Is Iodine Interstitial a Recombination Center in FAPbI₃? Effects of Temperature Revisited

On the basis of zero-temperature static electronic structure calculations, iodine interstitial has been considered as a recombination center in hybrid perovskites since its defect state is within the bandgap. Such a picture was also used to explain why light-induced lattice expansion improves the power conversion in hybrid perovskites. In this study, ab initio molecular dynamics simulations predict that, at room temperature, the iodine interstitial defect level falls below the valence band maximum (VBM), excluding it as an important recombination center. Nonadiabatic molecular dynamics simulations suggest that the elongation of carrier lifetime under strain is a result of weaker nonadiabatic coupling mainly due to the localization of conduction band minimum (CBM). These results demonstrate the importance of explicitly sampling structures at desired temperature and thus considering temperature effects on carrier dynamics beyond the harmonic approximation.