Cooperative Assembly Drives Buried Interface Engineering for Efficient Inverted Perovskite Solar Cells

Self‐assembled monolayers (SAMs) containing carbazole and phosphonic acid groups have emerged as effective hole‐transport layers (HTLs) for high‐performance inverted perovskite solar cells (PSCs). However, the intrinsic aggregation tendency of SAM molecules often compromises interfacial uniformity, inducing non‐radiative recombination and limiting device efficiency and stability. Here, we report a synergistically assembled chemically heterogeneous (SACH) interfacial layer constructed by integrating [4‐(3,6‐dimethyl‐9H‐carbazol‐9‐yl)butyl]phosphonic acid (Me‐4PACz) with carbazole‐9‐ethanol (CE). In this strategy, CE promotes favorable heteromolecular π‐associated and dispersion interactions with Me‐4PACz, thereby moderating excessive Me‐4PACz self‐association, improving interfacial uniformity, and enhancing charge extraction. Meanwhile, the hydroxyl group of CE supports an O─H···I − interaction with perovskite, contributing to interfacial defect passivation and suppressed buried‐interface recombination. As a result, devices employing the SACH layer achieve a PCE of 27.06% (certified 26.86%). Under maximum power point tracking in ambient air at 65°C, encapsulated SACH‐based devices retained 88.6% of their initial efficiency after 500 h. Large‐area perovskite modules (30 × 30 cm 2 ) further demonstrate promising performance with an efficiency of 21.90%, highlighting the broad applicability of this cooperative interfacial design for scalable perovskite photovoltaics.