotron Radiat. 2011, 18, 492– 496 DOI: 10.1107/S0909049511001828
Google Scholar
41
New developments in fabrication of high-energy-resolution analyzers for inelastic X-ray spectroscopy
Said Ayman H; Sinn Harald; Divan Ralu
Journal of synchrotron radiation (2011), 18 (Pt 3), 492-6 ISSN:.
In this work new improvements related to the fabrication of spherical bent analyzers for 1 meV energy-resolution inelastic X-ray scattering spectroscopy are presented. The new method includes the use of a two-dimensional bender to achieve the required radius of curvature for X-ray analyzers. The advantage of this method is the ability to monitor the focus during bending, which leads to higher-efficiency analyzers.
42
Sinn, H. Spectroscopy with meV energy resolution J. Phys.: Condens. Matter 2001, 13, 7525– 7537 DOI: 10.1088/0953-8984/13/34/305
Google Scholar
42
Spectroscopy with meV energy resolution
Sinn, Harald
Journal of Physics: Condensed Matter (2001), 13 (34), 7525-7537CODEN: JCOMEL; ISSN:0953-8984. (Institute of Physics Publishing)
A review. Inelastic x-ray scattering has become a powerful tool in condensed matter physics in recent years. This is due to the advent of the 3rd-generation synchrotron radiation sources, which provide an intense and collimated x-ray beam, and due to improvements in x-ray optics. This article is an introduction to the basic principles of inelastic x-ray scattering with meV resoln. In particular the geometric and crystal contributions for monochromator and analyzer crystals are discussed. Also, an estn. of phonon intensities, obtained with a meV spectrometer, is derived.
43
Burkel, E. Phonon spectroscopy by inelastic x-ray scattering Rep. Prog. Phys. 2000, 63, 171– 232 DOI: 10.1088/0034-4885/63/2/203
Google Scholar
43
Phonon spectroscopy by inelastic x-ray scattering
Burkel, Eberhard
Reports on Progress in Physics (2000), 63 (2), 171-232CODEN: RPPHAG; ISSN:0034-4885. (Institute of Physics Publishing)
A review with many refs. The present synchrotron sources with brilliant x-ray beams, due to high photon fluxes, small source sizes and high collimation, have revolutionized x-ray physics. Enormous progress was initiated in all established x-ray methods, with the aim of the development of new types of spectroscopy. This is particularly true for the spectroscopy of the dynamics in condensed matter. Meanwhile, there are 2 powerful x-ray methods with very high-energy resoln. available for the study of low energetic excitations like phonons. This review summarizes the developments of these methods focusing on these instrumental developments of the spectrometers using either crystal optics in close-to-backscattering geometry or nuclear resonant techniques. Applications to measurements of phonon dispersion curves and of phonon d. of states in ordered and disordered solids and in liqs. are presented. It is shown how x-ray results are stimulating improvements in the theor. approaches to the dynamics. New insights into the dynamics of liqs. are discussed. The sensitivities of the spectroscopies allow the study of vibrational behavior in very small amts. of material even in nanometer-sized thin films or particles. We can already analyze the phonon spectrum of a monolayered nuclear resonant isotope. Prospects of the techniques are also demonstrated.
44
Dorner, B. The scattering function and symmetry operations in the crystal. Coherent inelastic neutron scaterring in lattice dynamics; 1982; pp 16– 24.
Google Scholar
There is no corresponding record for this reference.
45
Chupas, P. J.; Qiu, X.; Hanson, J. C.; Lee, P. L.; Grey, C. P.; Billinge, S. J. L. Rapid-acquisition pair distribution function (RA-PDF) analysis J. Appl. Crystallogr. 2003, 36, 1342– 1347 DOI: 10.1107/S0021889803017564
Google Scholar
45
Rapid-acquisition pair distribution function (RA-PDF) analysis
Chupas, Peter J.; Qiu, Xiangyun; Hanson, Jonathan C.; Lee, Peter L.; Grey, Clare P.; Billinge, Simon J. L.
Journal of Applied Crystallography (2003), 36 (6), 1342-1347CODEN: JACGAR; ISSN:0021-8898. (Blackwell Publishing Ltd.)
An image-plate (IP) detector coupled with high-energy synchrotron radiation was used for at. pair distribution function (PDF) anal., with high probed momentum transfer Qmax ≤ 28.5 Å-1, from cryst. materials. Materials with different structural complexities were measured to test the validity of the quant. data anal. Exptl. results are presented for cryst. Ni, cryst. α-AlF3, and the layered Aurivillius type oxides α-Bi4V2O11 and γ-Bi4V1.7Ti0.3O10.85. Overall, the diffraction patterns show good counting statistics, with measuring time from one to tens of seconds. The PDFs obtained are of high quality. Structures may be refined from these PDFs, and the structural models are consistent with the published literature. Data sets from similar samples are highly reproducible.
46
Hammersley, A. P.; Svensson, S. O.; Hanfland, M.; Fitch, A. N.; Hausermann, D. Two-dimensional detector software: From real detector to idealised image or two-theta scan High Pressure Res. 1996, 14, 235– 248 DOI: 10.1080/08957959608201408
Google Scholar
There is no corresponding record for this reference.
47
Juhás, P.; Davis, T.; Farrow, C. L.; Billinge, S. J. L. PDFgetX3: a rapid and highly automatable program for processing powder diffraction data into total scattering pair distribution functions J. Appl. Crystallogr. 2013, 46, 560– 566 DOI: 10.1107/S0021889813005190
Google Scholar
47
PDFgetX3: a rapid and highly automatable program for processing powder diffraction data into total scattering pair distribution functions
Juhas, P.; Davis, T.; Farrow, C. L.; Billinge, S. J. L.
Journal of Applied Crystallography (2013), 46 (2), 560-566CODEN: JACGAR; ISSN:0021-8898. (International Union of Crystallography)
PDFgetX3 is a new software application for converting x-ray powder diffraction data to an at. pair distribution function (PDF). PDFgetX3 was designed for ease of use, speed and automated operation. The software can readily process hundreds of x-ray patterns within a few seconds and is thus useful for high-throughput PDF studies that measure numerous data sets as a function of time, temp. or other environmental parameters. In comparison to the preceding programs, PDFgetX3 requires fewer inputs and less user experience and it can be readily adopted by novice users. The live-plotting interactive feature allows the user to assess the effects of calcn. parameters and select their optimum values. PDFgetX3 uses an ad hoc data correction method, where the slowly changing structure-independent signal is filtered out to obtain coherent x-ray intensities that contain structure information. The output from PDFgetX3 was verified by processing exptl. PDFs from inorg., org. and nanosized samples and comparing them with their counterparts from a previous established software. In spite of the different algorithm, the obtained PDFs were nearly identical and yielded highly similar results when used in structure refinement. PDFgetX3 is written in the Python language and features a well documented reusable code base. The software can be used either as a standalone application or as a library of PDF processing functions that can be called from other Python scripts. The software is free for open academic research but requires paid license for com. use.
48
Yang, X.; Juhás, P.; Farrow, C. L.; Billinge, S. J. L. xPDFsuite: an end-to-end software solution for high throughput pair distribution function transformation, visualization and analysis. arXiv:1402.3163 [cond-mat] 2014.
Google Scholar
There is no corresponding record for this reference.
49
Farrow, C. L.; Juhas, P.; Liu, J. W.; Bryndin, D.; Božin, E. S.; Bloch, J.; Proffen, T.; Billinge, S. J. L. PDFfit2 and PDFgui: computer programs for studying nanostructure in crystals J. Phys.: Condens. Matter 2007, 19, 335219 DOI: 10.1088/0953-8984/19/33/335219
Google Scholar
49
PDFfit2 and PDFgui: computer programs for studying nanostructure in crystals
Farrow, C. L.; Juhas, P.; Liu, J. W.; Bryndin, D.; Bozin, E. S.; Bloch, J.; Proffen, Th; Billinge, S. J. L.
Journal of Physics: Condensed Matter (2007), 19 (33), 335219/1-335219/7CODEN: JCOMEL; ISSN:0953-8984. (Institute of Physics Publishing)
PDFfit2 is a program as well as a library for real-space refinement of crystal structures. It is capable of fitting a theor. three-dimensional (3D) structure to at. pair distribution function data and is ideal for nanoscale investigations. The fit system accounts for lattice consts., at. positions and anisotropic at. displacement parameters, correlated at. motion, and exptl. factors that may affect the data. The at. positions and thermal coeffs. can be constrained to follow the symmetry requirements of an arbitrary space group. The PDFfit2 engine is written in C++ and is accessible via Python, allowing it to inter-operate with other Python programs. PDFgui is a graphical interface built on the PDFfit2 engine. PDFgui organizes fits and simplifies many data anal. tasks, such as configuring and plotting multiple fits. PDFfit2 and PDFgui are freely available via the Internet.
50
Kresse, G.; Hafner, J. Ab initio molecular dynamics for liquid metals Phys. Rev. B: Condens. Matter Mater. Phys. 1993, 47, 558– 561 DOI: 10.1103/PhysRevB.47.558
Google Scholar
50
Ab initio molecular dynamics of liquid metals
Kresse, G.; Hafner, J.
Physical Review B: Condensed Matter and Materials Physics (1993), 47 (1), 558-61CODEN: PRBMDO; ISSN:0163-1829.
The authors present ab initio quantum-mech. mol.-dynamics calcns. based on the calcn. of the electronic ground state and of the Hellmann-Feynman forces in the local-d. approxn. at each mol.-dynamics step. This is possible using conjugate-gradient techniques for energy minimization, and predicting the wave functions for new ionic positions using sub-space alignment. This approach avoids the instabilities inherent in quantum-mech. mol.-dynamics calcns. for metals based on the use of a factitious Newtonian dynamics for the electronic degrees of freedom. This method gives perfect control of the adiabaticity and allows one to perform simulations over several picoseconds.
51
Togo, A.; Oba, F.; Tanaka, I. First-principles calculations of the ferroelastic transition between rutile-type and CaCl₂-type SiO₂ at high pressures Phys. Rev. B: Condens. Matter Mater. Phys. 2008, 78, 134106 DOI: 10.1103/PhysRevB.78.134106
Google Scholar
51
First-principles calculations of the ferroelastic transition between rutile-type and CaCl2-type SiO2 at high pressures
Togo, Atsushi; Oba, Fumiyasu; Tanaka, Isao
Physical Review B: Condensed Matter and Materials Physics (2008), 78 (13), 134106/1-134106/9CODEN: PRBMDO; ISSN:1098-0121. (American Physical Society)
The tetragonal to orthorhombic ferroelastic phase transition between rutile- and CaCl2-type SiO2 at high pressures was studied using 1st-principles calcns. and the Landau free-energy expansion. The phase transition is systematically studied in terms of characteristic phonon modes with B1g and Ag symmetries, shear moduli, transverse-acoustic mode, rotation angle of the SiO6 octahedra, spontaneous symmetry-breaking and vol. strains, and enthalpy. These phys. behaviors at the transition are well described using the Landau free-energy expansion parametrized by the 1st-principles calcns.
52
Togo, A.; Tanaka, I. First principles phonon calculations in materials science Scr. Mater. 2015, 108, 1– 5 DOI: 10.1016/j.scriptamat.2015.07.021
Google Scholar
52
First principles phonon calculations in materials science
Togo, Atsushi; Tanaka, Isao
Scripta Materialia (2015), 108 (), 1-5CODEN: SCMAF7; ISSN:1359-6462. (Elsevier Ltd.)
Phonon plays essential roles in dynamical behaviors and thermal properties, which are central topics in fundamental issues of materials science. The importance of first principles phonon calcns. cannot be overly emphasized. Phonopy is an open source code for such calcns. launched by the present authors, which has been world-widely used. Here we demonstrate phonon properties with fundamental equations and show examples how the phonon calcns. are applied in materials science.
53
Blöchl, P. E. Projector augmented-wave method Phys. Rev. B: Condens. Matter Mater. Phys. 1994, 50, 17953– 17979 DOI: 10.1103/PhysRevB.50.17953
Google Scholar
53
Projector augmented-wave method
Blochl
Physical review. B, Condensed matter (1994), 50 (24), 17953-17979 ISSN:0163-1829.
There is no expanded citation for this reference.
54
Kresse, G.; Joubert, D. From ultrasoft pseudopotentials to the projector augmented-wave method Phys. Rev. B: Condens. Matter Mater. Phys. 1999, 59, 1758– 1775 DOI: 10.1103/PhysRevB.59.1758
Google Scholar
54
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.
55
Momma, K.; Izumi, F. VESTA 3 for three-dimensional visualization of crystal, volumetric and morphology data J. Appl. Crystallogr. 2011, 44, 1272– 1276 DOI: 10.1107/S0021889811038970
Google Scholar
55
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.
56
Frost, J. M.; Butler, K. T.; Walsh, A. Molecular ferroelectric contributions to anomalous hysteresis in hybrid perovskite solar cells APL Mater. 2014, 2, 081506 DOI: 10.1063/1.4890246
Google Scholar
56
Molecular ferroelectric contributions to anomalous hysteresis in hybrid perovskite solar cells
Frost, Jarvist M.; Butler, Keith T.; Walsh, Aron
APL Materials (2014), 2 (8), 081506/1-081506/10CODEN: AMPADS; ISSN:2166-532X. (American Institute of Physics)
We report a model describing the mol. orientation disorder in CH3NH3PbI3, solving a classical Hamiltonian parametrised with electronic structure calcns., with the nature of the motions informed by ab initio mol. dynamics. We investigate the temp. and static elec. field dependence of the equil. ferroelec. (mol.) domain structure and resulting polarisability. A rich domain structure of twinned mol. dipoles is obsd., strongly varying as a function of temp. and applied elec. field. We propose that the internal elec. fields assocd. with microscopic polarisation domains contribute to hysteretic anomalies in the current-voltage response of hybrid org.-inorg. perovskite solar cells due to variations in electron-hole recombination in the bulk. (c) 2014 American Institute of Physics.

Cited By

Click to copy section linkSection link copied!

Explore this article's citation statements on scite.ai

This article is cited by 250 publications.

