Surface Passivation and Energy Alignment Modulation of n‐i‐p Perovskite Solar Cells with Self‐Assembled Molecule

Abstract Perovskite's surface defects trigger deep level traps and energy misalignment, resulting in substantial interface recombination and energy loss in perovskite solar cells (PSCs). Herein, 9‐fluoreneacetic acid (FAA), a self‐assembled molecule (SAM), is employed to passivate the interface defects and modulate energy alignment. SAM modification reduces the defect density from 6.37  ×  10 15 to 3.11  ×  10 15  cm −3 and produces a p‐type surface with an upward band bending, thus constructing a well‐defined n‐i‐p heterojunction for efficient charge separation. Accordingly, the target PSC realizes 24.75% power conversion efficiency (PCE) and retains 92% for 1100 h during maximum power point tracking (MPPT) at room temperature. Furthermore, over 80% of initial PCE has been reserved after 2500 h aging in 25–30% relative humidity (RH). This SAM strategy is expected to enhance the efficiency and stability for n‐i‐p PSCs.