A Reduction–Complexation Cascade Stabilizes the Buried NiOx/Perovskite Interface for High‐Performance Perovskite Solar Cells

The buried NiO x /perovskite interface is a critical bottleneck for inverted perovskite solar cells (PSCs), where interfacial defects and redox reactions jointly degrade efficiency and stability. Here, we introduce zinc diethylphosphinate (ZDP) as a molecularly engineered interlayer that initiates a coupled cascade reaction at this interface. The diethylphosphinate anion simultaneously consumes surface hydroxyl species on NiO x and reduces iodine to iodide within the perovskite, while the Zn 2+ cation further passivates ionic defects and forms a stabilizing complex. This reaction‐led process, complemented by enhanced interfacial hydrophobicity, concurrently optimizes energy alignment, promotes hole extraction, and improves perovskite crystallinity. Consequently, ZDP‐modified devices achieve champion power conversion efficiencies of 25.34% and 22.21% for 1.56 and 1.68 eV perovskites, respectively, with a large‐area (1.05 cm 2 ) cell reaching 23.71%. Unencapsulated devices retain 90.20% of their initial efficiency after 1440 h in N 2 . This work demonstrates that a reduction‐complexation cascade strategy effectively enhances both efficiency and stability of NiO x ‐based inverted PSCs.