Highly efficient and stable 2D/3D perovskite solar cells based on surface reconstruction and energy level alignment

Realizing simultaneous adjustment of energy levels and work functions in two-dimensional/three-dimensional (2D/3D) perovskite solar cells (PSCs) is a challenge. Here, a pseudohalide 3,5-bis (trifluoromethyl) benzylammonium tetrafluoroborate (TF-PMABF 4 ) was used to react with unreacted PbI 2 on the surface of 3D bulky perovskite to form a mixed halide of 2D perovskite denoted (TF-PMA) 2 FA 2 Pb 3 I 8 (BF 4 ) 2 . This novel 2D/3D perovskite enables the simultaneous adjustment of energy levels and work functions on the surface of active layers. Due to the significantly enhanced quality of 2D/3D perovskite film, decreased surface defects and increased charge carrier lifetime, the 2D/3D PSCs exhibit an outstanding power conversion efficiency (PCE) of 25.15% and a high V OC of 1.194 V. Importantly, 2D/3D PSCs exhibit remarkable enhancements in environmental stability, unencapsulated devices retaining more than 90% of their initial PCE at 50% humidity for 2,280 h.