Giant Phonon Tuning Effect via Pressure-Manipulated Polar Rotation in Perovskite MAPbI(3)

C Wang and YC Liu and SF Liu and B Li and Y Chen, JOURNAL OF PHYSICAL CHEMISTRY LETTERS, 9, 3029-3034 (2018).

DOI: 10.1021/acs.jpclett.8b01101

Perovskite MAPbI(3) that exhibits unique optoelectronic properties has emerged as a promising semiconductor material with a potential to revolutionize the photovoltaic industry. Inadequate understanding of the thermal instability and lattice dynamics of MAPbI(3), however, hinders its practical applications. Herein, combing molecular dynamics with a first principles-based interatomic potential and inelastic 4 neutron scattering measurements, we have performed an in-depth study of the lattice dynamics of MAPbI(3). The extremely large line widths of the optical phonons in the 3 tetragonal phase, which prevent direct experimental measurement of the phonon lifetimes, have been obtained for the first time. Our atomic-level study also reveals a giant pressure tuning effect on phonon scattering, which is related to the four-fold rotation of the MA(+) cations around the C-N axis. A hydrostatic pressure as low as 6 kbar can alter the phonon lifetime by more than 1 order of magnitude. This work is expected to pave the way for further phonon engineering and thermal optimization of MAPbI(3) and related perovskites.

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