Spin-Dependent Photovoltaic and Photogalvanic Responses of Optoelectronic Devices Based on Chiral Two-Dimensional Hybrid Organic–Inorganic Perovskites
- Jingying WangJingying WangDepartment of Physics & Astronomy, University of Utah, Salt Lake City, Utah 84112, United StatesMore by Jingying Wang
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- Haipeng LuHaipeng LuChemistry & Nanoscience Center, National Renewable Energy Laboratory, Golden, Colorado 80401, United StatesMore by Haipeng Lu
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- Xin PanXin PanDepartment of Physics & Astronomy, University of Utah, Salt Lake City, Utah 84112, United StatesMore by Xin Pan
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- Junwei XuJunwei XuStanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United StatesMore by Junwei Xu
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- Haoliang LiuHaoliang LiuDepartment of Physics & Astronomy, University of Utah, Salt Lake City, Utah 84112, United StatesMore by Haoliang Liu
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- Xiaojie LiuXiaojie LiuDepartment of Physics & Astronomy, University of Utah, Salt Lake City, Utah 84112, United StatesMore by Xiaojie Liu
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- Dipak R. KhanalDipak R. KhanalDepartment of Physics & Astronomy, University of Utah, Salt Lake City, Utah 84112, United StatesMore by Dipak R. Khanal
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- Michael F. ToneyMichael F. ToneyStanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United StatesMore by Michael F. Toney
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- Matthew C. BeardMatthew C. BeardChemistry & Nanoscience Center, National Renewable Energy Laboratory, Golden, Colorado 80401, United StatesMore by Matthew C. Beard
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- Z. Valy Vardeny*Z. Valy Vardeny*Email: [email protected]Department of Physics & Astronomy, University of Utah, Salt Lake City, Utah 84112, United StatesMore by Z. Valy Vardeny
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Abstract
Two-dimensional hybrid organic–inorganic perovskites (2D-HOIPs) that form natural multiple quantum wells have attracted increased research interest due to their interesting physics and potential applications in optoelectronic devices. Recent studies have shown that spintronics applications can also be introduced to 2D-HOIPs upon integrating chiral organic ligands into the organic layers. Here we report spin-dependent photovoltaic and photogalvanic responses of optoelectronic devices based on chiral 2D-HOIPs, namely, (R-MBA)2PbI4 and (S-MBA)2PbI4. The out-of-plane photocurrent response in vertical photovoltaic devices exhibits ∼10% difference upon right and left circularly polarized light (CPL) excitation, which originates from selective spin transport through the chiral multilayers. In contrast, the in-plane photocurrent response generated by CPL excitation of planar photoconductive devices shows a typical response of chirality-induced circular photogalvanic effect that originates from the Rashba splitting in the electronic bands of these compounds. Our studies may lead to potential applications of chiral 2D-HOIPs in optoelectronic devices that are sensitive to the light helicity.
Two-dimensional hybrid organic–inorganic perovskites (2D-HOIPs) are composed of alternating organic and inorganic layers, in which the electronic excitations are localized in the inorganic layers due to large potential barriers caused by the adjacent organic layers. (1,2) These materials have recently attracted increased interest due to extraordinary physics and potential optoelectronic applications coupled with solution-processed fabrication and chemical tunability that govern the active spectral range of these compounds. (3−6) Other studies have demonstrated that the 2D-HOIPs have also attractive spin-related properties, such as relatively long spin lifetime and Rashba spin splitting of the continuum bands and, therefore, may be also used for spintronic applications. (7−10) Recently, an interesting method of enhancing the spintronic properties of 2D-HOIPs has been advanced, in which chirality in the compound was introduced by chiral ligands in the organic layers that influence the electronic properties of the inorganic layers. (8,11−17)
Chirality is an important structural property of material systems. Right-handed and left-handed chiral materials have identical chemical composition and conformation, which cannot overlap by a mirror transformation; this also breaks the inversion symmetry. (17,18) It is noteworthy that chirality plays an important role in biological and pharmaceutical fields. (19,20) In addition, chirality also induces extraordinary optical and spin-related properties. For example, circularly polarized photoluminescence emission was demonstrated in chiral 2D-HOIPs, where ∼3% polarization degree was detected in the absence of magnetic field. (8,14,21,22) Also “spin filtering” has been achieved with layers of chiral material via the so-called chirality-induced spin selectivity (CISS), in which the transport of one electron spin species is favorable over the opposite species. (18,23−25)
Previously we reported spin-selective transport in chiral right-handed (R-MBA)2PbI4 and left-handed (S-MBA)2PbI4 methylbenzylammonium (MBA) lead iodide based spintronic devices; (11) their molecular structure is shown in Figure 1a. Due to the CISS process, we showed that the transport of one spin orientation in these 2D-HOIPs is enhanced over the other spin orientation, depending on the specific chirality of the perovskite. In the present work we study the photovoltaic and photogalvanic responses of optoelectronic devices based on these chiral 2D-HOIPs. In vertical photovoltaic devices we show that circularly polarized light (CPL) generates spin-oriented electrons and holes of which transport in the chiral 2D-HOIP device is preferentially filtered depending on the perovskite specific chirality. Consequently, the photocurrent is spin-polarized, and thus the device I–V characteristic response under CPL illumination depends on the excitation light helicity and the 2D-HOIP chirality. The largest obtained difference in the device photocurrent (ΔI/I) with different CPL sense was measured to be ∼10% at 7 K. In contrast, photovoltaic devices based on (rac-MBA)2PbI4, which is not chiral, do not differentiate between the left- and right-handed polarization of the CPL illumination. In addition we demonstrate that the photocurrent in planar photoconductive devices based on the same chiral 2D-HOIPs is also light-helicity-sensitive, showing a typical circular photogalvanic (CPGE) response that is due to Rashba splitting in the electronic bands. Importantly, the CPGE response changes polarity for right- and left-handed chiral 2D-HOIPs, indicating that the chirality plays an important role in the inversion symmetry breaking of these compounds. (18)
Figure 1
Figure 1. Structural characterizations of the chiral 2D-HOIPs. (a) Crystalline structure of the chiral 2D hybrid perovskite ((R/S-)methylbenzylammonium lead iodide, (R/S-MBA)2PbI4. GIWAXS of the (R-MBA)2PbI4 (b) and (S-MBA)2PbI4 (c) films. (d) Absorption spectra of (R/S/rac-MBA)2PbI4 films. (e) Circular dichroism (CD) spectra of (R/S/rac-MBA)2PbI4 films as denoted, measured at room temperature. The CD polarities of (R-MBA)2PbI4 and (S-MBA)2PbI4 are opposite to each other, whereas (rac-MBA)2PbI4 shows no CD. The absorption bands in (d) and CD bands in (e) due to exciton (EX) and interband (IB) are denoted.
Results and Discussion
ARTICLE SECTIONS
Materials Characterization
The chemical structure of chiral 2D-HOIPs (R/S-MBA)2PbI4 is illustrated in Figure 1a. The inorganic layer consists of PbI42– octahedra, which is the same as common 2D-HOIPs. However, here the organic layer is composed of organic ligands of methylbenzylammonium, (MBA)+. (26) This organic ligand comes with the left-handed and right-handed enantiomers (R-MBA)+ and (S-MBA)+, respectively, which introduce chirality into the 2D-HOIP multilayers. (27) Polycrystalline thin films of (R/S/rac-MBA)2PbI4 were formed by spin-casting of a 0.1 M solution, which is made by dissolving (R/S/rac-MBA)2PbI4 single crystals in dimethylformamide (DMF) solvent (see Methods section). Figure 1b and c show the crystalline structure characterized by grazing-incidence wide-angle X-ray scattering (GIWAXS), which presents intense Bragg spots for (R- and S-MBA)2PbI4 films, respectively. The observed GIWAXS results demonstrate very highly oriented crystal grains in the (R- or S-MBA)2PbI4 films, where the Bragg peaks may be assigned to the (h k l) peaks that are consistent with the same crystal structures observed in bulk single crystals. The extent of crystallographic texture is the same in both (R- and S-MBA)2PbI4 films, showing the sequence of chiral 2D-HOIP film (0 0 2l) peaks. X-ray diffraction (XRD) spectra obtained for (R/S-MBA)2PbI4 films are included in the Supporting Information Figure S1, as well as atomic force microscopy (AFM) images showing the films’ morphology. It is seen that the crystallization and morphology of (R- and S-MBA)2PbI4 films are identical, and thus the observed spin-dependent optoelectronic responses described below are representative of the chiral 2D-HOIPs and not obscured by the film morphology.
The absorption spectra of (R/S/rac-MBA)2PbI4 films are shown in Figure 1d. An exciton band at ∼2.5 eV is observed in all three HOIPs films, which is a common feature also in other 2D-HOIPs such as (PEA)2PbI4. (28,29) The films’ chirality was verified using circular dichroism (CD) in transmission geometry. The CD spectra of the (R/S-MBA)2PbI4 films are presented in Figure 1e. The obtained CD value is calculated from the relation (8,30,31)
where ΔA is the difference in the optical density (OD) between left circularly polarized (LCP) and right circularly polarized (RCP) light. Note that (R-MBA)2PbI4 and (S-MBA)2PbI4 show CD spectra with opposite polarity. At higher photon energy (>3 eV) the CD signal is related to the optical activity of the chiral organic ligands (namely, R/S-MBA+), whereas the CD signal near the exciton level (∼2.5 eV) shows that there is chirality transferred from the chiral organic layers to the inorganic layers. (18) In contrast, (rac-MBA)2PbI4 does not show a sizable CD signal. We also measured Faraday rotation spectra of the chiral HOIPs that are compatible with the CD spectra near the exciton energy, as shown in the Supporting Information Figure S2.
(1)
Photovoltaic Response
The photovoltaic device structure is illustrated in Figure 2a. Indium tin oxide (ITO) was used as bottom electrode (anode), covered with a thin film of PEDOT:PSS as hole transport layer. Subsequently, (R/S/rac-MBA)2PbI4 film was spin-coated onto the structure by spin-casting. A film of phenyl-C61-butyric acid methyl ester (PCBM) as an electron transport layer is then spin-coated onto the 2D-HOIP layer. The device was capped with an Al/Ca thin film as cathode. The I–V responses of (R/S/rac-MBA)2PbI4-based photovoltaic devices were measured using circularly polarized 486 nm laser light illumination with an intensity of 20 mW/cm2 at 7 K for all measurements.
Figure 2
Figure 2. Structure and I–V responses of the spin PV devices. (a) Schematic view of the spin photovoltaic device based on the MBA2PbI4 active layer. LCP and RCP light are used for the photocurrent generation. The I–V response of the photovoltaic devices based on (b) (rac-MBA)2PbI4, (c) (R-MBA)2PbI4, and (d) (S-MBA)2PbI4 measured at 7 K in the dark (black), with LCP (red) light, and with RCP (blue) light using light from a 486 nm laser at an intensity of 20 mW/cm2. The inset is a magnified view of the data around V = 0 V.
The obtained I–V responses of the two chiral 2D-HOIP-based devices are shown in Figure 2c and d. In Figure 2c, it is seen that the photocurrent response in the (R-MBA)2PbI4-based device is different under excitation of LCP light and RCP light. We note that the intensity of the LCP and RCP light is the same during the measurements (Suppporting Information Table S1). The short-circuit photocurrent, Isc, shows a difference 
when excited using LCP and RCP illumination, respectively. Interestingly, ΔI decreases with increasing bias voltage and vanishes at the open-circuit voltage of the device (Voc ≈ 0.55 V). This shows that Voc is predominantly determined by the electrical potential difference of the two electrodes rather than the chirality of the 2D-HOIP layer or the light circular polarization. We note that the I–V response has been measured multiple times on the same device and other devices to account for the variation in the measurements (Supporting Information Figures S3–S5). The (S-MBA)2PbI4-based device shows a similar I–V characteristic response to that of the (R-MBA)2PbI4-based device except that ΔI has opposite sign (Figure 2d). As a control experiment, the same measurements were carried out on a (rac-MBA)2PbI4-based device; the I–V response is plotted in Figure 2b. It is seen that there is no obvious difference in the photocurrent upon LCP and RCP illumination, respectively. This indicates that the difference in the photocurrent response upon CPL illumination for (R/S-MBA)2PbI4-based photovoltaic devices originates from the different chirality of the active 2D-HOIP layers.
when excited using LCP and RCP illumination, respectively. Interestingly, ΔI decreases with increasing bias voltage and vanishes at the open-circuit voltage of the device (Voc ≈ 0.55 V). This shows that Voc is predominantly determined by the electrical potential difference of the two electrodes rather than the chirality of the 2D-HOIP layer or the light circular polarization. We note that the I–V response has been measured multiple times on the same device and other devices to account for the variation in the measurements (Supporting Information Figures S3–S5). The (S-MBA)2PbI4-based device shows a similar I–V characteristic response to that of the (R-MBA)2PbI4-based device except that ΔI has opposite sign (Figure 2d). As a control experiment, the same measurements were carried out on a (rac-MBA)2PbI4-based device; the I–V response is plotted in Figure 2b. It is seen that there is no obvious difference in the photocurrent upon LCP and RCP illumination, respectively. This indicates that the difference in the photocurrent response upon CPL illumination for (R/S-MBA)2PbI4-based photovoltaic devices originates from the different chirality of the active 2D-HOIP layers.The relative photocurrent difference ΔI/I can be calculated by
where ILCP and IRCP are the photocurrents under LCP and RCP illumination, respectively. ΔI/I as a function of bias voltage is plotted in Figure 3a. It is seen that |ΔI/I| has a constant value of ∼10% independent of the bias voltage, with opposite sign for (R-MBA)2PbI4- and (S-MBA)2PbI4-based devices. Also the sharp perturbation jump around 0.55 V is due to a mathematical artifact related to the open-circuit condition, where in eq 2 the denominator I = 0 A. A plausible interpretation for the obtained significant difference in the device photocurrent response with CPL excitation is that it is related to the different light absorption caused by the CD of the chiral 2D-HOIP active layer. Since the absorption coefficients of LCP and RCP light are different in these compounds, the CPL light may photogenerate different exciton densities in the chiral 2D HOIP active layers depending on their chirality and light helicity. Consequently, upon exciton dissociation, this would lead to different photocarrier densities and, in turn, to different photocurrent for LCP and RCP excitations. (13,32,33)
(2)
Figure 3
Figure 3. Voltage dependence and action spectrum of 
. (a) Relative photocurrent difference, ΔI/I, of (R/S-MBA)2PbI4 spin PV devices as a function of bias voltage. (b) Action spectrum of ΔI/I in an (R-MBA)2PbI4-based PV device compared to the relative absorption difference ΔA/A of LCP and RCP light in an (R-MBA)2PbI4 film measured by CD.
To check the consequence of this interpretation, we measured the ΔI/I action spectrum, namely, ΔI/I, at zero bias voltage as a function of the excitation photon energy in an (R-MBA)2PbI4-based PV device. In this case a xenon lamp was used as the light source. The light was dispersed by a monochromator and then modulated by a photoelastic modulator (PEM). Since the excitation light intensity here is much weaker than the laser light intensity used before, the signal-to-noise ratio here is not as good. Nevertheless, a reliable ΔI/I action spectrum could be measured as seen in Figure 3b. For comparison, the relative absorption difference ΔA/A calculated by CD/(32 980 × absorbance) is also plotted in Figure 3b. (13,27) In contrast to the ΔA/A spectrum, the ΔI/I action spectrum has an onset at 2.4 eV and stays constant at ΔI/I ≈ 10% throughout, whereas the ΔA/A spectrum shows a clear modulation feature close to the exciton energy. The difference between ΔI/I and ΔA/A spectra demonstrates that ΔI does not originate solely from the different absorptions of the LCP and RCP light in the chiral active layer. Moreover it is clear from Figure 3b that ΔA/A is several orders of magnitude smaller than the obtained ΔI/I value of ∼10%. We thus conclude that the CD effect is not large enough to cause such a large ΔI/I. In contrast, ΔI/I in the (rac-MBA)2PbI4-based PV devices is not as sizable (Supporting Information Figure S8).
In our previous study, we demonstrated that chiral HOIPs can function as spin filters in spintronic devices due to the CISS effect, where the transport of electrons with one spin orientation is preferred due to the embedded chirality. (11) In the photovoltaic devices based on chiral HOIPs studied here, due to optical spin selection rules, spin-polarized carriers are generated upon CPL excitation. (9,34) Subsequently, during the transport of the spin-polarized electrons and holes through the chiral HOIP active layer, photocarriers with one spin orientation drift more easily than the other spin orientation, a process described by the CISS effect. (35) Consequently a different photocurrent response is generated when LCP and RCP light polarizations are used for a given chirality of the 2D-HOIP active layer. This phenomenon leads to spin-related optoelectronic device applications.
