Cation-Anion Synergy Enables Uniform and Stable SAMs for High-Efficiency Perovskite/TOPCon Tandem Solar Cells

Hole-selective self-assembled monolayers (SAMs) have recently boosted the efficiency of perovskite/silicon tandem solar cells (TSCs), but constructing dense, uniform, and particularly stable SAMs on textured surfaces remains challenging. Here, a cation-anion synergistic strategy is employed to suppress SAMs clustering and enhance molecular anchoring stability. The combined effects of cation-π interaction and phosphonic acid deprotonation enable the formation of high-quality SAMs and perovskite absorbers, while simultaneously improving their interfacial contact at the buried interface. The resulting wide-bandgap perovskite solar cells yielded a power conversion efficiency (PCE) of 23.04%, maintaining 84% of their initial efficiency after 1500 h of maximum power point (MPP) tracking under ISOS-L-1 protocol. Moreover, a 1 cm² monolithic perovskite/silicon tandem solar cell based on textured tunnel oxide passivated contacts (TOPCon) delivered an impressive efficiency of 32.13%, representing the highest reported value to date for perovskite/TOPCon tandems.