Hydrogen Bond‐Mediated Molecule‐Cation Passivation Pair for Efficient Perovskite Solar Cells

ABSTRACT Homogeneous and efficient surface passivation is crucial for achieving the high photovoltaic performance in perovskite solar cells (PSCs). In this work, we engineered a universal passivation strategy by constructing a hydrogen bond‐mediated molecule‐cation passivation pair for widely used ammonium cations (phenethylammonium (PEA + ), propane‐1,3‐diammonium (PDA 2+ ), (2‐(cyclohex‐1‐en‐1‐yl) ethan‐1‐aminium (CHEA + )). This strategy disperses the ammonium passivators by leveraging the hydrogen bond‐mediated interactions between 4‐amino‐3,5‐difluorobenzonitrile (AFBN) and ammonium cations, mitigating their disordered accumulation on the perovskite surface and enabling a laterally homogeneous passivation. Besides, the cyano moieties of AFBN interact with undercoordinated Pb 2+ , complemented by the amino groups, which engage in hydrogen bonding with I − sites, delivering effective passivation of multiple defects through combining the traditional ammonium salt. Consequently, the p‐i‐n devices treated with AFBN/PEACl and AFBN/PDAI 2 achieved remarkable power conversion efficiencies (PCEs) of 25.89% and 26.77%, respectively. Furthermore, the AFBN/CHEAI pair enabled a high efficiency of 25.88% in n‐i‐p PSC. Moreover, the unencapsulated HMPP‐PSCs also exhibit an enhanced device stability, maintaining 91.5% and 87.5% of their initial efficiencies after nearly 2500 h of aging in ambient air and heat soaking at 65°C for 800 h.