Circular Photogalvanic Response
We note that CISS occurs mainly for an out-of-plane photocurrent, as illustrated above; the in-plane transport in chiral HOIPs may not be as affected by CISS due to the geometry of the chiral organic ligands in the 2D-HOIPs. (25) Therefore, the in-plane photocurrent difference upon CPL illumination may not be as sizable. (3,18) On the contrary, we show here that the in-plane photocurrent is still quite sensitive to the light illumination helicity, via a different process, namely, the circular photogalvanic effect. (36−38) The conduction band (CB) bottom in HOIP consists of states with angular momentum J = 1/2, whereas the states at the valence band (VB) top have spin angular momentum S = 1/2. The optical transition selection rules for the angular momentum due to the light circular polarization require that the component of angular momentum changes by ΔmJ = ±1. In HOIP with strong spin–orbit coupling (SOC) and breaking of the inversion symmetry, it has been established that Rashba splitting occurs in the CB and to a lesser degree also in the VB. (16,39) The circularly polarized light creates nonequilibrium spin polarization between the two Rashba branches. Since the CPL excitation with two different helicity leads to electrons having group velocity that is opposite in direction and equal in magnitude along kx, the resulting photocurrents have opposite polarities. (7,40) At steady-state conditions and at bias voltage V = 0, the continuous generation of spin-polarized free carriers thus leads to photocurrent that is sensitive to the excitation light helicity; this is known as the circular photogalvanic effect, CPGE. (41) Importantly, the nonequilibrium spin-polarized photocurrent may also be generated via exciton absorption and subsequent dissociation if the excitons are spin polarized. This is indeed the situation in the chiral 2D-HOIP, where this mechanism falls in the category of spin-photogalvanic effect, or SPGE. (42,43)
Figure 4a illustrates the experimental setup for the CPGE measurements. A quartz quarter-wave plate (QWP) was used to modulate the light polarization of the incident light. α is the angle between the fast axis of the QWP and the incident light polarization. The light excitation intensity was modulated by a mechanical chopper at a frequency of 310 Hz. The in-plane photocurrent as a function of the angle α was measured by a phase-sensitive technique (see Methods). Importantly the photocurrent was obtained at zero bias voltage and at room temperature. We note that in addition to the CPGE (or SPGE) current associated with circularly polarized light, there is also a spin-independent photocurrent when the excitation light is linearly polarized (LP, for 
). This is known as the linear photogalvanic effect (LPGE). (36,37) Through a 360° rotation of the QWP angle α, the incident light polarization cycles through LP, RCP, LP, and LCP, and therefore the measured photogalvanic current, Jx′, contains both CPGE and LPGE current components given by the relation (36)
). This is known as the linear photogalvanic effect (LPGE). (36,37) Through a 360° rotation of the QWP angle α, the incident light polarization cycles through LP, RCP, LP, and LCP, and therefore the measured photogalvanic current, Jx′, contains both CPGE and LPGE current components given by the relation (36)(3)
Figure 4
Figure 4. Circular photogalvanic effect in chiral 2D-HOIP. (a) Experimental setup for measuring the photogalvanic current using a λ/4 plate; the angles α, θ, and ϕ′ are denoted. x′ indicates the current flow direction. Photogalvanic current vs the quarter-wave plate rotational angle, α for (b) the (R-MBA)2PbI4 and (c) the (S-MBA)2PbI4 films, measured at 520 nm using xenon lamp excitation at room temperature. The values of the CPGE coefficient C obtained from the fitting using eq 3 are denoted. (d) Action spectra of the obtained CPGE coefficient C for the two chiral 2D-HOIPs in the spectral range of the exciton absorption band. The data for (R-MBA)2PbI4 are multiplied by a factor of 3 in order to compare with the other chiral 2D-HOIP.
The 4α term is due to the LPGE, whereas the 2α term is generated by the CPGE; D represents a polarization-independent offset that originates from other effects such as photothermal effect, photovoltaic response, or a photo-Dember effect. (41,44−46)
Figure 4b and c show respectively the helicity-dependent in-plane photocurrent measured on planar devices fabricated on (R-MBA)2PbI4 and (S-MBA)2PbI4 crystal surfaces. As seen, the photocurrent changes substantially with the QWP rotation angle α. Importantly, the photocurrent response, PC, vs α is quite different for the two compounds with opposite chirality. Using eq 3 we fit the PC(α) response of the two chiral compounds to obtain the coefficients C, L, and D (see Supporting Information Table S2). We find a substantive contribution of CPGE in both compounds with a C/D ratio between 5% and 12%. This unambiguously shows that substantial Rashba splitting occurs in the continuum electronic bands in both chiral 2D-HOIP compounds. (16) This happens since the spin–orbit coupling is relatively strong here due to the heavy atoms in the HOIP building blocks and the lack of inversion symmetry that can be inferred from the chirality in the two compounds, a phenomenon known as chirality-driven symmetry breaking. (16) Moreover, as seen in Figure 4d the CPGE coefficient, C, has opposite sign for the two compounds with opposite chirality. This shows that the CPGE here is sensitive to the induced chirality of the 2D-HOIP, which is an exciting phenomenon. We interpret this chirality-sensitive CPGE as due to SPGE that originates from the photogenerated spin-polarized excitons. As seen in the excitation dependent on the helicity-dependent coefficient C shown in Figure 4d, the CPGE effect happens when the excitation light is on resonance with exciton absorption in the (R/S-MBA)2PbI4. In this case, depending on the specific chirality of the HOIP, the photogenerated exciton density is larger with one light helicity compared to the other. Following exciton ionization the spin-polarized excitons dissociate into spin-polarized photocarriers, which, in the case of Rashba splitting, occupy a preferred half in k-space having opposite group velocity for the two circular light polarizations. This, in turn, changes the CPGE phase and thus the C coefficient polarity. This observation introduces chirality as an important factor to the field of CPGE, as well as provides a tool to investigate the existence of chirality in semiconductors.
Conclusions
ARTICLE SECTIONS
In conclusion, the optoelectronic devices based on chiral perovskites integrate both exceptional optoelectronic properties of HOIPs and also spin selectivity typical of chiral materials. This provides an emerging type of photovoltaic device that is sensitive to the helicity of the circularly polarized light excitation that results in a photocurrent difference of ∼10% between LCP and RCP light illumination in devices based on chiral 2D-HOIPs. This observation demonstrates that chiral semiconductors can be used in optoelectronic devices for manipulating spin transport via the chirality-induced spin selectivity effect. We also showed that the chiral 2D-HOIP compounds possess a relatively large Rashba splitting in their electronic bands that is due to the large SOC and the chirality-driven inversion symmetry breaking caused by the induced chirality into the inorganic layers. This gives rise to the measured chirality-sensitive CPGE that we interpret as SPGE that originates from the selectively photogenerated spin-polarized excitons by the circularly polarized light excitation. Our studies provide an avenue to utilize chiral 2D-HOIPs in spintronic optoelectronic devices, in which spin-polarized current can be selectively photogenerated by the chirality of the chemical components and the light helicity.
Methods
ARTICLE SECTIONS
Materials
All chemicals were used as received unless otherwise indicated. (R)-(+)-α-Methylbenzylamine (R-MBA, 98%, ee 96%), (S)-(−)-α-methylbenzylamine (S-MBA, 98%, ee 98%), (±)-α-methylbenzylamine (rac-MBA, 99%), lead oxide (PbO, 99.999%), N,N-anhydrous-dimethylformamide (DMF), and 57% aqueous hydriodic acid (HI) solution (99.95%, distilled, stabilized by H3PO2) were purchased from Sigma-Aldrich.
Synthesis of (R-MBA)2PbI4, (S-MBA)2PbI4, and (rac-MBA)2PbI4 Single Crystals
A 200 mg amount of PbO (0.897 mmol), 200 μL (1.57 mmol) of R-, S-, or rac-MBA, and 6 mL of HI solution were loaded into a glass vial. Then the as-formed yellow precipitates were dissolved in an oil bath at 90 °C. The solution was slowly cooled to room temperature with a cooling rate of 1 °C/h, which leads to orange needles. These crystals were vacuum filtrated and rinsed with diethyl ether. The final product was dried in a vacuum overnight.
Preparation of (R-MBA)2PbI4, (S-MBA)2PbI4, and (rac-MBA)2PbI4 Thin Films
The substrates are cleaned by acetone and isopropanol in a sonicator for 10 min each, followed by an UV-ozone treatment for 15 min. The precursor solutions are prepared by dissolving the corresponding perovskite crystals in DMF with a concentration of 0.1 M. Thin films are then prepared by spin coating the precursor solution onto substrates with a rate of 4000 rpm for 30 s. The film is then followed by annealing at 100 °C for 10 min. Thin films on glass substrates are used for XRD and AFM measurements. Thin films on quartz substrates are used for optical (linear absorption and CD) measurements.
GIWAXS Measurements
The GIWAXS experiments were carried out in Stanford Synchrotron Radiation Lightsource (SSRL) beamline 11-3. The X-ray beam has a beam energy of 12.7 keV. The samples were deposited in NREL, shipped to SSRL, and stored in a glovebox. Before the experiments, the films were quickly brought to the beamline (within 5 min) and loaded in the N2-filled chamber in the hatch. The position of the sample was calibrated, and the incident angle was set to 1.12 deg. A 60 s exposure was used for each 2D diffraction image. All GIWAXS results were analyzed using the pygix package in Python.
CD Measurements
CD spectra of the perovskite films were carried out by a Jasco J-715 spectropolarimeter with the thin film placed in the beam path. The spectra were smoothed using an internal algorithm in the Jasco software package J-715 for Windows. The CD spectra were monitored from 200 to 600 nm with 0.2 nm resolution, and the data are presented as the raw CD signal.
PV Device Fabrication
The ITO bottom electrode on a glass substrate was patterned by wet etch photolithography. The ITO electrode was cleaned by sonication in acetone and isopropanol for 15 min. Subsequently the bottom electrode was treated by oxygen plasma for 10 min. A thin hole transport layer, poly(3,4-ethylenedioxythiophene) polystyrenesulfonate (PEDOT:PSS, Clevios P VP AI 4083), was annealed in air for 20 min at 150 °C. The chiral perovskite film was spin-coated on the pretreated ITO electrode inside a N2-filled glovebox (O2/H2O < 1 ppm). The sample was then annealed at 100 °C for 10 min. After cooling to ambient temperature, a 20 mg/mL solution of PCBM dissolved in anhydrous chlorobenzene (Sigma-Aldrich) was spin-coated at 800 rpm. The device was capped with a Ca (20 nm) and Al (100 nm) electrode that was thermally evaporated through a shadow mask with a cross configuration to the ITO electrode. The device area was 1 × 2 mm.
PV Device Measurements
Following the fabrication process the spin PV device was transferred to a closed-cycle cryostat for photovoltaic measurements. All measurements were done at 7 K, using 486 nm laser light at an intensity of 20 mW/cm2. A quarter-wave plate followed by a polarizer was used to filter circularly polarized light. The I–V response was measured by a four-point method using a Keithley 236 power supply and a Keithley 2000 multimeter.
CPGE Device and Measurements
For the device used for CPGE measurement, two 70 nm thick gold electrodes were deposited onto the crystals by e-beam evaporation through a shadow mask in a glovebox-integrated vacuum deposition chamber (Angstrom Engineering), which had a base pressure of 3 × 10–8 Torr (≈4 × 10–6 Pa). The gap between the electrodes was 0.5 mm. For the CPGE measurements, we used as pump excitation an incandescent light source from a xenon lamp, which was dispersed through a monochromator. Roughly 25% of the light beam was focused on the active area of the device, with an area of 0.5 mm × 0.75 mm, with an intensity of ∼8.0 mW/cm2. Due to the low intensity of the xenon lamp, we use a full-slit width of the monochromator to ensure the needed intensity for a measurable signal. The spectral resolution was estimated to be ∼10 meV.
Supporting Information
ARTICLE SECTIONS
The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsnano.0c05980.
| 1. | Charaterization of (R/S/rac-MBA)2PbI4 samples including AFM, XRD, CD, and Faraday rotation measurements; control experiment of I–V characteristics of photovoltaic devices based on chiral perovskites; dependence of ΔI/I signal for (rac-MBA)2PbI4 photovoltaic devices; summary of L and D coefficients for (R/S-MBA)2PbI4 given by fitting the CPGE response (PDF) | ||||
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Author Information
ARTICLE SECTIONS
- Z. Valy Vardeny - Department of Physics & Astronomy, University of Utah, Salt Lake City, Utah 84112, United States;
http://orcid.org/0000-0002-2298-398X;
- Haipeng Lu - Chemistry & Nanoscience Center, National Renewable Energy Laboratory, Golden, Colorado 80401, United States;http://orcid.org/0000-0003-0252-3086
- Michael F. Toney - Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States;http://orcid.org/0000-0002-7513-1166
- Matthew C. Beard - Chemistry & Nanoscience Center, National Renewable Energy Laboratory, Golden, Colorado 80401, United States;http://orcid.org/0000-0002-2711-1355
Acknowledgments
ARTICLE SECTIONS
This work was supported by the Center for Hybrid Organic Inorganic Semiconductors for Energy (CHOISE), an Energy Frontier Research Center funded by the Office of Basic Energy Sciences, Office of Science, within the U.S. The CPGE measurements and fabrication facility at the UofU were supported by the Department of Energy Office of Science, grant DE-SC0014579.
References
ARTICLE SECTIONS
This article references 46 other publications.
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- 4Tsai, H.; Nie, W.; Blancon, J. C.; Stoumpos, C. C.; Asadpour, R.; Harutyunyan, B.; Neukirch, A. J.; Verduzco, R.; Crochet, J. J.; Tretiak, S.; Pedesseau, L. High-Efficiency Two-Dimensional Ruddlesden–Popper Perovskite Solar Cells. Nature 2016, 536, 312– 316, DOI: 10.1038/nature18306[Crossref], [PubMed], [CAS], Google Scholar4https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XhtFahtrjF&md5=791893767414bd8fab1dc052fb1bdd12High-efficiency two-dimensional Ruddlesden-Popper perovskite solar cellsTsai, Hsinhan; Nie, Wanyi; Blancon, Jean-Christophe; Stoumpos, Constantinos C.; Asadpour, Reza; Harutyunyan, Boris; Neukirch, Amanda J.; Verduzco, Rafael; Crochet, Jared J.; Tretiak, Sergei; Pedesseau, Laurent; Even, Jacky; Alam, Muhammad A.; Gupta, Gautam; Lou, Jun; Ajayan, Pulickel M.; Bedzyk, Michael J.; Kanatzidis, Mercouri G.; Mohite, Aditya D.Nature (London, United Kingdom) (2016), 536 (7616), 312-316CODEN: NATUAS; ISSN:0028-0836. (Nature Publishing Group)Three-dimensional org.-inorg. perovskites have emerged as one of the most promising thin-film solar cell materials owing to their remarkable photophys. properties, which have led to power conversion efficiencies exceeding 20 per cent, with the prospect of further improvements towards the Shockley-Queisser limit for a single-junction solar cell (33.5 per cent). Besides efficiency, another crit. factor for photovoltaics and other optoelectronic applications is environmental stability and photostability under operating conditions. In contrast to their three-dimensional counterparts, Ruddlesden-Popper phases-layered two-dimensional perovskite films-have shown promising stability, but poor efficiency at only 4.73 per cent. This relatively poor efficiency is attributed to the inhibition of out-of-plane charge transport by the org. cations, which act like insulating spacing layers between the conducting inorg. slabs. Here we overcome this issue in layered perovskites by producing thin films of near-single-cryst. quality, in which the crystallog. planes of the inorg. perovskite component have a strongly preferential out-of-plane alignment with respect to the contacts in planar solar cells to facilitate efficient charge transport. We report a photovoltaic efficiency of 12.52 per cent with no hysteresis, and the devices exhibit greatly improved stability in comparison to their three-dimensional counterparts when subjected to light, humidity and heat stress tests. Unencapsulated two-dimensional perovskite devices retain over 60 per cent of their efficiency for over 2,250 h under const., std. (AM1.5G) illumination, and exhibit greater tolerance to 65 per cent relative humidity than do three-dimensional equiv. When the devices are encapsulated, the layered devices do not show any degrdn. under const. AM1.5G illumination or humidity. We anticipate that these results will lead to the growth of single-cryst., soln.-processed, layered, hybrid, perovskite thin films, which are essential for high-performance opto-electronic devices with technol. relevant long-term stability.
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- 7Zhai, Y.; Baniya, S.; Zhang, C.; Li, J.; Haney, P.; Sheng, C. X.; Ehrenfreund, E.; Vardeny, Z. V. Giant Rashba Splitting in 2D Organic-Inorganic Halide Perovskites Measured by Transient Spectroscopies. Sci. Adv. 2017, 3, e1700704 DOI: 10.1126/sciadv.1700704[Crossref], [PubMed], [CAS], Google Scholar7https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXntFGkurg%253D&md5=880cb9583ae4518c821a640ad5b902ebGiant Rashba splitting in 2D organic-inorganic halide perovskites measured by transient spectroscopiesZhai, Yaxin; Baniya, Sangita; Zhang, Chuang; Li, Junwen; Haney, Paul; Sheng, Chuan-Xiang; Ehrenfreund, Eitan; Vardeny, Zeev ValyScience Advances (2017), 3 (7), e1700704/1-e1700704/6CODEN: SACDAF; ISSN:2375-2548. (American Association for the Advancement of Science)Two-dimensional (2D) layered hybrid org.-inorg. halide perovskite semiconductors form natural "multiple quantum wells" that have strong spin-orbit coupling due to the heavy elements in their building blocks. This may lead to "Rashba splitting" close to the extrema in the electron bands. We have used a plethora of ultrafast transient, nonlinear optical spectroscopies and theor. calcns. to study the primary (excitons) and long-lived (free carriers) photoexcitations in thin films of 2D perovskite, namely, (C6H5C2H4NH3)2PbI4. The d. functional theory calcn. shows the occurrence of Rashba splitting in the plane perpendicular to the 2D barrier. From the electroabsorption spectrum and photoinduced absorption spectra from excitons and free carriers, we obtain a giant Rashba splitting in this compd., with energy splitting of (40 ± 5) meV and Rashba parameter of (1.6 ± 0.1) eV·Å, which are among the highest Rashba splitting size parameters reported so far. This finding shows that 2D hybrid perovskites have great promise for potential applications in spintronics.
- 8Long, G.; Jiang, C.; Sabatini, R.; Yang, Z.; Wei, M.; Quan, L. N.; Liang, Q.; Rasmita, A.; Askerka, M.; Walters, G.; Gong, X. Spin Control in Reduced-Dimensional Chiral Perovskites. Nat. Photonics 2018, 12, 528– 533, DOI: 10.1038/s41566-018-0220-6[Crossref], [CAS], Google Scholar8https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhsV2isLnF&md5=0a921b1f3b06b1d53a12d0336eed4899Spin control in reduced-dimensional chiral perovskitesLong, Guankui; Jiang, Chongyun; Sabatini, Randy; Yang, Zhenyu; Wei, Mingyang; Quan, Li Na; Liang, Qiuming; Rasmita, Abdullah; Askerka, Mikhail; Walters, Grant; Gong, Xiwen; Xing, Jun; Wen, Xinglin; Quintero-Bermudez, Rafael; Yuan, Haifeng; Xing, Guichuan; Wang, X. Renshaw; Song, Datong; Voznyy, Oleksandr; Zhang, Mingtao; Hoogland, Sjoerd; Gao, Weibo; Xiong, Qihua; Sargent, Edward H.Nature Photonics (2018), 12 (9), 528-533CODEN: NPAHBY; ISSN:1749-4885. (Nature Research)A review. Hybrid org.-inorg. perovskites exhibit strong spin-orbit coupling1, spin-dependent optical selection rules2,3 and large Rashba splitting4-8. These characteristics make them promising candidates for spintronic devices9 with photonic interfaces. Here we report that spin polarization in perovskites can be controlled through chem. design as well as by a magnetic field. We obtain both spin-polarized photon absorption and spin-polarized photoluminescence in reduced-dimensional chiral perovskites through combined strategies of chirality transfer and energy funnelling. A 3% spin-polarized photoluminescence is obsd. even in the absence of an applied external magnetic field owing to the different emission rates of σ+ and σ- polarized photoluminescence. Three-dimensional perovskites achieve a comparable degree of photoluminescence polarization only under an external magnetic field of 5 T. Our findings pave the way for chiral perovskites as powerful spintronic materials.