Alexander Angeloski, Pablo Galaviz, Richard A. Mole, Ross O. Piltz, Andrew M. McDonagh, Courtney Ennis, Dominique Appadoo. Manipulating a Thermosalient Crystal Using Selective Deuteration. Journal of the American Chemical Society 2025, 147 (9) , 8032-8047. https://doi.org/10.1021/jacs.5c01140
Zeping Ou, Yu Jie Zheng, Chen Li, Kuan Sun. Role of A-Site Cation Hydrogen Bonds in Hybrid Organic–Inorganic Perovskites: A Theoretical Insight. The Journal of Physical Chemistry Letters 2025, 16 (3) , 802-810. https://doi.org/10.1021/acs.jpclett.4c03211
Pelayo Marin-Villa, Mattia Gaboardi, Boby Joseph, Frederico Alabarse, Jeff Armstrong, Kacper Drużbicki, Felix Fernandez-Alonso. Methylammonium Lead Iodide across Physical Space: Phase Boundaries and Structural Collapse. The Journal of Physical Chemistry Letters 2025, 16 (1) , 184-190. https://doi.org/10.1021/acs.jpclett.4c03336
Yongheng Li, Haichang Guo, Ziyan Gao, Wujuan Yan, Haiyu He, Bin Wei, Jie Sun, Junyan Liu, Cong Lu, Yuiga Nakamura, Wei Luo, Xueyun Wang, Bai Song, Jiawang Hong. Dynamic Local Order and Ultralow Thermal Conductivity of Cs2AgBiBr6. Nano Letters 2025, 25 (1) , 401-409. https://doi.org/10.1021/acs.nanolett.4c05171
Colin M. Hylton-Farrington, Richard C. Remsing. Dynamic Local Symmetry Fluctuations of Electron Density in Halide Perovskites. Chemistry of Materials 2024, 36 (19) , 9442-9459. https://doi.org/10.1021/acs.chemmater.4c01121
Vincent J.-Y. Lim, Marcello Righetto, Siyu Yan, Jay B. Patel, Thomas Siday, Benjamin Putland, Kyle M. McCall, Maximilian T. Sirtl, Yuliia Kominko, Jiali Peng, Qianqian Lin, Thomas Bein, Maksym Kovalenko, Henry J. Snaith, Michael B. Johnston, Laura M. Herz. Contrasting Ultra-Low Frequency Raman and Infrared Modes in Emerging Metal Halides for Photovoltaics. ACS Energy Letters 2024, 9 (8) , 4127-4135. https://doi.org/10.1021/acsenergylett.4c01473
Lishan Liu, Mingxia Xu, Pengpeng Cheng, Xiangxin Tian, Xinguang Xu, Xutang Tao, Zeliang Gao. Isotope Synergetic Effect on Hybrid Organic–Inorganic Perovskite Single Crystal Carrier Transport and High-Performance Photodetectors. ACS Materials Letters 2024, 6 (8) , 3834-3843. https://doi.org/10.1021/acsmaterialslett.4c00956
Lin X. Chen, Junko Yano. Deciphering Photoinduced Catalytic Reaction Mechanisms in Natural and Artificial Photosynthetic Systems on Multiple Temporal and Spatial Scales Using X-ray Probes. Chemical Reviews 2024, 124 (9) , 5421-5469. https://doi.org/10.1021/acs.chemrev.3c00560
Andrew Squires, Evan Constable, Joseph Horvat, Dominique Appadoo, Ruth Plathe, R. A. Lewis, Kirrily C. Rule. Terahertz Vibrational Dynamics and DFT Calculations for the Quantum Spin Chain Linarite, PbCuSO4(OH)2. The Journal of Physical Chemistry A 2024, 128 (10) , 1767-1775. https://doi.org/10.1021/acs.jpca.3c06926
Mantas Simenas, Anna Gagor, Juras Banys, Miroslaw Maczka. Phase Transitions and Dynamics in Mixed Three- and Low-Dimensional Lead Halide Perovskites. Chemical Reviews 2024, 124 (5) , 2281-2326. https://doi.org/10.1021/acs.chemrev.3c00532
Jeehong Park, Soonsang Huh, Young Woo Choi, Donghee Kang, Minsoo Kim, Donghan Kim, Soohyung Park, Hyoung Joon Choi, Changyoung Kim, Yeonjin Yi. Visualizing the Low-Energy Electronic Structure of Prototypical Hybrid Halide Perovskite through Clear Band Measurements. ACS Nano 2024, 18 (10) , 7570-7579. https://doi.org/10.1021/acsnano.3c12587
Gregory Moller, Colette M. Sullivan, Andrew P. Cantrell, Masoud Mardani, Alexander S. Bieber, Theo Siegrist, Lea Nienhaus. Upconversion at Solid/Liquid Interfaces Using Perovskite Single Crystal Triplet Sensitizers. Chemistry of Materials 2024, 36 (4) , 1941-1946. https://doi.org/10.1021/acs.chemmater.3c02778
Maryna I. Bodnarchuk, Leon G. Feld, Chenglian Zhu, Simon C. Boehme, Federica Bertolotti, Jonathan Avaro, Marcel Aebli, Showkat Hassan Mir, Norberto Masciocchi, Rolf Erni, Sudip Chakraborty, Antonietta Guagliardi, Gabriele Rainò, Maksym V. Kovalenko. Colloidal Aziridinium Lead Bromide Quantum Dots. ACS Nano 2024, 18 (7) , 5684-5697. https://doi.org/10.1021/acsnano.3c11579
Kacper Drużbicki, Pablo Gila-Herranz, Pelayo Marin-Villa, Mattia Gaboardi, Jeff Armstrong, Felix Fernandez-Alonso. Cation Dynamics as Structure Explorer in Hybrid Perovskites─The Case of MAPbI3. Crystal Growth & Design 2024, 24 (1) , 391-404. https://doi.org/10.1021/acs.cgd.3c01112
Xia Liang, Johan Klarbring, William J. Baldwin, Zhenzhu Li, Gábor Csányi, Aron Walsh. Structural Dynamics Descriptors for Metal Halide Perovskites. The Journal of Physical Chemistry C 2023, 127 (38) , 19141-19151. https://doi.org/10.1021/acs.jpcc.3c03377
Julia Wiktor, Erik Fransson, Dominik Kubicki, Paul Erhart. Quantifying Dynamic Tilting in Halide Perovskites: Chemical Trends and Local Correlations. Chemistry of Materials 2023, 35 (17) , 6737-6744. https://doi.org/10.1021/acs.chemmater.3c00933
Ibrahim Dursun, Maxwell W. Terban, Yuanze Xu, Xiaoyu Zhang, Sanjit Ghose, Mingxing Li, Pranab Sarker, Hao Li, Mircea Cotlet, Tao Wei, Deyu Lu, Qiuming Yu. Temperature-Dependent Optical and Structural Properties of Chiral Two-Dimensional Hybrid Lead-Iodide Perovskites. The Journal of Physical Chemistry C 2023, 127 (31) , 15423-15434. https://doi.org/10.1021/acs.jpcc.3c04296
Xiangyu Xing, Jiayi Li, John P. Breen, Hemamala I. Karunadasa, Michael D. Fayer. Structural Dynamics of a Novel Pseudohalide Perovskite Cs2Pb(SeCN)2Br2 Investigated with Nonlinear Infrared Spectroscopy. The Journal of Physical Chemistry C 2023, 127 (29) , 14283-14292. https://doi.org/10.1021/acs.jpcc.3c02251
Jianhui Fu, Sankaran Ramesh, Jia Wei Melvin Lim, Tze Chien Sum. Carriers, Quasi-particles, and Collective Excitations in Halide Perovskites. Chemical Reviews 2023, 123 (13) , 8154-8231. https://doi.org/10.1021/acs.chemrev.2c00843
Rodrigo Szostak, Agnaldo de Souza Gonçalves, Jilian Nei de Freitas, Paulo E. Marchezi, Francineide Lopes de Araújo, Hélio Cesar Nogueira Tolentino, Michael F. Toney, Francisco das Chagas Marques, Ana Flavia Nogueira. In Situ and Operando Characterizations of Metal Halide Perovskite and Solar Cells: Insights from Lab-Sized Devices to Upscaling Processes. Chemical Reviews 2023, 123 (6) , 3160-3236. https://doi.org/10.1021/acs.chemrev.2c00382
Marta Morana, Julia Wiktor, Mauro Coduri, Rossella Chiara, Carlotta Giacobbe, Eleanor Lawrence Bright, Francesco Ambrosio, Filippo De Angelis, Lorenzo Malavasi. Cubic or Not Cubic? Combined Experimental and Computational Investigation of the Short-Range Order of Tin Halide Perovskites. The Journal of Physical Chemistry Letters 2023, 14 (8) , 2178-2186. https://doi.org/10.1021/acs.jpclett.3c00105
Fei Cao, Dejian Yu, Mykola Telychko, Jiong Lu, Peiyuan Pang, Chenliang Su, Guichuan Xing. Navigating the Site-Distinct Energy Conversion Properties of Perovskite Quantum Wells. ACS Energy Letters 2023, 8 (2) , 1236-1265. https://doi.org/10.1021/acsenergylett.2c02080
Paul Till, Ryo Asakura, Arndt Remhof, Wolfgang G. Zeier. On the Local Structure in Ordered and Disordered Closo-hydroborate Solid Electrolytes. The Journal of Physical Chemistry C 2023, 127 (2) , 987-993. https://doi.org/10.1021/acs.jpcc.2c07835
Sayan Maity, Suraj Verma, Lavanya M. Ramaniah, Varadharajan Srinivasan. Deciphering the Nature of Temperature-Induced Phases of MAPbBr3 by Ab Initio Molecular Dynamics. Chemistry of Materials 2022, 34 (23) , 10459-10469. https://doi.org/10.1021/acs.chemmater.2c02453
Randy Burns, Siphelo Ngqoloda, Stephen C. Klue, Evguenia Karapetrova, Christopher J. Arendse, Suchismita Guha. Temperature-Dependent Phase Stable Hybrid Halide Perovskite Films by Chemical Vapor Deposition. ACS Applied Electronic Materials 2022, 4 (9) , 4258-4264. https://doi.org/10.1021/acsaelm.2c00449
Pelayo Marín-Villa, Ana Arauzo, Kacper Drużbicki, Felix Fernandez-Alonso. Unraveling the Ordered Phase of the Quintessential Hybrid Perovskite MAPbI3─Thermophysics to the Rescue. The Journal of Physical Chemistry Letters 2022, 13 (36) , 8422-8428. https://doi.org/10.1021/acs.jpclett.2c02208
Xiangzhou Zhu, Sebastián Caicedo-Dávila, Christian Gehrmann, David A. Egger. Probing the Disorder Inside the Cubic Unit Cell of Halide Perovskites from First-Principles. ACS Applied Materials & Interfaces 2022, 14 (20) , 22973-22981. https://doi.org/10.1021/acsami.1c23099
Carolyne Chepkemboi, Kyle Jorgensen, Janell Sato, Geneva Laurita. Strategies and Considerations for Least-Squares Analysis of Total Scattering Data. ACS Omega 2022, 7 (17) , 14402-14411. https://doi.org/10.1021/acsomega.2c01285
Oliviero Cannelli, Julia Wiktor, Nicola Colonna, Ludmila Leroy, Michele Puppin, Camila Bacellar, Ilia Sadykov, Franziska Krieg, Grigory Smolentsev, Maksym V. Kovalenko, Alfredo Pasquarello, Majed Chergui, Giulia F. Mancini. Atomic-Level Description of Thermal Fluctuations in Inorganic Lead Halide Perovskites. The Journal of Physical Chemistry Letters 2022, 13 (15) , 3382-3391. https://doi.org/10.1021/acs.jpclett.2c00281
Götz Schuck, Daniel M. Többens, Dirk Wallacher, Nico Grimm, Tong Sy Tien, Susan Schorr. Temperature-Dependent EXAFS Measurements of the Pb L3-Edge Allow Quantification of the Anharmonicity of the Lead–Halide Bond of Chlorine-Substituted Methylammonium (MA) Lead Triiodide. The Journal of Physical Chemistry C 2022, 126 (12) , 5388-5402. https://doi.org/10.1021/acs.jpcc.1c05750
Weijian Tao, Yao Zhang, Haiming Zhu. Dynamic Exciton Polaron in Two-Dimensional Lead Halide Perovskites and Implications for Optoelectronic Applications. Accounts of Chemical Research 2022, 55 (3) , 345-353. https://doi.org/10.1021/acs.accounts.1c00626
Feng Zhang, Izuru Karimata, Houng-Wei Wang, Takashi Tachikawa, Keisuke Tominaga, Michitoshi Hayashi, Tetsuo Sasaki. Terahertz Spectroscopic Measurements and Solid-State Density Functional Calculations on CH3NH3PbBr3 Perovskites: Short-Range Order of Methylammonium. The Journal of Physical Chemistry C 2022, 126 (1) , 339-348. https://doi.org/10.1021/acs.jpcc.1c06988
Ningbo Fan, Xue Ma, Bin Xu. Effect of Iodine Octahedral Rotations on Dipole Ordering in Organic–Inorganic Hybrid Perovskite CH3NH3PbI3. The Journal of Physical Chemistry C 2022, 126 (1) , 779-785. https://doi.org/10.1021/acs.jpcc.1c09230
Maxwell W. Terban, Simon J. L. Billinge. Structural Analysis of Molecular Materials Using the Pair Distribution Function. Chemical Reviews 2022, 122 (1) , 1208-1272. https://doi.org/10.1021/acs.chemrev.1c00237
Waldemar Kaiser, Marcelo Carignano, Asma A. Alothman, Edoardo Mosconi, Ali Kachmar, William A. Goddard III, Filippo De Angelis. First-Principles Molecular Dynamics in Metal-Halide Perovskites: Contrasting Generalized Gradient Approximation and Hybrid Functionals. The Journal of Physical Chemistry Letters 2021, 12 (49) , 11886-11893. https://doi.org/10.1021/acs.jpclett.1c03428
Satoshi Tominaka, Izuru Karimata, Takahide Matsuoka, Moeri Sakamoto, Takahito Nakajima, Koji Ohara, Takashi Tachikawa. Dynamic Symmetry Conversion in Mixed-Halide Hybrid Perovskite upon Illumination. ACS Energy Letters 2021, 6 (11) , 3858-3863. https://doi.org/10.1021/acsenergylett.1c01798
Menno Bokdam, Jonathan Lahnsteiner, D. D. Sarma. Exploring Librational Pathways with on-the-Fly Machine-Learning Force Fields: Methylammonium Molecules in MAPbX3 (X = I, Br, Cl) Perovskites. The Journal of Physical Chemistry C 2021, 125 (38) , 21077-21086. https://doi.org/10.1021/acs.jpcc.1c06835
Ruo Xi Yang, Liang Z. Tan. First-Principles Characterization of Surface Phonons of Halide Perovskite CsPbI3 and Their Role in Stabilization. The Journal of Physical Chemistry Letters 2021, 12 (38) , 9253-9261. https://doi.org/10.1021/acs.jpclett.1c02515
Daniel B. Straus, Hillary E. Mitchell Warden, Robert J. Cava. s–p Mixing in Stereochemically Active Lone Pairs Drives the Formation of 1D Chains of Lead Bromide Square Pyramids. Inorganic Chemistry 2021, 60 (17) , 12676-12680. https://doi.org/10.1021/acs.inorgchem.1c01277
Saswata Halder, Amit Kessel, Noa Mazurski, Uriel Levy. Thermal Transport in Engineered Hybrid Organic–Inorganic Perovskite Metasurfaces. The Journal of Physical Chemistry C 2021, 125 (28) , 15134-15144. https://doi.org/10.1021/acs.jpcc.0c10187
Oliviero Cannelli, Nicola Colonna, Michele Puppin, Thomas C. Rossi, Dominik Kinschel, Ludmila M. D. Leroy, Janina Löffler, James M. Budarz, Anne Marie March, Gilles Doumy, Andre Al Haddad, Ming-Feng Tu, Yoshiaki Kumagai, Donald Walko, Grigory Smolentsev, Franziska Krieg, Simon C. Boehme, Maksym V. Kovalenko, Majed Chergui, Giulia F. Mancini. Quantifying Photoinduced Polaronic Distortions in Inorganic Lead Halide Perovskite Nanocrystals. Journal of the American Chemical Society 2021, 143 (24) , 9048-9059. https://doi.org/10.1021/jacs.1c02403
Manas Likhit Holekevi Chandrappa, Zhuoying Zhu, David P. Fenning, Shyue Ping Ong. Correlated Octahedral Rotation and Organic Cation Reorientation Assist Halide Ion Migration in Lead Halide Perovskites. Chemistry of Materials 2021, 33 (12) , 4672-4678. https://doi.org/10.1021/acs.chemmater.1c01175
Maximilian J. Schilcher, Paul J. Robinson, David J. Abramovitch, Liang Z. Tan, Andrew M. Rappe, David R. Reichman, David A. Egger. The Significance of Polarons and Dynamic Disorder in Halide Perovskites. ACS Energy Letters 2021, 6 (6) , 2162-2173. https://doi.org/10.1021/acsenergylett.1c00506
Loreta A. Muscarella, Eline M. Hutter, Jarvist M. Frost, Gianluca G. Grimaldi, Jan Versluis, Huib J. Bakker, Bruno Ehrler. Accelerated Hot-Carrier Cooling in MAPbI3 Perovskite by Pressure-Induced Lattice Compression. The Journal of Physical Chemistry Letters 2021, 12 (17) , 4118-4124. https://doi.org/10.1021/acs.jpclett.1c00676
Kacper Drużbicki, Rasmus Lavén, Jeff Armstrong, Lorenzo Malavasi, Felix Fernandez-Alonso, Maths Karlsson. Cation Dynamics and Structural Stabilization in Formamidinium Lead Iodide Perovskites. The Journal of Physical Chemistry Letters 2021, 12 (14) , 3503-3508. https://doi.org/10.1021/acs.jpclett.1c00616
Tomoyasu Yokoyama, Satoru Ohuchi, Taisuke Matsui, Yukihiro Kaneko, Takao Sasagawa. Low-Cost Computing of the Thermophysical Properties of Organic–Inorganic Halide Perovskites by Density Functional Theory Combined with the Three-Dimensional Reference Interaction Site Method. The Journal of Physical Chemistry C 2021, 125 (12) , 6601-6610. https://doi.org/10.1021/acs.jpcc.1c01171
Alexander D. Christodoulides, Peijun Guo, Lingyun Dai, Justin M. Hoffman, Xiaotong Li, Xiaobing Zuo, Daniel Rosenmann, Alexandra Brumberg, Mercouri G. Kanatzidis, Richard D. Schaller, Jonathan A. Malen. Signatures of Coherent Phonon Transport in Ultralow Thermal Conductivity Two-Dimensional Ruddlesden–Popper Phase Perovskites. ACS Nano 2021, 15 (3) , 4165-4172. https://doi.org/10.1021/acsnano.0c03595
Feifan Wang, Yongping Fu, Mark E. Ziffer, Yanan Dai, Sebastian F. Maehrlein, X.-Y. Zhu. Solvated Electrons in Solids—Ferroelectric Large Polarons in Lead Halide Perovskites. Journal of the American Chemical Society 2021, 143 (1) , 5-16. https://doi.org/10.1021/jacs.0c10943
Annalise E. Maughan, Eve M. Mozur, Andrew M. Candia, James R. Neilson. Ferroelastic Phase Transition in Formamidinium Tin(IV) Iodide Driven by Organic–Inorganic Coupling. Inorganic Chemistry 2020, 59 (19) , 14399-14406. https://doi.org/10.1021/acs.inorgchem.0c02158
