Local Polar Fluctuations in Lead Halide Perovskite Crystals

Omer Yaffe, Yinsheng Guo, Liang Z. Tan, David A. Egger, Trevor Hull, Constantinos C. Stoumpos, Fan Zheng, Tony F. Heinz, Leeor Kronik, Mercouri G. Kanatzidis, Jonathan S. Owen, Andrew M. Rappe, Marcos A. Pimenta, Louis E. Brus

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Hybrid lead-halide perovskites have emerged as an excellent class of photovoltaic materials. Recent reports suggest that the organic molecular cation is responsible for local polar fluctuations that inhibit carrier recombination. We combine low-frequency Raman scattering with first-principles molecular dynamics (MD) to study the fundamental nature of these local polar fluctuations. Our observations of a strong central peak in the cubic phase of both hybrid (CH3NH3PbBr3) and all-inorganic (CsPbBr3) lead-halide perovskites show that anharmonic, local polar fluctuations are intrinsic to the general lead-halide perovskite structure, and not unique to the dipolar organic cation. MD simulations indicate that head-to-head Cs motion coupled to Br face expansion, occurring on a few hundred femtosecond time scale, drives the local polar fluctuations in CsPbBr3.

Original languageEnglish
Article number136001
JournalPhysical Review Letters
Issue number13
StatePublished - 31 Mar 2017
Externally publishedYes

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© 2017 American Physical Society. American Physical Society.


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