- 9Giovanni, D.; Chong, W. K.; Dewi, H. A.; Thirumal, K.; Neogi, I.; Ramesh, R.; Mhaisalkar, S.; Mathews, N.; Sum, T. C. Tunable Room-Temperature Spin-Selective Optical Stark Effect in Solution-Processed Layered Halide Perovskites. Sci. Adv. 2016, 2, e1600477 DOI: 10.1126/sciadv.1600477[Crossref], [PubMed], [CAS], Google Scholar9https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhslaksbrM&md5=997cfdd9c90bbbf3cbea9574ec109ae1Tunable room-temperature spin-selective optical Stark effect in solution-processed layered halide perovskitesGiovanni, David; Chong, Wee Kiang; Dewi, Herlina Arianita; Thirumal, Krishnamoorthy; Neogi, Ishita; Ramesh, Ramamoorthy; Mhaisalkar, Subodh; Mathews, Nripan; Sum, Tze ChienScience Advances (2016), 2 (6), e1600477/1-e1600477/6CODEN: SACDAF; ISSN:2375-2548. (American Association for the Advancement of Science)Ultrafast spin manipulation for opto-spin logic applications requires material systems that have strong spin-selective light-matter interaction. Conventional inorg. semiconductor nanostructures [for example, epitaxial II to VI quantum dots and III to V multiple quantum wells (MQWs)] are considered forerunners but encounter challenges such as lattice matching and cryogenic cooling requirements. Two-dimensional halide perovskite semiconductors, combining intrinsic tunable MQW structures and large oscillator strengths with facile soln. processability, can offer breakthroughs in this area. We demonstrate novel room-temp., strong ultrafast spin-selective optical Stark effect in soln.-processed (C6H4FC2H4NH3)2PbI4 perovskite thin films. Exciton spin states are selectively tuned by ∼6.3 meV using circularly polarized optical pulses without any external photonic cavity (i.e., corresponding to a Rabi energy of ∼55 meV and equiv. to applying a 70 T magnetic field), which is much larger than any conventional system. The facile halide and org. replacement in these perovskites affords control of the dielec. confinement and thus presents a straightforward strategy for tuning light-matter coupling strength.
- 10Chen, X.; Lu, H.; Li, Z.; Zhai, Y.; Ndione, P. F.; Berry, J. J.; Zhu, K.; Yang, Y.; Beard, M. C. Impact of Layer Thickness on the Charge Carrier and Spin Coherence Lifetime in Two-Dimensional Layered Perovskite Single Crystals. ACS Energy Lett. 2018, 3, 2273– 2279, DOI: 10.1021/acsenergylett.8b01315[ACS Full Text
], [CAS], Google Scholar10https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhs1SnsLnE&md5=ddeca3f7f2b4f2e0c57f665b4a29812dImpact of Layer Thickness on the Charge Carrier and Spin Coherence Lifetime in Two-Dimensional Layered Perovskite Single CrystalsChen, Xihan; Lu, Haipeng; Li, Zhen; Zhai, Yaxin; Ndione, Paul F.; Berry, Joseph J.; Zhu, Kai; Yang, Ye; Beard, Matthew C.ACS Energy Letters (2018), 3 (9), 2273-2279CODEN: AELCCP; ISSN:2380-8195. (American Chemical Society)The authors report the charge carrier recombination rate and spin coherence lifetimes in single crystals of two-dimensional (2D) Ruddlesden-Popper perovskites PEA2PbI4·(MAPbI3)n-1 (PEA, phenethylammonium; MA, methylammonium; n = 1, 2, 3, 4). Layer thickness-dependent charge carrier recombination rates are obsd., with the fastest rates for n = 1 because of the large exciton binding energy, and the slowest rates are obsd. for n = 2. Room-temp. spin coherence times also show a nonmonotonic layer thickness dependence with an increasing spin coherence lifetime with increasing layer thickness from n = 1 to n = 4, followed by a decrease in lifetime from n = 4 to ∞. The longest coherence lifetime of ∼7 ps is obsd. in the n = 4 sample. The authors' results are consistent with two contributions: Rashba splitting increases the spin coherence lifetime going from the n = ∞ to the layered systems, while phonon scattering, which increases for smaller layers, decreases the spin coherence lifetime. The interplay between these two factors contributes to the layer thickness dependence. - 11Lu, H.; Wang, J.; Xiao, C.; Pan, X.; Chen, X.; Brunecky, R.; Berry, J. J.; Zhu, K.; Beard, M. C.; Vardeny, Z. V. Spin-Dependent Charge Transport through 2D Chiral Hybrid Lead-Iodide Perovskites. Sci. Adv. 2019, 5, eaay0571 DOI: 10.1126/sciadv.aay0571
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- 14Ma, J.; Fang, C.; Chen, C.; Jin, L.; Wang, J.; Wang, S.; Tang, J.; Li, D. Chiral 2D Perovskites with a High Degree of Circularly Polarized Photoluminescence. ACS Nano 2019, 13, 3659– 3665, DOI: 10.1021/acsnano.9b00302[ACS Full Text], [CAS], Google Scholar14https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXksF2kt70%253D&md5=95ba823537ea8a9ed5c685cfef781570Chiral 2D Perovskites with a High Degree of Circularly Polarized PhotoluminescenceMa, Jiaqi; Fang, Chen; Chen, Chao; Jin, Long; Wang, Jiaqi; Wang, Shuai; Tang, Jiang; Li, DehuiACS Nano (2019), 13 (3), 3659-3665CODEN: ANCAC3; ISSN:1936-0851. (American Chemical Society)Chiral materials are of particular interest and have a wide range of potential applications in life science, material science, spintronic, and optoelectronic devices. Two-dimensional (2D) hybrid org.-inorg. lead halide perovskites have attracted increasing attention. Incorporating the chiral org. ligands into the layered lead iodide frameworks would introduce strong chirality in pure 2D perovskites for potential applications in circularly polarized light (CPL) emission and detection; nonetheless, studies on those aspects are still in their infancy. Here, we report on the strong CPL emission and sensitive CPL detection in the visible-wavelength range in pure chiral (R-/S-MBA)2PbI4 (MBA = C6H5C2H4NH3) 2D perovskites, which are successfully synthesized with a needle shape and millimeter size by incorporating the chiral mols. The chiral 2D perovskites (R-MBA)2PbI4 and (S-MBA)2PbI4 exhibit an av. degree of circularly polarized photoluminescence (PL) of 9.6% and 10.1% at 77 K, resp., and a max. degree of the circularly polarized PL of 17.6% is achieved in (S-MBA)2PbI4. The degree of circularly polarized PL dramatically decreases with increasing temp., implying that the lattice distortion induced by the incorporated chiral mols. and/or temp.-dependent spin flipping might be the origin for the obsd. chirality. Finally, CPL detection has been achieved with decent performance in our chiral 2D perovskite microplate/MoS2 heterostructural devices. The high degree of the circularly polarized PL and excellent CPL detection together with the layered nature of pure chiral 2D perovskites enables them to be a class of very promising materials for developing and exploring spin assocd. electronic devices based on the chiral 2D perovskites.
- 15Wang, L.; Xue, Y.; Cui, M.; Huang, Y.; Xu, H.; Qin, C.; Yang, J.; Dai, H.; Yuan, M. A Chiral Reduced-Dimension Perovskite for an Efficient Flexible Circularly Polarized Light Photodetector. Angew. Chem. 2020, 132, 6504– 6512, DOI: 10.1002/ange.201915912
- 16Jana, M. K.; Song, R.; Liu, H.; Khanal, D. R.; Janke, S. M.; Zhao, R.; Liu, C.; Vardeny, Z. V.; Blum, V.; Mitzi, D. B. Organic-to-Inorganic Structural Chirality Transfer in a 2D Hybrid Perovskite and Impact on Rashba-Dresselhaus Spin-Orbit Coupling. Nat. Commun. 2020, 11, 1– 10, DOI: 10.1038/s41467-020-18485-7
- 17Lu, H.; Xiao, C.; Song, R.; Li, T.; Maughan, A. E.; Levin, A.; Brunecky, R.; Berry, J. J.; Mitzi, D. B.; Blum, V.; Beard, M. C. Distorted Chiral Two-Dimensional Tin Iodide Perovskites for Spin Polarized Charge Highly Transport. J. Am. Chem. Soc. 2020, 142, 13030– 13040, DOI: 10.1021/jacs.0c03899[ACS Full Text], [CAS], Google Scholar17https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXhtlSisb7P&md5=ce2f4a7b10e2171b4cb7c0303cc875daHighly Distorted Chiral Two-Dimensional Tin Iodide Perovskites for Spin Polarized Charge TransportLu, Haipeng; Xiao, Chuanxiao; Song, Ruyi; Li, Tianyang; Maughan, Annalise E.; Levin, Andrew; Brunecky, Roman; Berry, Joseph J.; Mitzi, David B.; Blum, Volker; Beard, Matthew C.Journal of the American Chemical Society (2020), 142 (30), 13030-13040CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)Incorporating chiral org. mols. into org./inorg. hybrid 2D metal-halide perovskites results in a novel family of chiral hybrid semiconductors with unique spin-dependent properties. The embedded chiral org. moieties induce a chiroptical response from the inorg. metal-halide sublattice. However, the structural interplay between the chiral org. mols. and the inorg. sublattice, as well as their synergic effect on the resulting electronic band structure need to be explored in a broader material scope. Here we present three new layered tin iodide perovskites templated by chiral (R/S-)methylbenzylammonium (R/S-MBA), i.e., (R-/S-MBA)2SnI4, and their racemic phase (rac-MBA)2SnI4. These MBA2SnI4 compds. exhibit the largest level of octahedral bond distortion compared to any other reported layered tin iodide perovskite. The incorporation of chiral MBA cations leads to circularly polarized absorption from the inorg. Sn-I sublattice, displaying chiroptical activity in the 300-500 nm wavelength range. The bandgap and chiroptical activity are modulated by alloying Sn with Pb, in the series of (MBA)2Pb1-xSnxI4. Finally, we show that vertical charge transport through oriented (R-/S-MBA)2SnI4 thin films is highly spin-dependent, arising from a chiral-induced spin selectivity (CISS) effect. We demonstrate a spin-polarization in the current-voltage characteristics as high as 94%. Our work shows the tremendous potential of these chiral hybrid semiconductors for controlling both spin and charge degrees of freedom.
- 18Naaman, R.; Waldeck, D. H. Chiral-Induced Spin Selectivity Effect. J. Phys. Chem. Lett. 2012, 3, 2178– 2187, DOI: 10.1021/jz300793y[ACS Full Text], [CAS], Google Scholar18https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XhtV2gs7rJ&md5=c036f2be4c63575311396690f1aaa3b5Chiral-Induced Spin Selectivity EffectNaaman, R.; Waldeck, David H.Journal of Physical Chemistry Letters (2012), 3 (16), 2178-2187CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)A review. The chiral-induced spin selectivity (CISS) effect was recently established exptl. and theor. Here, we review some of the new findings and discuss applications that can result from special properties of this effect, like the redn. of the elastic backscattering in electron transfer through chiral mols. The CISS effect opens the possibility of using chiral mols. in spintronics applications and for providing a deeper understanding of spin-selective processes in biol.
- 19Cahn, R. S.; Ingold, C.; Prelog, V. Specification of Molecular Chirality. Angew. Chem., Int. Ed. Engl. 1966, 5, 385– 415, DOI: 10.1002/anie.196603851[Crossref], [CAS], Google Scholar19https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaF28XktFKitLk%253D&md5=6c0330b150d5c8dc9045afcdd073d6d2Specification of molecular chiralityCahn, R. S.; Ingold, Christopher; Prelog, V.Angewandte Chemie, International Edition in English (1966), 5 (4), 385-415CODEN: ACIEAY; ISSN:0570-0833.A discussion of mol. conformation with 39 references.
- 20Kasprzyk-Hordern, B. Pharmacologically Active Compounds in the Environment and Their Chirality. Chem. Soc. Rev. 2010, 39, 4466– 4503, DOI: 10.1039/c000408c[Crossref], [PubMed], [CAS], Google Scholar20https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXhtlShtb3J&md5=8fe00731e6fc2763aec5869cd12f3b3cPharmacologically active compounds in the environment and their chiralityKasprzyk-Hordern, BarbaraChemical Society Reviews (2010), 39 (11), 4466-4503CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)A review. Pharmacol. active compds. including both legally used pharmaceuticals and illicit drugs are potent environmental contaminants. Extensive research has been undertaken over the recent years to understand their environmental fate and toxicity. The one very important phenomenon that has been overlooked by environmental researchers studying the fate of pharmacol. active compds. in the environment is their chirality. Chiral drugs can exist in the form of enantiomers, which have similar physicochem. properties but differ in their biol. properties such as distribution, metab. and excretion, as these processes (due to stereospecific interactions of enantiomers with biol. systems) usually favor one enantiomer over the other. Addnl., due to different pharmacol. activity, enantiomers of chiral drugs can differ in toxicity. Furthermore, degrdn. of chiral drugs during wastewater treatment and in the environment can be stereoselective and can lead to chiral products of varied toxicity. The distribution of different enantiomers of the same chiral drug in the aquatic environment and biota can also be stereoselective. Biol. processes can lead to stereoselective enrichment or depletion of the enantiomeric compn. of chiral drugs. As a result the very same drug might reveal different activity and toxicity and this will depend on its origin and exposure to several factors governing its fate in the environment. In this crit. review a discussion of the importance of chirality of pharmacol. active compds. in the environmental context is undertaken and suggestions for directions in further research are made. Several groups of chiral drugs of major environmental relevance are discussed and their pharmacol. action and disposition in the body is also outlined as it is a key factor in developing a full understanding of their environmental occurrence, fate and toxicity. This review will be of interest to environmental scientists, esp. those interested in issues assocd. with environmental contamination with pharmacol. active compds. and chiral pollutants. As the review will outline current state of knowledge on chiral drugs, it will be of value to anyone interested in the phenomenon of chirality, chiral drugs, their stereoselective disposition in the body and environmental fate.
- 21Huang, P. J.; Taniguchi, K.; Miyasaka, H. Bulk Photovoltaic Effect in a Pair of Chiral–Polar Layered Perovskite-Type Lead Iodides Altered by Chirality of Organic Cations. J. Am. Chem. Soc. 2019, 141, 14520– 14523, DOI: 10.1021/jacs.9b06815[ACS Full Text], [CAS], Google Scholar21https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXhslSqtr7P&md5=a221c27b563ddd888e0859b92338db42Bulk Photovoltaic Effect in a Pair of Chiral-Polar Layered Perovskite-Type Lead Iodides Altered by Chirality of Organic CationsHuang, Po-Jung; Taniguchi, Kouji; Miyasaka, HitoshiJournal of the American Chemical Society (2019), 141 (37), 14520-14523CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)The bulk photovoltaic effect (BPVE) is a promising optoelectronic phenomenon for generating a steady-state photocurrent without a bias voltage. Nevertheless, the simple and rational design of materials exhibiting the BPVE remains an important topic in the relevant fields. Here, the observation is reported of the BPVE in a simple chiral-polar pair of layered perovskite-type lead iodides in the crystal space group of P1 (#1), which were synthesized by assembling R- and S-chiral org. cations, resp. The sign of the zero-bias photocurrent is altered by the R/S-chirality of the assembled cations, which define the direction of elec. polarization derived from the elec. dipole moment of each chiral org. cation aligned in a crystal. The strategy of chirality control in a crystal is expected to be useful when searching for BPVE materials.
- 22Dong, Y.; Zhang, Y.; Li, X.; Feng, Y.; Zhang, H.; Xu, J. Chiral Perovskites: Promising Materials toward Next-Generation Optoelectronics. Small 2019, 15, 1902237, DOI: 10.1002/smll.201902237
- 23Bloom, B. P.; Kiran, V.; Varade, V.; Naaman, R.; Waldeck, D. H. Spin Selective Charge Transport through Cysteine Capped Cdse Quantum Dots. Nano Lett. 2016, 16, 4583– 4589, DOI: 10.1021/acs.nanolett.6b01880[ACS Full Text], [CAS], Google Scholar23https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XhtVCjsbbP&md5=d9d9c79487a78879a093346b3fa9263cSpin selective charge transport through cysteine capped CdSe quantum dotsBloom, Brian P.; Kiran, Vankayala; Varade, Vaibhav; Naaman, Ron; Waldeck, David. H.Nano Letters (2016), 16 (7), 4583-4589CODEN: NALEFD; ISSN:1530-6984. (American Chemical Society)This work demonstrates that chiral imprinted CdSe quantum dots (QDs) can act as spin selective filters for charge transport. The spin filtering properties of chiral nanoparticles were investigated by magnetic conductive-probe at. force microscopy (mCP-AFM) measurements and magnetoresistance measurements. The mCP-AFM measurements show that the chirality of the quantum dots and the magnetic orientation of the tip affect the current-voltage curves. Similarly, magnetoresistance measurements demonstrate that the elec. transport through films of chiral quantum dots correlates with the chiroptical properties of the QD. The spin filtering properties of chiral quantum dots may prove useful in future applications, for example, photovoltaics, spintronics, and other spin-driven devices.
- 24Xie, Z.; Markus, T. Z.; Cohen, S. R.; Vager, Z.; Gutierrez, R.; Naaman, R. Spin Specific Electron Conduction through DNA Oligomers. Nano Lett. 2011, 11, 4652– 4655, DOI: 10.1021/nl2021637[ACS Full Text], [CAS], Google Scholar24https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXhtlSltLjM&md5=14c0cbed382e1a57b0d656eeacf88238Spin Specific Electron Conduction through DNA OligomersXie, Zuoti; Markus, Tal Z.; Cohen, Sidney R.; Vager, Zeev; Gutierrez, Rafael; Naaman, RonNano Letters (2011), 11 (11), 4652-4655CODEN: NALEFD; ISSN:1530-6984. (American Chemical Society)Spin-based properties, applications, and devices are commonly related to magnetic effects and to magnetic materials. Most of the development in spintronics is currently based on inorg. materials. Despite the fact that the magnetoresistance effect was obsd. in org. materials, until now spin selectivity of org. based spintronics devices originated from an inorg. ferromagnetic electrode and was not detd. by the org. mols. themselves. Conduction through double-stranded DNA oligomers is spin selective, demonstrating a true org. spin filter. The selectivity exceeds that of any known system at room temp. The spin dependent resistivity indicates that the effect cannot result solely from the at. spin-orbit coupling and must relate to a special property resulting from the chirality symmetry. The results may reflect on the importance of spin in detg. electron transfer rates through biol. systems.
