Photoinduced Localized Hole Delays Nonradiative Electron-Hole Recombination in Cesium-Lead Halide Perovskites: A Time-Domain Ab Initio Analysis.

All-inorganic perovskites have attracted intense interest as promising photovoltaic materials due to their excellent performance. Using time domain density functional theory combined with nonadiabatic (NA) molecular dynamics, we demonstrate that a photoinduced localized polaron-like hole greatly delays the nonradiative electron-hole recombination relative to the structure with delocalized free charge of the CsPbBr. This is because localized charge carriers diminish overlap between electron and hole wave functions and decrease the NA coupling by a factor of 6. In addition, polaron formation increases the band gap of CsPbBr, slowing down recombination further. The smaller NA coupling and larger band gap compete successfully with the longer decoherence time, extending the recombination to tens of nanoseconds. The calculated recombination times show excellent agreement with experiment. Our study reveals the atomistic mechanisms underlying the suppression of recombination upon formation of localized polaron-like holes and advances our understanding of the excited-state dynamics of all-inorganic perovskite solar cells.