Stabilizing Grain Boundary Grooves in p‐i‐n Perovskite Solar Cells via Dual‐Site Locking Riveting

ABSTRACT The formation of grain boundaries and grooves inherent to perovskite films severely hinders interfacial charge extraction and induces non‐radiative recombination, thereby limiting both photovoltaic efficiency and long‐term stability of devices. Here, we introduce a dual‐site locking strategy using a bifunctional molecule, 4‐chloro‐phenethylammonium halide (4Cl‐PEAX, X═Cl, Br, I), to simultaneously anchor Pb and I sites at the grain boundaries. This locking effectively rivets the grain boundary grooves (GBGs), creating a compact, flattened, and energetically well‐aligned interface that promotes charge transport and suppresses non‐radiative losses. Among the series, 4Cl‐PEAI, with the highest dipole moment, delivers the greatest improvement, yielding p‐i‐n perovskite solar cells (PSCs) with a power conversion efficiency (PCE) of 26.73% with an open‐circuit voltage ( V OC ) of 1.20 V and a fill factor (FF) of 86%, while retaining over 90% of their initial efficiency after prolonged storage and continuous operation. This dual‐site interfacial riveting approach offers a general design principle for enhancing the mechanical and chemical stability of high‐performance perovskite photovoltaics.