Entropy-driven structural transition and kinetic trapping in formamidinium lead iodide perovskite

Tianran Chen, Benjamin J. Foley, Changwon Park, Craig M. Brown, Leland W. Harriger, Jooseop Lee, Jacob Ruff, Mina Yoon, Joshua J. Choi, Seung Hun Lee

Research output: Contribution to journalArticlepeer-review

224 Scopus citations

Abstract

A challenge of hybrid perovskite solar cells is device instability, which calls for an understanding of the perovskite structural stability and phase transitions. Using neutron diffraction and first-principles calculations on formamidinium lead iodide (FAPbI3), we show that the entropy contribution to the Gibbs free energy caused by isotropic rotations of the FA+ cation plays a crucial role in the cubic-To-hexagonal structural phase transition. Furthermore, we observe that the cubic-To-hexagonal phase transition exhibits a large thermal hysteresis. Our first-principles calculations confirm the existence of a potential barrier between the cubic and hexagonal structures, which provides an explanation for the observed thermal hysteresis. By exploiting the potential barrier, we demonstrate kinetic trapping of the cubic phase, desirable for solar cells, even at 8.2 K by thermal quenching.

Original languageEnglish
Article numbere1601650
JournalScience Advances
Volume2
Issue number10
DOIs
StatePublished - Oct 2016

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