Two Birds With One Stone: Modifier Interfacial Engineering for High‐Efficiency Stable p‐i‐n All‐Inorganic Perovskite/Organic Tandem Solar Cells

ABSTRACT All‐inorganic perovskite solar cells are photovoltaic research hotspots due to their excellent thermal stability. To boost efficiency, ZnO is used as an electron transport material for its high mobility and energy level matching with inorganic perovskites. However, abundant surface defects on CsPbI 2 Br trigger undesirable interfacial reactions with ZnO, seriously limiting device performance and long‐term stability. Herein, a two‐birds‐with‐one‐stone interfacial modifier based on HTPT (4‐hydroxy‐6‐(trifluoromethyl)pyrimidine‐2‐thiol) is utilized. S, O, and N heteroatoms in HTPT passivate defects via multi‐site coordination, reducing reactive sites. The steric effect of CF 3 partially reduces direct contact between perovskite and ZnO, and various interfacial effects, including surface energy variation, interfacial dipole modulation, wettability, and hydrophobicity, jointly regulate the overall interface properties, constructing an effective strategy for suppressing interfacial interdiffusion and slowing interfacial degradation rates. Modified single‐junction p‐i‐n devices reach a record 17.34% efficiency with 1.32 V open‐circuit voltage and robust stability (T 80 = 864 h at 85°C, T 92 = 1000 h under maximum power point tracking (MPPT) at 30°C). P‐i‐n CsPbI 2 Br/PM6:eC9:PC61BM two‐terminal tandem cells were fabricated. The fabricated CsPbI 2 Br/organic tandem cells yield top efficiencies of 24.25% (0.08 cm 2 ) and 22.81% (1.02 cm 2 ) among p‐i‐n all‐inorganic perovskite/organic tandems and maintain decent thermal and MPPT stability.