Elucidating the atomistic origin of anharmonicity in tetragonal CH3NH3PbI3 with Raman scattering

Rituraj Sharma, Zhenbang Dai, Lingyuan Gao, Thomas M. Brenner, Lena Yadgarov, Jiahao Zhang, Yevgeny Rakita, Roman Korobko, Andrew M. Rappe, Omer Yaffe

Research output: Contribution to journalArticlepeer-review

36 Scopus citations

Abstract

Halide perovskite (HP) semiconductors exhibit unique strong coupling between the electronic and structural dynamics. We use Raman polarization-orientation (PO) measurements and ab initio molecular dynamics (AIMD) to investigate the origin and temperature evolution of the strong structural anharmonicity throughout the tetragonal phase of CH3NH3PbI3. Raman PO measurements reveal a soft modelike spectral feature. This mode shows an unusual continuous increase in damping with temperature which is indicative of an anharmonic potential surface. The analysis of AIMD trajectories identifies two major sources of anharmonicity: the orientational unlocking of the [CH3NH3]+ ions and large-amplitude octahedral tilting that continuously increases with temperature. Our work suggests that the standard phonon picture cannot describe the structural dynamics of tetragonal CH3NH3PbI3.

Original languageEnglish
Article number092401
JournalPhysical Review Materials
Volume4
Issue number9
DOIs
StatePublished - Sep 2020
Externally publishedYes

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