Laura Piveteau, Marcel Aebli, Nuri Yazdani, Marthe Millen, Lukas Korosec, Franziska Krieg, Bogdan M. Benin, Viktoriia Morad, Christophe Piveteau, Toni Shiroka, Aleix Comas-Vives, Christophe Copéret, Aaron M. Lindenberg, Vanessa Wood, René Verel, Maksym V. Kovalenko. Bulk and Nanocrystalline Cesium Lead-Halide Perovskites as Seen by Halide Magnetic Resonance. ACS Central Science 2020, 6 (7) , 1138-1149. https://doi.org/10.1021/acscentsci.0c00587
Ji-Sang Park, Zhenzhu Li, Jacob N. Wilson, Wan-Jian Yin, Aron Walsh. Hexagonal Stacking Faults Act as Hole-Blocking Layers in Lead Halide Perovskites. ACS Energy Letters 2020, 5 (7) , 2231-2233. https://doi.org/10.1021/acsenergylett.0c01124
Adedayo M. Sanni, Sydney N. Lavan, Aaron S. Rury. Anharmonic Molecular Vibrational Probes of Dynamical Organic–Inorganic Interactions in Two-Dimensional Hybrid Lead Iodide Perovskites. The Journal of Physical Chemistry C 2020, 124 (25) , 13942-13955. https://doi.org/10.1021/acs.jpcc.0c04573
Oskar Schuster, Peter Wientjes, Shreetu Shrestha, Ievgen Levchuk, Mykhailo Sytnyk, Gebhard J. Matt, Andres Osvet, Miroslaw Batentschuk, Wolfgang Heiss, Christoph J. Brabec, Thomas Fauster, Daniel Niesner. Looking beyond the Surface: The Band Gap of Bulk Methylammonium Lead Iodide. Nano Letters 2020, 20 (5) , 3090-3097. https://doi.org/10.1021/acs.nanolett.9b05068
Jack Yang, Yutao Wang, Tom Wu, Sean Li. Correlating the Composition-Dependent Structural and Electronic Dynamics of Inorganic Mixed Halide Perovskites. Chemistry of Materials 2020, 32 (6) , 2470-2481. https://doi.org/10.1021/acs.chemmater.9b04995
Kimberley J. Savill, Matthew T. Klug, Rebecca L. Milot, Henry J. Snaith, Laura M. Herz. Charge-Carrier Cooling and Polarization Memory Loss in Formamidinium Tin Triiodide. The Journal of Physical Chemistry Letters 2019, 10 (20) , 6038-6047. https://doi.org/10.1021/acs.jpclett.9b02353
Ayala V. Cohen, David A. Egger, Andrew M. Rappe, Leeor Kronik. Breakdown of the Static Picture of Defect Energetics in Halide Perovskites: The Case of the Br Vacancy in CsPbBr3. The Journal of Physical Chemistry Letters 2019, 10 (16) , 4490-4498. https://doi.org/10.1021/acs.jpclett.9b01855
Lingling Mao, Constantinos C. Stoumpos, Mercouri G. Kanatzidis. Two-Dimensional Hybrid Halide Perovskites: Principles and Promises. Journal of the American Chemical Society 2019, 141 (3) , 1171-1190. https://doi.org/10.1021/jacs.8b10851
Hao Ma, Yunwei Ma, Heng Wang, Carla Slebodnick, Ahmet Alatas, Jeffrey J. Urban, Zhiting Tian. Experimental Phonon Dispersion and Lifetimes of Tetragonal CH3NH3PbI3 Perovskite Crystals. The Journal of Physical Chemistry Letters 2019, 10 (1) , 1-6. https://doi.org/10.1021/acs.jpclett.8b03419
Gregor Kieslich, Jonathan Michael Skelton, Jeff Armstrong, Yue Wu, Fengxia Wei, Katrine Louise Svane, Aron Walsh, Keith T. Butler. Hydrogen Bonding versus Entropy: Revealing the Underlying Thermodynamics of the Hybrid Organic–Inorganic Perovskite [CH3NH3]PbBr3. Chemistry of Materials 2018, 30 (24) , 8782-8788. https://doi.org/10.1021/acs.chemmater.8b03164
Andrea Bernasconi, Katharine Page, Zhenbang Dai, Liang Z. Tan, Andrew M. Rappe, Lorenzo Malavasi. Ubiquitous Short-Range Distortion of Hybrid Perovskites and Hydrogen-Bonding Role: the MAPbCl3 Case. The Journal of Physical Chemistry C 2018, 122 (49) , 28265-28272. https://doi.org/10.1021/acs.jpcc.8b10086
Matthew Z. Mayers, Liang Z. Tan, David A. Egger, Andrew M. Rappe, David R. Reichman. How Lattice and Charge Fluctuations Control Carrier Dynamics in Halide Perovskites. Nano Letters 2018, 18 (12) , 8041-8046. https://doi.org/10.1021/acs.nanolett.8b04276
Dibyajyoti Ghosh, Alexander R. Smith, Alison B. Walker, M. Saiful Islam. Mixed A-Cation Perovskites for Solar Cells: Atomic-Scale Insights Into Structural Distortion, Hydrogen Bonding, and Electronic Properties. Chemistry of Materials 2018, 30 (15) , 5194-5204. https://doi.org/10.1021/acs.chemmater.8b01851
Francesco Cordero, Floriana Craciun, Francesco Trequattrini, Patrizia Imperatori, Anna Maria Paoletti, Giovanna Pennesi. Competition between Polar and Antiferrodistortive Modes and Correlated Dynamics of the Methylammonium Molecules in MAPbI3 from Anelastic and Dielectric Measurements. The Journal of Physical Chemistry Letters 2018, 9 (15) , 4401-4406. https://doi.org/10.1021/acs.jpclett.8b01761
Annalise E. Maughan, Alex M. Ganose, Mohammed A. Almaker, David O. Scanlon, James R. Neilson. Tolerance Factor and Cooperative Tilting Effects in Vacancy-Ordered Double Perovskite Halides. Chemistry of Materials 2018, 30 (11) , 3909-3919. https://doi.org/10.1021/acs.chemmater.8b01549
Jingfeng Song, Zhiyong Xiao, Bo Chen, Spencer Prockish, Xuegang Chen, Anil Rajapitamahuni, Le Zhang, Jinsong Huang, Xia Hong. Enhanced Piezoelectric Response in Hybrid Lead Halide Perovskite Thin Films via Interfacing with Ferroelectric PbZr0.2Ti0.8O3. ACS Applied Materials & Interfaces 2018, 10 (22) , 19218-19225. https://doi.org/10.1021/acsami.8b03403
Yuxi Wang, Renxing Lin, Pengchen Zhu, Qinghui Zheng, Qianjin Wang, Deyu Li, Jia Zhu. Cation Dynamics Governed Thermal Properties of Lead Halide Perovskite Nanowires. Nano Letters 2018, 18 (5) , 2772-2779. https://doi.org/10.1021/acs.nanolett.7b04437
Arthur Marronnier, Guido Roma, Soline Boyer-Richard, Laurent Pedesseau, Jean-Marc Jancu, Yvan Bonnassieux, Claudine Katan, Constantinos C. Stoumpos, Mercouri G. Kanatzidis, Jacky Even. Anharmonicity and Disorder in the Black Phases of Cesium Lead Iodide Used for Stable Inorganic Perovskite Solar Cells. ACS Nano 2018, 12 (4) , 3477-3486. https://doi.org/10.1021/acsnano.8b00267
Victoria C. A. Taylor, Devendra Tiwari, Marta Duchi, Paul M. Donaldson, Ian P. Clark, David J. Fermin, and Thomas A. A. Oliver . Investigating the Role of the Organic Cation in Formamidinium Lead Iodide Perovskite Using Ultrafast Spectroscopy. The Journal of Physical Chemistry Letters 2018, 9 (4) , 895-901. https://doi.org/10.1021/acs.jpclett.7b03296
Annalise E. Maughan, Alex M. Ganose, Andrew M. Candia, Juliette T. Granger, David O. Scanlon, and James R. Neilson . Anharmonicity and Octahedral Tilting in Hybrid Vacancy-Ordered Double Perovskites. Chemistry of Materials 2018, 30 (2) , 472-483. https://doi.org/10.1021/acs.chemmater.7b04516
Emily C. Schueller, Geneva Laurita, Douglas H. Fabini, Constantinos C. Stoumpos, Mercouri G. Kanatzidis, and Ram Seshadri . Crystal Structure Evolution and Notable Thermal Expansion in Hybrid Perovskites Formamidinium Tin Iodide and Formamidinium Lead Bromide. Inorganic Chemistry 2018, 57 (2) , 695-701. https://doi.org/10.1021/acs.inorgchem.7b02576
Katrine L. Svane, Alexander C. Forse, Clare P. Grey, Gregor Kieslich, Anthony K. Cheetham, Aron Walsh, and Keith T. Butler . How Strong Is the Hydrogen Bond in Hybrid Perovskites?. The Journal of Physical Chemistry Letters 2017, 8 (24) , 6154-6159. https://doi.org/10.1021/acs.jpclett.7b03106
Eve M. Mozur, Annalise E. Maughan, Yongqiang Cheng, Ashfia Huq, Niina Jalarvo, Luke L. Daemen, and James R. Neilson . Orientational Glass Formation in Substituted Hybrid Perovskites. Chemistry of Materials 2017, 29 (23) , 10168-10177. https://doi.org/10.1021/acs.chemmater.7b04017
Jarvist Moore Frost, Lucy D. Whalley, and Aron Walsh . Slow Cooling of Hot Polarons in Halide Perovskite Solar Cells. ACS Energy Letters 2017, 2 (12) , 2647-2652. https://doi.org/10.1021/acsenergylett.7b00862
Ana L. Montero-Alejo, E. Menéndez-Proupin, P. Palacios, P. Wahnón, and J. C. Conesa . Ferroelectric Domains May Lead to Two-Dimensional Confinement of Holes, but not of Electrons, in CH3NH3PbI3 Perovskite. The Journal of Physical Chemistry C 2017, 121 (48) , 26698-26705. https://doi.org/10.1021/acs.jpcc.7b09625
Douglas H. Fabini, Ting Ann Siaw, Constantinos C. Stoumpos, Geneva Laurita, Daniel Olds, Katharine Page, Jerry G. Hu, Mercouri G. Kanatzidis, Songi Han, and Ram Seshadri . Universal Dynamics of Molecular Reorientation in Hybrid Lead Iodide Perovskites. Journal of the American Chemical Society 2017, 139 (46) , 16875-16884. https://doi.org/10.1021/jacs.7b09536
Mischa Bonn, Kiyoshi Miyata, Euan Hendry, and X.-Y. Zhu . Role of Dielectric Drag in Polaron Mobility in Lead Halide Perovskites. ACS Energy Letters 2017, 2 (11) , 2555-2562. https://doi.org/10.1021/acsenergylett.7b00717
Peijun Guo, Yi Xia, Jue Gong, Constantinos C. Stoumpos, Kyle M. McCall, Grant C. B. Alexander, Zhiyuan Ma, Hua Zhou, David J. Gosztola, John B. Ketterson, Mercouri G. Kanatzidis, Tao Xu, Maria K. Y. Chan, and Richard D. Schaller . Polar Fluctuations in Metal Halide Perovskites Uncovered by Acoustic Phonon Anomalies. ACS Energy Letters 2017, 2 (10) , 2463-2469. https://doi.org/10.1021/acsenergylett.7b00790
Ruo Xi Yang, Jonathan M. Skelton, E. Lora da Silva, Jarvist M. Frost, and Aron Walsh . Spontaneous Octahedral Tilting in the Cubic Inorganic Cesium Halide Perovskites CsSnX3 and CsPbX3 (X = F, Cl, Br, I). The Journal of Physical Chemistry Letters 2017, 8 (19) , 4720-4726. https://doi.org/10.1021/acs.jpclett.7b02423
Giselle A. Elbaz, Wee-Liat Ong, Evan A. Doud, Philip Kim, Daniel W. Paley, Xavier Roy, and Jonathan A. Malen . Phonon Speed, Not Scattering, Differentiates Thermal Transport in Lead Halide Perovskites. Nano Letters 2017, 17 (9) , 5734-5739. https://doi.org/10.1021/acs.nanolett.7b02696
Luis K. Ono, Emilio J. Juarez-Perez, Yabing Qi. Progress on Perovskite Materials and Solar Cells with Mixed Cations and Halide Anions. ACS Applied Materials & Interfaces 2017, 9 (36) , 30197-30246. https://doi.org/10.1021/acsami.7b06001
Jia-Yue Yang and Ming Hu . Temperature-Induced Large Broadening and Blue Shift in the Electronic Band Structure and Optical Absorption of Methylammonium Lead Iodide Perovskite. The Journal of Physical Chemistry Letters 2017, 8 (16) , 3720-3725. https://doi.org/10.1021/acs.jpclett.7b01719
Arthur Marronnier, Heejae Lee, Bernard Geffroy, Jacky Even, Yvan Bonnassieux, and Guido Roma . Structural Instabilities Related to Highly Anharmonic Phonons in Halide Perovskites. The Journal of Physical Chemistry Letters 2017, 8 (12) , 2659-2665. https://doi.org/10.1021/acs.jpclett.7b00807
Matthew R. Linaburg, Eric T. McClure, Jackson D. Majher, and Patrick M. Woodward . Cs1–xRbxPbCl3 and Cs1–xRbxPbBr3 Solid Solutions: Understanding Octahedral Tilting in Lead Halide Perovskites. Chemistry of Materials 2017, 29 (8) , 3507-3514. https://doi.org/10.1021/acs.chemmater.6b05372
Federica Bertolotti, Loredana Protesescu, Maksym V. Kovalenko, Sergii Yakunin, Antonio Cervellino, Simon J. L. Billinge, Maxwell W. Terban, Jan Skov Pedersen, Norberto Masciocchi, Antonietta Guagliardi. Coherent Nanotwins and Dynamic Disorder in Cesium Lead Halide Perovskite Nanocrystals. ACS Nano 2017, 11 (4) , 3819-3831. https://doi.org/10.1021/acsnano.7b00017
Byungkyun Kang and Koushik Biswas . Preferential CH3NH3+ Alignment and Octahedral Tilting Affect Charge Localization in Cubic Phase CH3NH3PbI3. The Journal of Physical Chemistry C 2017, 121 (15) , 8319-8326. https://doi.org/10.1021/acs.jpcc.7b01184
Andrea Bernasconi and Lorenzo Malavasi . Direct Evidence of Permanent Octahedra Distortion in MAPbBr3 Hybrid Perovskite. ACS Energy Letters 2017, 2 (4) , 863-868. https://doi.org/10.1021/acsenergylett.7b00139
Liang Z. Tan, Fan Zheng, and Andrew M. Rappe . Intermolecular Interactions in Hybrid Perovskites Understood from a Combined Density Functional Theory and Effective Hamiltonian Approach. ACS Energy Letters 2017, 2 (4) , 937-942. https://doi.org/10.1021/acsenergylett.7b00159
Oleg Selig, Aditya Sadhanala, Christian Müller, Robert Lovrincic, Zhuoying Chen, Yves L. A. Rezus, Jarvist M. Frost, Thomas L. C. Jansen, and Artem A. Bakulin . Organic Cation Rotation and Immobilization in Pure and Mixed Methylammonium Lead-Halide Perovskites. Journal of the American Chemical Society 2017, 139 (11) , 4068-4074. https://doi.org/10.1021/jacs.6b12239
Kyle T. Munson, Christopher Grieco, Eric R. Kennehan, Robert J. Stewart, and John B. Asbury . Time-Resolved Infrared Spectroscopy Directly Probes Free and Trapped Carriers in Organo-Halide Perovskites. ACS Energy Letters 2017, 2 (3) , 651-658. https://doi.org/10.1021/acsenergylett.7b00033
Laura T. Schelhas, Jeffrey A. Christians, Joseph J. Berry, Michael F. Toney, Christopher J. Tassone, Joseph M. Luther, and Kevin H. Stone . Monitoring a Silent Phase Transition in CH3NH3PbI3 Solar Cells via Operando X-ray Diffraction. ACS Energy Letters 2016, 1 (5) , 1007-1012. https://doi.org/10.1021/acsenergylett.6b00441
Ziyi Zhang, Songya Wang, Changcheng Chen, Minghong Sun, Zhengjun Wang, Yan Cai, Yali Tuo, Yuxi Du, Zhao Han, Xiongfei Yun, Xiaoning Guan, Shaohang Shi, Jiangzhou Xie, Gang Liu, Pengfei Lu. Design of photovoltaic materials assisted by machine learning and the mechanical tunability under micro-strain. Journal of Materials Science & Technology 2025, 227 , 108-121. https://doi.org/10.1016/j.jmst.2024.11.055
Yue Tang, Yipeng Wang, Xinlu Cheng, Pengfei Lu, Hong Zhang. Strain and composition engineering of excited-state carrier recombination dynamics in GaAs/GaP and GaAs/AlAs superlattices: insights from time-domain nonadiabatic molecular dynamics simulations. Journal of Materials Chemistry A 2025, 13 (16) , 11530-11539. https://doi.org/10.1039/D5TA00296F
Yong Wang, Yu Wang, Tiarnan A. S. Doherty, Samuel D. Stranks, Feng Gao, Deren Yang. Octahedral units in halide perovskites. Nature Reviews Chemistry 2025, 9 (4) , 261-277. https://doi.org/10.1038/s41570-025-00687-6
Xiao-Tian Quan, Xiang-Hui Chang, Wen-Guang Li, Qi-Jun Liu, Zheng-Tang Liu. First-principles study of the electronic, vibrational, thermodynamic properties and phase stability of orthorhombic KClO4 under pressure. Journal of Solid State Chemistry 2025, 343 , 125134. https://doi.org/10.1016/j.jssc.2024.125134
Shambhavee Annurakshita, G. Krishnamurthy Grandhi, Noolu Srinivasa Manikanta Viswanath, Adriana Pecoraro, Matias Schildt, Sami Toikkonen, Ana Belén Muñoz-García, Michele Pavone, Mikko J. Huttunen, Paola Vivo. Structural-disorder-induced enhancement of second-harmonic generation in bismuth-based perovskite-inspired materials. Newton 2025, 1 , 100056. https://doi.org/10.1016/j.newton.2025.100056
Kuniyuki Miwa, Souichi Sakamoto, Ken Funo, Akihito Ishizaki. Coarse-grained description of anharmonic lattice environments affecting the quantum dynamics of charge carriers. Physical Review Research 2025, 7 (1) https://doi.org/10.1103/PhysRevResearch.7.013323
Wenjuan Jiang, Cheng Peng, Haokun Jiang, Mingzhe Zhu, Zhongmin Zhou. Ion-migration-induced dual interface dipoles for high-performance perovskite solar cells. Matter 2025, 32 , 102085. https://doi.org/10.1016/j.matt.2025.102085
Burak Guzelturk, Joshua Portner, Justin Ondry, Samira Ghanbarzadeh, Mia Tarantola, Ahhyun Jeong, Thomas Field, Alicia M. Chandler, Eliza Wieman, Thomas R. Hopper, Nicolas E. Watkins, Jin Yu, Xinxin Cheng, Ming‐Fu Lin, Duan Luo, Patrick L. Kramer, Xiaozhe Shen, Alexander H. Reid, Olaf Borkiewicz, Uta Ruett, Xiaoyi Zhang, Aaron M. Lindenberg, Jihong Ma, Richard D. Schaller, Dmitri V. Talapin, Benjamin L. Cotts. Ultrafast Symmetry Control in Photoexcited Quantum Dots. Advanced Materials 2025, 37 (4) https://doi.org/10.1002/adma.202414196
Hui‐Seon Kim, Nam‐Gyu Park. Soft Lattice and Phase Stability of α‐FAPbI 3. Advanced Energy Materials 2025, 15 (2) https://doi.org/10.1002/aenm.202400089
Jia‐Kai Hu, Yu‐Ju Lee, Cheng‐Chieh Wu, Chi‐Hung Lee, Chun‐Ming Wu, Hung‐Cheng Wu, Kazuhiro Nawa, Katsuki Kinjo, Taku J. Sato, Pai‐Chun Wei. Dual Crystal‐Liquid Thermal Transport Behavior in MAPbCl 3. Small 2025, 21 (4) https://doi.org/10.1002/smll.202408773

