Engineering phonon scattering in perovskite MAPbI3 via hydrostatic pressure

Abstract

Perovskite MAPbI3 exhibits outstanding optoelectronic properties, but its thermal instability still hinders its practical applications. Previous studies showed that the thermal properties are closely related to the combined characteristics of the inorganic framework lattice vibrations and the organic cations jumping rotational modes, but the detailed microscopic mechanisms are yet to be fully understood. In this presentation, the pressure effects on phonon scattering in MAPbI3 are discussed based on the results obtained from molecular dynamics simulations and inelastic neutron scattering measurements. Using the mode decomposition technique, we have obtained the phonon lifetimes, including those of the optical modes which have very large linewidths. Most interestingly, we find that the phonon scattering in the tetragonal phase is very sensitive to compression. A small hydrostatic pressure of several kbar can lead to significant changes of phonon lifetimes due to the four-fold rotation of the MA+ cations around the C-N axis. Our results provide a better understanding of the lattice dynamics of MAPbI3 and important insight into the pressure phonon relationship. The large pressure response of phonon scattering is expected to pave the way for further thermal engineering of MAPbI3 and related perovskites.