Anharmonic fluctuations govern the band gap of halide perovskites

Stefan A. Seidl, Xiangzhou Zhu, Guy Reuveni, Sigalit Aharon, Christian Gehrmann, Sebastián Caicedo-Dávila, Omer Yaffe, David A. Egger

Research output: Contribution to journalArticlepeer-review

5 Scopus citations

Abstract

We determine the impact of anharmonic thermal vibrations on the fundamental band gap of CsPbBr3, a prototypical model system for the broader class of halide perovskite semiconductors. Through first-principles molecular dynamics and stochastic calculations, we find that anharmonic fluctuations are a key effect in the electronic structure of these materials. We present experimental and theoretical evidence that important characteristics, such as a mildly changing band-gap value across a temperature range that includes phase transitions cannot be explained by harmonic phonons thermally perturbing an average crystal structure and symmetry. Instead, the thermal characteristics of the electronic structure are microscopically connected to anharmonic vibrational contributions to the band gap that reach a fairly large magnitude of 450 meV at 425 K.

Original languageEnglish
Article numberL092401
JournalPhysical Review Materials
Volume7
Issue number9
DOIs
StatePublished - Aug 2023
Externally publishedYes

Bibliographical note

Publisher Copyright:
© 2023 American Physical Society.

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