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

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 barri

SUBMITTER: Chen T 

PROVIDER: S-EPMC5088641 | biostudies-literature | 2016 Oct

REPOSITORIES: biostudies-literature