Buried Interface‐Driven Synergistic Homogenization of Self‐Assembled Monolayer and Wide‐Bandgap Perovskite for Efficient and Stable Solar Cells

ABSTRACT Wide‐bandgap (WBG) perovskite solar cells (PSCs) have attracted considerable interest due to their diverse photovoltaic applications, particularly as top cells in tandem solar cell configurations. However, the efficiency and stability of these devices are often limited by inhomogeneity in both the hole‐selective self‐assembled monolayer (SAM) and the mixed‐halide WBG perovskite layer. Here, we propose a buried interface‐driven synergistic homogenization strategy to address these challenges. This strategy involves inserting copper fluoride (CuF 2 ) between the FTO substrate and MeO‐2PACz SAM layer, which promotes the formation of a uniform coverage of the MeO‐2PACz layer with suppressed aggregation due to the strong interaction between CuF 2 and MeO‐2PACz. The improved homogeneity of MeO‐2PACz not only facilitates the interfacial hole extraction but also favors the deposition of high‐quality Cs 0.3 MA 0.15 FA 0.55 PbI 2.7 Br 0.3 perovskite. The resultant perovskite films exhibit superior crystallinity, phase homogeneity, and reduced trap density. Collectively, the optimized devices achieve a champion efficiency of 23.33%. Furthermore, after 1500 h of continuous operation at the maximum power point (MPP), the optimized device retains 90% of its initial efficiency, demonstrating excellent operational stability.