Thienyl Self‐Assembled Molecule Enabled Stable Perovskite/TOPCon Silicon Tandem

ABSTRACT In mixed‐component wide bandgap (WBG) perovskites, the elusive (111) crystal orientation confers enhanced operational stability compared to the conventional (100) orientation, yet typically compromises photovoltaic performance, presenting a critical stability–efficiency trade‐off that remains unresolved. We report a thienyl‐based self‐assembled monolayer (SAM) as an additive in perovskite inks that templates preferential (111) perovskite crystallization. Besides, this SAM is found to spontaneously segregate at perovskite grain boundaries, where strong Pb‐S bonding establishes a stable passivating interlayer while the conjugated thienyl moiety facilitates the regulation of energy band alignment. Implemented in perovskite/TOPCon tandem solar cells, this approach yields a champion power conversion efficiency of 33.00% (certified 32.56%). Crucially, the tandem devices demonstrate substantially improved operational stability, especially for photothermal stress, retaining > 89.8% of initial performance after 1000 h of continuous operation at 65°C under 1‐sun illumination, validating the critical role of thienyl‐based SAM in stabilizing perovskite‐based tandem photovoltaics.