Load more citations

Download PDF

Get e-Alerts

ACS Energy Letters

Cite this: ACS Energy Lett. 2016, 1, 4, 880–887

Click to copy citationCitation copied!

https://doi.org/10.1021/acsenergylett.6b00381

Published September 21, 2016

Request reuse permissions

Article Views

Altmetric

Citations

250

Learn about these metrics

Article Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.

Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.

The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated.

Abstract
High Resolution Image
Download MS PowerPoint Slide
Figure 1
Figure 1. Inelastic scattering spectra plotted from the Brillouin zone center to the zone edge. (a–d) M_TA₂ and X_TA illustrate what a typical dependence looks like. The dashed curve is only to guide the eye. In contrast, the M_TA₁ and R_TA at the zone edge have magnitudes larger even than the Bragg tail. (e) Sketch of the motion of the observed anharmonic modes with the idealized A-site cation (CH₃NH₃⁺) position represented in blue, the B-site cation (Pb²⁺) in gray at the center of the octahedra, and the X-site anion (I^–) in purple. Animations of these modes, and several others, are available online at https://dx.doi.org/10.6084/m9.figshare.3408394.
High Resolution Image
Download MS PowerPoint Slide
Figure 2
Figure 2. Measured and calculated dispersion curves. (a) The X, M, and R LA and TA modes and one TO branch measured by HERIX are plotted. The 1σ uncertainty in ζ and phonon energy (by fitting) are generally less than the size of the marker. The lines (sine fits) are only to guide the eye. At the zone edge of M and R, the phonon energy becomes small and overdamped; therefore, we fit to a Lorentzian peak convoluted with the resolution function and centered at ℏω = 0 meV and plot bars with height equal to the half-width at half-maximum of the Lorentzian. (b) Calculated phonon dispersion curves become imaginary along M_TA₁ and R_TA, as expected for a soft mode.
High Resolution Image
Download MS PowerPoint Slide
Figure 3
Figure 3. Local symmetry breaking in CH₃NH₃PbI₃ at 350 K. (a,b) Distortions from cubic symmetry generate anisotropic cavities and couple to motion of the CH₃NH₃⁺ ion, which we represent as off-centered and oriented along the long axis of the cavity. (c) DFT-based lattice dynamic calculations show that the energy minimum at the R point at 350 K is displaced in a double-well potential that causes local symmetry breaking. (d) Comparison of the experimental PDF (purple) to cubic (Pm3M), centrosymmetric (I4/mcm), and noncentrosymmetric (I4cm) tetragonal models (blue) shows a superior fit for the low-symmetry models at low r (2–8 Å). However, the models perform oppositely at high r with the high-symmetry cubic structure giving the best agreement to the data in the 12–50 Å region. The residuals (orange) are scaled ×3 for clarity.
High Resolution Image
Download MS PowerPoint Slide
Figure 4
Figure 4. Temperature dependence of inelastic scattering spectra. (a,b) Intensity as a function of temperature is measured at the X, M, and R points (ΔCounts is equal to the intensity of the measured mode at a given temperature less the intensity of the least intense peak in the temperature series). Scattering at the X point has little temperature dependence, while scattering at the M point slightly increases in intensity with decreasing temperature. In contrast, scattering at the R point responds dramatically, increasing sharply upon approaching the phase transition temperature due to the emergence of a Bragg peak in the tetragonal phase. This response indicates that the phase transition is driven by condensation of the R_TA mode at 330 K.
High Resolution Image
Download MS PowerPoint Slide
References
This article references 56 other publications.
1. 1
  Choi, J. J.; Yang, X.; Norman, Z. M.; Billinge, S. J. L.; Owen, J. S. Structure of Methylammonium Lead Iodide Within Mesoporous Titanium Dioxide: Active Material in High-Performance Perovskite Solar Cells Nano Lett. 2014, 14, 127– 133 DOI: 10.1021/nl403514x
  1
  Structure of Methylammonium Lead Iodide Within Mesoporous Titanium Dioxide: Active Material in High-Performance Perovskite Solar Cells
  Choi, Joshua J.; Yang, Xiaohao; Norman, Zachariah M.; Billinge, Simon J. L.; Owen, Jonathan S.
  Nano Letters (2014), 14 (1), 127-133CODEN: NALEFD; ISSN:1530-6984. (American Chemical Society)
  The authors report the structure of methylammonium Pb-(II) iodide perovskite in mesoporous TiO2, as used in high-performance solar cells. Pair distribution function anal. of x-ray scattering reveals a 2. component nanostructure: one component with medium range cryst. order (30 atom %) and another with only local structural coherence (70 atom %). The nanostructuring correlates with a blueshift of the absorption onset and increases the photoluminescence. The findings underscore the importance of fully characterizing and controlling the structure for improved solar cell efficiency.
2. 2
  Walsh, A.; Scanlon, D. O.; Chen, S.; Gong, X. G.; Wei, S.-H. Self-Regulation Mechanism for Charged Point Defects in Hybrid Halide Perovskites Angew. Chem., Int. Ed. 2015, 54, 1791– 1794 DOI: 10.1002/anie.201409740
  2
  Self-regulation mechanism for charged point defects in hybrid halide perovskites
  Walsh, Aron; Scanlon, David O.; Chen, Shiyou; Gong, X. G.; Wei, Su-Huai
  Angewandte Chemie, International Edition (2015), 54 (6), 1791-1794CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
  Hybrid halide perovskites such as methylammonium lead iodide (CH3NH3PbI3) exhibit unusually low free-carrier concns. despite being processed at low-temps. from soln. We demonstrate, through quantum mech. calcns., that an origin of this phenomenon is a prevalence of ionic over electronic disorder in stoichiometric materials. Schottky defect formation provides a mechanism to self-regulate the concn. of charge carriers through ionic compensation of charged point defects. The equil. charged vacancy concn. is predicted to exceed 0.4 % at room temp. This behavior, which goes against established defect conventions for inorg. semiconductors, has implications for photovoltaic performance.
3. 3
  Poglitsch, A.; Weber, D. Dynamic disorder in methylammoniumtrihalogenoplumbates (II) observed by millimeter-wave spectroscopy J. Chem. Phys. 1987, 87, 6373– 6378 DOI: 10.1063/1.453467
  3
  Dynamic disorder in methylammonium trihaloplumbates(II) observed by millimeter-wave spectroscopy
  Poglitsch, A.; Weber, D.
  Journal of Chemical Physics (1987), 87 (11), 6373-8CODEN: JCPSA6; ISSN:0021-9606.
  The temp.-dependent structure of cryst. methylammonium trihaloplumbates(II) CH3NH3+PbX3- (X = Cl, Br, I) as detd. by x-ray diffraction, was compared with measurements of the temp.-dependent complex permittivity at frequencies of 50-150 GHz. The dielec. measurements reveal a ps relaxation process which corresponds to a dynamic disorder of the methylammonium group in the high-temp. phases of the trihaloplumbates.
4. 4
  Yaffe, O. The nature of dynamic disorder in lead halide perovskite crystals. arXiv:1604.08107 [cond-mat] 2016.
  There is no corresponding record for this reference.
5. 5
  Stranks, S. D.; Snaith, H. J. Metal-halide perovskites for photovoltaic and light-emitting devices Nat. Nanotechnol. 2015, 10, 391– 402 DOI: 10.1038/nnano.2015.90
  5
  Metal-halide perovskites for photovoltaic and light-emitting devices
  Stranks, Samuel D.; Snaith, Henry J.
  Nature Nanotechnology (2015), 10 (5), 391-402CODEN: NNAABX; ISSN:1748-3387. (Nature Publishing Group)
  A review. Metal-halide perovskites are cryst. materials originally developed out of scientific curiosity. Unexpectedly, solar cells incorporating these perovskites are rapidly emerging as serious contenders to rival the leading photovoltaic technologies. Power conversion efficiencies have jumped from 3% to over 20% in just four years of academic research. Here, we review the rapid progress in perovskite solar cells, as well as their promising use in light-emitting devices. In particular, we describe the broad tunability and fabrication methods of these materials, the current understanding of the operation of state-of-the-art solar cells and we highlight the properties that have delivered light-emitting diodes and lasers. We discuss key thermal and operational stability challenges facing perovskites, and give an outlook of future research avenues that might bring perovskite technol. to commercialization.
6. 6
  Green, M. A.; Emery, K.; Hishikawa, Y.; Warta, W.; Dunlop, E. D. Solar cell efficiency tables (version 47) Prog. Photovoltaics 2016, 24, 3– 11 DOI: 10.1002/pip.2728
  There is no corresponding record for this reference.
7. 7
  Glazer, A. M. Simple ways of determining perovskite structures Acta Crystallogr., Sect. A: Cryst. Phys., Diffr., Theor. Gen. Crystallogr. 1975, 31, 756– 762 DOI: 10.1107/S0567739475001635
  There is no corresponding record for this reference.
8. 8
  Benedek, N. A.; Fennie, C. J. Why Are There So Few Perovskite Ferroelectrics? J. Phys. Chem. C 2013, 117, 13339– 13349 DOI: 10.1021/jp402046t
  8
  Why Are There So Few Perovskite Ferroelectrics?
  Benedek, Nicole A.; Fennie, Craig J.
  Journal of Physical Chemistry C (2013), 117 (26), 13339-13349CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)
  The authors use a combination of symmetry arguments and 1st-principles calcns. to explore the connection between structural distortions and ferroelectricity in the perovskite family of materials. The authors explain the role of octahedral rotations in suppressing ferroelectricity in these materials and show that, as the tolerance factor decreases, rotations alone cannot fully suppress ferroelectricity. The results show that it is cation displacements (hidden in Glazer notation) that accompany the rotations, rather than the rotations themselves, that play the decisive role in suppressing ferroelectricity in these cases. The authors use the knowledge gained in the anal. of this problem to explain the origin of ferroelectricity in R3c materials such as FeTiO3 and ZnSnO3 and to suggest strategies for the design and synthesis of new perovskite ferroelecs. The results have implications not only for the fundamental crystal chem. of the perovskites but also for the discovery of new functional materials.
9. 9
  Frost, J. M.; Butler, K. T.; Brivio, F.; Hendon, C. H.; van Schilfgaarde, M.; Walsh, A. Atomistic Origins of High-Performance in Hybrid Halide Perovskite Solar Cells Nano Lett. 2014, 14, 2584– 2590 DOI: 10.1021/nl500390f
  9
  Atomistic Origins of High-Performance in Hybrid Halide Perovskite Solar Cells
  Frost, Jarvist M.; Butler, Keith T.; Brivio, Federico; Hendon, Christopher H.; van Schilfgaarde, Mark; Walsh, Aron
  Nano Letters (2014), 14 (5), 2584-2590CODEN: NALEFD; ISSN:1530-6984. (American Chemical Society)
  The performance of organometallic perovskite solar cells has rapidly surpassed that of both conventional dye-sensitized and org. photovoltaics. High-power conversion efficiency can be realized in both mesoporous and thin-film device architectures. The authors address the origin of this success in the context of the materials chem. and physics of the bulk perovskite as described by electronic structure calcns. In addn. to the basic optoelectronic properties essential for an efficient photovoltaic device (spectrally suitable band gap, high optical absorption, low carrier effective masses), the materials are structurally and compositionally flexible. As the authors show, hybrid perovskites exhibit spontaneous elec. polarization; the authors also suggest ways in which this can be tuned through judicious choice of the org. cation. The presence of ferroelec. domains will result in internal junctions that may aid sepn. of photoexcited electron and hole pairs, and redn. of recombination through segregation of charge carriers. The combination of high dielec. const. and low effective mass promotes both Wannier-Mott exciton sepn. and effective ionization of donor and acceptor defects. The photoferroic effect could be exploited in nanostructured films to generate a higher open circuit voltage and may contribute to the current-voltage hysteresis obsd. in perovskite solar cells.
10. 10
  Ma, J.; Wang, L.-W. Nanoscale Charge Localization Induced by Random Orientations of Organic Molecules in Hybrid Perovskite CH 3NH 3PbI 3 Nano Lett. 2015, 15, 248– 253 DOI: 10.1021/nl503494y
  There is no corresponding record for this reference.
11. 11
  Zhu, X. Y.; Podzorov, V. Charge Carriers in Hybrid Organic-Inorganic Lead Halide Perovskites Might Be Protected as Large Polarons J. Phys. Chem. Lett. 2015, 6, 4758– 4761 DOI: 10.1021/acs.jpclett.5b02462
  11
  Charge Carriers in Hybrid Organic-Inorganic Lead Halide Perovskites Might Be Protected as Large Polarons
  Zhu, X.-Y.; Podzorov, V.
  Journal of Physical Chemistry Letters (2015), 6 (23), 4758-4761CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
  Large polaron that provides the protection of charge carrier is explained in terms of carrier diffusion length,electron hole recombination rates, charge carrier and Hall mobility and low carrier scattering rate.
12. 12
  Liu, S.; Zheng, F.; Koocher, N. Z.; Takenaka, H.; Wang, F.; Rappe, A. M. Ferroelectric Domain Wall Induced Band Gap Reduction and Charge Separation in Organometal Halide Perovskites J. Phys. Chem. Lett. 2015, 6, 693– 699 DOI: 10.1021/jz502666j
  12
  Ferroelectric domain wall induced band gap reduction and charge separation in organometal halide perovskites
  Liu, Shi; Zheng, Fan; Koocher, Nathan Z.; Takenaka, Hiroyuki; Wang, Fenggong; Rappe, Andrew M.
  Journal of Physical Chemistry Letters (2015), 6 (4), 693-699CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
  Organometal halide perovskites have been intensely studied in the past 5 years, inspired by their certified high photovoltaic power conversion efficiency. Some of these materials are room-temp. ferroelecs. The presence of switchable ferroelec. domains in methylammonium lead triiodide, CH3NH3PbI3, has recently been obsd. via piezoresponse force microscopy. Here, we focus on the structural and electronic properties of ferroelec. domain walls in CH3NH3PbX3 (X = Cl, Br, I). We find that organometal halide perovskites can form both charged and uncharged domain walls due to the flexible orientational order of the org. mols. The electronic band gaps for domain structures possessing 180 and 90° walls are estd. with d. functional theory. It is found that the presence of charged domain walls will significantly reduce the band gap by 20-40%, while the presence of uncharged domain walls has no substantial impact on the band gap. We demonstrate that charged domain walls can serve as segregated channels for the motions of charge carriers. These results highlight the importance of ferroelec. domain walls in hybrid perovskites for photovoltaic applications and suggest a possible avenue for device optimization through domain patterning.
13. 13
  Stoumpos, C. C.; Malliakas, C. D.; Kanatzidis, M. G. Semiconducting tin and lead iodide perovskites with organic cations: phase transitions, high mobilities, and near-infrared photoluminescent properties Inorg. Chem. 2013, 52, 9019– 9038 DOI: 10.1021/ic401215x
  13
  Semiconducting Tin and Lead Iodide Perovskites with Organic Cations: Phase Transitions, High Mobilities, and Near-Infrared Photoluminescent Properties
  Stoumpos, Constantinos C.; Malliakas, Christos D.; Kanatzidis, Mercouri G.
  Inorganic Chemistry (2013), 52 (15), 9019-9038CODEN: INOCAJ; ISSN:0020-1669. (American Chemical Society)
  A broad org.-inorg. series of hybrid metal iodide perovskites AMI3, where A is the methylammonium (MeNH3+) or formamidinium (HC(NH2)2+) cation and M is Sn (1 and 2) or Pb (3 and 4) are reported. The compds. were prepd. through a variety of synthetic approaches, and the nature of the resulting materials is discussed in terms of their thermal stability and optical and electronic properties. The chem. and phys. properties of these materials strongly depend on the prepn. method. Single crystal x-ray diffraction anal. of 1-4 classifies the compds. in the perovskite structural family. Structural phase transitions were obsd. and studied by temp.-dependent single crystal x-ray diffraction in the 100-400 K range. The charge transport properties of the materials are discussed in conjunction with diffuse reflectance studies in the mid-IR region that display characteristic absorption features. Temp.-dependent studies show a strong dependence of the resistivity as a function of the crystal structure. Optical absorption measurements indicate that 1-4 behave as direct-gap semiconductors with energy band gaps distributed at 1.25-1.75 eV. The compds. exhibit an intense near-IR luminescence (PL) emission in the 700-1000 nm range (1.1-1.7 eV) at room temp. Solid solns. between the Sn and Pb compds. are readily accessible throughout the compn. range. The optical properties such as energy band gap, emission intensity, and wavelength can be readily controlled for the isostructural series of solid solns. MeNH3Sn1-xPbxI3 (5). The charge transport type in these materials was characterized by Seebeck coeff. and Hall-effect measurements. The compds. behave as p- or n-type semiconductors depending on the prepn. method. The samples with the lowest carrier concn. are prepd. from soln. and are n-type; p-type samples can be obtained through solid state reactions exposed in air in a controllable manner. In the case of Sn compds., there is a facile tendency toward oxidn. which causes the materials to be doped with Sn4+ and thus behave as p-type semiconductors displaying metal-like cond. The compds. appear to possess very high estd. electron and hole mobilities that exceed 2000 cm2/(V s) and 300 cm2/(V s), resp., as shown in the case of MeNH3SnI3 (1). The authors also compare the properties of the title hybrid materials with those of the all-inorg. CsSnI3 and CsPbI3 prepd. using identical synthetic methods.