- 25Mondal, P. C.; Fontanesi, C.; Waldeck, D. H.; Naaman, R. Spin-Dependent Transport through Chiral Molecules Studied by Spin-Dependent Electrochemistry. Acc. Chem. Res. 2016, 49, 2560– 2568, DOI: 10.1021/acs.accounts.6b00446[ACS Full Text], [CAS], Google Scholar25https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XhslSqtLnE&md5=df9208ec171f00e24c88a03fede4c0a6Spin-Dependent Transport through Chiral Molecules Studied by Spin-Dependent ElectrochemistryMondal, Prakash Chandra; Fontanesi, Claudio; Waldeck, David H.; Naaman, RonAccounts of Chemical Research (2016), 49 (11), 2560-2568CODEN: ACHRE4; ISSN:0001-4842. (American Chemical Society)A review. Mol. spintronics (spin + electronics), which aims to exploit both the spin degree of freedom and the electron charge in mol. devices, has recently received massive attention. The authors' recent expts. on mol. spintronics employ chiral mols. which have the unexpected property of acting as spin filters, by way of an effect the authors call chiral-induced spin selectivity (CISS). In this Account, new types of spin-dependent electrochem. measurements and their use to probe the spin-dependent charge transport properties of nonmagnetic chiral conductive polymers and biomols., such as oligopeptides, L/D cysteine, cytochrome c, bacteriorhodopsin (bR), and oligopeptide-CdSe nanoparticles (NPs) hybrid structures are discussed. Spin-dependent electrochem. measurements were carried out by employing ferromagnetic electrodes modified with chiral mols. used as the working electrode. Redox probes were used either in soln. or when directly attached to the ferromagnetic electrodes. During the electrochem. measurements, the ferromagnetic electrode was magnetized either with its magnetic moment pointing UP or DOWN using a permanent magnet (H = 0.5 T), placed underneath the chem. modified ferromagnetic electrodes. The spin polarization of the current is at 5-30%, even in the case of small chiral mols. Chiral films of the L- and D-cysteine tethered with a redox-active dye, toluidine blue O, show spin polarization that depends on the chirality. Because the Ni electrodes are susceptible to corrosion, the authors explored the effect of coating them with a thin Au overlayer. The effect of the Au layer on the spin polarization of the electrons ejected from the electrode was studied. The role of the structure of the protein on the spin selective transport was also studied as a function of bias voltage and the effect of protein denaturation was revealed. In addn. to dark measurements, the authors also describe photoelectrochem. measurements in which light was used to affect the spin selective electron transport through the chiral mols. The authors describe how the excitation of a chromophore (such as CdSe nanoparticles), which is attached to a chiral working electrode, can flip the preferred spin orientation of the photocurrent, when measured under the identical conditions. Thus, chirality-induced spin polarization, when combined with light and magnetic field effects, opens new avenues for the study of the spin transport properties of chiral mols. and biomols. and for creating new types of spintronic devices in which light and mol. chirality provide new functions and properties.
- 26Billing, D. G.; Lemmerer, A. Synthesis and Crystal Structures of Inorganic–Organic Hybrids Incorporating an Aromatic Amine with a Chiral Functional Group. CrystEngComm 2006, 8, 686– 695, DOI: 10.1039/B606987H[Crossref], [CAS], Google Scholar26https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD28Xps1Sjurc%253D&md5=ccd6703bf7079618eb800ca1722aa040Synthesis and crystal structures of inorganic-organic hybrids incorporating an aromatic amine with a chiral functional groupBilling, David G.; Lemmerer, AndreasCrystEngComm (2006), 8 (9), 686-695CODEN: CRECF4; ISSN:1466-8033. (Royal Society of Chemistry)The authors report the synthesis and the crystal structure of inorg.-org. hybrids contg. various lead halides as the inorg. motif and a primary amine as the org. constituent, namely (R)-, (S)- and racemic 1-phenylethylamine (L). Within the structures obtained, three different inorg. motifs are displayed by the lead halide octahedra: 1-dimensional polymeric face-sharing chains PbCl3((R)-LH), PbBr3((R)-LH), PbI3((R)-LH) and PbI3((S)-LH); 1-dimensional polymeric corner-sharing chains PbCl5((±)-LH)3 and PbBr5((±)-LH)3; and 2-dimensional corner-sharing layers PbI4((S)-LH)2 and PbI4((S)-LH)2. The changes in geometry and intermol. interactions such as H bonding and pi stacking are discussed and compared between the eight structures.
- 27Ahn, J.; Lee, E.; Tan, J.; Yang, W.; Kim, B.; Moon, J. A New Class of Chiral Semiconductors: Chiral-Organic-Molecule-Incorporating Organic–Inorganic Hybrid Perovskites. Mater. Horiz. 2017, 4, 851– 856, DOI: 10.1039/C7MH00197E[Crossref], [CAS], Google Scholar27https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXovFGjs7g%253D&md5=a655175acd344e7724527d3bbf6d4982A new class of chiral semiconductors: chiral-organic-molecule-incorporating organic-inorganic hybrid perovskitesAhn, Jihoon; Lee, Eunsong; Tan, Jeiwan; Yang, Wooseok; Kim, Bokyung; Moon, JoohoMaterials Horizons (2017), 4 (5), 851-856CODEN: MHAOBM; ISSN:2051-6355. (Royal Society of Chemistry)An org.-inorg. hybrid perovskite incorporating chiral org. mols. is demonstrated as a new class of chiral semiconductors. Chiral perovskites exhibit oppositely-signed CD (CD) according to the S- and R-configurations of chiral orgs. The CD signals can be also varied by changing the cryst. orientation and thickness of the chiral perovskite films.
- 28Cao, D. H.; Stoumpos, C. C.; Farha, O. K.; Hupp, J. T.; Kanatzidis, M. G. 2D Homologous Perovskites as Light-Absorbing Materials for Solar Cell Applications. J. Am. Chem. Soc. 2015, 137, 7843– 7850, DOI: 10.1021/jacs.5b03796[ACS Full Text], [CAS], Google Scholar28https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXptFWrtL8%253D&md5=850fa45ea65c55307e5c9cbf435889122D Homologous Perovskites as Light-Absorbing Materials for Solar Cell ApplicationsCao, Duyen H.; Stoumpos, Constantinos C.; Farha, Omar K.; Hupp, Joseph T.; Kanatzidis, Mercouri G.Journal of the American Chemical Society (2015), 137 (24), 7843-7850CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)We report on the fabrication and properties of the semiconducting 2D (CH3(CH2)3NH3)2(CH3NH3)n-1PbnI3n+1 (n = 1, 2, 3, and 4) perovskite thin films. The band gaps of the series decrease with increasing n values, from 2.24 eV (CH3(CH2)3NH3)2PbI4 (n = 1) to 1.52 eV CH3NH3PbI3 (n = ∞). The compds. exhibit strong light absorption in the visible region, accompanied by strong photoluminescence at room temp., rendering them promising light absorbers for photovoltaic applications. Moreover, we find that thin films of the semi-2D perovskites display an ultrahigh surface coverage as a result of the unusual film self-assembly that orients the [PbnI3n+1]- layers perpendicular to the substrates. We have successfully implemented this 2D perovskite family in solid-state solar cells, and obtained an initial power conversion efficiency of 4.02%, featuring an open-circuit voltage (Voc) of 929 mV and a short-circuit c.d. (Jsc) of 9.42 mA/cm2 from the n = 3 compd. This result is even more encouraging considering that the device retains its performance after long exposure to a high-humidity environment. Overall, the homologous 2D halide perovskites define a promising class of stable and efficient light-absorbing materials for solid-state photovoltaics and other applications.
- 29Katan, C.; Mercier, N.; Even, J. Quantum and Dielectric Confinement Effects in Lower-Dimensional Hybrid Perovskite Semiconductors. Chem. Rev. 2019, 119, 3140– 3192, DOI: 10.1021/acs.chemrev.8b00417[ACS Full Text], [CAS], Google Scholar29https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXnvVeisg%253D%253D&md5=3a9ad3f2412701bea686f412e190256cQuantum and dielectric confinement effects in lower-dimensional hybrid perovskite semiconductorsKatan, Claudine; Mercier, Nicolas; Even, JackyChemical Reviews (Washington, DC, United States) (2019), 119 (5), 3140-3192CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)Hybrid halide perovskites are now superstar materials leading the field of low-cost thin film photovoltaics technologies. Following the surge for more efficient and stable 3D bulk alloys, multilayered halide perovskites and colloidal perovskite nanostructures appeared in 2016 as viable alternative solns. to this challenge, largely exceeding the original proof of concept made in 2009 and 2014, resp. This triggered renewed interest in lower-dimensional hybrid halide perovskites and at the same time increasingly more numerous and differentiated applications. The present paper is a review of the past and present literature on both colloidal nanostructures and multilayered compds., emphasizing that availability of accurate structural information is of dramatic importance to reach a fair understanding of quantum and dielec. confinement effects. Layered halide perovskites occupy a special place in the history of halide perovskites, with a large no. of seminal papers in the 1980s and 1990s. In recent years, the rationalization of structure-properties relationship has greatly benefited from new theor. approaches dedicated to their electronic structures and optoelectronic properties, as well as a growing no. of contributions based on modern exptl. techniques. This is a necessary step to provide in-depth tools to decipher their extensive chem. engineering possibilities which surpass the ones of their 3D bulk counterparts. Comparisons to classical semiconductor nanostructures and 2D van der Waals heterostructures are also stressed. Since 2015, colloidal nanostructures have undergone a quick development for applications based on light emission. Although intensively studied in the last two years by various spectroscopy techniques, the description of quantum and dielec. confinement effects on their optoelectronic properties is still in its infancy.
- 30Riehl, J. P.; Richardson, F. S. Circularly Polarized Luminescence Spectroscopy. Chem. Rev. 1986, 1, 1– 16, DOI: 10.1021/cr00071a001
- 31Lightner, D. A.; Gurst, J. E. Organic Conformational Analysis and Stereochemistry from Circular Dichroism Spectroscopy; John Wiley & Sons: New York, 2000; Vol. 23, pp 47– 51.Google ScholarThere is no corresponding record for this reference.
- 32Yang, Y.; Da Costa, R. C.; Fuchter, M. J.; Campbell, A. J. Circularly Polarized Light Detection by a Chiral Organic Semiconductor Transistor. Nat. Photonics 2013, 7, 634– 638, DOI: 10.1038/nphoton.2013.176[Crossref], [CAS], Google Scholar32https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXhtFCis7jI&md5=5b033d9e8e90487f1a2d97101a6fd3e3Circularly polarized light detection by a chiral organic semiconductor transistorYang, Ying; da Costa, Rosenildo Correa; Fuchter, Matthew J.; Campbell, Alasdair J.Nature Photonics (2013), 7 (8), 634-638CODEN: NPAHBY; ISSN:1749-4885. (Nature Publishing Group)Circularly polarized light is central to many photonic technologies, including circularly polarized ellipsometry-based tomog., optical communication of spin information and quantum-based optical computing and information processing. To develop these technologies to their full potential requires the realization of miniature, integrated devices that are capable of detecting the chirality or handedness' of circularly polarized light. Org. field-effect transistors, in which the active semiconducting layer is an org. material, allow the simple fabrication of ultrathin, compact devices. Here we demonstrate a circularly polarized light-detecting org. field-effect transistor based on an asym. pure, helically shaped chiral semiconducting mol. known as a helicene. Importantly, we find a highly specific photoresponse to circularly polarized light, which is directly related to the handedness of the helicene mol. We believe that this opens up the possibility for the detection of the chirality of circularly polarized light in a highly integrated photonic platform.
- 33Li, W.; Coppens, Z. J.; Besteiro, L. V.; Wang, W.; Govorov, A. O.; Valentine, J. Circularly Polarized Light Detection with Hot Electrons in Chiral Plasmonic Metamaterials. Nat. Commun. 2015, 6, 1– 7, DOI: 10.1038/ncomms9379
- 34Odenthal, P.; Talmadge, W.; Gundlach, N.; Wang, R.; Zhang, C.; Sun, D.; Yu, Z. G.; Vardeny, Z. V.; Li, Y. S. Spin-Polarized Exciton Quantum Beating in Hybrid Organic-Inorganic Perovskites. Nat. Phys. 2017, 13, 894– 899, DOI: 10.1038/nphys4145[Crossref], [CAS], Google Scholar34https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXovVGqs7w%253D&md5=bdce2164c1f38d59c856a5fafce95606Spin-polarized exciton quantum beating in hybrid organic-inorganic perovskitesOdenthal, Patrick; Talmadge, William; Gundlach, Nathan; Wang, Ruizhi; Zhang, Chuang; Sun, Dali; Yu, Zhi-Gang; Valy Vardeny, Z.; Li, Yan S.Nature Physics (2017), 13 (9), 894-899CODEN: NPAHAX; ISSN:1745-2473. (Nature Publishing Group)Hybrid org.-inorg. perovskites have emerged as a new class of semiconductors that exhibit excellent performance as active layers in photovoltaic solar cells. These compds. are also highly promising materials for the field of spintronics due to their large and tunable spin-orbit coupling, spin-dependent optical selection rules, and their predicted elec. tunable Rashba spin splitting. Here we demonstrate the optical orientation of excitons and optical detection of spin-polarized exciton quantum beating in polycryst. films of the hybrid perovskite CH3NH3PbClxI3-x. Time-resolved Faraday rotation measurement in zero magnetic field reveals unexpectedly long spin lifetimes exceeding 1 ns at 4 K, despite the large spin-orbit couplings of the heavy lead and iodine atoms. The quantum beating of exciton states in transverse magnetic fields shows two distinct frequencies, corresponding to two g-factors of 2.63 and -0.33, which we assign to electrons and holes, resp. These results provide a basic picture of the exciton states in hybrid perovskites, and suggest they hold potential for spintronic applications.
- 35Naaman, R.; Paltiel, Y.; Waldeck, D. H. Chiral Molecules and the Spin Selectivity Effect. J. Phys. Chem. Lett. 2020, 11, 3660– 3666, DOI: 10.1021/acs.jpclett.0c00474[ACS Full Text], [CAS], Google Scholar35https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXnt1Wjs7k%253D&md5=b3f6ff4184526a4c43117c481a58f614Chiral Molecules and the Spin Selectivity EffectNaaman, R.; Paltiel, Y.; Waldeck, D. H.Journal of Physical Chemistry Letters (2020), 11 (9), 3660-3666CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)A review. This Perspective discusses recent expts. that bear on the chiral induced spin selectivity (CISS) mechanism and its manifestation in electronic and magnetic properties of chiral mols. and materials. Although the discussion emphasizes newer expts., such as the magnetization dependence of chiral mol. interactions with ferromagnetic surfaces, early expts., which reveal the nonlinear scaling of the spin filtering with applied potential, are described also. In many of the theor. studies, one has had to invoke unusually large spin-orbit couplings in order to reproduce the large spin filtering obsd. in expts. Expts. imply that exchange interactions and Pauli exclusion constraints are an important aspect of CISS. They also demonstrate the spin-dependent charge flow between a ferromagnetic substrate and chiral mols. With these insights in mind, a simplified model is described in which the chiral mol.'s spin polarization is enhanced by a spin blockade effect to generate large spin filtering.
- 36Liu, X.; Chanana, A.; Huynh, U.; Xue, F.; Haney, P.; Blair, S.; Jiang, X.; Vardeny, Z. V. Circular Photogalvanic Spectroscopy of Rashba Splitting in 2D Hybrid Organic–Inorganic Perovskite Multiple Quantum Wells. Nat. Commun. 2020, 11, 1– 8, DOI: 10.1038/s41467-019-14073-6
- 37Niesner, D.; Hauck, M.; Shrestha, S.; Levchuk, I.; Matt, G. J.; Osvet, A.; Batentschuk, M.; Brabec, C.; Weber, H. B.; Fauster, T. Structural Fluctuations Cause Spin-Split States in Tetragonal (CH3NH3)PbI3 as Evidenced by the Circular Photogalvanic Effect. Proc. Natl. Acad. Sci. U. S. A. 2018, 115, 9509– 9514, DOI: 10.1073/pnas.1805422115[Crossref], [PubMed], [CAS], Google Scholar37https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXitVKhu77E&md5=0b8bcf94ba379a0a025500656ce58ad4Structural fluctuations cause spin-split states in tetragonal (CH3NH3)PbI3 as evidenced by the circular photogalvanic effectNiesner, Daniel; Hauck, Martin; Shrestha, Shreetu; Levchuk, Ievgen; Matt, Gebhard J.; Osvet, Andres; Batentschuk, Miroslaw; Brabec, Christoph; Weber, Heiko B.; Fauster, ThomasProceedings of the National Academy of Sciences of the United States of America (2018), 115 (38), 9509-9514CODEN: PNASA6; ISSN:0027-8424. (National Academy of Sciences)Lead halide perovskites are used in thin-film solar cells, which owe their high efficiency to the long lifetimes of photocarriers. Various calcns. find that a dynamical Rashba effect could significantly contribute to these long lifetimes. This effect is predicted to cause a spin splitting of the electronic bands of inversion-sym. cryst. materials at finite temps., resulting in a slightly indirect band gap. Direct exptl. evidence of the existence or the strength of the spin splitting is lacking. Here, we resonantly excite photocurrents in single cryst. (CH3NH3)PbI3 with circularly polarized light to clarify the existence of spin splittings in the band structure. We observe a circular photogalvanic effect, i.e., the photocurrent depends on the light helicity, in both orthorhombic and tetragonal (CH3NH3)PbI3. At room temp., the effect peaks for excitation photon energies ΔE=110 meV below the direct optical band gap. Temp.-dependent measurements reveal a sign change of the effect at the orthorhombic-tetragonal phase transition, indicating different microscopic origins in the two phases. Within the tetragonal phase, both ΔE and the amplitude of the circular photogalvanic effect increase with temp. Our findings support a dynamical Rashba effect in this phase, i.e., a spin splitting caused by thermally induced structural fluctuations which break inversion symmetry.
