Charge transport in complex halide perovskites from first principles calculations*

Halide perovskites are attractive materials for solar energy conversion applications due to their strong light-matter interactions, structural tunability, and the relative ease with which they can be synthesized and processed. In metal halide perovskites, an important aspect in the energy conversion process is the underlying nature of the charge transport. Recent high-pressure measurements up to 50 GPa on a mixed-valent metal halide perovskite reveal a 12 order of magnitude increase in conductivity relative to ambient pressure and suggest that the charge transport is polaronic in nature. However a detailed picture of the underlying microscopic mechanism is still missing. Using first principles DFT calculations, we calculate the electronic structure and elucidate charge transport mechanisms, specifically focusing on the rich interplay between Jahn-Teller distortions, charge disproportionation, and polaronic hopping as a function of externally applied pressure. Our findings provide insight into the precise nature of the charge transport further guiding the design of next-generation halide perovskite-based photovoltaic devices.