14. 14
  Baikie, T.; Barrow, N. S.; Fang, Y.; Keenan, P. J.; Slater, P. R.; Piltz, R. O.; Gutmann, M.; Mhaisalkar, S. G.; White, T. J. A combined single crystal neutron/X-ray diffraction and solid-state nuclear magnetic resonance study of the hybrid perovskites CH 3NH 3PbX 3(X = I, Br and Cl) J. Mater. Chem. A 2015, 3, 9298– 9307 DOI: 10.1039/C5TA01125F
  14
  A combined single crystal neutron/X-ray diffraction and solid-state nuclear magnetic resonance study of the hybrid perovskites CH3NH3PbX3 (X = I, Br and Cl)
  Baikie, Tom; Barrow, Nathan S.; Fang, Yanan; Keenan, Philip J.; Slater, Peter R.; Piltz, Ross O.; Gutmann, Matthias; Mhaisalkar, Subodh G.; White, Tim J.
  Journal of Materials Chemistry A: Materials for Energy and Sustainability (2015), 3 (17), 9298-9307CODEN: JMCAET; ISSN:2050-7496. (Royal Society of Chemistry)
  The 1H and 13C NMR spectra in methylammonium lead halide perovskites, CH3NH3PbX3 (X = I, Br and Cl) show that the CH3NH3+ units undergo dynamic reorientation, as the org. component tumbles in the perovskite cage. In addn., the differences in the anomalously long relaxation times of the protons assocd. with the CH3 and not the NH3 groups indicate that only the amine end of the CH3NH3+ group is interacting with the inorg. network. Using this information, we have refined some single crystal X-ray and neutron diffraction data to probe their unusual structures in more detail. Furthermore, impedance spectroscopy has been used to monitor the high-temp. phase transition of CH3NH3PbI3, which confirms a significant increase in cond., when it is in its high temp. and higher symmetry structural regime. The optical band-gaps of each halide perovskite were detd. using UV-visible spectroscopy and are consistent with previous reports.
15. 15
  Stroppa, A.; Quarti, C.; De Angelis, F.; Picozzi, S. Ferroelectric Polarization of CH3NH3PbI3: A Detailed Study Based on Density Functional Theory and Symmetry Mode Analysis J. Phys. Chem. Lett. 2015, 6, 2223– 2231 DOI: 10.1021/acs.jpclett.5b00542
  15
  Ferroelectric Polarization of CH3NH3PbI3: A Detailed Study Based on Density Functional Theory and Symmetry Mode Analysis
  Stroppa, Alessandro; Quarti, Claudio; De Angelis, Filippo; Picozzi, Silvia
  Journal of Physical Chemistry Letters (2015), 6 (12), 2223-2231CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
  Ferroelectricity in halide perovskites currently represents a crucial issue, as it may have an important role for the enhancement of solar cells efficiency. Simulations of ferroelec. properties based on d. functional theory are conceptually more demanding compared with conventional inorg. ferroelecs. due to the presence of both org. and inorg. components in the same compd. Here the authors present a detailed study focused on the prototypical CH3NH3PbI3 perovskite. By using d. functional theory combined with symmetry mode anal., the authors disentangle the contributions of the methylammonium cations and the role of the inorg. framework, therefore suggesting possible routes to enhance the polarization in this compd. The authors' est. of the polarization for the tetragonal phase at low temp. is ∼4.42 μC/cm2, which is substantially lower than that of traditional perovskite oxides.
16. 16
  Beilsten-Edmands, J.; Eperon, G. E.; Johnson, R. D.; Snaith, H. J.; Radaelli, P. G. Non-ferroelectric nature of the conductance hysteresis in CH3NH3PbI3 perovskite-based photovoltaic devices Appl. Phys. Lett. 2015, 106, 173502 DOI: 10.1063/1.4919109
  16
  Non-ferroelectric nature of the conductance hysteresis in CH3NH3PbI3 perovskite-based photovoltaic devices
  Beilsten-Edmands, J.; Eperon, G. E.; Johnson, R. D.; Snaith, H. J.; Radaelli, P. G.
  Applied Physics Letters (2015), 106 (17), 173502/1-173502/5CODEN: APPLAB; ISSN:0003-6951. (American Institute of Physics)
  We present measurements of conductance hysteresis on CH3NH3PbI3 perovskite thin films, performed using the double-wave method, in order to investigate the possibility of a ferroelec. response. A strong frequency dependence of the hysteresis is obsd. in the range of 0.1-150 Hz, with a hysteretic charge d. in excess of 1000 μC cm-2 at frequencies below 0.4 Hz, a behavior uncharacteristic of a ferroelec. response. We show that the obsd. hysteretic conductance, as well as the presence of a double arc in the impedance spectroscopy, can be fully explained by the migration of mobile ions under bias on a timescale of seconds. Our measurements place an upper limit of ≈ 1 μC cm-2 on any intrinsic frequency-independent polarization, ruling out ferroelectricity as the main cause of current-voltage hysteresis and providing further evidence of the importance of ionic migration in modifying the efficiency of CH3NH3PbI3 devices. (c) 2015 American Institute of Physics.
17. 17
  Fujii, Y.; Hoshino, S.; Yamada, Y.; Shirane, G. Neutron-scattering study on phase transitions of CsPb Cl3 Phys. Rev. B 1974, 9, 4549– 4559 DOI: 10.1103/PhysRevB.9.4549
  There is no corresponding record for this reference.
18. 18
  Swainson, I. P.; Hammond, R. P.; Soullière, C.; Knop, O.; Massa, W. Phase transitions in the perovskite methylammonium lead bromide, CH3ND3PbBr3 J. Solid State Chem. 2003, 176, 97– 104 DOI: 10.1016/S0022-4596(03)00352-9
  18
  Phase transitions in the perovskite methylammonium lead bromide, CH3ND3PbBr3
  Swainson, I. P.; Hammond, R. P.; Soulliere, C.; Knop, O.; Massa, W.
  Journal of Solid State Chemistry (2003), 176 (1), 97-104CODEN: JSSCBI; ISSN:0022-4596. (Elsevier Science)
  The structure of phase IV of methylammonium lead bromide, CH3ND3PbBr3, is shown from Rietveld refinement of neutron powder diffraction data to be centrosym., with space group Pnma: Z = 4; a 7.9434(4), b 11.8499(5), c 8.5918(4) Å at 11 K; Rwp = 2.34% Rp = 1.81%. This corresponds to one of the pure tilt transitions, a-b+a-, commonly obsd. in perovskites. Addnl. distortions not required by pure tilting are found in the PbBr6 octahedra, and apparently the structure optimizes the H bonding between the methylammonium cation and the framework. It is likely that the lowest temp. phase of the corresponding iodide also has this structure. The structure is compared to the available data for that of other Pnma perovskites. A brief comparison to the higher temp. phases in which the methylammonium ion is disordered is given.
19. 19
  Chi, L.; Swainson, I.; Cranswick, L.; Her, J.-H.; Stephens, P.; Knop, O. The ordered phase of methylammonium lead chloride CH3ND3PbCl3 J. Solid State Chem. 2005, 178, 1376– 1385 DOI: 10.1016/j.jssc.2004.12.037
  19
  The ordered phase of methylammonium lead chloride CH3ND3PbCl3
  Chi, Lisheng; Swainson, Ian; Cranswick, Lachlan; Her, Jae-Hyuk; Stephens, Peter; Knop, Osvald
  Journal of Solid State Chemistry (2005), 178 (5), 1376-1385CODEN: JSSCBI; ISSN:0022-4596. (Elsevier)
  The perovskite-structured compd. methylammonium lead chloride orders into a low-temp. phase of space group Pnma, in which at 80 K each of the orthorhombic axes a 11.1747(2), b 11.3552(1) and c 11.2820(1) Å is doubled with respect to the room temp. disordered cubic phase (a 5.669 Å). Crystallog. data and at. coordinates are given. The structure was solved by ab initio methods using the programs EXPO and FOX. This unusual cell basis for space group Pnma is not that of a std. tilt system. This phase, in which the methylammonium ions, are ordered shows distorted octahedra. The octahedra possess a bond angle variance of 60.663°2 and a quadratic elongation of 1.018, and are more distorted than those in the ordered phase of methylammonium lead bromide. There is also an alternating long and short Pb-Cl bond along a, due to an off-center displacement of Pb within the octahedron. Probably the most rigid unit is actually the methylammonium cation, rather than the PbCl6 octahedra, in agreement with existing spectroscopic data.
20. 20
  Swainson, I. P.; Stock, C.; Parker, S. F.; Van Eijck, L.; Russina, M.; Taylor, J. W. From soft harmonic phonons to fast relaxational dynamics in CH3NH3PbBr3 Phys. Rev. B: Condens. Matter Mater. Phys. 2015, 92, 100303 DOI: 10.1103/PhysRevB.92.100303
  20
  From soft harmonic phonons to fast relaxational dynamics in CH3NH3PbBr3
  Swainson, I. P.; Stock, C.; Parker, S. F.; Van Eijck, L.; Russina, M.; Taylor, J. W.
  Physical Review B: Condensed Matter and Materials Physics (2015), 92 (10), 100303/1-100303/5CODEN: PRBMDO; ISSN:1098-0121. (American Physical Society)
  The lead-halide perovskites, including CH3NH3PbBr3, are components in cost effective, highly efficient photovoltaics, where the interactions of the mol. cations with the inorg. framework are suggested to influence the electronic and ferroelec. properties. CH3NH3PbBr3 undergoes a series of structural transitions assocd. with orientational order of the CH3NH3 (methylammonium) mol. cation and tilting of the PbBr3 host framework. We apply high-resoln. neutron scattering to study the soft harmonic phonons assocd. with these transitions, and find a strong coupling between the PbBr3 framework and the quasistatic CH3NH3 dynamics at low energy transfers. At higher energy transfers, we observe a PbBr6 octahedra soft mode driving a transition at 150 K from bound mol. excitations at low temps. to relatively fast relaxational excitations that extend up to ∼50-100 meV. We suggest that these temporally overdamped dynamics enables possible indirect band gap processes in these materials that are related to the enhanced photovoltaic properties.
21. 21
  Wasylishen, R. E.; Knop, O.; Macdonald, J. B. Cation rotation in methylammonium lead halides Solid State Commun. 1985, 56, 581– 582 DOI: 10.1016/0038-1098(85)90959-7
  21
  Cation rotation in methylammonium lead halides
  Wasylishen, R. E.; Knop, Osvald; Macdonald, J. B.
  Solid State Communications (1985), 56 (7), 581-2CODEN: SSCOA4; ISSN:0038-1098.
  2H and 14N NMR spectra of the simple perovskites MeNH3PbX3 (X = Cl, Br, I) reveal the existence of several phases. In the high-temp. phase I the long spin-lattice relaxation times T1 of both nuclei and the absence of quadrupole splitting indicate extremely rapid overall reorientation of the C-N axis of the cation in a potential of cubic symmetry. In phase II of the bromide and iodide, both T1 and the small quadrupole splitting show unusual variation with temp. In the lowest-temp. phase, rotations of the C-N axis are restricted.
22. 22
  Leguy, A. M. A.; Frost, J. M.; McMahon, A. P.; Sakai, V. G.; Kochelmann, W.; Law, C.; Li, X.; Foglia, F.; Walsh, A.; O’Regan, B. C.; Nelson, J.; Cabral, J. T.; Barnes, P. R. F. The dynamics of methylammonium ions in hybrid organic-inorganic perovskite solar cells Nat. Commun. 2015, 6, 7124 DOI: 10.1038/ncomms8124
  22
  The dynamics of methylammonium ions in hybrid organic-inorganic perovskite solar cells
  Leguy Aurelien M A; McMahon Andrew P; Nelson Jenny; Barnes Piers R F; Frost Jarvist Moore; Walsh Aron; Sakai Victoria Garcia; Kochelmann W; Law ChunHung; Li Xiaoe; O'Regan Brian C; Foglia Fabrizia; Cabral Joao T
  Nature communications (2015), 6 (), 7124 ISSN:.
  Methylammonium lead iodide perovskite can make high-efficiency solar cells, which also show an unexplained photocurrent hysteresis dependent on the device-poling history. Here we report quasielastic neutron scattering measurements showing that dipolar CH3NH3(+) ions reorientate between the faces, corners or edges of the pseudo-cubic lattice cages in CH3NH3PbI3 crystals with a room temperature residence time of ∼14 ps. Free rotation, π-flips and ionic diffusion are ruled out within a 1-200-ps time window. Monte Carlo simulations of interacting CH3NH3(+) dipoles realigning within a 3D lattice suggest that the scattering measurements may be explained by the stabilization of CH3NH3(+) in either antiferroelectric or ferroelectric domains. Collective realignment of CH3NH3(+) to screen a device's built-in potential could reduce photovoltaic performance. However, we estimate the timescale for a domain wall to traverse a typical device to be ∼0.1-1 ms, faster than most observed hysteresis.
23. 23
  Chen, T.; Foley, B. J.; Ipek, B.; Tyagi, M.; Copley, J. R. D.; Brown, C. M.; Choi, J. J.; Lee, S.-H. Rotational dynamics of organic cations in the CH 3 NH 3 PbI 3 perovskite Phys. Chem. Chem. Phys. 2015, 17, 31278– 31286 DOI: 10.1039/C5CP05348J
  There is no corresponding record for this reference.
24. 24
  Quarti, C.; Mosconi, E.; De Angelis, F. Interplay of Orientational Order and Electronic Structure in Methylammonium Lead Iodide: Implications for Solar Cell Operation Chem. Mater. 2014, 26, 6557– 6569 DOI: 10.1021/cm5032046
  24
  Interplay of Orientational Order and Electronic Structure in Methylammonium Lead Iodide: Implications for Solar Cell
  Quarti, Claudio; Mosconi, Edoardo; De Angelis, Filippo
  Chemistry of Materials (2014), 26 (22), 6557-6569CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)
  The ab initio electronic structure and Car-Parrinello mol. dynamics simulations are reported for several structural models of the prototype MAPbI3 perovskite for solar cells applications. Both configurations having a preferred orientation are considered of the MA cations, giving rise to a net dipole alignment, and configurations with an isotropic distribution of the MA cations, resp. representative of polar (ferroelec.) and apolar (antiferroelec.) structures. The calcns. demonstrate the preferred stability of a set of polar structures over apolar ones, with an energy difference within 0.1 eV and a conversion barrier within 0.2 eV per unit cell (four MAPbI3), thus possibly accessible at room temp. Ferroelec.-like orientations lead to a quasi I4cm structure for the inorg. component, characterized by lack of inversion symmetry, while the antiferroelec.-like orientations are assocd. to a quasi I4/mcm structure. Ab initio mol. dynamics simulations on the polar structures show no mol. rotations in the investigated time-scale, while several MA rotations are obsd. in the same time scale for the considered apolar structure, which is thus characterized by a higher disorder. The I4cm and I4/mcm types of structure have markedly different band structures, despite showing a relatively small band gap variation. Simulations carried out on finite surface slabs demonstrate that a net orientation of the MA cations gives rise to a strong bending in the valence and conduction bands, which could definitely assist charge sepn. and reduce carrier recombination, provided one is able to effectively stabilize polar compared to apolar structures. The results could contribute an important step toward an in-depth comprehension of the basic properties of organohalide perovskites, assisting a further optimization of their photovoltaic response.
25. 25
  Brivio, F.; Frost, J. M.; Skelton, J. M.; Jackson, A. J.; Weber, O. J.; Weller, M. T.; Goñi, A. R.; Leguy, A. M. A.; Barnes, P. R. F.; Walsh, A. Lattice dynamics and vibrational spectra of the orthorhombic, tetragonal, and cubic phases of methylammonium lead iodide Phys. Rev. B: Condens. Matter Mater. Phys. 2015, 92, 144308 DOI: 10.1103/PhysRevB.92.144308
  25
  Lattice dynamics and vibrational spectra of the orthorhombic, tetragonal, and cubic phases of methylammonium lead iodide
  Brivio, Federico; Frost, Jarvist M.; Skelton, Jonathan M.; Jackson, Adam J.; Weber, Oliver J.; Weller, Mark T.; Goni, Alejandro R.; Leguy, Aurelien M. A.; Barnes, Piers R. F.; Walsh, Aron
  Physical Review B: Condensed Matter and Materials Physics (2015), 92 (14), 144308/1-144308/8CODEN: PRBMDO; ISSN:1098-0121. (American Physical Society)
  The hybrid halide perovskite CH3NH3PbI3 exhibits a complex structural behavior, with successive transitions between orthorhombic, tetragonal, and cubic polymorphs around 165 and 327 K. Herein we report first-principles lattice dynamics (phonon spectrum) for each phase of CH3NH3PbI3. The equil. structures compare well to solns. of temp.-dependent powder neutron diffraction. By following the normal modes, we calc. IR and Raman intensities of the vibrations, and compare them to the measurement of a single crystal where the Raman laser is controlled to avoid degrdn. of the sample. Despite a clear sepn. in energy between low-frequency modes assocd. with the inorg. (PbI3-)n network and high-frequency modes of the org. CH3NH3+ cation, significant coupling between them is found, which emphasizes the interplay between mol. orientation and the corner-sharing octahedral networks in the structural transformations. Soft modes are found at the boundary of the Brillouin zone of the cubic phase, consistent with displacive instabilities and anharmonicity involving tilting of the PbI6 octahedra around room temp.
26. 26
  Quarti, C.; Mosconi, E.; Ball, J. M.; D’Innocenzo, V.; Tao, C.; Pathak, S.; Snaith, H. J.; Petrozza, A.; De Angelis, F. Structural and optical properties of methylammonium lead iodide across the tetragonal to cubic phase transition: implications for perovskite solar cells Energy Environ. Sci. 2016, 9, 155– 163 DOI: 10.1039/C5EE02925B
  26
  Structural and optical properties of methylammonium lead iodide across the tetragonal to cubic phase transition: implications for perovskite solar cells
