Hydrogen migration, surface accumulation, and nonradiative recombination in perovskite solar cells

Abstract

Perovskite solar cells (PSCs) have achieved efficiencies exceeding 27%, yet their performance remains limited by defect-induced nonradiative recombination. Although hydrogen interstitials (H_i) are conventionally considered as bulk defects, this study reveals the dynamic instability of H_i within the bulk lattice of FAPbI₃, which drives spontaneous migration to surface sites due to thermodynamic stabilization at the interface. By combining all-atom molecular dynamics (AAMD) with nonadiabatic molecular dynamics (NAMD), we elucidate the migration pathway of H_i and its electronic implications. Surface-trapped H_i induces significant lattice distortion, resulting in the formation of deep-level defect states and a modified potential energy landscape. This reorganization reduces the electron capture barrier (ΔE_n decreasing from 0.09 eV to 0.03 eV) and the hole capture barrier (ΔE_p dropping from 0.24 eV to 0.17 eV), and increases carrier capture coefficients by an order of magnitude (from 10⁻⁸ cm³ s⁻¹ to 10⁻⁷ cm³ s⁻¹). Strengthened vibronic interactions and enhanced nonadiabatic couplings shorten the carrier lifetime from 0.8 ns (bulk H_i) to 0.1 ns (surface H_i), indicating surface-accumulated H_i is the dominant nonradiative recombination source rather than bulk H_i. These findings emphasize that interfacial hydrogen management, rather than conventional bulk passivation, is critical for designing suppression strategies to overcome performance limitations in PSCs.