Buried Interface Modification for High Performance and Stable Inverted Perovskite Solar Cells

Abstract Residual stress can cause distortion of the perovskite lattice, resulting in the formation of local defects such as dislocation and vacancy. These defects serve as non‐radiative recombination centers and significantly affect the stability of perovskite films.‌ In this study, triphenylamine derivative (TAPC) was designed as an effective passivating agent. The resulting modified molecular layer established a gradient arrangement of thermal expansion coefficients between the hole transport layer (HTL) and the perovskite, effectively mitigating stress accumulation within the perovskite film. This modification concurrently enhanced hole transport capability and optimized the energy level alignment. Consequently, the power conversion efficiency (PCE) of the optimized perovskite solar cell (PSCs) increased from 24.22% to 26.05%, with the fill factor (FF) rising from 83.2% to 85.2%. Furthermore, the device achieved the lowest open‐circuit voltage ( V oc ) loss reported for comparable 1.55 eV bandgap PSCs, while maintaining excellent long‐term stability. Importantly, this strategy also enabled a corresponding flexible PSC (F‐PSCs) to achieve a remarkable PCE of 24.39%. Collectively, these results demonstrate a promising pathway for buried interface modification of perovskite films and the fabrication of high‐performance F‐PSCs.