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.