Orientation Manipulation and Defect Passivation for Perovskite Solar Cells by a Natural Compound

Different facets in perovskite crystals exhibit distinct atomic arrangements, influencing their electronic, physical, and chemical properties. Perovskite films incorporating tin oxide (SnO2) as the electron transport layer face challenges in facet regulation. This study reveals that tea saponin (TS), a natural compound serves as a SnO2 modifier, facilitates optimal growth of perovskite crystals on the (111) facet. The modification promotes preferential crystal orientation through hydrogen bond and Lewis coordination. TS forms a chelate with SnO2, resulting in a smoother film and n‐type doping, leading to improved carrier extraction and reduced defects. The TS‐modified perovskite solar cells achieve a champion efficiency of 24.2%, leveraging from an obvious enhancement of open‐circuit voltage (Voc) of 1.18 V and fill factor (FF) of 82.8%. The devices also demonstrate enhanced humidity tolerance and storage stability, ensuring improved stability without encapsulation. A versatile SnO2 modifier, namely tea saponin (TS), has been demonstrated to significantly enhance carrier extraction capabilities and aid in the optimal growth of perovskite on the (111) facet. As a corollary, the perovskite solar cell based on TS‐modified SnO2 exhibits a notable improvement in Voc and FF, ultimately achieving a superior PCE of 24.2% with improved storage stability.