Lattice dynamical properties of halide-perovskites from infra-red spectroscopy and first-principles calculations

Halide perovskites (HaPs) are intriguing optoelectronic materials. It is of particular interest to understand how the outstanding optoelectronic properties of HaPs are related to their vibrational properties, especially in light of the possibility that phonons might be the dominant source of scattering for charge carriers at room temperature. Studying the lattice dynamics of the all-inorganic CsPbBr₃ as well as the hybrid MAPbBr₃, we here present our findings on how the A-site cation as well as its potential orientation effects influence the vibrational properties of HaPs. To this end, we show results from first-principles calculations, based on density functional theory, and compare these with experimental data obtained from far infra-red spectroscopy. Finally, we present results related to the LO phonons that are not infra-red active, but inherently contained in our calculations and experimentally accessible through reflectance measurements.