Nonmonotonic Strain Dependence of Defect-Assisted Nonradiative Recombination in MAPbI 3 Revealed by Nonadiabatic Dynamics

Here, we employed ab initio nonadiabatic molecular dynamics simulations to investigate the carrier dynamics in methylammonium lead iodide (MAPbI₃) perovskites with lead vacancies under tensile strain. Our results reveal that moderate strain effectively suppresses nonradiative recombination and extends carrier lifetimes, while excessive strain accelerates carrier recombination due to the formation of deeper trap states, negatively affecting device performance. Significant tensile strain induces the formation of I-I dimers, leading to severe local lattice distortion characterized by the elongation of Pb-I bonds and the shortening of I-I bonds at the lead vacancy sites. Furthermore, the bandgap increases with tensile strain, attributed to the stronger antibonding character in the valence band compared to the conduction band. This work provides valuable insights into defect-mediated carrier relaxation dynamics and offers theoretical guidance for defect engineering in perovskite solar cells and related devices.