Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session K69: Fundamental Properties of Metal Halide Perovskites IVRecordings Available
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Sponsoring Units: DMP Chair: Sandhya Susarla, Lawrence Berkeley National Laboratory Room: Hyatt Regency Hotel -Jackson Park A |
Tuesday, March 15, 2022 3:00PM - 3:12PM |
K69.00001: Controlling structural and transport properties of organic-inorganic halide perovskite films using chemical vapor deposition Randy Burns, Christopher J Arendse, Stephen Klue, Barbara Lavina, Suchismita Guha Chemical vapor deposition (CVD), a low-cost and a scalable deposition technique, allows the growth of methylammonium lead iodide (MAPbI3) films without the use of solvents. This fabrication method substantially increases the air stability while also inducing the stable cubic phase at room temperature and at pressures as low as 0.25 GPa. MAPbI3 thin films were grown by a facile two-step low-pressure vapor deposition process in a single reactor. This method results in films which are usually in the tetragonal phase (space group: I4/mcm) and occasionally in the cubic phase under ambient conditions. High-pressure synchrotron-based X-ray diffraction studies from CVD-grown MAPbI3 crystallites show that the sample remains in the cubic phase (space group: Im3¯) between 0.25 and 3.0 GPa. Temperature-dependent transport measurements show sharp anomalies, correlating with the structural changes. For the room temperature cubic phase-film, a dramatic decrease in resistivity is observed in comparison with typical films, indicating the possible suppression of the ionic contribution to the transport. Additionally, a drastic decrease in resistivity is observed for MAPbBr3 single crystals, produced by the ITC method, under low pressure. Mixed halide films that exhibit an unanticipated structural phase stability from 20 K to 300 K were also grown using CVD. |
Tuesday, March 15, 2022 3:12PM - 3:24PM |
K69.00002: Weak Magnetic Field-Dependent Optical Properties of Lead Bromide Perovskites Rory W Butler, Randy Burns, Dallar Babaian, Matthew Anderson, Carsten A Ullrich, Maria Morrell, Yangchuan Xing, Jaewon Lee, Ping Yu, Suchismita Guha The strong spin-orbit coupling in lead halide perovskites, when inversion symmetry is lifted, has provided opportunities for investigating the Rashba effect in these systems. Moreover, the strong orbital moment plays a significant role in enhancing the optoelectronic properties in the presence of external magnetic fields in lead halide perovskites. Here, we evaluate the effect of weak magnetic fields (< 1 T) on the photoluminescence (PL) properties of CsPbBr3 nanocrystals (NCs) and single crystal of CH3NH3PbBr3. Along with an enhancement in the PL intensity as a function of an external magnetic field, which is observed in both lead bromide perovskites, the PL emission red-shifts in CsPbBr3 NCs. Density-functional theory calculations of the electronic band-edge in CsPbBr3 show almost no change in the energy gap as a function of the external magnetic field. The experimental results thus suggest the role of mixing of the triplet and singlet excitonic states under weak magnetic fields. This is further deduced from an enhancement in PL lifetimes as a function of the field in CsPbBr3. In CH3NH3PbBr3, an increase in PL intensity is observed under weak magnetic fields; however, no changes in the peak energy or PL lifetimes are observed. |
Tuesday, March 15, 2022 3:24PM - 3:36PM |
K69.00003: A First-Principles Investigation of Cs Rattling inCsPbI3crystals Charith R DeSilva, Mario F Borunda Halide perovskites have been one of the most heavily investigated solar cell materials since their efficacy was first demonstrated in 2009. One of the most studied inorganic halide perovskites is cesium lead iodide (CsPbI3), which has shown high efficiencies and decreased volatility compared to its organic-inorganic hybrid counterparts. However, one major issue that CsPbI3 still faces is that it is unstable at room temperature. This problem is fascinating as most tolerance-factor calculations predict that CsPbI3 should be stable in its perovskite phase. One explanation for this instability is that the Cs atom rattles between two sites near room temperature, one with a much lower coordination number than the other. We study this rattling using density functional theory and Car-Parrinello molecular dynamics. We show how the rattling evolves for temperatures between 100K to 295K, how that affects the other thermodynamic properties of the materials, and how it compares back to experimental results. These results can be used to elucidate further the importance of Cs rattling on the stability of inorganic halide perovskites. |
