π-π Stacking at the Perovskite/C 60 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 (C 60 ), and the properties of this interface have received little attention before. Here, the underlying properties of the 2D perovskite/C 60 interface by taking the 2D TEA 2 PbX 4 (TEA = C 6 H 10 NS; 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 C 60 molecule, strengthening the interaction force with C 60 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 cm 2 ) and 18.08% (1.0 cm 2 ) 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.