  Quarti, Claudio; Mosconi, Edoardo; Ball, James M.; D'Innocenzo, Valerio; Tao, Chen; Pathak, Sandeep; Snaith, Henry J.; Petrozza, Annamaria; De Angelis, Filippo
  Energy & Environmental Science (2016), 9 (1), 155-163CODEN: EESNBY; ISSN:1754-5706. (Royal Society of Chemistry)
  We report temp. resolved UV-vis absorption and spectral photocurrent response measurements of MAPbI3 thin films and solar cells, together with ab initio simulations, to investigate the changes in material properties occurring across the tetragonal to cubic phase transition. We find that the MAPbI3 band-gap does not abruptly change when exceeding the tetragonal to cubic transition temp., but it rather monotonically blue-shifts following the same temp. evolution obsd. within the tetragonal phase. Car-Parrinello mol. dynamics simulations demonstrate that the high temp. phase corresponds on av. to the expected sym. cubic structure assigned from XRD measurements, but that the system strongly deviates from such a structure in the sub-picosecond time scale. Thus, on the time scale of electronic transitions, the material seldom experiences a cubic environment, rather an increasingly distorted tetragonal one. This result explains the absence of dramatic changes in the optical of MAPbI3 across the explored temp. range of 270-420 K, which could have important consequences for the practical uptake of perovskite solar cells.
27. 27
  Gindl, W.; Gupta, H. S. Cell-wall hardness and Young’s modulus of melamine-modified spruce wood by nano-indentation Composites, Part A 2002, 33, 1141– 1145 DOI: 10.1016/S1359-835X(02)00080-5
  27
  Cell-wall hardness and Young's modulus of melamine-modified spruce wood by nano-indentation
  Gindl, W.; Gupta, H. S.
  Composites, Part A: Applied Science and Manufacturing (2002), 33A (8), 1141-1145CODEN: CASMFJ; ISSN:1359-835X. (Elsevier Science Ltd.)
  Samples of spruce wood were infiltrated with a melamine-HCHO resin. After curing of the resin, a melamine concn. of 24% (vol./vol.) was measured in the secondary cell walls of melamine resin-treated wood. Nano-indentation tests revealed an av. Young's modulus of 16.1 GPa and a hardness of 0.24 GPa for untreated secondary cell walls. In the melamine resin-treated cell walls, an increase in the Young's modulus of 33% to 21.4 GPa was obsd. With 115%, i.e. 0.52 GPa, the increase in longitudinal hardness because of melamine-HCHO resin treatment was even more pronounced. This proves clearly that melamine resin treatment of wood improves mech. properties of cell walls. Thus, treatment of wood with melamine-HCHO resin shows a considerable potential to improve mech. properties, as desired for applications where large stresses normal to grain arise.
28. 28
  Pisoni, A.; Jaćimović, J.; Barišić, O. S.; Spina, M.; Gaal, R.; Forró, L.; Horváth, E. Ultra-Low Thermal Conductivity in Organic-Inorganic Hybrid Perovskite CH 3NH 3PbI 3 J. Phys. Chem. Lett. 2014, 5, 2488– 2492 DOI: 10.1021/jz5012109
  28
  Ultra-Low Thermal Conductivity in Organic-Inorganic Hybrid Perovskite CH3NH3PbI3
  Pisoni, Andrea; Jacimovic, Jacim; Barisic, Osor S.; Spina, Massimo; Gaal, Richard; Forro, Laszlo; Horvath, Endre
  Journal of Physical Chemistry Letters (2014), 5 (14), 2488-2492CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
  The authors report on the temp. dependence of thermal cond. of single cryst. and polycryst. organometallic perovskite CH3NH3PbI3. The comparable abs. values and temp. dependence of the two samples' morphologies indicate the minor role of the grain boundaries on the heat transport. Theor. modeling demonstrates the importance of the resonant scattering in both specimens. The interaction between phonon waves and rotational degrees of freedom of CH3NH3+ sublattice emerges as the dominant mechanism for attenuation of heat transport and for ultralow thermal cond. of 0.5 W/(Km) at room temp.
29. 29
  Delaire, O.; Ma, J.; Marty, K.; May, A. F.; McGuire, M. A.; Du, M.-H.; Singh, D. J.; Podlesnyak, A.; Ehlers, G.; Lumsden, M. D.; Sales, B. C. Giant anharmonic phonon scattering in PbTe Nat. Mater. 2011, 10, 614– 619 DOI: 10.1038/nmat3035
  29
  Giant anharmonic phonon scattering in PbTe
  Delaire, O.; Ma, J.; Marty, K.; May, A. F.; McGuire, M. A.; Du, M-H.; Singh, D. J.; Podlesnyak, A.; Ehlers, G.; Lumsden, M. D.; Sales, B. C.
  Nature Materials (2011), 10 (8), 614-619CODEN: NMAACR; ISSN:1476-1122. (Nature Publishing Group)
  Understanding the microscopic processes affecting the bulk thermal cond. is crucial to develop more efficient thermoelec. materials. PbTe is currently one of the leading thermoelec. materials, largely thanks to its low thermal cond. However, the origin of this low thermal cond. in a simple rocksalt structure has so far been elusive. Using a combination of inelastic neutron scattering measurements and first-principles computations of the phonons, we identify a strong anharmonic coupling between the ferroelec. transverse optic mode and the longitudinal acoustic modes in PbTe. This interaction extends over a large portion of reciprocal space, and directly affects the heat-carrying longitudinal acoustic phonons. The longitudinal acoustic-transverse optic anharmonic coupling is likely to play a central role in explaining the low thermal cond. of PbTe. The present results provide a microscopic picture of why many good thermoelec. materials are found near a lattice instability of the ferroelec. type.
30. 30
  Li, C. W.; Hong, J.; May, A. F.; Bansal, D.; Chi, S.; Hong, T.; Ehlers, G.; Delaire, O. Orbitally driven giant phonon anharmonicity in SnSe Nat. Phys. 2015, 11, 1063– 1069 DOI: 10.1038/nphys3492
  30
  Orbitally driven giant phonon anharmonicity in SnSe
  Li, C. W.; Hong, J.; May, A. F.; Bansal, D.; Chi, S.; Hong, T.; Ehlers, G.; Delaire, O.
  Nature Physics (2015), 11 (12), 1063-1069CODEN: NPAHAX; ISSN:1745-2473. (Nature Publishing Group)
  Understanding elementary excitations and their couplings in condensed matter systems is crit. for developing better energy-conversion devices. In thermoelec. materials, the heat-to-electricity conversion efficiency is directly improved by suppressing the propagation of phonon quasiparticles responsible for macroscopic thermal transport. The current record material for thermoelec. conversion efficiency, SnSe, has an ultralow thermal cond., but the mechanism behind the strong phonon scattering remains largely unknown. From inelastic neutron scattering measurements and first-principles simulations, we mapped the four-dimensional phonon dispersion surfaces of SnSe, and found the origin of the ionic-potential anharmonicity responsible for the unique properties of SnSe. We show that the giant phonon scattering arises from an unstable electronic structure, with orbital interactions leading to a ferroelec.-like lattice instability. The present results provide a microscopic picture connecting electronic structure and phonon anharmonicity in SnSe, and offers new insights on how electron-phonon and phonon-phonon interactions may lead to the realization of ultralow thermal cond.
31. 31
  Karakus, M.; Jensen, S. A.; D’Angelo, F.; Turchinovich, D.; Bonn, M.; Cánovas, E. Phonon-Electron Scattering Limits Free Charge Mobility in Methylammonium Lead Iodide Perovskites J. Phys. Chem. Lett. 2015, 6, 4991– 4996 DOI: 10.1021/acs.jpclett.5b02485
  31
  Phonon-Electron Scattering Limits Free Charge Mobility in Methylammonium Lead Iodide Perovskites
  Karakus, Melike; Jensen, Soeren A.; D'Angelo, Francesco; Turchinovich, Dmitry; Bonn, Mischa; Canovas, Enrique
  Journal of Physical Chemistry Letters (2015), 6 (24), 4991-4996CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
  The nature of the photocond. in soln.-processed films of methylammonium lead iodide perovskite was studied by detg. the variation of the photoconductive response with temp. Ultrabroadband terahertz (THz) photocond. spectra in the 0.3-10 THz range can be reproduced well by a simple Drude-like response at room temp., where free charge carrier motion was characterized by an av. scattering time. The scattering time detd. from Drude fits in the 0.3-2THz region increases from ∼4 fs at 300 K (tetragonal phase; mobility of ∼27 cm2 V-1 s-1) to almost ∼25 fs at 77 K (orthorhombic phase, mobility of ∼150 cm2 V-1 s-1). For the tetragonal phase (temp. range 150 < T < 300 K) the scattering time shows a approx. T-3/2 dependence, approaching the theor. limit for pure acoustic phonon (deformation potential) scattering. Hence, electron-phonon, rather than impurity scattering, sets the upper limit on free charge transport for this perovskite.
32. 32
  Frost, J. M.; Walsh, A. What Is Moving in Hybrid Halide Perovskite Solar Cells? Acc. Chem. Res. 2016, 49, 528– 535 DOI: 10.1021/acs.accounts.5b00431
  32
  What Is Moving in Hybrid Halide Perovskite Solar Cells?
  Frost, Jarvist M.; Walsh, Aron
  Accounts of Chemical Research (2016), 49 (3), 528-535CODEN: ACHRE4; ISSN:0001-4842. (American Chemical Society)
  Org.-inorg. semiconductors, which adopt the perovskite crystal structure, have perturbed the landscape of contemporary photovoltaics research. High-efficiency solar cells can be produced with soln.-processed active layers. The materials are earth abundant, and the simple processing required suggests that high-throughput and low-cost manuf. at scale should be possible.While these materials bear considerable similarity to traditional inorg. semiconductors, there are notable differences in their optoelectronic behavior. A key distinction of these materials is that they are phys. soft, leading to considerable thermally activated motion.In this Account, we discuss the internal motion of methylammonium lead iodide (CH3NH3PbI3) and formamidinium lead iodide ([CH(NH2)2]PbI3), covering: (i) mol. rotation-libration in the cuboctahedral cavity; (ii) drift and diffusion of large electron and hole polarons; (iii) transport of charged ionic defects. These processes give rise to a range of properties that are unconventional for photovoltaic materials, including frequency-dependent permittivity, low electron-hole recombination rates, and current-voltage hysteresis. Multiscale simulations, drawing from electronic structure, ab initio mol. dynamic and Monte Carlo computational techniques, have been combined with neutron diffraction measurements, quasi-elastic neutron scattering, and ultrafast vibrational spectroscopy to qualify the nature and time scales of the motions. Electron and hole motion occurs on a femtosecond time scale. Mol. libration is a sub-picosecond process. Mol. rotations occur with a time const. of several picoseconds depending on the cation. Recent exptl. evidence and theor. models for simultaneous electron and ion transport in these materials has been presented, suggesting they are mixed-mode conductors with similarities to fast-ion conducting metal oxide perovskites developed for battery and fuel cell applications. We expound on the implications of these effects for the photovoltaic action.The temporal behavior displayed by hybrid perovskites introduces a sensitivity in materials characterization to the time and length scale of the measurement, as well as the history of each sample. It also poses significant challenges for accurate materials modeling and device simulations. There are large differences between the av. and local crystal structures, and the nature of charge transport is too complex to be described by common one-dimensional drift-diffusion models. Herein, we critically discuss the atomistic origin of the dynamic processes and the assocd. chem. disorder intrinsic to cryst. hybrid perovskite semiconductors.
33. 33
  Weller, M. T.; Weber, O. J.; Henry, P. F.; Di Pumpo, A. M.; Hansen, T. C. Complete structure and cation orientation in the perovskite photovoltaic methylammonium lead iodide between 100 and 352 K Chem. Commun. 2015, 51, 4180– 4183 DOI: 10.1039/C4CC09944C
  33
  Complete structure and cation orientation in the perovskite photovoltaic methylammonium lead iodide between 100 and 352 K
  Weller, Mark T.; Weber, Oliver J.; Henry, Paul F.; Di Pumpo, Antonietta M.; Hansen, Thomas C.
  Chemical Communications (Cambridge, United Kingdom) (2015), 51 (20), 4180-4183CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)
  The methylammonium cation in [CH3NH3]PbI3 demonstrates increasing positional disorder on heating from 100 K to 352 K. In the tetragonal phase, stable between 165 K and 327 K, the cation is disordered over four sites directed toward the faces of the distorted cubic [PbI3]- framework and migrates towards the cavity center with increasing temp. Crystallog. data and at. coordinates are given.
34. 34
  Ren, Y.; Oswald, I. W. H.; Wang, X.; McCandless, G. T.; Chan, J. Y. Orientation of Organic Cations in Hybrid Inorganic-Organic Perovskite CH₃NH₃PbI₃ from Subatomic Resolution Single Crystal Neutron Diffraction Structural Studies Cryst. Growth Des. 2016, 16, 2945– 2951 DOI: 10.1021/acs.cgd.6b00297
  34
  Orientation of Organic Cations in Hybrid Inorganic-Organic Perovskite CH3NH3PbI3 from Subatomic Resolution Single Crystal Neutron Diffraction Structural Studies
  Ren, Yixin; Oswald, Iain W. H.; Wang, Xiaoping; McCandless, Gregory T.; Chan, Julia Y.
  Crystal Growth & Design (2016), 16 (5), 2945-2951CODEN: CGDEFU; ISSN:1528-7483. (American Chemical Society)
  The authors report the crystal growth of well-faceted single crystals of methylammonium lead iodide, MeNH3PbI3, and detailed single crystal neutron diffraction structural studies aimed at elucidating the orientation of the methylammonium (MeNH3+) cation in the tetragonal and cubic phases of the hybrid inorg.-org. perovskite. Room temp. expts. reveal a tetragonal structure where the protonated amine substituent (-NH3+) of the cation is disordered in 4 positions, each preferentially located near the neighboring I of the [PbI6] octahedra, while the Me substituent (-Me) is disordered in 8 positions located near the body position of the unit cell. High temp. expts. show a cubic structure where the cation aligns along the [011] (edge), the [111] (diagonal), and the [100] (face) directions of the unit cell. The resulting site occupancy ratio suggests the MeNH3+ cation resides primarily along the [011] direction, in agreement with reported DFT calcns. One important feature that was obsd. for both tetragonal and cubic structures measured at 295 and 350 K, resp., is the middle point of the C-N bond being located off-center from the high symmetry sites in the crystal structure, induced by the formation of H bond-like interactions between the -NH3+ substituent of the org. cation and the I atoms of [PbI6] octahedra.
35. 35
  Brivio, F.; Butler, K. T.; Walsh, A.; van Schilfgaarde, M. Relativistic quasiparticle self-consistent electronic structure of hybrid halide perovskite photovoltaic absorbers Phys. Rev. B: Condens. Matter Mater. Phys. 2014, 89, 155204 DOI: 10.1103/PhysRevB.89.155204
  35
  Relativistic quasiparticle self-consistent electronic structure of hybrid halide perovskite photovoltaic absorbers
  Brivio, Federico; Butler, Keith T.; Walsh, Aron; van Schilfgaarde, Mark
  Physical Review B: Condensed Matter and Materials Physics (2014), 89 (15), 155204/1-155204/6CODEN: PRBMDO; ISSN:1098-0121. (American Physical Society)
  Solar cells based on a light absorbing layer of the organometal halide perovskite CH3NH3PbI3 have recently surpassed 15% conversion efficiency, though how these materials work remains largely unknown. We analyze the electronic structure and optical properties within the quasiparticle self-consistent GW approxn. While this compd. bears some similarity to conventional sp semiconductors, it also displays unique features. Quasiparticle self-consistency is essential for an accurate description of the band structure: Band gaps are much larger than what is predicted by the local-d. approxn. (LDA) or GW based on the LDA. Valence band dispersions are modified in a very unusual manner. In addn., spin-orbit coupling strongly modifies the band structure and gives rise to unconventional dispersion relations and a Dresselhaus splitting at the band edges. The av. hole mass is small, which partially accounts for the long diffusion lengths obsd. The surface ionization potential (work function) is calcd. to be 5.7 eV with respect to the vacuum level, explaining efficient carrier transfer to TiO2 and Au elec. contacts.
36. 36
  Kocsis, S. Lattice scattering mobility of electrons in GaP Phys. Status Solidi A 1975, 28, 133– 138 DOI: 10.1002/pssa.2210280113
  There is no corresponding record for this reference.
37. 37
  Worhatch, R. J.; Kim, H.; Swainson, I. P.; Yonkeu, A. L.; Billinge, S. J. L. Study of Local Structure in Selected Organic-Inorganic Perovskites in the Pm3m Phase Chem. Mater. 2008, 20, 1272– 1277 DOI: 10.1021/cm702668d
  There is no corresponding record for this reference.
38. 38
  Spingler, B.; Schnidrig, S.; Todorova, T.; Wild, F. Some thoughts about the single crystal growth of small molecules CrystEngComm 2012, 14, 751– 757 DOI: 10.1039/C1CE05624G
  38
  Some thoughts about the single crystal growth of small molecules
  Spingler, Bernhard; Schnidrig, Stephan; Todorova, Tonya; Wild, Ferdinand
  CrystEngComm (2012), 14 (3), 751-757CODEN: CRECF4; ISSN:1466-8033. (Royal Society of Chemistry)