- 38Li, J.; Haney, P. M. Circular Photogalvanic Effect in Organometal Halide Perovskite CH3NH3PbI3. Appl. Phys. Lett. 2016, 109, 193903, DOI: 10.1063/1.4967176[Crossref], [PubMed], [CAS], Google Scholar38https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XhvVehtLnE&md5=c333486aa97da414e6ba982656ae2768Circular photogalvanic effect in organometal halide perovskite CH3NH3PbI3Li, Junwen; Haney, Paul M.Applied Physics Letters (2016), 109 (19), 193903/1-193903/4CODEN: APPLAB; ISSN:0003-6951. (American Institute of Physics)We study the circular photogalvanic effect in the organometal halide perovskite solar cell absorber CH3NH3PbI3. The calcd. photocurrent d. for a system with broken inversion symmetry is about 10-9 A/W, comparable to the previously studied quantum well and bulk Rashba systems. The circular photogalvanic effect relies on inversion symmetry breaking, so that by tuning the optical penetration depth, the degree of inversion symmetry breaking can be probed at different depths from the sample surface. We propose that measurements of this effect may clarify the presence or absence of inversion symmetry, which remains a controversial issue and has been argued to play an important role in the high conversion efficiency of this material. (c) 2016 American Institute of Physics.
- 39Kepenekian, M.; Robles, R.; Katan, C.; Sapori, D.; Pedesseau, L.; Even, J. Rashba and Dresselhaus Effects in Hybrid Organic–Inorganic Perovskites: From Basics to Devices. ACS Nano 2015, 9, 11557– 11567, DOI: 10.1021/acsnano.5b04409[ACS Full Text], [CAS], Google Scholar39https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhsVKls7%252FO&md5=a93f1115ebeec2e507b4d1121483510eRashba and Dresselhaus Effects in Hybrid Organic-Inorganic Perovskites: From Basics to DevicesKepenekian, Mikael; Robles, Roberto; Katan, Claudine; Sapori, Daniel; Pedesseau, Laurent; Even, JackyACS Nano (2015), 9 (12), 11557-11567CODEN: ANCAC3; ISSN:1936-0851. (American Chemical Society)A review. The authors use symmetry anal., d. functional theory calcns., and k·p modeling to scrutinize Rashba and Dresselhaus effects in hybrid org.-inorg. halide perovskites. These perovskites are at the center of a recent revolution in the field of photovoltaics but also demonstrated potential for optoelectronic applications such as transistors and light emitters. Due to a large spin-orbit coupling of the most frequently used metals, they are also predicted to offer a promising avenue for spin-based applications. With an in-depth inspection of the electronic structures and bulk lattice symmetries of a variety of systems, the authors analyze the origin of the spin splitting in two- and three-dimensional hybrid perovskites. Low-dimensional nanostructures made of CH3NH3PbX3 (X = I, Br) lead to spin splittings that can be controlled by an applied elec. field. These findings further open the door for a perovskite-based spintronics.
- 40Yin, J.; Maity, P.; Xu, L.; El-Zohry, A. M.; Li, H.; Bakr, O. M.; Brédas, J. L.; Mohammed, O. F. Layer-Dependent Rashba Band Splitting in 2D Hybrid Perovskites. Chem. Mater. 2018, 30, 8538– 8545, DOI: 10.1021/acs.chemmater.8b03436[ACS Full Text], [CAS], Google Scholar40https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhvFWkt73F&md5=9871d9c805263166198c3797776c1affLayer-Dependent Rashba Band Splitting in 2D Hybrid PerovskitesYin, Jun; Maity, Partha; Xu, Liangjin; El-Zohry, Ahmed M.; Li, Hong; Bakr, Osman M.; Bredas, Jean-Luc; Mohammed, Omar F.Chemistry of Materials (2018), 30 (23), 8538-8545CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)The strong spin-orbit coupling (SOC) in perovskite materials due to the presence of heavy atoms induces interesting electronic characteristics, such as Rashba band splitting. In spite of several recent reports on Rashba effects in 2-dimensional perovskites, the impacts of the nature of surface termination and of the no. of inorg. layers on the extent of Rashba band splitting still remain to be detd. Here, using a combination of d. functional theory (DFT) calcns. and time-resolved laser spectroscopy, the authors provide a comprehensive understanding of the Rashba band splitting of the prototype 3-dimensional MAPbI3 and of 2-dimensional Ruddlesden-Popper (RP) hybrid perovskites. Significant structural distortions assocd. with different surface terminations are responsible for the obsd. Rashba effect in 2-dimensional perovskites. The authors' theor. and exptl. data clearly indicate that the intrinsic Rashba splitting occurs in the perovskite crystals with an even no. of inorg. layers (n = 2), but not for the ones with an odd no. of layers (n = 1 and n = 3). These findings not only provide a possible explanation for the elongated electron-hole recombination in perovskites but also elucidate the significant impact of the no. of inorg. layers on the electronic properties of 2-dimensional perovskites.
- 41Ganichev, S. D.; Prettl, W. Spin Photocurrents in Quantum Wells. J. Phys.: Condens. Matter 2003, 15, R935, DOI: 10.1088/0953-8984/15/20/204[Crossref], [CAS], Google Scholar41https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3sXltleqs78%253D&md5=936672fec3476927df679fc7bcdb2443Spin photocurrents in quantum wellsGanichev, S. D.; Prettl, W.Journal of Physics: Condensed Matter (2003), 15 (20), R935-R983CODEN: JCOMEL; ISSN:0953-8984. (Institute of Physics Publishing)A review discussing spin photocurrents generated by homogeneous optical excitation with circularly polarized radiation in quantum wells (QWs). The absorption of circularly polarized light results in optical spin orientation due to the transfer of the angular momentum of photons to electrons of a two-dimensional electron gas. It is shown that in QWs belonging to one of the gyrotropic crystal classes a non-equil. spin polarization of uniformly distributed electrons causes a directed motion of electrons in the plane of the QW. A characteristic feature of this elec. current, which occurs in unbiased samples, is that it reverses its direction upon changing the radiation helicity from left-handed to right-handed and vice versa. Two microscopic mechanisms are responsible for the occurrence of an elec. current linked to a uniform spin polarization in a QW: the spin polarization-induced circular photogalvanic effect and the spin-galvanic effect. In both effects the current flow is driven by an asym. distribution of spin-polarized carriers in k-space of systems with lifted spin degeneracy due to k-linear terms in the Hamiltonian. Spin photocurrents provide methods to investigate spin relaxation and to reach a conclusion as regards the inplane symmetry of QWs. The effect can also be utilized to develop fast detectors for detg. the degree of circular polarization of a radiation beam. Furthermore, spin photocurrents under IR excitation were used to demonstrate and investigate monopolar spin orientation of free carriers.
- 42Golub, L. E. Spin-Splitting-Induced Photogalvanic Effect in Quantum Wells. Phys. Rev. B: Condens. Matter Mater. Phys. 2003, 67, 235320, DOI: 10.1103/PhysRevB.67.235320[Crossref], [CAS], Google Scholar42https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3sXlsVKhtbc%253D&md5=7288ac8b79f799d5e51dbf0a9db3947dSpin-splitting-induced photogalvanic effect in quantum wellsGolub, L. E.Physical Review B: Condensed Matter and Materials Physics (2003), 67 (23), 235320/1-235320/7CODEN: PRBMDO; ISSN:0163-1829. (American Physical Society)A theory of the circular photogalvanic effect caused by spin splitting in quantum wells is developed. Direct interband transitions between the hole and electron size-quantized subbands are considered. It is shown that the photocurrent value and direction depend strongly on the form of the spin-orbit interaction. The currents induced by structure-, bulk-, and interface-inversion asymmetry are investigated. The photocurrent excitation spectra caused by spin splittings in both conduction and valence bands are calcd.
- 43Giglberger, S.; Golub, L. E.; Bel’kov, V. V.; Danilov, S. N.; Schuh, D.; Gerl, C.; Rohlfing, F.; Stahl, J.; Wegscheider, W.; Weiss, D.; Prettl, W. Rashba and Dresselhaus Spin Splittings in Semiconductor Quantum Wells Measured by Spin Photocurrents. Phys. Rev. B: Condens. Matter Mater. Phys. 2007, 75, 035327, DOI: 10.1103/PhysRevB.75.035327[Crossref], [CAS], Google Scholar43https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXhs1eksL8%253D&md5=5bceec5eb34afe725ba9133a35e44ab6Rashba and Dresselhaus spin splittings in semiconductor quantum wells measured by spin photocurrentsGiglberger, S.; Golub, L. E.; Bel'kov, V. V.; Danilov, S. N.; Schuh, D.; Gerl, C.; Rohlfing, F.; Stahl, J.; Wegscheider, W.; Weiss, D.; Prettl, W.; Ganichev, S. D.Physical Review B: Condensed Matter and Materials Physics (2007), 75 (3), 035327/1-035327/8CODEN: PRBMDO; ISSN:1098-0121. (American Physical Society)The spin-galvanic effect and the circular photogalvanic effect induced by terahertz radiation are applied to det. the relative strengths of Rashba and Dresselhaus band spin splitting in (001)-grown GaAs and InAs based 2d electron systems. Shifting the δ-doping plane from one side of the quantum well to the other results in a change of sign of the photocurrent caused by Rashba spin splitting while the sign of the Dresselhaus term induced photocurrent remains. The measurements give the necessary feedback for technologists looking for structures with equal Rashba and Dresselhaus spin splittings or perfectly sym. structures with zero Rashba const.
- 44McIver, J.; Hsieh, D.; Steinberg, H.; Jarillo-Herrero, P.; Gedik, N. Control over Topological Insulator Photocurrents with Light Polarization. Nat. Nanotechnol. 2012, 7, 96, DOI: 10.1038/nnano.2011.214[Crossref], [CAS], Google Scholar44https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXhsFGktL%252FL&md5=84c2a7b6849057feaf25a9f021932f08Control over topological insulator photocurrents with light polarizationMcIver, J. W.; Hsieh, D.; Steinberg, H.; Jarillo-Herrero, P.; Gedik, N.Nature Nanotechnology (2012), 7 (2), 96-100CODEN: NNAABX; ISSN:1748-3387. (Nature Publishing Group)Three-dimensional topol. insulators represent a new quantum phase of matter with spin-polarized surface states that are protected from backscattering. The static electronic properties of these surface states have been comprehensively imaged by both photoemission and tunnelling spectroscopies. Theorists have proposed that topol. surface states can also exhibit novel electronic responses to light, such as topol. quantum phase transitions and spin-polarized elec. currents. However, the effects of optically driving a topol. insulator out of equil. have remained largely unexplored exptl., and no photocurrents have been measured. Here, we show that illuminating the topol. insulator Bi2Se3 with circularly polarized light generates a photocurrent that originates from topol. helical Dirac fermions, and that reversing the helicity of the light reverses the direction of the photocurrent. We also observe a photocurrent that is controlled by the linear polarization of light and argue that it may also have a topol. surface state origin. This approach may allow the probing of dynamic properties of topol. insulators and lead to novel opto-spintronic devices.
- 45Obraztsov, P. A.; Lyashenko, D.; Chizhov, P. A.; Konishi, K.; Nemoto, N.; Kuwata-Gonokami, M.; Welch, E.; Obraztsov, A. N.; Zakhidov, A. Ultrafast Zero-Bias Photocurrent and Terahertz Emission in Hybrid Perovskites. Commun. Phys. 2018, 1, 1– 7, DOI: 10.1038/s42005-018-0013-8[Crossref], [CAS], Google Scholar45https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXpvV2lsbk%253D&md5=00cd77affa5cf5528a7fa15ca163fb2fUltrafast zero-bias photocurrent and terahertz emission in hybrid perovskitesObraztsov, Petr A.; Lyashenko, Dmitry; Chizhov, Pavel A.; Konishi, Kuniaki; Nemoto, Natsuki; Kuwata-Gonokami, Makoto; Welch, Eric; Obraztsov, Alexander N.; Zakhidov, AlexCommunications Physics (2018), 1 (1), 1-7CODEN: CPOHDJ; ISSN:2399-3650. (Nature Research)Methylammonium lead iodide is a benchmark hybrid org. perovskite material used for low-cost printed solar cells with a power conversion efficiency of over 20%. Nevertheless, the nature of light-matter interaction in hybrid perovskites and the exact phys. mechanism underlying device operation are currently debated. Here, we report room temp., ultrafast photocurrent generation, and free-space terahertz emission from unbiased hybrid perovskites induced by femtosecond light pulses. The polarization dependence of the obsd. photoresponse is consistent with the bulk photovoltaic effect caused by a combination of injection and shift currents. Observation of this type of photocurrents sheds light on the low recombination and long carrier diffusion lengths arising from the indirect bandgap in CH3NH3PbI3. Naturally ballistic shift and injection photocurrents may enable third-generation perovskite solar cells with efficiency exceeding the Shockley-Queisser limit. The demonstrated control over photocurrents with light polarization also opens new venues toward perovskite spintronics and tunable THz devices.
- 46Osterhoudt, G. B.; Diebel, L. K.; Gray, M. J.; Yang, X.; Stanco, J.; Huang, X.; Shen, B.; Ni, N.; Moll, P. J.; Ran, Y.; Burch, K. S. Colossal Mid-Infrared Bulk Photovoltaic Effect in a Type-I Weyl Semimetal. Nat. Mater. 2019, 18, 471– 475, DOI: 10.1038/s41563-019-0297-4[Crossref], [PubMed], [CAS], Google Scholar46https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXmsV2isrk%253D&md5=cc7490082181aa505b4f04c545a34ea1Colossal mid-infrared bulk photovoltaic effect in a type-I Weyl semimetalOsterhoudt, Gavin B.; Diebel, Laura K.; Gray, Mason J.; Yang, Xu; Stanco, John; Huang, Xiangwei; Shen, Bing; Ni, Ni; Moll, Philip J. W.; Ran, Ying; Burch, Kenneth S.Nature Materials (2019), 18 (5), 471-475CODEN: NMAACR; ISSN:1476-1122. (Nature Research)Broadband, efficient and fast conversion of light to electricity is crucial for sensing and clean energy. The bulk photovoltaic effect (BPVE) is a second-order nonlinear optical effect that intrinsically converts light into elec. current. Here, we demonstrate a large mid-IR BPVE in microscopic devices of the Weyl semimetal TaAs. This discovery results from combining recent developments in Weyl semimetals, focused-ion beam fabrication and theor. works suggesting a connection between BPVE and topol. We also present a detailed symmetry anal. that allows us to sep. the shift current response from photothermal effects. The magnitude and wavelength range of the assigned shift current may impact optical detectors, clean energy and topol., and demonstrate the utility of Weyl semimetals for practical applications.
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Abstract
Figure 1
Figure 1. Structural characterizations of the chiral 2D-HOIPs. (a) Crystalline structure of the chiral 2D hybrid perovskite ((R/S-)methylbenzylammonium lead iodide, (R/S-MBA)2PbI4. GIWAXS of the (R-MBA)2PbI4 (b) and (S-MBA)2PbI4 (c) films. (d) Absorption spectra of (R/S/rac-MBA)2PbI4 films. (e) Circular dichroism (CD) spectra of (R/S/rac-MBA)2PbI4 films as denoted, measured at room temperature. The CD polarities of (R-MBA)2PbI4 and (S-MBA)2PbI4 are opposite to each other, whereas (rac-MBA)2PbI4 shows no CD. The absorption bands in (d) and CD bands in (e) due to exciton (EX) and interband (IB) are denoted.
Figure 2
Figure 2. Structure and I–V responses of the spin PV devices. (a) Schematic view of the spin photovoltaic device based on the MBA2PbI4 active layer. LCP and RCP light are used for the photocurrent generation. The I–V response of the photovoltaic devices based on (b) (rac-MBA)2PbI4, (c) (R-MBA)2PbI4, and (d) (S-MBA)2PbI4 measured at 7 K in the dark (black), with LCP (red) light, and with RCP (blue) light using light from a 486 nm laser at an intensity of 20 mW/cm2. The inset is a magnified view of the data around V = 0 V.
Figure 3
Figure 3. Voltage dependence and action spectrum of
. (a) Relative photocurrent difference, ΔI/I, of (R/S-MBA)2PbI4 spin PV devices as a function of bias voltage. (b) Action spectrum of ΔI/I in an (R-MBA)2PbI4-based PV device compared to the relative absorption difference ΔA/A of LCP and RCP light in an (R-MBA)2PbI4 film measured by CD.Figure 4
Figure 4. Circular photogalvanic effect in chiral 2D-HOIP. (a) Experimental setup for measuring the photogalvanic current using a λ/4 plate; the angles α, θ, and ϕ′ are denoted. x′ indicates the current flow direction. Photogalvanic current vs the quarter-wave plate rotational angle, α for (b) the (R-MBA)2PbI4 and (c) the (S-MBA)2PbI4 films, measured at 520 nm using xenon lamp excitation at room temperature. The values of the CPGE coefficient C obtained from the fitting using eq 3 are denoted. (d) Action spectra of the obtained CPGE coefficient C for the two chiral 2D-HOIPs in the spectral range of the exciton absorption band. The data for (R-MBA)2PbI4 are multiplied by a factor of 3 in order to compare with the other chiral 2D-HOIP.
References
ARTICLE SECTIONSThis article references 46 other publications.
