π-π Stacking at the Perovskite/C₆₀ Interface Enables High-Efficiency Wide-Bandgap Perovskite Solar Cells

Interface passivation is a key method for improving the efficiency of perovskite solar cells, and 2D/3D perovskite heterojunction is the mainstream passivation strategy. However, the passivation layer also produces a new interface between 2D perovskite and fullerene (C₆₀), and the properties of this interface have received little attention before. Here, the underlying properties of the 2D perovskite/C₆₀ interface by taking the 2D TEA₂PbX₄ (TEA = C₆H₁₀NS; X = I, Br, Cl) passivator as an example are systematically expounded. It is found that the 2D perovskite preferentially exhibits (002) orientation with the outermost surface featuring an oriented arrangement of TEACl, where the thiophene groups face outward. The outward thiophene groups further form a strong π-π stacking system with C₆₀ molecule, strengthening the interaction force with C₆₀ and facilitating the creation of a superior interface. Based on the vacuum-assisted blade coating, wide-bandgap (WBG, 1.77 eV) perovskite solar cells achieved impressive records of 19.28% (0.09 cm²) and 18.08% (1.0 cm²) inefficiency, respectively. This research not only provides a new understanding of interface processing for future perovskite solar cells but also lays a solid foundation for realizing efficient large-area devices.