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 × 10¹⁵ to 3.11 × 10¹⁵ 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.