4-biphenylcarboxylic acid as defect passivation for high-efficient perovskite solar cells

Metal halide perovskite solar cells (PSCs) have been considered as one of the most promising candidates for clean and renewable energy sources, but the existence of the detrimental defects at the surface and grain boundaries seriously deteriorates the power conversion efficiency (PCE) and stability of PSCs. Defect passivation has been verified to efficiently enhance the PCE and stability of PSCs. Herein, a kind of 4-biphenylcarboxylic acid (4-BBC) is first utilized to passivate the perovskite film by a post-treatment strategy, finally improving the performance of PSCs. The carbonyl group of 4-BBC as Lewis base can interact with the uncoordinated Pb2+ ions to heal the I- vacancy defects, and its hydroxyl group can form hydrogen bond with I- anion of the perovskite to suppress the I- ionic migration. The hydrophobic biphenyl group of 4-BBC can also be beneficial to improve the stability of the perovskite film. As a result, the inverted PSCs with 4-BBC passivation indicate a best PCE (20.32 %) with lower hysteresis index (HI) of 0.39 % and better stability in comparison with the control PSCs (PCE = 18.71 %). The synergistic passivation of 4-BBC developed in this work offers an effective strategy for the fabrication of highly efficient and stable PSCs.