Tuesday, March 15, 2022 3:36PM - 3:48PM |
K69.00004: Lead-free All-perovskite Tandem Solar Cell Arman Duha, Mario F Borunda This talk will present our simulation results of a lead-free all-perovskite tandem solar cell obtained with the SCAPS-1D simulation tool. The cell model was calibrated with experimental data of the perovskite cell. First, the top and bottom subcells, consisting of MAGeI3, and FASnI3, respectively, were optimized individually by varying material properties such as thickness, electron affinity, and capture cross-section. These standalone optimized subcells are then utilized for the tandem structure. The optimal tandem cell thickness was determined based on short circuit current density (JSC) matching of the standalone subcells by varying the subcells’ thickness. A matching JSC of 14.70 mA/cm2 was obtained for the top and bottom subcell thickness of 983 nm and 1600 nm, respectively. At this current matching condition, the simulation shows that a tandem cell would yield a high open-circuit voltage (VOC) of 2.63 V, resulting in an efficiency of 30.85%, significantly higher than that of each cell. |
Tuesday, March 15, 2022 3:48PM - 4:00PM |
K69.00005: Charge transport in complex halide perovskites from first principles calculations Armin Eghdami, Jonah B Haber, Nathan R Wolf, Hemamala I Karunadasa, Jeffrey B Neaton Halide perovskites are attractive materials for solar energy conversion applications due to their strong light-matter interactions, structural tunability, and the relative ease with which they can be synthesized and processed. In metal halide perovskites, an important aspect in the energy conversion process is the underlying nature of the charge transport. Recent high-pressure measurements up to 50 GPa on a mixed-valent metal halide perovskite reveal a 12 order of magnitude increase in conductivity relative to ambient pressure and suggest that the charge transport is polaronic in nature. However a detailed picture of the underlying microscopic mechanism is still missing. Using first principles DFT calculations, we calculate the electronic structure and elucidate charge transport mechanisms, specifically focusing on the rich interplay between Jahn-Teller distortions, charge disproportionation, and polaronic hopping as a function of externally applied pressure. Our findings provide insight into the precise nature of the charge transport further guiding the design of next-generation halide perovskite-based photovoltaic devices. |
Tuesday, March 15, 2022 4:00PM - 4:12PM |
K69.00006: A computational study of self-trapped excitons in metal halide perovskites Mariami Rusishvili, Yu Jin, Giulia Galli Recently, a series of lead-free halide perovskites with efficient broad band emission have been discovered, which show promise for photovoltaic applications [1]. These discoveries have motivated many studies of the electronic structure of these systems; however, several controversies are present in the literature regarding the level of first-principles electronic structure theory required to accurately describe emission processes from self-trapped excitons in halide perovskites. We present a systematic study of the electronic properties of Cs4SnX6(X=Br;I) and Cs2AgInCl6 using hybrid density functional theory (DFT), and we compare results obtained with constrained DFT and time-dependent DFT for photoluminescence spectra. We discuss the sensitivity of the results to the choice of hybrid functionals (including HSE [2] and dielectric-dependent hybrid [3]), and we show that TDDFT and CDFT yield results that differ by up to 0.5 eV for energy gaps, for the systems considered here. We also discuss comparisons with experiments conducted at different temperatures. |
Tuesday, March 15, 2022 4:12PM - 4:24PM |
