• A vertical interfacial engineering strategy via dual-interface modification (Sn(OTF)2 at NiOx/perovskite, 4-Fluorophenylethylamine chloride (F-PEA) at perovskite/C60) solves energy-level mismatches in two-step-processed (TSP) p-i-n PSCs, boosting PCE to 25.6%.
• Sn(OTF)2 enhances NiOx conductivity, suppresses ion migration, and forms a Pb-Sn perovskite interlayer; F-PEA eliminates PbI2, forming a 2D capping layer for defect passivation.
• Optimized NiOx-based TSP p-i-n PSCs retain 84% initial power conversion efficiency after 720-h light illumination, providing design principles for 26%-efficiency devices.
• The study reveals that residual PbI2 clusters in TSP films cause Schottky heterojunctions and energy-level mismatches, which are effectively mitigated by the dual-interface modification.