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- 8Long, G.; Jiang, C.; Sabatini, R.; Yang, Z.; Wei, M.; Quan, L. N.; Liang, Q.; Rasmita, A.; Askerka, M.; Walters, G.; Gong, X. Spin Control in Reduced-Dimensional Chiral Perovskites. Nat. Photonics 2018, 12, 528– 533, DOI: 10.1038/s41566-018-0220-6[Crossref], [CAS], Google Scholar8https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhsV2isLnF&md5=0a921b1f3b06b1d53a12d0336eed4899Spin control in reduced-dimensional chiral perovskitesLong, Guankui; Jiang, Chongyun; Sabatini, Randy; Yang, Zhenyu; Wei, Mingyang; Quan, Li Na; Liang, Qiuming; Rasmita, Abdullah; Askerka, Mikhail; Walters, Grant; Gong, Xiwen; Xing, Jun; Wen, Xinglin; Quintero-Bermudez, Rafael; Yuan, Haifeng; Xing, Guichuan; Wang, X. Renshaw; Song, Datong; Voznyy, Oleksandr; Zhang, Mingtao; Hoogland, Sjoerd; Gao, Weibo; Xiong, Qihua; Sargent, Edward H.Nature Photonics (2018), 12 (9), 528-533CODEN: NPAHBY; ISSN:1749-4885. (Nature Research)A review. Hybrid org.-inorg. perovskites exhibit strong spin-orbit coupling1, spin-dependent optical selection rules2,3 and large Rashba splitting4-8. These characteristics make them promising candidates for spintronic devices9 with photonic interfaces. Here we report that spin polarization in perovskites can be controlled through chem. design as well as by a magnetic field. We obtain both spin-polarized photon absorption and spin-polarized photoluminescence in reduced-dimensional chiral perovskites through combined strategies of chirality transfer and energy funnelling. A 3% spin-polarized photoluminescence is obsd. even in the absence of an applied external magnetic field owing to the different emission rates of σ+ and σ- polarized photoluminescence. Three-dimensional perovskites achieve a comparable degree of photoluminescence polarization only under an external magnetic field of 5 T. Our findings pave the way for chiral perovskites as powerful spintronic materials.
- 9Giovanni, D.; Chong, W. K.; Dewi, H. A.; Thirumal, K.; Neogi, I.; Ramesh, R.; Mhaisalkar, S.; Mathews, N.; Sum, T. C. Tunable Room-Temperature Spin-Selective Optical Stark Effect in Solution-Processed Layered Halide Perovskites. Sci. Adv. 2016, 2, e1600477 DOI: 10.1126/sciadv.1600477[Crossref], [PubMed], [CAS], Google Scholar9https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhslaksbrM&md5=997cfdd9c90bbbf3cbea9574ec109ae1Tunable room-temperature spin-selective optical Stark effect in solution-processed layered halide perovskitesGiovanni, David; Chong, Wee Kiang; Dewi, Herlina Arianita; Thirumal, Krishnamoorthy; Neogi, Ishita; Ramesh, Ramamoorthy; Mhaisalkar, Subodh; Mathews, Nripan; Sum, Tze ChienScience Advances (2016), 2 (6), e1600477/1-e1600477/6CODEN: SACDAF; ISSN:2375-2548. (American Association for the Advancement of Science)Ultrafast spin manipulation for opto-spin logic applications requires material systems that have strong spin-selective light-matter interaction. Conventional inorg. semiconductor nanostructures [for example, epitaxial II to VI quantum dots and III to V multiple quantum wells (MQWs)] are considered forerunners but encounter challenges such as lattice matching and cryogenic cooling requirements. Two-dimensional halide perovskite semiconductors, combining intrinsic tunable MQW structures and large oscillator strengths with facile soln. processability, can offer breakthroughs in this area. We demonstrate novel room-temp., strong ultrafast spin-selective optical Stark effect in soln.-processed (C6H4FC2H4NH3)2PbI4 perovskite thin films. Exciton spin states are selectively tuned by ∼6.3 meV using circularly polarized optical pulses without any external photonic cavity (i.e., corresponding to a Rabi energy of ∼55 meV and equiv. to applying a 70 T magnetic field), which is much larger than any conventional system. The facile halide and org. replacement in these perovskites affords control of the dielec. confinement and thus presents a straightforward strategy for tuning light-matter coupling strength.
- 10Chen, X.; Lu, H.; Li, Z.; Zhai, Y.; Ndione, P. F.; Berry, J. J.; Zhu, K.; Yang, Y.; Beard, M. C. Impact of Layer Thickness on the Charge Carrier and Spin Coherence Lifetime in Two-Dimensional Layered Perovskite Single Crystals. ACS Energy Lett. 2018, 3, 2273– 2279, DOI: 10.1021/acsenergylett.8b01315[ACS Full Text], [CAS], Google Scholar10https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhs1SnsLnE&md5=ddeca3f7f2b4f2e0c57f665b4a29812dImpact of Layer Thickness on the Charge Carrier and Spin Coherence Lifetime in Two-Dimensional Layered Perovskite Single CrystalsChen, Xihan; Lu, Haipeng; Li, Zhen; Zhai, Yaxin; Ndione, Paul F.; Berry, Joseph J.; Zhu, Kai; Yang, Ye; Beard, Matthew C.ACS Energy Letters (2018), 3 (9), 2273-2279CODEN: AELCCP; ISSN:2380-8195. (American Chemical Society)The authors report the charge carrier recombination rate and spin coherence lifetimes in single crystals of two-dimensional (2D) Ruddlesden-Popper perovskites PEA2PbI4·(MAPbI3)n-1 (PEA, phenethylammonium; MA, methylammonium; n = 1, 2, 3, 4). Layer thickness-dependent charge carrier recombination rates are obsd., with the fastest rates for n = 1 because of the large exciton binding energy, and the slowest rates are obsd. for n = 2. Room-temp. spin coherence times also show a nonmonotonic layer thickness dependence with an increasing spin coherence lifetime with increasing layer thickness from n = 1 to n = 4, followed by a decrease in lifetime from n = 4 to ∞. The longest coherence lifetime of ∼7 ps is obsd. in the n = 4 sample. The authors' results are consistent with two contributions: Rashba splitting increases the spin coherence lifetime going from the n = ∞ to the layered systems, while phonon scattering, which increases for smaller layers, decreases the spin coherence lifetime. The interplay between these two factors contributes to the layer thickness dependence.
- 11Lu, H.; Wang, J.; Xiao, C.; Pan, X.; Chen, X.; Brunecky, R.; Berry, J. J.; Zhu, K.; Beard, M. C.; Vardeny, Z. V. Spin-Dependent Charge Transport through 2D Chiral Hybrid Lead-Iodide Perovskites. Sci. Adv. 2019, 5, eaay0571 DOI: 10.1126/sciadv.aay0571
- 12Long, G.; Sabatini, R.; Saidaminov, M. I.; Lakhwani, G.; Rasmita, A.; Liu, X.; Sargent, E. H.; Gao, W. Chiral-Perovskite Optoelectronics. Nat. Rev. Mater. 2020, 5, 1– 17, DOI: 10.1038/s41578-020-0181-5
- 13Chen, C.; Gao, L.; Gao, W.; Ge, C.; Du, X.; Li, Z.; Yang, Y.; Niu, G.; Tang, J. Circularly Polarized Light Detection Using Chiral Hybrid Perovskite. Nat. Commun. 2019, 10, 1– 7, DOI: 10.1038/s41467-019-09942-z[Crossref], [PubMed], [CAS], Google Scholar13https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXitlSqs7rJ&md5=e57d144885384832207772a89dad74f8Decoupling of mechanical properties and ionic conductivity in supramolecular lithium ion conductorsMackanic, David G.; Yan, Xuzhou; Zhang, Qiuhong; Matsuhisa, Naoji; Yu, Zhiao; Jiang, Yuanwen; Manika, Tuheen; Lopez, Jeffrey; Yan, Hongping; Liu, Kai; Chen, Xiaodong; Cui, Yi; Bao, ZhenanNature Communications (2019), 10 (1), 1-11CODEN: NCAOBW; ISSN:2041-1723. (Nature Research)The emergence of wearable electronics puts batteries closer to the human skin, exacerbating the need for battery materials that are robust, highly ionically conductive, and stretchable. Herein, we introduce a supramol. design as an effective strategy to overcome the canonical tradeoff between mech. robustness and ionic cond. in polymer electrolytes. The supramol. lithium ion conductor utilizes orthogonally functional H-bonding domains and ion-conducting domains to create a polymer electrolyte with unprecedented toughness (29.3 MJ m-3) and high ionic cond. (1.2 × 10-4 S cm-1 at 25°C). Implementation of the supramol. ion conductor as a binder material allows for the creation of stretchable lithium-ion battery electrodes with strain capability of over 900% via a conventional slurry process. The supramol. nature of these battery components enables intimate bonding at the electrode-electrolyte interface. Combination of these stretchable components leads to a stretchable battery with a capacity of 1.1 mAh cm-2 that functions even when stretched to 70% strain. The method reported here of decoupling ionic cond. from mech. properties opens a promising route to create high-toughness ion transport materials for energy storage applications.
- 14Ma, J.; Fang, C.; Chen, C.; Jin, L.; Wang, J.; Wang, S.; Tang, J.; Li, D. Chiral 2D Perovskites with a High Degree of Circularly Polarized Photoluminescence. ACS Nano 2019, 13, 3659– 3665, DOI: 10.1021/acsnano.9b00302[ACS Full Text], [CAS], Google Scholar14https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXksF2kt70%253D&md5=95ba823537ea8a9ed5c685cfef781570Chiral 2D Perovskites with a High Degree of Circularly Polarized PhotoluminescenceMa, Jiaqi; Fang, Chen; Chen, Chao; Jin, Long; Wang, Jiaqi; Wang, Shuai; Tang, Jiang; Li, DehuiACS Nano (2019), 13 (3), 3659-3665CODEN: ANCAC3; ISSN:1936-0851. (American Chemical Society)Chiral materials are of particular interest and have a wide range of potential applications in life science, material science, spintronic, and optoelectronic devices. Two-dimensional (2D) hybrid org.-inorg. lead halide perovskites have attracted increasing attention. Incorporating the chiral org. ligands into the layered lead iodide frameworks would introduce strong chirality in pure 2D perovskites for potential applications in circularly polarized light (CPL) emission and detection; nonetheless, studies on those aspects are still in their infancy. Here, we report on the strong CPL emission and sensitive CPL detection in the visible-wavelength range in pure chiral (R-/S-MBA)2PbI4 (MBA = C6H5C2H4NH3) 2D perovskites, which are successfully synthesized with a needle shape and millimeter size by incorporating the chiral mols. The chiral 2D perovskites (R-MBA)2PbI4 and (S-MBA)2PbI4 exhibit an av. degree of circularly polarized photoluminescence (PL) of 9.6% and 10.1% at 77 K, resp., and a max. degree of the circularly polarized PL of 17.6% is achieved in (S-MBA)2PbI4. The degree of circularly polarized PL dramatically decreases with increasing temp., implying that the lattice distortion induced by the incorporated chiral mols. and/or temp.-dependent spin flipping might be the origin for the obsd. chirality. Finally, CPL detection has been achieved with decent performance in our chiral 2D perovskite microplate/MoS2 heterostructural devices. The high degree of the circularly polarized PL and excellent CPL detection together with the layered nature of pure chiral 2D perovskites enables them to be a class of very promising materials for developing and exploring spin assocd. electronic devices based on the chiral 2D perovskites.
- 15Wang, L.; Xue, Y.; Cui, M.; Huang, Y.; Xu, H.; Qin, C.; Yang, J.; Dai, H.; Yuan, M. A Chiral Reduced-Dimension Perovskite for an Efficient Flexible Circularly Polarized Light Photodetector. Angew. Chem. 2020, 132, 6504– 6512, DOI: 10.1002/ange.201915912
- 16Jana, M. K.; Song, R.; Liu, H.; Khanal, D. R.; Janke, S. M.; Zhao, R.; Liu, C.; Vardeny, Z. V.; Blum, V.; Mitzi, D. B. Organic-to-Inorganic Structural Chirality Transfer in a 2D Hybrid Perovskite and Impact on Rashba-Dresselhaus Spin-Orbit Coupling. Nat. Commun. 2020, 11, 1– 10, DOI: 10.1038/s41467-020-18485-7
- 17Lu, H.; Xiao, C.; Song, R.; Li, T.; Maughan, A. E.; Levin, A.; Brunecky, R.; Berry, J. J.; Mitzi, D. B.; Blum, V.; Beard, M. C. Distorted Chiral Two-Dimensional Tin Iodide Perovskites for Spin Polarized Charge Highly Transport. J. Am. Chem. Soc. 2020, 142, 13030– 13040, DOI: 10.1021/jacs.0c03899[ACS Full Text], [CAS], Google Scholar17https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXhtlSisb7P&md5=ce2f4a7b10e2171b4cb7c0303cc875daHighly Distorted Chiral Two-Dimensional Tin Iodide Perovskites for Spin Polarized Charge TransportLu, Haipeng; Xiao, Chuanxiao; Song, Ruyi; Li, Tianyang; Maughan, Annalise E.; Levin, Andrew; Brunecky, Roman; Berry, Joseph J.; Mitzi, David B.; Blum, Volker; Beard, Matthew C.Journal of the American Chemical Society (2020), 142 (30), 13030-13040CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)Incorporating chiral org. mols. into org./inorg. hybrid 2D metal-halide perovskites results in a novel family of chiral hybrid semiconductors with unique spin-dependent properties. The embedded chiral org. moieties induce a chiroptical response from the inorg. metal-halide sublattice. However, the structural interplay between the chiral org. mols. and the inorg. sublattice, as well as their synergic effect on the resulting electronic band structure need to be explored in a broader material scope. Here we present three new layered tin iodide perovskites templated by chiral (R/S-)methylbenzylammonium (R/S-MBA), i.e., (R-/S-MBA)2SnI4, and their racemic phase (rac-MBA)2SnI4. These MBA2SnI4 compds. exhibit the largest level of octahedral bond distortion compared to any other reported layered tin iodide perovskite. The incorporation of chiral MBA cations leads to circularly polarized absorption from the inorg. Sn-I sublattice, displaying chiroptical activity in the 300-500 nm wavelength range. The bandgap and chiroptical activity are modulated by alloying Sn with Pb, in the series of (MBA)2Pb1-xSnxI4. Finally, we show that vertical charge transport through oriented (R-/S-MBA)2SnI4 thin films is highly spin-dependent, arising from a chiral-induced spin selectivity (CISS) effect. We demonstrate a spin-polarization in the current-voltage characteristics as high as 94%. Our work shows the tremendous potential of these chiral hybrid semiconductors for controlling both spin and charge degrees of freedom.
- 18Naaman, R.; Waldeck, D. H. Chiral-Induced Spin Selectivity Effect. J. Phys. Chem. Lett. 2012, 3, 2178– 2187, DOI: 10.1021/jz300793y[ACS Full Text], [CAS], Google Scholar18https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XhtV2gs7rJ&md5=c036f2be4c63575311396690f1aaa3b5Chiral-Induced Spin Selectivity EffectNaaman, R.; Waldeck, David H.Journal of Physical Chemistry Letters (2012), 3 (16), 2178-2187CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)A review. The chiral-induced spin selectivity (CISS) effect was recently established exptl. and theor. Here, we review some of the new findings and discuss applications that can result from special properties of this effect, like the redn. of the elastic backscattering in electron transfer through chiral mols. The CISS effect opens the possibility of using chiral mols. in spintronics applications and for providing a deeper understanding of spin-selective processes in biol.
- 19Cahn, R. S.; Ingold, C.; Prelog, V. Specification of Molecular Chirality. Angew. Chem., Int. Ed. Engl. 1966, 5, 385– 415, DOI: 10.1002/anie.196603851[Crossref], [CAS], Google Scholar19https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaF28XktFKitLk%253D&md5=6c0330b150d5c8dc9045afcdd073d6d2Specification of molecular chiralityCahn, R. S.; Ingold, Christopher; Prelog, V.Angewandte Chemie, International Edition in English (1966), 5 (4), 385-415CODEN: ACIEAY; ISSN:0570-0833.A discussion of mol. conformation with 39 references.
- 20Kasprzyk-Hordern, B. Pharmacologically Active Compounds in the Environment and Their Chirality. Chem. Soc. Rev. 2010, 39, 4466– 4503, DOI: 10.1039/c000408c[Crossref], [PubMed], [CAS], Google Scholar20https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXhtlShtb3J&md5=8fe00731e6fc2763aec5869cd12f3b3cPharmacologically active compounds in the environment and their chiralityKasprzyk-Hordern, BarbaraChemical Society Reviews (2010), 39 (11), 4466-4503CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)A review. Pharmacol. active compds. including both legally used pharmaceuticals and illicit drugs are potent environmental contaminants. Extensive research has been undertaken over the recent years to understand their environmental fate and toxicity. The one very important phenomenon that has been overlooked by environmental researchers studying the fate of pharmacol. active compds. in the environment is their chirality. Chiral drugs can exist in the form of enantiomers, which have similar physicochem. properties but differ in their biol. properties such as distribution, metab. and excretion, as these processes (due to stereospecific interactions of enantiomers with biol. systems) usually favor one enantiomer over the other. Addnl., due to different pharmacol. activity, enantiomers of chiral drugs can differ in toxicity. Furthermore, degrdn. of chiral drugs during wastewater treatment and in the environment can be stereoselective and can lead to chiral products of varied toxicity. The distribution of different enantiomers of the same chiral drug in the aquatic environment and biota can also be stereoselective. Biol. processes can lead to stereoselective enrichment or depletion of the enantiomeric compn. of chiral drugs. As a result the very same drug might reveal different activity and toxicity and this will depend on its origin and exposure to several factors governing its fate in the environment. In this crit. review a discussion of the importance of chirality of pharmacol. active compds. in the environmental context is undertaken and suggestions for directions in further research are made. Several groups of chiral drugs of major environmental relevance are discussed and their pharmacol. action and disposition in the body is also outlined as it is a key factor in developing a full understanding of their environmental occurrence, fate and toxicity. This review will be of interest to environmental scientists, esp. those interested in issues assocd. with environmental contamination with pharmacol. active compds. and chiral pollutants. As the review will outline current state of knowledge on chiral drugs, it will be of value to anyone interested in the phenomenon of chirality, chiral drugs, their stereoselective disposition in the body and environmental fate.
- 21Huang, P. J.; Taniguchi, K.; Miyasaka, H. Bulk Photovoltaic Effect in a Pair of Chiral–Polar Layered Perovskite-Type Lead Iodides Altered by Chirality of Organic Cations. J. Am. Chem. Soc. 2019, 141, 14520– 14523, DOI: 10.1021/jacs.9b06815[ACS Full Text], [CAS], Google Scholar21https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXhslSqtr7P&md5=a221c27b563ddd888e0859b92338db42Bulk Photovoltaic Effect in a Pair of Chiral-Polar Layered Perovskite-Type Lead Iodides Altered by Chirality of Organic CationsHuang, Po-Jung; Taniguchi, Kouji; Miyasaka, HitoshiJournal of the American Chemical Society (2019), 141 (37), 14520-14523CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)The bulk photovoltaic effect (BPVE) is a promising optoelectronic phenomenon for generating a steady-state photocurrent without a bias voltage. Nevertheless, the simple and rational design of materials exhibiting the BPVE remains an important topic in the relevant fields. Here, the observation is reported of the BPVE in a simple chiral-polar pair of layered perovskite-type lead iodides in the crystal space group of P1 (#1), which were synthesized by assembling R- and S-chiral org. cations, resp. The sign of the zero-bias photocurrent is altered by the R/S-chirality of the assembled cations, which define the direction of elec. polarization derived from the elec. dipole moment of each chiral org. cation aligned in a crystal. The strategy of chirality control in a crystal is expected to be useful when searching for BPVE materials.
