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

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.