K69.00007: Enhanced Optical Response Observed at CsPbX3 Nanocube/m-TiO2/Au Micro-Pyramid Interface Halle C Helfrich, Aaron J Austin, Phadindra Wagle, Nate Dice, Elena Echeverria, Shoukath Sulthana, Mario F Borunda, Dave McIlroy, Andrew J Yost CsPbX3 perovskite nanoparticles have attracted the attention of many researchers due to their brilliant luminescence, broad color tunability and facile synthesis. The behavior of any layered optical device is regulated by the properties of its interface(s). This makes in-depth studies of the response to impinging photons at these interface(s) extremely valuable. In this presentation the optical reflection spectroscopy response at the interface of CsPbBr3-xAx (A=Cl, I) nanocubes with a plasmonic nanostructure is discussed. CsPbBr3-xAx (A=Cl, I) nanocubes, emitting in the red, green and blue wavelengths, were synthesized via a Schlenck line and hot injection method. The resulting nanocubes were roughly 7.2 nm in length along the side as measured by transmission electron microscopy. The plasmonic nanostructure consisted of a mesoporous anatase-TiO2 thin film coated on top of Au micro pyramids, which exhibit signatures of surface plasmon polaritons. Prominent peaks are observed in the reflection spectroscopy measurements at the interface between nanocubes and plasmonic nanostructure, which suggests there is a combination of SPP-Exciton, Phonon-Exciton, Photon-Exciton coupling and surface diffraction occurring at these interfaces. |
Tuesday, March 15, 2022 4:24PM - 4:36PM |
K69.00008: On-site, deterministic, and scalable growth of perovskite nanocrystals Patricia Jastrzebska-Perfect, Weikun Zhu, Peter Satterthwaite, Farnaz Niroui Effective integration of metal halide perovskite nanocrystals into optoelectronic devices requires new strategies for their controlled growth and precise positioning. To this end, several in-situ growth techniques through solution or vapor phase processing have been developed. However, existing approaches do not accommodate deterministic growth of sub-50 nm crystals and lack nanoscale positioning control. Here, we present in-situ growth of sub-50 nm all-inorganic perovskite nanocrystals with < 100 nm positioning control. In our approach, arrays of uniformly-sized nanocrystals are synthesized via lithographically-patterned, surface-functionalized topographical templates, which allow for in-situ growth of crystals through asymmetric wetting of the precursor solution. With this technique, we can systematically control the size and surface encapsulation of the nanocrystals. We will present these capabilities and the corresponding structural and optical properties of the resulting particles. Overall, by enabling deterministic yet scalable growth of perovskite nanocrystals, our approach can facilitate integration of these materials into practical nanoscale optoelectronic devices and systems. |
Tuesday, March 15, 2022 4:36PM - 4:48PM Withdrawn |
K69.00009: DIffuse Neutron and X-Ray Scattering from Inorganic Halide Perovskites Matthew J Krogstad, Alex Rettie, Stephan Rosenkranz, Duck Young Chung, Mercouri G Kanatzidis, Feng Ye, Yaohua Liu, Jinsong Huang, Haotong Wei, Xing He, Tyson L Lanigan-Atkins, Olivier Delaire, Raymond Osborn Halide perovskites have enjoyed significant attention over the past several years due to their intriguing optoelectronic properties, both in hybrid organic-inorganic and pure inorganic forms. In both cases, the long carrier lifetimes underpinning these properties appear to be strongly coupled to local structure. Diffuse neutron and x-ray scattering measurements on the inorganic halide perovskites CsPbBr3, CsSnBr3, CsPbCl3, and Cs2AgBiBr6 show clear similarities in diffuse scattering, all showing a network of rods indicative of two-dimensional correlations. Neutron scattering measurements from CORELLI show that this scattering is quasi-static, consistent with an overdamped two-dimensional phonon. This static scattering can be further modelled via correlated tilts in the halide octahedron, with the octahedral tilt systems that define the low temperature structure persisting at higher temperatures in a short-range form. The commonality of this feature suggests that short-range order is a defining part of the physics in these systems. |
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