- 22Dong, Y.; Zhang, Y.; Li, X.; Feng, Y.; Zhang, H.; Xu, J. Chiral Perovskites: Promising Materials toward Next-Generation Optoelectronics. Small 2019, 15, 1902237, DOI: 10.1002/smll.201902237
- 23Bloom, B. P.; Kiran, V.; Varade, V.; Naaman, R.; Waldeck, D. H. Spin Selective Charge Transport through Cysteine Capped Cdse Quantum Dots. Nano Lett. 2016, 16, 4583– 4589, DOI: 10.1021/acs.nanolett.6b01880[ACS Full Text], [CAS], Google Scholar23https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XhtVCjsbbP&md5=d9d9c79487a78879a093346b3fa9263cSpin selective charge transport through cysteine capped CdSe quantum dotsBloom, Brian P.; Kiran, Vankayala; Varade, Vaibhav; Naaman, Ron; Waldeck, David. H.Nano Letters (2016), 16 (7), 4583-4589CODEN: NALEFD; ISSN:1530-6984. (American Chemical Society)This work demonstrates that chiral imprinted CdSe quantum dots (QDs) can act as spin selective filters for charge transport. The spin filtering properties of chiral nanoparticles were investigated by magnetic conductive-probe at. force microscopy (mCP-AFM) measurements and magnetoresistance measurements. The mCP-AFM measurements show that the chirality of the quantum dots and the magnetic orientation of the tip affect the current-voltage curves. Similarly, magnetoresistance measurements demonstrate that the elec. transport through films of chiral quantum dots correlates with the chiroptical properties of the QD. The spin filtering properties of chiral quantum dots may prove useful in future applications, for example, photovoltaics, spintronics, and other spin-driven devices.
- 24Xie, Z.; Markus, T. Z.; Cohen, S. R.; Vager, Z.; Gutierrez, R.; Naaman, R. Spin Specific Electron Conduction through DNA Oligomers. Nano Lett. 2011, 11, 4652– 4655, DOI: 10.1021/nl2021637[ACS Full Text], [CAS], Google Scholar24https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXhtlSltLjM&md5=14c0cbed382e1a57b0d656eeacf88238Spin Specific Electron Conduction through DNA OligomersXie, Zuoti; Markus, Tal Z.; Cohen, Sidney R.; Vager, Zeev; Gutierrez, Rafael; Naaman, RonNano Letters (2011), 11 (11), 4652-4655CODEN: NALEFD; ISSN:1530-6984. (American Chemical Society)Spin-based properties, applications, and devices are commonly related to magnetic effects and to magnetic materials. Most of the development in spintronics is currently based on inorg. materials. Despite the fact that the magnetoresistance effect was obsd. in org. materials, until now spin selectivity of org. based spintronics devices originated from an inorg. ferromagnetic electrode and was not detd. by the org. mols. themselves. Conduction through double-stranded DNA oligomers is spin selective, demonstrating a true org. spin filter. The selectivity exceeds that of any known system at room temp. The spin dependent resistivity indicates that the effect cannot result solely from the at. spin-orbit coupling and must relate to a special property resulting from the chirality symmetry. The results may reflect on the importance of spin in detg. electron transfer rates through biol. systems.
- 25Mondal, P. C.; Fontanesi, C.; Waldeck, D. H.; Naaman, R. Spin-Dependent Transport through Chiral Molecules Studied by Spin-Dependent Electrochemistry. Acc. Chem. Res. 2016, 49, 2560– 2568, DOI: 10.1021/acs.accounts.6b00446[ACS Full Text], [CAS], Google Scholar25https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XhslSqtLnE&md5=df9208ec171f00e24c88a03fede4c0a6Spin-Dependent Transport through Chiral Molecules Studied by Spin-Dependent ElectrochemistryMondal, Prakash Chandra; Fontanesi, Claudio; Waldeck, David H.; Naaman, RonAccounts of Chemical Research (2016), 49 (11), 2560-2568CODEN: ACHRE4; ISSN:0001-4842. (American Chemical Society)A review. Mol. spintronics (spin + electronics), which aims to exploit both the spin degree of freedom and the electron charge in mol. devices, has recently received massive attention. The authors' recent expts. on mol. spintronics employ chiral mols. which have the unexpected property of acting as spin filters, by way of an effect the authors call chiral-induced spin selectivity (CISS). In this Account, new types of spin-dependent electrochem. measurements and their use to probe the spin-dependent charge transport properties of nonmagnetic chiral conductive polymers and biomols., such as oligopeptides, L/D cysteine, cytochrome c, bacteriorhodopsin (bR), and oligopeptide-CdSe nanoparticles (NPs) hybrid structures are discussed. Spin-dependent electrochem. measurements were carried out by employing ferromagnetic electrodes modified with chiral mols. used as the working electrode. Redox probes were used either in soln. or when directly attached to the ferromagnetic electrodes. During the electrochem. measurements, the ferromagnetic electrode was magnetized either with its magnetic moment pointing UP or DOWN using a permanent magnet (H = 0.5 T), placed underneath the chem. modified ferromagnetic electrodes. The spin polarization of the current is at 5-30%, even in the case of small chiral mols. Chiral films of the L- and D-cysteine tethered with a redox-active dye, toluidine blue O, show spin polarization that depends on the chirality. Because the Ni electrodes are susceptible to corrosion, the authors explored the effect of coating them with a thin Au overlayer. The effect of the Au layer on the spin polarization of the electrons ejected from the electrode was studied. The role of the structure of the protein on the spin selective transport was also studied as a function of bias voltage and the effect of protein denaturation was revealed. In addn. to dark measurements, the authors also describe photoelectrochem. measurements in which light was used to affect the spin selective electron transport through the chiral mols. The authors describe how the excitation of a chromophore (such as CdSe nanoparticles), which is attached to a chiral working electrode, can flip the preferred spin orientation of the photocurrent, when measured under the identical conditions. Thus, chirality-induced spin polarization, when combined with light and magnetic field effects, opens new avenues for the study of the spin transport properties of chiral mols. and biomols. and for creating new types of spintronic devices in which light and mol. chirality provide new functions and properties.
- 26Billing, D. G.; Lemmerer, A. Synthesis and Crystal Structures of Inorganic–Organic Hybrids Incorporating an Aromatic Amine with a Chiral Functional Group. CrystEngComm 2006, 8, 686– 695, DOI: 10.1039/B606987H[Crossref], [CAS], Google Scholar26https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD28Xps1Sjurc%253D&md5=ccd6703bf7079618eb800ca1722aa040Synthesis and crystal structures of inorganic-organic hybrids incorporating an aromatic amine with a chiral functional groupBilling, David G.; Lemmerer, AndreasCrystEngComm (2006), 8 (9), 686-695CODEN: CRECF4; ISSN:1466-8033. (Royal Society of Chemistry)The authors report the synthesis and the crystal structure of inorg.-org. hybrids contg. various lead halides as the inorg. motif and a primary amine as the org. constituent, namely (R)-, (S)- and racemic 1-phenylethylamine (L). Within the structures obtained, three different inorg. motifs are displayed by the lead halide octahedra: 1-dimensional polymeric face-sharing chains PbCl3((R)-LH), PbBr3((R)-LH), PbI3((R)-LH) and PbI3((S)-LH); 1-dimensional polymeric corner-sharing chains PbCl5((±)-LH)3 and PbBr5((±)-LH)3; and 2-dimensional corner-sharing layers PbI4((S)-LH)2 and PbI4((S)-LH)2. The changes in geometry and intermol. interactions such as H bonding and pi stacking are discussed and compared between the eight structures.
- 27Ahn, J.; Lee, E.; Tan, J.; Yang, W.; Kim, B.; Moon, J. A New Class of Chiral Semiconductors: Chiral-Organic-Molecule-Incorporating Organic–Inorganic Hybrid Perovskites. Mater. Horiz. 2017, 4, 851– 856, DOI: 10.1039/C7MH00197E[Crossref], [CAS], Google Scholar27https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXovFGjs7g%253D&md5=a655175acd344e7724527d3bbf6d4982A new class of chiral semiconductors: chiral-organic-molecule-incorporating organic-inorganic hybrid perovskitesAhn, Jihoon; Lee, Eunsong; Tan, Jeiwan; Yang, Wooseok; Kim, Bokyung; Moon, JoohoMaterials Horizons (2017), 4 (5), 851-856CODEN: MHAOBM; ISSN:2051-6355. (Royal Society of Chemistry)An org.-inorg. hybrid perovskite incorporating chiral org. mols. is demonstrated as a new class of chiral semiconductors. Chiral perovskites exhibit oppositely-signed CD (CD) according to the S- and R-configurations of chiral orgs. The CD signals can be also varied by changing the cryst. orientation and thickness of the chiral perovskite films.
- 28Cao, D. H.; Stoumpos, C. C.; Farha, O. K.; Hupp, J. T.; Kanatzidis, M. G. 2D Homologous Perovskites as Light-Absorbing Materials for Solar Cell Applications. J. Am. Chem. Soc. 2015, 137, 7843– 7850, DOI: 10.1021/jacs.5b03796[ACS Full Text], [CAS], Google Scholar28https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXptFWrtL8%253D&md5=850fa45ea65c55307e5c9cbf435889122D Homologous Perovskites as Light-Absorbing Materials for Solar Cell ApplicationsCao, Duyen H.; Stoumpos, Constantinos C.; Farha, Omar K.; Hupp, Joseph T.; Kanatzidis, Mercouri G.Journal of the American Chemical Society (2015), 137 (24), 7843-7850CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)We report on the fabrication and properties of the semiconducting 2D (CH3(CH2)3NH3)2(CH3NH3)n-1PbnI3n+1 (n = 1, 2, 3, and 4) perovskite thin films. The band gaps of the series decrease with increasing n values, from 2.24 eV (CH3(CH2)3NH3)2PbI4 (n = 1) to 1.52 eV CH3NH3PbI3 (n = ∞). The compds. exhibit strong light absorption in the visible region, accompanied by strong photoluminescence at room temp., rendering them promising light absorbers for photovoltaic applications. Moreover, we find that thin films of the semi-2D perovskites display an ultrahigh surface coverage as a result of the unusual film self-assembly that orients the [PbnI3n+1]- layers perpendicular to the substrates. We have successfully implemented this 2D perovskite family in solid-state solar cells, and obtained an initial power conversion efficiency of 4.02%, featuring an open-circuit voltage (Voc) of 929 mV and a short-circuit c.d. (Jsc) of 9.42 mA/cm2 from the n = 3 compd. This result is even more encouraging considering that the device retains its performance after long exposure to a high-humidity environment. Overall, the homologous 2D halide perovskites define a promising class of stable and efficient light-absorbing materials for solid-state photovoltaics and other applications.
- 29Katan, C.; Mercier, N.; Even, J. Quantum and Dielectric Confinement Effects in Lower-Dimensional Hybrid Perovskite Semiconductors. Chem. Rev. 2019, 119, 3140– 3192, DOI: 10.1021/acs.chemrev.8b00417[ACS Full Text], [CAS], Google Scholar29https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXnvVeisg%253D%253D&md5=3a9ad3f2412701bea686f412e190256cQuantum and dielectric confinement effects in lower-dimensional hybrid perovskite semiconductorsKatan, Claudine; Mercier, Nicolas; Even, JackyChemical Reviews (Washington, DC, United States) (2019), 119 (5), 3140-3192CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)Hybrid halide perovskites are now superstar materials leading the field of low-cost thin film photovoltaics technologies. Following the surge for more efficient and stable 3D bulk alloys, multilayered halide perovskites and colloidal perovskite nanostructures appeared in 2016 as viable alternative solns. to this challenge, largely exceeding the original proof of concept made in 2009 and 2014, resp. This triggered renewed interest in lower-dimensional hybrid halide perovskites and at the same time increasingly more numerous and differentiated applications. The present paper is a review of the past and present literature on both colloidal nanostructures and multilayered compds., emphasizing that availability of accurate structural information is of dramatic importance to reach a fair understanding of quantum and dielec. confinement effects. Layered halide perovskites occupy a special place in the history of halide perovskites, with a large no. of seminal papers in the 1980s and 1990s. In recent years, the rationalization of structure-properties relationship has greatly benefited from new theor. approaches dedicated to their electronic structures and optoelectronic properties, as well as a growing no. of contributions based on modern exptl. techniques. This is a necessary step to provide in-depth tools to decipher their extensive chem. engineering possibilities which surpass the ones of their 3D bulk counterparts. Comparisons to classical semiconductor nanostructures and 2D van der Waals heterostructures are also stressed. Since 2015, colloidal nanostructures have undergone a quick development for applications based on light emission. Although intensively studied in the last two years by various spectroscopy techniques, the description of quantum and dielec. confinement effects on their optoelectronic properties is still in its infancy.
- 30Riehl, J. P.; Richardson, F. S. Circularly Polarized Luminescence Spectroscopy. Chem. Rev. 1986, 1, 1– 16, DOI: 10.1021/cr00071a001
- 31Lightner, D. A.; Gurst, J. E. Organic Conformational Analysis and Stereochemistry from Circular Dichroism Spectroscopy; John Wiley & Sons: New York, 2000; Vol. 23, pp 47– 51.Google ScholarThere is no corresponding record for this reference.
- 32Yang, Y.; Da Costa, R. C.; Fuchter, M. J.; Campbell, A. J. Circularly Polarized Light Detection by a Chiral Organic Semiconductor Transistor. Nat. Photonics 2013, 7, 634– 638, DOI: 10.1038/nphoton.2013.176[Crossref], [CAS], Google Scholar32https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXhtFCis7jI&md5=5b033d9e8e90487f1a2d97101a6fd3e3Circularly polarized light detection by a chiral organic semiconductor transistorYang, Ying; da Costa, Rosenildo Correa; Fuchter, Matthew J.; Campbell, Alasdair J.Nature Photonics (2013), 7 (8), 634-638CODEN: NPAHBY; ISSN:1749-4885. (Nature Publishing Group)Circularly polarized light is central to many photonic technologies, including circularly polarized ellipsometry-based tomog., optical communication of spin information and quantum-based optical computing and information processing. To develop these technologies to their full potential requires the realization of miniature, integrated devices that are capable of detecting the chirality or handedness' of circularly polarized light. Org. field-effect transistors, in which the active semiconducting layer is an org. material, allow the simple fabrication of ultrathin, compact devices. Here we demonstrate a circularly polarized light-detecting org. field-effect transistor based on an asym. pure, helically shaped chiral semiconducting mol. known as a helicene. Importantly, we find a highly specific photoresponse to circularly polarized light, which is directly related to the handedness of the helicene mol. We believe that this opens up the possibility for the detection of the chirality of circularly polarized light in a highly integrated photonic platform.
- 33Li, W.; Coppens, Z. J.; Besteiro, L. V.; Wang, W.; Govorov, A. O.; Valentine, J. Circularly Polarized Light Detection with Hot Electrons in Chiral Plasmonic Metamaterials. Nat. Commun. 2015, 6, 1– 7, DOI: 10.1038/ncomms9379
- 34Odenthal, P.; Talmadge, W.; Gundlach, N.; Wang, R.; Zhang, C.; Sun, D.; Yu, Z. G.; Vardeny, Z. V.; Li, Y. S. Spin-Polarized Exciton Quantum Beating in Hybrid Organic-Inorganic Perovskites. Nat. Phys. 2017, 13, 894– 899, DOI: 10.1038/nphys4145[Crossref], [CAS], Google Scholar34https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXovVGqs7w%253D&md5=bdce2164c1f38d59c856a5fafce95606Spin-polarized exciton quantum beating in hybrid organic-inorganic perovskitesOdenthal, Patrick; Talmadge, William; Gundlach, Nathan; Wang, Ruizhi; Zhang, Chuang; Sun, Dali; Yu, Zhi-Gang; Valy Vardeny, Z.; Li, Yan S.Nature Physics (2017), 13 (9), 894-899CODEN: NPAHAX; ISSN:1745-2473. (Nature Publishing Group)Hybrid org.-inorg. perovskites have emerged as a new class of semiconductors that exhibit excellent performance as active layers in photovoltaic solar cells. These compds. are also highly promising materials for the field of spintronics due to their large and tunable spin-orbit coupling, spin-dependent optical selection rules, and their predicted elec. tunable Rashba spin splitting. Here we demonstrate the optical orientation of excitons and optical detection of spin-polarized exciton quantum beating in polycryst. films of the hybrid perovskite CH3NH3PbClxI3-x. Time-resolved Faraday rotation measurement in zero magnetic field reveals unexpectedly long spin lifetimes exceeding 1 ns at 4 K, despite the large spin-orbit couplings of the heavy lead and iodine atoms. The quantum beating of exciton states in transverse magnetic fields shows two distinct frequencies, corresponding to two g-factors of 2.63 and -0.33, which we assign to electrons and holes, resp. These results provide a basic picture of the exciton states in hybrid perovskites, and suggest they hold potential for spintronic applications.
- 35Naaman, R.; Paltiel, Y.; Waldeck, D. H. Chiral Molecules and the Spin Selectivity Effect. J. Phys. Chem. Lett. 2020, 11, 3660– 3666, DOI: 10.1021/acs.jpclett.0c00474[ACS Full Text], [CAS], Google Scholar35https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXnt1Wjs7k%253D&md5=b3f6ff4184526a4c43117c481a58f614Chiral Molecules and the Spin Selectivity EffectNaaman, R.; Paltiel, Y.; Waldeck, D. H.Journal of Physical Chemistry Letters (2020), 11 (9), 3660-3666CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)A review. This Perspective discusses recent expts. that bear on the chiral induced spin selectivity (CISS) mechanism and its manifestation in electronic and magnetic properties of chiral mols. and materials. Although the discussion emphasizes newer expts., such as the magnetization dependence of chiral mol. interactions with ferromagnetic surfaces, early expts., which reveal the nonlinear scaling of the spin filtering with applied potential, are described also. In many of the theor. studies, one has had to invoke unusually large spin-orbit couplings in order to reproduce the large spin filtering obsd. in expts. Expts. imply that exchange interactions and Pauli exclusion constraints are an important aspect of CISS. They also demonstrate the spin-dependent charge flow between a ferromagnetic substrate and chiral mols. With these insights in mind, a simplified model is described in which the chiral mol.'s spin polarization is enhanced by a spin blockade effect to generate large spin filtering.
