Synergistic Defect Passivation via Multiple Effects for High-Efficiency and Stable Perovskite Solar Cells

Recently, organic-inorganic perovskite solar cells (PSCs) have garnered significant research interest, achieving a remarkable power conversion efficiency (PCE) of 27.3%. However, the defects at the surfaces and grain boundaries of perovskite films induce severe nonradiative recombination, hindering further improvements in both efficiency and stability of PSCs. Defect passivation is believed to be an effective strategy to unlock the full potential of PSCs. Herein, we report a multi-effect synergistic defect passivation strategy enabled by 2-thiopheneethylammonium bromine (2-ThEABr). We demonstrate that the 2-ThEABr molecule serves a dual role: It facilitates the formation of a two-dimensional (2D) perovskite on the 3D perovskite, whereas its bromine (Br) and sulfur (S) atoms concurrently passivate halide vacancies and undercoordinated Pb²⁺ sites. Furthermore, the S-Pb interaction between the 2-ThEABr and perovskite could enhance the contact strength of the 2D and 3D perovskite surfaces. Owing to this synergistic passivation, the strategy exhibited excellent universality, delivering substantial PCE enhancements across PSCs with various compositions. Remarkably, the Cs_0.05FA_0.95PbI₃-PSCs with 2-ThEABr achieved a champion PCE of 24.75% with a high open-circuit voltage (V_OC) of 1.190 V. Moreover, the perovskite film passivated with 2-ThEABr exhibited significantly improved stability, with unencapsulated devices retaining 85% of their initial efficiency after 1200 h of aging.