Reconfiguration toward Self‐Assembled Monolayer Passivation for High‐Performance Perovskite Solar Cells

Abstract Self‐assembled monolayers (SAMs) with unique ordered structures and varied anchoring groups have emerged as an excellent interfacial strategy for perovskite solar cells (PSCs). Herein, 3‐carboxypropyl‐triphenyl phosphonium bromide with the participation of the fullerene derivative [6,6]‐phenyl‐C₆₁‐butyric acid (PCBA) as functionalized C‐PCBA SAM, is introduced to stably modify the TiO₂/perovskite interface. In the meantime, with strong fullerene cage–iodide interaction, ordered C‐PCBA SAM can passivate interfacial defects and improve the electron transportation. A high efficiency of 24.8% and stabilized power output of 23.9%, are achieved with negligible hysteresis, which is among the best performances for TiO₂ planar PSCs. This modified cell also exhibits significantly improved stabilities under different testing conditions; non‐encapsulated devices can maintain 95% of initial efficiency after 1000 h thermal stability testing at 85 °C and 85% after 700 h continuous illumination (≈100 mW cm⁻²) and maximum‐power‐point tracking. This work provides valuable inspiration for developing highly efficient and stable PSCs by using a convenient SAM reconfiguration strategy.