  This highlight critically compares various techniques to grow single crystals when only a few milligrams are available of the compd. of interest. The authors describe vapor diffusion, evapn., cooling, and layering techniques, as well as crystn. in gels. A table of successfully applied solvent/antisolvent combinations for initial screening is given. Addnl., a comprehensive table of 107 solvents with their b.ps., densities and dielec. consts. helps to optimize the crystal growth.
39. 39
  Glaser, T.; Müller, C.; Sendner, M.; Krekeler, C.; Semonin, O. E.; Hull, T. D.; Yaffe, O.; Owen, J. S.; Kowalsky, W.; Pucci, A.; Lovrinčić, R. Infrared Spectroscopic Study of Vibrational Modes in Methylammonium Lead Halide Perovskites J. Phys. Chem. Lett. 2015, 6, 2913– 2918 DOI: 10.1021/acs.jpclett.5b01309
  39
  Infrared Spectroscopic Study of Vibrational Modes in Methylammonium Lead Halide Perovskites
  Glaser, Tobias; Mueller, Christian; Sendner, Michael; Krekeler, Christian; Semonin, Octavi E.; Hull, Trevor D.; Yaffe, Omer; Owen, Jonathan S.; Kowalsky, Wolfgang; Pucci, Annemarie; Lovrincic, Robert
  Journal of Physical Chemistry Letters (2015), 6 (15), 2913-2918CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
  The org. cation and its interplay with the inorg. lattice underlie the exceptional optoelectronic properties of organo-metallic halide perovskites. Herein the authors report high-quality IR spectroscopic measurements of methylammonium lead halide perovskite (CH3NH3Pb(I/Br/Cl)3) films and single crystals at room temp., from which the dielec. function in the studied spectral range is derived. Comparison with electronic structure calcns. in vacuum of the free methylammonium cation allows for a detailed peak assignment. The authors analyze the shifts of the vibrational peak positions between the different halides and infer the extent of interaction between org. moiety and the surrounding inorg. cage. The positions of the NH3+ stretching vibrations point to significant hydrogen bonding between the methylammonium and the halides for all three perovskites.
40. 40
  Toellner, T. S.; Alatas, A.; Said, A. H. Six-reflection meV-monochromator for synchrotron radiation J. Synchrotron Radiat. 2011, 18, 605– 611 DOI: 10.1107/S0909049511017535
  40
  Six-reflection meV-monochromator for synchrotron radiation
  Toellner T S; Alatas A; Said A H
  Journal of synchrotron radiation (2011), 18 (Pt 4), 605-11 ISSN:.
  An in-line monochromatization scheme suitable for 10-40 keV synchrotron radiation is presented based on the use of six crystal reflections that achieves meV and sub-meV bandwidths with high efficiency. The theoretical spectral efficiency surpasses all previous multicrystal designs and approaches that of single room-temperature back-reflecting crystals. This article presents the designs of two such devices along with their theoretical and measured performances.
41. 41
  Said, A. H.; Sinn, H.; Divan, R. New developments in fabrication of high-energy-resolution analyzers for inelastic X-ray spectroscopy J. Synchrotron Radiat. 2011, 18, 492– 496 DOI: 10.1107/S0909049511001828
  41
  New developments in fabrication of high-energy-resolution analyzers for inelastic X-ray spectroscopy
  Said Ayman H; Sinn Harald; Divan Ralu
  Journal of synchrotron radiation (2011), 18 (Pt 3), 492-6 ISSN:.
  In this work new improvements related to the fabrication of spherical bent analyzers for 1 meV energy-resolution inelastic X-ray scattering spectroscopy are presented. The new method includes the use of a two-dimensional bender to achieve the required radius of curvature for X-ray analyzers. The advantage of this method is the ability to monitor the focus during bending, which leads to higher-efficiency analyzers.
42. 42
  Sinn, H. Spectroscopy with meV energy resolution J. Phys.: Condens. Matter 2001, 13, 7525– 7537 DOI: 10.1088/0953-8984/13/34/305
  42
  Spectroscopy with meV energy resolution
  Sinn, Harald
  Journal of Physics: Condensed Matter (2001), 13 (34), 7525-7537CODEN: JCOMEL; ISSN:0953-8984. (Institute of Physics Publishing)
  A review. Inelastic x-ray scattering has become a powerful tool in condensed matter physics in recent years. This is due to the advent of the 3rd-generation synchrotron radiation sources, which provide an intense and collimated x-ray beam, and due to improvements in x-ray optics. This article is an introduction to the basic principles of inelastic x-ray scattering with meV resoln. In particular the geometric and crystal contributions for monochromator and analyzer crystals are discussed. Also, an estn. of phonon intensities, obtained with a meV spectrometer, is derived.
43. 43
  Burkel, E. Phonon spectroscopy by inelastic x-ray scattering Rep. Prog. Phys. 2000, 63, 171– 232 DOI: 10.1088/0034-4885/63/2/203
  43
  Phonon spectroscopy by inelastic x-ray scattering
  Burkel, Eberhard
  Reports on Progress in Physics (2000), 63 (2), 171-232CODEN: RPPHAG; ISSN:0034-4885. (Institute of Physics Publishing)
  A review with many refs. The present synchrotron sources with brilliant x-ray beams, due to high photon fluxes, small source sizes and high collimation, have revolutionized x-ray physics. Enormous progress was initiated in all established x-ray methods, with the aim of the development of new types of spectroscopy. This is particularly true for the spectroscopy of the dynamics in condensed matter. Meanwhile, there are 2 powerful x-ray methods with very high-energy resoln. available for the study of low energetic excitations like phonons. This review summarizes the developments of these methods focusing on these instrumental developments of the spectrometers using either crystal optics in close-to-backscattering geometry or nuclear resonant techniques. Applications to measurements of phonon dispersion curves and of phonon d. of states in ordered and disordered solids and in liqs. are presented. It is shown how x-ray results are stimulating improvements in the theor. approaches to the dynamics. New insights into the dynamics of liqs. are discussed. The sensitivities of the spectroscopies allow the study of vibrational behavior in very small amts. of material even in nanometer-sized thin films or particles. We can already analyze the phonon spectrum of a monolayered nuclear resonant isotope. Prospects of the techniques are also demonstrated.
44. 44
  Dorner, B. The scattering function and symmetry operations in the crystal. Coherent inelastic neutron scaterring in lattice dynamics; 1982; pp 16– 24.
  There is no corresponding record for this reference.
45. 45
  Chupas, P. J.; Qiu, X.; Hanson, J. C.; Lee, P. L.; Grey, C. P.; Billinge, S. J. L. Rapid-acquisition pair distribution function (RA-PDF) analysis J. Appl. Crystallogr. 2003, 36, 1342– 1347 DOI: 10.1107/S0021889803017564
  45
  Rapid-acquisition pair distribution function (RA-PDF) analysis
  Chupas, Peter J.; Qiu, Xiangyun; Hanson, Jonathan C.; Lee, Peter L.; Grey, Clare P.; Billinge, Simon J. L.
  Journal of Applied Crystallography (2003), 36 (6), 1342-1347CODEN: JACGAR; ISSN:0021-8898. (Blackwell Publishing Ltd.)
  An image-plate (IP) detector coupled with high-energy synchrotron radiation was used for at. pair distribution function (PDF) anal., with high probed momentum transfer Qmax ≤ 28.5 Å-1, from cryst. materials. Materials with different structural complexities were measured to test the validity of the quant. data anal. Exptl. results are presented for cryst. Ni, cryst. α-AlF3, and the layered Aurivillius type oxides α-Bi4V2O11 and γ-Bi4V1.7Ti0.3O10.85. Overall, the diffraction patterns show good counting statistics, with measuring time from one to tens of seconds. The PDFs obtained are of high quality. Structures may be refined from these PDFs, and the structural models are consistent with the published literature. Data sets from similar samples are highly reproducible.
46. 46
  Hammersley, A. P.; Svensson, S. O.; Hanfland, M.; Fitch, A. N.; Hausermann, D. Two-dimensional detector software: From real detector to idealised image or two-theta scan High Pressure Res. 1996, 14, 235– 248 DOI: 10.1080/08957959608201408
  There is no corresponding record for this reference.
47. 47
  Juhás, P.; Davis, T.; Farrow, C. L.; Billinge, S. J. L. PDFgetX3: a rapid and highly automatable program for processing powder diffraction data into total scattering pair distribution functions J. Appl. Crystallogr. 2013, 46, 560– 566 DOI: 10.1107/S0021889813005190
  47
  PDFgetX3: a rapid and highly automatable program for processing powder diffraction data into total scattering pair distribution functions
  Juhas, P.; Davis, T.; Farrow, C. L.; Billinge, S. J. L.
  Journal of Applied Crystallography (2013), 46 (2), 560-566CODEN: JACGAR; ISSN:0021-8898. (International Union of Crystallography)
  PDFgetX3 is a new software application for converting x-ray powder diffraction data to an at. pair distribution function (PDF). PDFgetX3 was designed for ease of use, speed and automated operation. The software can readily process hundreds of x-ray patterns within a few seconds and is thus useful for high-throughput PDF studies that measure numerous data sets as a function of time, temp. or other environmental parameters. In comparison to the preceding programs, PDFgetX3 requires fewer inputs and less user experience and it can be readily adopted by novice users. The live-plotting interactive feature allows the user to assess the effects of calcn. parameters and select their optimum values. PDFgetX3 uses an ad hoc data correction method, where the slowly changing structure-independent signal is filtered out to obtain coherent x-ray intensities that contain structure information. The output from PDFgetX3 was verified by processing exptl. PDFs from inorg., org. and nanosized samples and comparing them with their counterparts from a previous established software. In spite of the different algorithm, the obtained PDFs were nearly identical and yielded highly similar results when used in structure refinement. PDFgetX3 is written in the Python language and features a well documented reusable code base. The software can be used either as a standalone application or as a library of PDF processing functions that can be called from other Python scripts. The software is free for open academic research but requires paid license for com. use.
48. 48
  Yang, X.; Juhás, P.; Farrow, C. L.; Billinge, S. J. L. xPDFsuite: an end-to-end software solution for high throughput pair distribution function transformation, visualization and analysis. arXiv:1402.3163 [cond-mat] 2014.
  There is no corresponding record for this reference.
49. 49
  Farrow, C. L.; Juhas, P.; Liu, J. W.; Bryndin, D.; Božin, E. S.; Bloch, J.; Proffen, T.; Billinge, S. J. L. PDFfit2 and PDFgui: computer programs for studying nanostructure in crystals J. Phys.: Condens. Matter 2007, 19, 335219 DOI: 10.1088/0953-8984/19/33/335219
  49
  PDFfit2 and PDFgui: computer programs for studying nanostructure in crystals
  Farrow, C. L.; Juhas, P.; Liu, J. W.; Bryndin, D.; Bozin, E. S.; Bloch, J.; Proffen, Th; Billinge, S. J. L.
  Journal of Physics: Condensed Matter (2007), 19 (33), 335219/1-335219/7CODEN: JCOMEL; ISSN:0953-8984. (Institute of Physics Publishing)
  PDFfit2 is a program as well as a library for real-space refinement of crystal structures. It is capable of fitting a theor. three-dimensional (3D) structure to at. pair distribution function data and is ideal for nanoscale investigations. The fit system accounts for lattice consts., at. positions and anisotropic at. displacement parameters, correlated at. motion, and exptl. factors that may affect the data. The at. positions and thermal coeffs. can be constrained to follow the symmetry requirements of an arbitrary space group. The PDFfit2 engine is written in C++ and is accessible via Python, allowing it to inter-operate with other Python programs. PDFgui is a graphical interface built on the PDFfit2 engine. PDFgui organizes fits and simplifies many data anal. tasks, such as configuring and plotting multiple fits. PDFfit2 and PDFgui are freely available via the Internet.
50. 50
  Kresse, G.; Hafner, J. Ab initio molecular dynamics for liquid metals Phys. Rev. B: Condens. Matter Mater. Phys. 1993, 47, 558– 561 DOI: 10.1103/PhysRevB.47.558
  50
  Ab initio molecular dynamics of liquid metals
  Kresse, G.; Hafner, J.
  Physical Review B: Condensed Matter and Materials Physics (1993), 47 (1), 558-61CODEN: PRBMDO; ISSN:0163-1829.
  The authors present ab initio quantum-mech. mol.-dynamics calcns. based on the calcn. of the electronic ground state and of the Hellmann-Feynman forces in the local-d. approxn. at each mol.-dynamics step. This is possible using conjugate-gradient techniques for energy minimization, and predicting the wave functions for new ionic positions using sub-space alignment. This approach avoids the instabilities inherent in quantum-mech. mol.-dynamics calcns. for metals based on the use of a factitious Newtonian dynamics for the electronic degrees of freedom. This method gives perfect control of the adiabaticity and allows one to perform simulations over several picoseconds.
51. 51
  Togo, A.; Oba, F.; Tanaka, I. First-principles calculations of the ferroelastic transition between rutile-type and CaCl₂-type SiO₂ at high pressures Phys. Rev. B: Condens. Matter Mater. Phys. 2008, 78, 134106 DOI: 10.1103/PhysRevB.78.134106
  51
  First-principles calculations of the ferroelastic transition between rutile-type and CaCl2-type SiO2 at high pressures
  Togo, Atsushi; Oba, Fumiyasu; Tanaka, Isao
  Physical Review B: Condensed Matter and Materials Physics (2008), 78 (13), 134106/1-134106/9CODEN: PRBMDO; ISSN:1098-0121. (American Physical Society)
  The tetragonal to orthorhombic ferroelastic phase transition between rutile- and CaCl2-type SiO2 at high pressures was studied using 1st-principles calcns. and the Landau free-energy expansion. The phase transition is systematically studied in terms of characteristic phonon modes with B1g and Ag symmetries, shear moduli, transverse-acoustic mode, rotation angle of the SiO6 octahedra, spontaneous symmetry-breaking and vol. strains, and enthalpy. These phys. behaviors at the transition are well described using the Landau free-energy expansion parametrized by the 1st-principles calcns.
52. 52
  Togo, A.; Tanaka, I. First principles phonon calculations in materials science Scr. Mater. 2015, 108, 1– 5 DOI: 10.1016/j.scriptamat.2015.07.021
  52
  First principles phonon calculations in materials science
  Togo, Atsushi; Tanaka, Isao
  Scripta Materialia (2015), 108 (), 1-5CODEN: SCMAF7; ISSN:1359-6462. (Elsevier Ltd.)
  Phonon plays essential roles in dynamical behaviors and thermal properties, which are central topics in fundamental issues of materials science. The importance of first principles phonon calcns. cannot be overly emphasized. Phonopy is an open source code for such calcns. launched by the present authors, which has been world-widely used. Here we demonstrate phonon properties with fundamental equations and show examples how the phonon calcns. are applied in materials science.
53. 53
  Blöchl, P. E. Projector augmented-wave method Phys. Rev. B: Condens. Matter Mater. Phys. 1994, 50, 17953– 17979 DOI: 10.1103/PhysRevB.50.17953
  53
  Projector augmented-wave method
  Blochl
  Physical review. B, Condensed matter (1994), 50 (24), 17953-17979 ISSN:0163-1829.
  There is no expanded citation for this reference.
54. 54
  Kresse, G.; Joubert, D. From ultrasoft pseudopotentials to the projector augmented-wave method Phys. Rev. B: Condens. Matter Mater. Phys. 1999, 59, 1758– 1775 DOI: 10.1103/PhysRevB.59.1758
  54
  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.
55. 55
  Momma, K.; Izumi, F. VESTA 3 for three-dimensional visualization of crystal, volumetric and morphology data J. Appl. Crystallogr. 2011, 44, 1272– 1276 DOI: 10.1107/S0021889811038970
  55
  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.
56. 56
  Frost, J. M.; Butler, K. T.; Walsh, A. Molecular ferroelectric contributions to anomalous hysteresis in hybrid perovskite solar cells APL Mater. 2014, 2, 081506 DOI: 10.1063/1.4890246
  56
  Molecular ferroelectric contributions to anomalous hysteresis in hybrid perovskite solar cells
  Frost, Jarvist M.; Butler, Keith T.; Walsh, Aron
  APL Materials (2014), 2 (8), 081506/1-081506/10CODEN: AMPADS; ISSN:2166-532X. (American Institute of Physics)
  We report a model describing the mol. orientation disorder in CH3NH3PbI3, solving a classical Hamiltonian parametrised with electronic structure calcns., with the nature of the motions informed by ab initio mol. dynamics. We investigate the temp. and static elec. field dependence of the equil. ferroelec. (mol.) domain structure and resulting polarisability. A rich domain structure of twinned mol. dipoles is obsd., strongly varying as a function of temp. and applied elec. field. We propose that the internal elec. fields assocd. with microscopic polarisation domains contribute to hysteretic anomalies in the current-voltage response of hybrid org.-inorg. perovskite solar cells due to variations in electron-hole recombination in the bulk. (c) 2014 American Institute of Physics.
Supporting Information
Supporting Information
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsenergylett.6b00381.
- Figures showing the crystal of CH₃NH₃PbI₃ used for HERIX measurements, HERIX spectra fitting, calculated potential energy surfaces for ion displacement in CH₃NH₃PbI₃ comparison of PDF refinements, HERIX energy scans as a function of temperature, and evidence of sample instability in the X-ray beam as well as a table of extracted elastic constants (PDF)
- nz6b00381_si_001.pdf (3.47 MB)
Terms & Conditions

