SN2−Reaction− Bonding‐Heterointerface Strengthens Buried Adhesion and Orientation for Advanced Perovskite Solar Cells

Abstract Traditionally weak buried interaction without customized chemical bonding always goes against the formation of high‐−quality perovskite film that highly determines the efficiency and stability of perovskite solar cells. To address this issue, herein, we propose a bimolecular nucleophilic substitution reaction (S N 2) driving strategy to idealize the robust buried interface by simultaneously decorating underlying substrate and functionalizing [PbX 6 ] 4− octahedral framework with iodoacetamide and thiol molecules, respectively. Theoretical and experimental results demonstrate that a strong S N 2 reaction between exposed halogen and thiol group in two molecules occurs, which not only benefits the reinforcement of buried adhesion, but also triggers target‐point‐oriented crystallization, synergistically upgrading the upper perovskite film quality and accelerating interfacial charge extraction–transfer behavior. Benefiting from the suppressed nonradiative recombination, as a result, an all‐air‐processed carbon–based all‐inorganic CsPbI 2 Br device achieves an enhanced efficiency of 15.14 %, more importantly, with significantly prolonged long‐term stability under harsh conditions. This unique reaction–driven buried interface provides a new path for manipulating perovskite growth and obtaining advanced perovskite photovoltaics.