The Impact of Lattice and Charge Fluctuations on Carrier Dynamics in Halide Perovskites

While halide perovskites (HaPs) have shown great technological promise for use as materials in energy devices, several of their unique optoelectronic properties remain incompletely understood. We develop a microscopic theory that is aimed at describing pertinent physical effects related to the carrier transport and optical properties of HaPs. It captures the nuclear displacements to all orders and goes beyond assuming linear electron-phonon coupling in calculating the dynamics of carriers and band gap characteristics. We combine the theory with first-principles calculations and apply it to the paradigm HaP compound MAPbI₃. Our results explain intriguing experimental findings related to the charge-carrier mobility and optical properties, including their temperature dependencies. The findings of our work demonstrate that orbital overlap fluctuations in the lead-halide structure play a leading role in determining the optoelectronic features of HaPs.