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.

You have not visited any articles yet, Please visit some articles to see contents here.

All Types

Direct Observation of Dynamic Symmetry Breaking above Room Temperature in Methylammonium Lead Iodide Perovskite
Click to copy article linkArticle link copied!

ACS Energy Letters

Publication History

Abstract

Subjects

Figure 1

Figure 2

Figure 3

Figure 4

Experimental Section

Supporting Information

Terms & Conditions

Author Information

Acknowledgment

Added in Proof

References

Cited By

ACS Energy Letters

Publication History

Article Views

Altmetric

Citations

Recommended Articles

Abstract

Figure 1

Figure 2

Figure 3

Figure 4

References

Supporting Information

Supporting Information

Terms & Conditions

Direct Observation of Dynamic Symmetry Breaking above Room Temperature in Methylammonium Lead Iodide PerovskiteClick to copy article linkArticle link copied!

ACS Energy Letters

Abstract

Figure 1

Figure 2

Figure 3

Figure 4

Experimental Section

Supporting Information

Terms & Conditions

Author Information

Acknowledgment

Added in Proof

References

Cited By

ACS Energy Letters

Article Views

Altmetric

Citations

Recommended Articles

Abstract

Figure 1

Figure 2

Figure 3

Figure 4

References

Supporting Information

Supporting Information

Terms & Conditions

Direct Observation of Dynamic Symmetry Breaking above Room Temperature in Methylammonium Lead Iodide Perovskite
Click to copy article linkArticle link copied!