Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session F69: 2D Metal Halide PerovskitesFocus Recordings Available
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Sponsoring Units: DMP Chair: Joseph Beckwith, Princeton University Room: Hyatt Regency Hotel -Jackson Park A |
Tuesday, March 15, 2022 8:00AM - 8:36AM |
F69.00001: Excitons and the Rashba effect in 2D perovskites Invited Speaker: Michael W Swift Halide perovskites exhibit remarkable excitonic properties. Radiative recombination in cube-shaped CsPbBr3 NCs is extremely fast at low temperature, which was previously proposed to arise from a bright exciton ground state. Reducing the dimensionality has the potential to increase recombination rates even further, due to the large exciton binding energy and narrow photoluminescence (PL). Two approaches to dimensionality reduction are collodial nanoplatelets and 2D perovskites. |
Tuesday, March 15, 2022 8:36AM - 8:48AM |
F69.00002: Precise Exciton Binding Energies in Two-Dimensional Metal Halide Perovskites John S Colton, Carrie E McClure, Kameron Hansen, Louisa Whittaker-Brooks Metal halide perovskites are of great current interest for optical applications; however state-of-the-art techniques to measure basic properties such as the band gap and exciton binding energy continue to produce inconsistent values. This is the case even for 2D MHPs where the large separation between excitonic and bandgap absorption should make such measurements more straightforward. To remedy this, we have been able to use the established theory of a 2D Wannier exciton in a uniform electric field to analyze the electroabsorption (EA) response of an archetypal 2D MHP system, phenethylammonium lead iodide (PEA2PbI4). The high level of agreement between the electroabsorption simulation and measurement allows us to deduce the exciton's Bohr radius, transition dipole moment, polarizability, reduced effective mass, and most importantly determine the exciton binding energy with only 2% uncertainty. The high precision of these measurements will allow future studies to accurately determine the influence of chemical and environmental factors on the optoelectronic properties of MHPs and thereby increase the tunability of this important class of materials. |
Tuesday, March 15, 2022 8:48AM - 9:00AM |
F69.00003: Developing Exciton Tunability in Two-Dimensional Metal-Halide Perovskites Kameron Hansen, John S Colton, Carrie E McClure, Luisa Whittaker-Brooks Inspired by the wide range of optoelectronic tunability that was achieved in the 1980s and 90s for III-V quantum wells systems, we seek to develop the tunability of 2D metal halide perovskite (2D MHP) quantum wells through the large catalog of molecules and atoms that naturally crystalize into the Ruddlesden-Popper A2BX4 crystal structure, where A represents an organic cation (barrier layer) and BX4 represents the metal-halide semiconductor (well layer). We have developed a highly precise and reproducible method for measuring the band gap energy and exciton binding energy of 2D MHPs. We apply this method to a wide range of A2BX4 compositions in order to explore the parameter space of band gaps and exciton binding energies that are accessible within this class of quantum wells, and we extrapolate our results to draw implications for exciton tunability in 3D MHPs. |
Tuesday, March 15, 2022 9:00AM - 9:12AM |
F69.00004: Dielectric Spectroscopy on 2D and 3D Metal Halide Perovskites Using an Interdigitated Electrode Geometry Carrie E McClure, Kameron Hansen, John S Colton Metal halide perovskites are a class of 2D and 3D materials that are currently being studied for use in solar energy and other applications. Permittivity is connected to other important characteristics of these materials such as exciton binding energy, effective mass, and transition dipole moment, but has proven challenging to accurately measure. Using experimental measurements of the impedance of perovskite layers on interdigitated electrodes, we have been able to develop a model which allows us to deduce the frequency dependence of permittivity in these materials. The results show permittivity values for high frequencies (13 MHz) in the range of 4.1-5.1 for PEA2PbI4 (PEPI) and 12-45 for MAPbI3 (MAPI), with details depending on the specific sample. |
Tuesday, March 15, 2022 9:12AM - 9:24AM Withdrawn |
F69.00005: Trion formation in two-dimensional Ruddlesden-Popper lead iodide perovskites Minh T Pham, Sajeevi S Withanage, M. Tuan Trinh, Xiaomei Jiang Two-dimensional Ruddlesden-Popper (2D RP) perovskites are promising light-emitting materials thanks to their high photoluminescence quantum yields and tunable emission wavelengths.[1] In low dimension semiconductor structure, the formation of trion, a complex bound state of an exciton and an electron or a hole, is highly possible. For example, trion formation and its dynamics have been observed and extensively studied in 2D transition metal dichalcogenides (TMDs)[2] and hybrid perovskite quantum dots (PQDs)[3]. It is reported that trion formation in the material determines its luminescence efficiency and emission energy, and therefore the suppression of trion formation is important for photoluminescence quantum yield enhancement.[4] Presently, there is a debate on the origin of the lower energy emission peak in 2D perovskites which was assigned to be biexciton, trap state, in gap exciton, magnetic dipole emission, and possibly trion. Here, we present our work on the dynamics of the low energy emission peak in 2D hybrid perovskite, phenyl-ethyl ammonium lead iodide (PEA)2PbI4, by time-resolved magneto photoluminescence and electrical doping photoluminescence spectroscopies. |
Tuesday, March 15, 2022 9:24AM - 9:36AM |
