Highly efficient and stable perovskite photovoltaics enabled by multifunctional crosslinked n⁺-type interlayer

Tin dioxide (SnO₂) stands as a premier electron transport layer in n-i-p perovskite solar cells (PSCs), yet interfacial defect-induced carrier recombination and energy-level misalignment impede its commercialization. Herein, we engineer a multifunctional polymeric interlayer by introducing polymerizable dimethyldiallylammonium chloride (DADMAC) at the SnO₂/perovskite interface. The densely cross-linked P-DADMAC network reinforces mechanical interlocking, enhancing interfacial adhesion and stress dissipation. Concurrently, chloride ions (Cl⁻) from P-DADMAC synergistically passivate defects at both the perovskite buried interface and SnO₂ surface, inducing a graded n⁺-type band bending. This energy-band engineering reduces the heterojunction energy-level offset by 0.24 eV, thereby facilitating efficient charge extraction and minimizing non-radiative losses. Consequently, n-i-p devices achieve a power conversion efficiency (PCE) of 26.34% with a fill factor (FF) of 85.84% (certified: 26.27%), while a 25 cm² module (active area: 14 cm²) attains 22.03% PCE (FF > 80%). This work establishes a paradigm for interfacial multifunctionalization in high-performance photovoltaics.