Anharmonic Motion-Induced Self-Passivation of Hydrogen Defects in Hybrid Organic-Inorganic Perovskites: Ab Initio...

Hydrogen defects in hybrid organic-inorganic perovskites have garnered increasing attention due to their impact on device performance. Using nonadiabatic molecular dynamics on CH₃NH₃PbI₃, we demonstrate that anharmonic motions at room temperature facilitate the formation of a stable Pb-N coordination bond between the Pb²⁺ ion and the CH₂NH₃ molecule in the presence of a negatively charged hydrogen interstitial defect. This bond eliminates the midgap hole trap state arising from the lone-pair electrons on the nitrogen of the dissociated CH₃NH₃⁺ cation at 0 K, enabling defect self-healing. It also reduces nonadiabatic coupling by decreasing the electron-hole wave function overlap and slows decoherence by suppressing thermal fluctuations. The reduced coupling, combined with a slight increase in the bandgap, dominates over the slower decoherence, extending the charge carrier lifetime to over 1.5 times that of the pristine system. This study establishes a self-passivation mechanism for hydrogen defects in perovskites under operational conditions.