Tuning perovskite recombination by hydrogen interstitial oxidation state

Nonradiative recombination represents a critical performance limitation in perovskites. Combining time-dependent density functional theory (TD-DFT) with nonadiabatic molecular dynamics (NAMD), we elucidate how the oxidation states of hydrogen interstitial defects (H⁰ _i, H_i ⁺, and H_i ^-) dictate recombination dynamics in FAPbI₃. The recombination lifetime depends on the oxidation state, varying over three orders of magnitude, from a short time of 0.1 ns (H⁰ _i) to prolonged times of 44 ns (H_i ⁺) and 72 ns (H_i ^-). H⁰ _i introduces a deep-level defect state, enhancing nonadiabatic coupling between band edges from 0.35 meV to 1.56 meV. Chlorine passivation (Cl@H⁰ _i) neutralizes H⁰ _i defects by eliminating the deep trapping state, stabilizing the lattice and reducing nonadiabatic coupling to 0.30 meV. This passivation enhances the carrier lifetime by 2-3 orders of magnitude, ultimately reaching 87 ns. Our findings establish a map of oxidation-state-dependent recombination for hydrogen interstitials and provide atomistic insights for developing defect passivation strategies for high-performance perovskites.