F69.00006: Thermoelectric Performance of Two-Dimensional Halide Perovskites Featuring Conjugated Ligands Sheng-Ning Hsu, Bryan W Boudouris, Letian Dou Sn-based halide perovskites are promising for thermoelectric (TE) device application because of their high electrical conductivity and their low thermal conductivity. However, conventional three-dimensional Sn-based perovskite are not stable under typical TE device operating conditions. Reducing the dimensionality of Sn-based perovskite improves both the environmental stability and the TE performance by reducing the thermal conductivity. Here, we demonstrate the carrier concentration and temperature dependence of Seebeck coefficients and electrical conductivity of the n = 2 Sn-based 2D perovskites featuring a conjugated ligand, namely (4Tm)2FASn2I7, where 4Tm is 2-(3″′,4′-dimethyl[2,2′:5′,2″:5″,2″′-quaterthiophen]-5-yl)ethan-1-ammonium. By doping with SnI4, we were able to tune the carrier concentration from 2 × 1018 to 1.2 × 1019 cm-3 and observed a corresponding trend in TE performance. With optimized doping, (4Tm)2FASn2I7 showed promising power factor of 5.42±3.07 (average) and 7.07 (champion) μW m-1 K-2 at 343 K with an electrical conductivity of 5.07 S cm-1 and Seebeck coefficient of 118.1 μV K-1. Importantly, these thin films show excellent operational stability (i.e., for over 100 h) at 313 K. |
Tuesday, March 15, 2022 9:36AM - 9:48AM |
F69.00007: Magneto-optical studies of chiral 2D hybrid perovskites. Dipak Khanal, Zeev V Vardeny We have used a number of cw optical techniques for studying films of chiral 2D hybrid organic inorganic perovskites. These spectroscopies include circular dichroism (CD) and magneto-CD, Faraday rotation, circularly polarized photoluminescence (CPL), circular photogalvanic effect (CPGE), and electro-absorption. We found that all spectra contain sizable contributions from both excitons and interband transition, from which the exciton binding energy can be derived. In particular from the CPGE excitation spectrum we obtained the Rashba splitting energy. We also found that the CPL increases substantially at low temperature, in accordance with the CD spectrum. |
Tuesday, March 15, 2022 9:48AM - 10:00AM |
F69.00008: Bright and dark excitons in two-dimensional hybrid perovskites film Xiaomei Jiang, Chuang Zhang, Peter C Sercel, Stephen McGrill, Dmitry Serenov, Z. Valy Vardeny Recently 2D hybrid organic-inorganic perovskites (2D-HOIP) with Ruddlesden-Popper structure have been studied extensively. Due to dielectric confinement and quantum confinement, excitons in 2D-HOIP have much larger binding energy and smaller radius compared with their 3D HOIP counterparts; consequently, excitonic effects are more pronounced in these systems. In this work, we present a comprehensive study of the exciton fine structure utilizing magnetic field induced polarization of photoluminescence in a model 2D-HOIP, 2D-phenethylammonium lead iodide (2D-PEPI), both in Faraday and Voigt configurations with fields up to 25 Tesla. From the exciton field induced circular and linear polarizations we have identified two pairs of exciton states: the ‘bright’ exciton pair (X/Y) and the ‘dark’ exciton pair D/Z. Their related zero-field splitting (fine structure) and g-values have been determined. |
Tuesday, March 15, 2022 10:00AM - 10:12AM |
F69.00009: Tuning Rashba and Dresselhaus effect in 2D Pb-I-based perovskites Benedikt Maurer, Christian W Vorwerk, Claudia Draxl Huge spin-orbit coupling in combination with broken inversion symmetry leads to considerable Rashba and Dresselhaus splitting in hybride halide perovskites. This indicates that such effects will not only affect their optoelectronic properties but also those of their two-dimensional layered relatives. This work aims at understanding how different ways of symmetry breaking influence these effects in those materials. For this purpose, model structures with composition Csn+1PbnI3n+1 are adopted where the organic compounds are replaced by Cs atoms. Using the all-electron full-potential density-functional-theory code exciting, the impact of atomic displacement on the band structure is systematically studied for n=1, 2, 3 and ∞. The displacement patterns that yield Rashba or Dresselhaus splitting are identified, and the amount of the splitting is determined as a function of displacement. Furthermore, the spin textures in the electronic states around the band gap are analyzed to differentiate between Rashba and Dresselhaus effects. This study reveals in-plane Pb displacements as the origin of the strongest effects. |
Tuesday, March 15, 2022 10:12AM - 10:24AM |
F69.00010: Additive Engineered Quasi Two-dimensional Dion-Jacobson Phase Perovskite with p-Xylylene diamine Organic Spacer for Highly Efficient and Stable Solar Cells YUKTA ., Soumitra Satapathi, Rohit D Chavan, Pankaj Yadav Two-dimensional (2D) Dion-Jacobson (DJ) organic-inorganic halide perovskites have recently emerged as promising photovoltaic materials due to their unique photophysical properties, as rich structural diversity and superb ambient stability. Here, we demonstrate additive engineering of p-Xylylene diamine organic spacer-based n-4 phase 2D D-J perovskite for efficient and stable solar cells applications. We observe significant improvement of film morphology, phase purity, crystallinity and carrier mobility after ammonium thiocyanate (NH4SCN) additive treatment as evidenced by UV-visible spectroscopy, XRD and SEM. Transient and impedance spectroscopy confirm the suppression of defects in additive treated perovskite films. The PCE of the NH4SCN treated perovskite device increased significantly from 12.9% to 17% wrt untreated device. The unencapsulated NH4SCN treated perovskite devices maintains 75% of its initial PCE after 1000 h of continuous storage with a humidity level of 50 ± 5%. |
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