Origin of the anomalous Pb-Br bond dynamics in formamidinium lead bromide perovskites

Harishchandra Singh, Ruixiang Fei, Yevgeny Rakita, Michael Kulbak, David Cahen, Andrew M. Rappe, Anatoly I. Frenkel

Research output: Contribution to journalArticlepeer-review

14 Scopus citations

Abstract

Extended x-ray absorption fine structure spectroscopy of the light-harvesting formamidinium lead bromide (FAPbBr3) perovskite, a system with attractive optoelectronic performance, shows anomalously large variance in Pb-Br bond length, some 50% larger than in its inorganic CsPbBr3 counterpart. Using first-principles molecular dynamics simulations, we find a significant contribution to this variance coming from the FA cation, and show that the FA does not just tumble in its cuboctahedral Br12 cage, but instead stochastically sticks to, and detaches from one of the 12 nearest Br atoms after another, leading to the large variance in Pb-Br bond length. Our results demonstrate dynamic coupling between the FA-Br moiety and perovskite cage vibrations, and that tunability in dynamics can be achieved by changing the cation type and perovskite lattice parameter. Thus, our results provide information that needs to be considered in any of the intensely debated models of electron-phonon coupling in lead halide perovskites.

Original languageEnglish
Article number054302
JournalPhysical Review B
Volume101
Issue number5
DOIs
StatePublished - 1 Feb 2020
Externally publishedYes

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

Fingerprint

Dive into the research topics of 'Origin of the anomalous Pb-Br bond dynamics in formamidinium lead bromide perovskites'. Together they form a unique fingerprint.

Cite this