24.96%‐Efficiency FACsPbI₃ Perovskite Solar Cells Enabled by an Asymmetric 1,3‐Thiazole‐2,4‐Diammonium

Abstract Surmounting complicated defects at the electron transport layer (ETL) and perovskite interface plays a non‐trivial role in improving efficiency and stability of perovskite solar cells (PSCs). Herein, an asymmetric interface modification strategy (AIMS) is developed to passivate the defects from both a SnO₂ ETL and the perovskite buried surface via incorporating 1,3‐thiazole‐2,4‐diammonium (TDA) into the SnO₂/perovskite interface. Detailed experimental and calculated results demonstrate that N3 (the nitrogen atom bonding to the imine) in the TDA preferentially cures the free hydroxyl (OH), oxygen vacancy (V_O), and the Sn‐related defects on the SnO₂ surface, while N1 (the nitrogen atom bonding to the vinyl) is more inclined to passivate the Pb²⁺ and I⁻ related defects at the perovskite buried surface. As a result, the TDA‐modified FACsPbI₃ PSC yields a champion power conversion efficiency (PCE) of 24.96% with a gratifying open‐circuit voltage (V_oc) of 1.20 V. In addition, the optimized PSCs exhibit charming air‐operational stability with the unencapsulated device sustaining 97.04% of its initial PCE after storage in air conditions for 1400 h. The encapsulated device maintains 90.21% of its initial PCE after maximum power point tracking for 500 h.