Tuning perovskite recombination by hydrogen interstitial oxidation state

Abstract

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.