Reinforcing the Buried Interface Enables Efficient and Stable Wide‐Bandgap Perovskite Solar Cells for Perovskite/Silicon Tandems

Abstract Self‐assembled monolayer (SAM)‐based hole transport materials (HTMs) with chemical modifiability are crucial for achieving high‐efficiency inverted perovskite solar cells (PSCs). Although demonstrating excellent device efficiencies, SAMs often suffer from long‐term instability issues, resulting in poor device longevity. Herein, a novel SAM material, [(7,14‐dioxo‐7,14‐dihydroquinolino[2,3‐b] acridine‐5,12‐diyl) bis(butane‐4,1‐diyl)] bis (phosphonic acid) (DPAQA), is designed, equipped with two phosphonic acid anchoring groups. This structure can bind to both the perovskite and fluorine‐doped tin oxide (FTO) simultaneously, thereby enhancing the adhesion between the perovskite and the substrate and improving device stability. Additionally, the phosphonic acid groups that face upward can passivate defects at the buried surface of the perovskite, thereby reducing non‐radiative recombination at the interface. When utilizing a co‐SAMs strategy that mixes DPAQA with conventional SAM (4PADCB), single‐junction PSCs (with a 1.67 eV bandgap) and perovskite/silicon tandem cells achieve power conversion efficiencies (PCEs) of 22.3% and 31.2%, respectively. Besides, single‐junction PSCs employing the co‐SAMs strategy exhibit enhanced thermal stability, without significant PCE decay after 242 h of thermal aging at 85 °C, compared to 86.1% retention for the control. Additionally, the perovskite/silicon tandem cell based on co‐SAMs retains 94.0% of its initial PCE after 718 h of damp‐heat storage (85 °C and 85% RH).