Interfacial Bridge Using a cis‐Fulleropyrrolidine for Efficient Planar Perovskite Solar Cells with Enhanced Stability

Abstract Fullerene derivatives, especially after purposely functionalization, have potential to efficiently passivate interfacial defects between perovskites and electron transport layers. In this work, a fullerene derivative with amine functional group, 2,5‐diphenyl C₆₀ fulleropyrrolidine (DPC₆₀), is synthesized and employed as an interfacial layer between a perovskite and SnO₂ in planar perovskite solar cells (PSCs). The cis‐configuration and the specific amine group of DPC₆₀ effectively enhance the chemical interaction between the perovskite and DPC₆₀, promoting the passivation of perovskite defects at the interface. The suitable energy level of DPC₆₀ and the improved conductivity of the SnO₂/DPC₆₀ film facilitate the electron extraction from the perovskite layer. As a result, PSCs incorporated with DPC₆₀ reach a PCE of 20.4% with high reproducibility, which is much higher than that of the bare SnO₂ based devices (18.8%). Furthermore, the hydrophobic DPC₆₀ layer suppresses heterogeneous nucleation and improves the crystallinity of the perovskite film, resulting in better device stability, retaining 82% of its initial efficiency after 200 h of 1 sun continuous irradiation and thermal ageing (55 ± 5 °C).