Interfacial Regulation by a Multifunctional Self‐Assembled Material for High‐Performance Inverted Perovskite Solar Cells

Self‐assembled materials (SAMs) represent an emerging class of hole‐selective contact materials for inverted perovskite solar cells (PSCs). In this work, we report a multifunctional SAM named T4 for regulating the buried FTO/SAM/perovskite interface. T4 combines a phosphonic‐acid anchoring group with a heteroatom‐incorporated fused aromatic terminal group, enabling coupled interfacial effects including improved SAM loading/packing, interfacial electronic‐structure modulation, and sulfur‐involved interaction with Pb‐containing species. These combined effects improve the buried‐interface quality, suppress interfacial recombination losses, and promote hole‐selective charge collection. Consequently, T4‐based inverted PSCs achieve a champion power conversion efficiency of 26.67% and retain approximately 90% of their initial efficiency after 800 h of continuous maximum power point tracking. This work highlights the potential of multifunctional SAM design for regulating buried interfaces in efficient and stable perovskite photovoltaics.