Interface-Engineered Composite Self-Assembled Monolayers Driving Efficient and Stable Wide-Bandgap Perovskite and Tandem Solar Cells

Wide-bandgap (WBG) perovskite solar cells (PSCs) based on self-assembled monolayers (SAMs) have demonstrated impressive efficiencies, though their performance and longevity remain substantially compromised by poor wettability during film formation, defects, and energy-level misalignment at the interfaces. Herein, we develop an interface regulation strategy employing a tris(4-carboxyphenyl)phosphine oxide (TC) modified [4-(7<i>H</i>-benzimidazol-7-yl)butyl]phosphonic acid (4PADCB) to construct a multifunctional composite SAM (Co-SAM). The incorporation of TC molecules significantly enhances the interfacial wetting characteristics and crystallization quality of WBG perovskites, effectively passivating defects, optimizing energy-level alignment, and facilitating selective charge transport. This Co-SAM strategy yields impressive device performance: 1.68 eV WBG PSCs achieve a champion power conversion efficiency (PCE) of 22.40% while maintaining >90% of initial efficiency after 1440 h of ambient storage. Furthermore, perovskite/silicon tandem solar cells fabricated using this approach reach a PCE of 30.74%. Our work establishes a new paradigm in interfacial molecular engineering for highly efficient and operationally stable tandem photovoltaics.