Merocyanine with Hole-Transporting Ability and Efficient Defect Passivation Effect for Perovskite Solar Cells

Development of charge-transporting molecules that can simultaneously passivate multiple surface defects of perovskites is highly desirable for further performance increase of perovskite solar cells (PVSCs). Herein, we describe a simple strategy for designing a passivation molecule with good hole mobility based on conjugated merocyanine dye. Remarkably, we reveal that merocyanine with zwitterionic resonance structure character in the ground state can efficiently passivate the deep-level defects such as lead/iodide vacancies and eliminate the negative effects of neutral iodine defects, leading to an effective reduction of charge recombination and a preferred band bending at the surface of the perovskite film for hole extraction. Therefore, a significant increase in power conversion efficiency (PCE) from 19.78% to 22.04% is achieved for the dye-treated conventional n-i-p PVSCs. Our work shows a new molecular platform for designing efficient defect passivation molecules for perovskites.