- 36Liu, X.; Chanana, A.; Huynh, U.; Xue, F.; Haney, P.; Blair, S.; Jiang, X.; Vardeny, Z. V. Circular Photogalvanic Spectroscopy of Rashba Splitting in 2D Hybrid Organic–Inorganic Perovskite Multiple Quantum Wells. Nat. Commun. 2020, 11, 1– 8, DOI: 10.1038/s41467-019-14073-6
- 37Niesner, D.; Hauck, M.; Shrestha, S.; Levchuk, I.; Matt, G. J.; Osvet, A.; Batentschuk, M.; Brabec, C.; Weber, H. B.; Fauster, T. Structural Fluctuations Cause Spin-Split States in Tetragonal (CH3NH3)PbI3 as Evidenced by the Circular Photogalvanic Effect. Proc. Natl. Acad. Sci. U. S. A. 2018, 115, 9509– 9514, DOI: 10.1073/pnas.1805422115[Crossref], [PubMed], [CAS], Google Scholar37https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXitVKhu77E&md5=0b8bcf94ba379a0a025500656ce58ad4Structural fluctuations cause spin-split states in tetragonal (CH3NH3)PbI3 as evidenced by the circular photogalvanic effectNiesner, Daniel; Hauck, Martin; Shrestha, Shreetu; Levchuk, Ievgen; Matt, Gebhard J.; Osvet, Andres; Batentschuk, Miroslaw; Brabec, Christoph; Weber, Heiko B.; Fauster, ThomasProceedings of the National Academy of Sciences of the United States of America (2018), 115 (38), 9509-9514CODEN: PNASA6; ISSN:0027-8424. (National Academy of Sciences)Lead halide perovskites are used in thin-film solar cells, which owe their high efficiency to the long lifetimes of photocarriers. Various calcns. find that a dynamical Rashba effect could significantly contribute to these long lifetimes. This effect is predicted to cause a spin splitting of the electronic bands of inversion-sym. cryst. materials at finite temps., resulting in a slightly indirect band gap. Direct exptl. evidence of the existence or the strength of the spin splitting is lacking. Here, we resonantly excite photocurrents in single cryst. (CH3NH3)PbI3 with circularly polarized light to clarify the existence of spin splittings in the band structure. We observe a circular photogalvanic effect, i.e., the photocurrent depends on the light helicity, in both orthorhombic and tetragonal (CH3NH3)PbI3. At room temp., the effect peaks for excitation photon energies ΔE=110 meV below the direct optical band gap. Temp.-dependent measurements reveal a sign change of the effect at the orthorhombic-tetragonal phase transition, indicating different microscopic origins in the two phases. Within the tetragonal phase, both ΔE and the amplitude of the circular photogalvanic effect increase with temp. Our findings support a dynamical Rashba effect in this phase, i.e., a spin splitting caused by thermally induced structural fluctuations which break inversion symmetry.
- 38Li, J.; Haney, P. M. Circular Photogalvanic Effect in Organometal Halide Perovskite CH3NH3PbI3. Appl. Phys. Lett. 2016, 109, 193903, DOI: 10.1063/1.4967176[Crossref], [PubMed], [CAS], Google Scholar38https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XhvVehtLnE&md5=c333486aa97da414e6ba982656ae2768Circular photogalvanic effect in organometal halide perovskite CH3NH3PbI3Li, Junwen; Haney, Paul M.Applied Physics Letters (2016), 109 (19), 193903/1-193903/4CODEN: APPLAB; ISSN:0003-6951. (American Institute of Physics)We study the circular photogalvanic effect in the organometal halide perovskite solar cell absorber CH3NH3PbI3. The calcd. photocurrent d. for a system with broken inversion symmetry is about 10-9 A/W, comparable to the previously studied quantum well and bulk Rashba systems. The circular photogalvanic effect relies on inversion symmetry breaking, so that by tuning the optical penetration depth, the degree of inversion symmetry breaking can be probed at different depths from the sample surface. We propose that measurements of this effect may clarify the presence or absence of inversion symmetry, which remains a controversial issue and has been argued to play an important role in the high conversion efficiency of this material. (c) 2016 American Institute of Physics.
- 39Kepenekian, M.; Robles, R.; Katan, C.; Sapori, D.; Pedesseau, L.; Even, J. Rashba and Dresselhaus Effects in Hybrid Organic–Inorganic Perovskites: From Basics to Devices. ACS Nano 2015, 9, 11557– 11567, DOI: 10.1021/acsnano.5b04409[ACS Full Text], [CAS], Google Scholar39https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhsVKls7%252FO&md5=a93f1115ebeec2e507b4d1121483510eRashba and Dresselhaus Effects in Hybrid Organic-Inorganic Perovskites: From Basics to DevicesKepenekian, Mikael; Robles, Roberto; Katan, Claudine; Sapori, Daniel; Pedesseau, Laurent; Even, JackyACS Nano (2015), 9 (12), 11557-11567CODEN: ANCAC3; ISSN:1936-0851. (American Chemical Society)A review. The authors use symmetry anal., d. functional theory calcns., and k·p modeling to scrutinize Rashba and Dresselhaus effects in hybrid org.-inorg. halide perovskites. These perovskites are at the center of a recent revolution in the field of photovoltaics but also demonstrated potential for optoelectronic applications such as transistors and light emitters. Due to a large spin-orbit coupling of the most frequently used metals, they are also predicted to offer a promising avenue for spin-based applications. With an in-depth inspection of the electronic structures and bulk lattice symmetries of a variety of systems, the authors analyze the origin of the spin splitting in two- and three-dimensional hybrid perovskites. Low-dimensional nanostructures made of CH3NH3PbX3 (X = I, Br) lead to spin splittings that can be controlled by an applied elec. field. These findings further open the door for a perovskite-based spintronics.
- 40Yin, J.; Maity, P.; Xu, L.; El-Zohry, A. M.; Li, H.; Bakr, O. M.; Brédas, J. L.; Mohammed, O. F. Layer-Dependent Rashba Band Splitting in 2D Hybrid Perovskites. Chem. Mater. 2018, 30, 8538– 8545, DOI: 10.1021/acs.chemmater.8b03436[ACS Full Text], [CAS], Google Scholar40https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhvFWkt73F&md5=9871d9c805263166198c3797776c1affLayer-Dependent Rashba Band Splitting in 2D Hybrid PerovskitesYin, Jun; Maity, Partha; Xu, Liangjin; El-Zohry, Ahmed M.; Li, Hong; Bakr, Osman M.; Bredas, Jean-Luc; Mohammed, Omar F.Chemistry of Materials (2018), 30 (23), 8538-8545CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)The strong spin-orbit coupling (SOC) in perovskite materials due to the presence of heavy atoms induces interesting electronic characteristics, such as Rashba band splitting. In spite of several recent reports on Rashba effects in 2-dimensional perovskites, the impacts of the nature of surface termination and of the no. of inorg. layers on the extent of Rashba band splitting still remain to be detd. Here, using a combination of d. functional theory (DFT) calcns. and time-resolved laser spectroscopy, the authors provide a comprehensive understanding of the Rashba band splitting of the prototype 3-dimensional MAPbI3 and of 2-dimensional Ruddlesden-Popper (RP) hybrid perovskites. Significant structural distortions assocd. with different surface terminations are responsible for the obsd. Rashba effect in 2-dimensional perovskites. The authors' theor. and exptl. data clearly indicate that the intrinsic Rashba splitting occurs in the perovskite crystals with an even no. of inorg. layers (n = 2), but not for the ones with an odd no. of layers (n = 1 and n = 3). These findings not only provide a possible explanation for the elongated electron-hole recombination in perovskites but also elucidate the significant impact of the no. of inorg. layers on the electronic properties of 2-dimensional perovskites.
- 41Ganichev, S. D.; Prettl, W. Spin Photocurrents in Quantum Wells. J. Phys.: Condens. Matter 2003, 15, R935, DOI: 10.1088/0953-8984/15/20/204[Crossref], [CAS], Google Scholar41https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3sXltleqs78%253D&md5=936672fec3476927df679fc7bcdb2443Spin photocurrents in quantum wellsGanichev, S. D.; Prettl, W.Journal of Physics: Condensed Matter (2003), 15 (20), R935-R983CODEN: JCOMEL; ISSN:0953-8984. (Institute of Physics Publishing)A review discussing spin photocurrents generated by homogeneous optical excitation with circularly polarized radiation in quantum wells (QWs). The absorption of circularly polarized light results in optical spin orientation due to the transfer of the angular momentum of photons to electrons of a two-dimensional electron gas. It is shown that in QWs belonging to one of the gyrotropic crystal classes a non-equil. spin polarization of uniformly distributed electrons causes a directed motion of electrons in the plane of the QW. A characteristic feature of this elec. current, which occurs in unbiased samples, is that it reverses its direction upon changing the radiation helicity from left-handed to right-handed and vice versa. Two microscopic mechanisms are responsible for the occurrence of an elec. current linked to a uniform spin polarization in a QW: the spin polarization-induced circular photogalvanic effect and the spin-galvanic effect. In both effects the current flow is driven by an asym. distribution of spin-polarized carriers in k-space of systems with lifted spin degeneracy due to k-linear terms in the Hamiltonian. Spin photocurrents provide methods to investigate spin relaxation and to reach a conclusion as regards the inplane symmetry of QWs. The effect can also be utilized to develop fast detectors for detg. the degree of circular polarization of a radiation beam. Furthermore, spin photocurrents under IR excitation were used to demonstrate and investigate monopolar spin orientation of free carriers.
- 42Golub, L. E. Spin-Splitting-Induced Photogalvanic Effect in Quantum Wells. Phys. Rev. B: Condens. Matter Mater. Phys. 2003, 67, 235320, DOI: 10.1103/PhysRevB.67.235320[Crossref], [CAS], Google Scholar42https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3sXlsVKhtbc%253D&md5=7288ac8b79f799d5e51dbf0a9db3947dSpin-splitting-induced photogalvanic effect in quantum wellsGolub, L. E.Physical Review B: Condensed Matter and Materials Physics (2003), 67 (23), 235320/1-235320/7CODEN: PRBMDO; ISSN:0163-1829. (American Physical Society)A theory of the circular photogalvanic effect caused by spin splitting in quantum wells is developed. Direct interband transitions between the hole and electron size-quantized subbands are considered. It is shown that the photocurrent value and direction depend strongly on the form of the spin-orbit interaction. The currents induced by structure-, bulk-, and interface-inversion asymmetry are investigated. The photocurrent excitation spectra caused by spin splittings in both conduction and valence bands are calcd.
- 43Giglberger, S.; Golub, L. E.; Bel’kov, V. V.; Danilov, S. N.; Schuh, D.; Gerl, C.; Rohlfing, F.; Stahl, J.; Wegscheider, W.; Weiss, D.; Prettl, W. Rashba and Dresselhaus Spin Splittings in Semiconductor Quantum Wells Measured by Spin Photocurrents. Phys. Rev. B: Condens. Matter Mater. Phys. 2007, 75, 035327, DOI: 10.1103/PhysRevB.75.035327[Crossref], [CAS], Google Scholar43https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXhs1eksL8%253D&md5=5bceec5eb34afe725ba9133a35e44ab6Rashba and Dresselhaus spin splittings in semiconductor quantum wells measured by spin photocurrentsGiglberger, S.; Golub, L. E.; Bel'kov, V. V.; Danilov, S. N.; Schuh, D.; Gerl, C.; Rohlfing, F.; Stahl, J.; Wegscheider, W.; Weiss, D.; Prettl, W.; Ganichev, S. D.Physical Review B: Condensed Matter and Materials Physics (2007), 75 (3), 035327/1-035327/8CODEN: PRBMDO; ISSN:1098-0121. (American Physical Society)The spin-galvanic effect and the circular photogalvanic effect induced by terahertz radiation are applied to det. the relative strengths of Rashba and Dresselhaus band spin splitting in (001)-grown GaAs and InAs based 2d electron systems. Shifting the δ-doping plane from one side of the quantum well to the other results in a change of sign of the photocurrent caused by Rashba spin splitting while the sign of the Dresselhaus term induced photocurrent remains. The measurements give the necessary feedback for technologists looking for structures with equal Rashba and Dresselhaus spin splittings or perfectly sym. structures with zero Rashba const.
- 44McIver, J.; Hsieh, D.; Steinberg, H.; Jarillo-Herrero, P.; Gedik, N. Control over Topological Insulator Photocurrents with Light Polarization. Nat. Nanotechnol. 2012, 7, 96, DOI: 10.1038/nnano.2011.214[Crossref], [CAS], Google Scholar44https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXhsFGktL%252FL&md5=84c2a7b6849057feaf25a9f021932f08Control over topological insulator photocurrents with light polarizationMcIver, J. W.; Hsieh, D.; Steinberg, H.; Jarillo-Herrero, P.; Gedik, N.Nature Nanotechnology (2012), 7 (2), 96-100CODEN: NNAABX; ISSN:1748-3387. (Nature Publishing Group)Three-dimensional topol. insulators represent a new quantum phase of matter with spin-polarized surface states that are protected from backscattering. The static electronic properties of these surface states have been comprehensively imaged by both photoemission and tunnelling spectroscopies. Theorists have proposed that topol. surface states can also exhibit novel electronic responses to light, such as topol. quantum phase transitions and spin-polarized elec. currents. However, the effects of optically driving a topol. insulator out of equil. have remained largely unexplored exptl., and no photocurrents have been measured. Here, we show that illuminating the topol. insulator Bi2Se3 with circularly polarized light generates a photocurrent that originates from topol. helical Dirac fermions, and that reversing the helicity of the light reverses the direction of the photocurrent. We also observe a photocurrent that is controlled by the linear polarization of light and argue that it may also have a topol. surface state origin. This approach may allow the probing of dynamic properties of topol. insulators and lead to novel opto-spintronic devices.
- 45Obraztsov, P. A.; Lyashenko, D.; Chizhov, P. A.; Konishi, K.; Nemoto, N.; Kuwata-Gonokami, M.; Welch, E.; Obraztsov, A. N.; Zakhidov, A. Ultrafast Zero-Bias Photocurrent and Terahertz Emission in Hybrid Perovskites. Commun. Phys. 2018, 1, 1– 7, DOI: 10.1038/s42005-018-0013-8[Crossref], [CAS], Google Scholar45https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXpvV2lsbk%253D&md5=00cd77affa5cf5528a7fa15ca163fb2fUltrafast zero-bias photocurrent and terahertz emission in hybrid perovskitesObraztsov, Petr A.; Lyashenko, Dmitry; Chizhov, Pavel A.; Konishi, Kuniaki; Nemoto, Natsuki; Kuwata-Gonokami, Makoto; Welch, Eric; Obraztsov, Alexander N.; Zakhidov, AlexCommunications Physics (2018), 1 (1), 1-7CODEN: CPOHDJ; ISSN:2399-3650. (Nature Research)Methylammonium lead iodide is a benchmark hybrid org. perovskite material used for low-cost printed solar cells with a power conversion efficiency of over 20%. Nevertheless, the nature of light-matter interaction in hybrid perovskites and the exact phys. mechanism underlying device operation are currently debated. Here, we report room temp., ultrafast photocurrent generation, and free-space terahertz emission from unbiased hybrid perovskites induced by femtosecond light pulses. The polarization dependence of the obsd. photoresponse is consistent with the bulk photovoltaic effect caused by a combination of injection and shift currents. Observation of this type of photocurrents sheds light on the low recombination and long carrier diffusion lengths arising from the indirect bandgap in CH3NH3PbI3. Naturally ballistic shift and injection photocurrents may enable third-generation perovskite solar cells with efficiency exceeding the Shockley-Queisser limit. The demonstrated control over photocurrents with light polarization also opens new venues toward perovskite spintronics and tunable THz devices.
- 46Osterhoudt, G. B.; Diebel, L. K.; Gray, M. J.; Yang, X.; Stanco, J.; Huang, X.; Shen, B.; Ni, N.; Moll, P. J.; Ran, Y.; Burch, K. S. Colossal Mid-Infrared Bulk Photovoltaic Effect in a Type-I Weyl Semimetal. Nat. Mater. 2019, 18, 471– 475, DOI: 10.1038/s41563-019-0297-4[Crossref], [PubMed], [CAS], Google Scholar46https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXmsV2isrk%253D&md5=cc7490082181aa505b4f04c545a34ea1Colossal mid-infrared bulk photovoltaic effect in a type-I Weyl semimetalOsterhoudt, Gavin B.; Diebel, Laura K.; Gray, Mason J.; Yang, Xu; Stanco, John; Huang, Xiangwei; Shen, Bing; Ni, Ni; Moll, Philip J. W.; Ran, Ying; Burch, Kenneth S.Nature Materials (2019), 18 (5), 471-475CODEN: NMAACR; ISSN:1476-1122. (Nature Research)Broadband, efficient and fast conversion of light to electricity is crucial for sensing and clean energy. The bulk photovoltaic effect (BPVE) is a second-order nonlinear optical effect that intrinsically converts light into elec. current. Here, we demonstrate a large mid-IR BPVE in microscopic devices of the Weyl semimetal TaAs. This discovery results from combining recent developments in Weyl semimetals, focused-ion beam fabrication and theor. works suggesting a connection between BPVE and topol. We also present a detailed symmetry anal. that allows us to sep. the shift current response from photothermal effects. The magnitude and wavelength range of the assigned shift current may impact optical detectors, clean energy and topol., and demonstrate the utility of Weyl semimetals for practical applications.
Supporting Information
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ARTICLE SECTIONSThe Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsnano.0c05980.
1. Charaterization of (R/S/rac-MBA)2PbI4 samples including AFM, XRD, CD, and Faraday rotation measurements; control experiment of I–V characteristics of photovoltaic devices based on chiral perovskites; dependence of ΔI/I signal for (rac-MBA)2PbI4 photovoltaic devices; summary of L and D coefficients for (R/S-MBA)2PbI4 given by fitting the CPGE response (PDF)
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