Regensburg 2022 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 32: Perovskite and Photovoltaics 4 (joint session HL/CPP/KFM)
CPP 32.3: Vortrag
Mittwoch, 7. September 2022, 15:30–15:45, H34
Transversal halide motion enables sharp optical absorption profiles in halide perovskites — •Sebastián Caicedo-Dávila, Christian Gehrmann, Xiangzhou Zhu, and David A. Egger — Department of Physics, Technical University of Munich, Garching, Germany
Despite their strong vibrational anharmonicity, halide perovskites (HaPs) exhibit favorable optoelectronic properties, which facilitate their outstanding performance in solar cells, comparable to high-quality inorganic semiconductors. In this contribution, we explore the mechanisms and consequences of dynamic structural flexibility in CsPbBr3 using first-principles molecular dynamics based on density-functional theory. We show that large Br displacements occur on planes that are transversal to the Pb-Br-Pb bonding axis. This transversality is concurrent with vibrational anharmonicity, results in short-ranged disorder correlations, and sharpens the joint-density of states rise at finite temperature. Finally, we contrast these results to the case of PbTe, which shares key properties with CsPbBr3 but cannot exhibit any transversality, to show that this system features wider band-edge distributions and longer-ranged disorder correlations. These findings are relevant for connecting the structural flexibility and bonding of the halide perovskite structure with the sharp optical absorption of these materials.