Unravelling the Effects of Pressure-Induced Suppressed Electron-Hole Recombination in CsPbBr Perovskite: Time-Domain ab Initio Analysis.

Using nonadiabatic (NA) molecular dynamics simulations, we demonstrate pressure-dependent electron-hole recombination in all-inorganic CsPbBr perovskite. In particular, electron-hole recombination under 1 atm takes place in several hundred picoseconds, agreeing well with experiments. An increase of pressure causes PbBr octahedron distortion, including contraction of both Pb-Br-Pb angles and Pb-Br bond lengths, leading to a decrease in decoherence time and NA coupling and thus slowing electron-hole recombination. When the pressure reaches a critical pressure of 1.20 GPa, a phase transition occurs in which the charge carrier lifetime is longest and extends to several nanoseconds. When the pressure is increased over the threshold, the shrinkage of Pb-Br bond length is inhibited and the contraction of Pb-Br-Pb angles primarily induced the PbBr octahedron distortion. Such a situation gives rise to a mild NA coupling and decoherence time, restoring the recombination time to over half of a nanosecond. Our study uncovers the mechanisms for the pressure-suppressed charge recombination and provides an advanced route toward further development of photovoltaic performance of perovskite materials.