Synergistic Hematite‐Fullerene Electron‐Extracting Layers for Improved Efficiency and Stability in Perovskite Solar Cells

Hematite, α‐Fe2O3, is arising as a promising electron‐extraction material in perovskite solar cells, yet present α‐Fe2O3‐based perovskite solar cells still show unsatisfactory efficiencies owing to large charge recombination. In this contribution, phenyl‐C61‐butyric acid methyl ester (PCBM) and α‐Fe2O3 synergistically worked together as the electron transport layer (ETL) in planar heterojunction perovskite solar cells. The introduction of fullerene at the top of the α‐Fe2O3 ETL improved the crystallinity of CH3NH3PbI3 perovskite and facilitated electron extraction. As a consequence, a substantially retarded charge recombination largely boosted the short‐circuit current density and power conversion efficiency of perovskite solar cells. The optimized perovskite solar cells with α‐Fe2O3/PCBM ETL showed a competitive power conversion efficiency of 14.2 %, which is 20 % higher than that of pristine α‐Fe2O3‐based solar cells. Moreover, α‐Fe2O3/PCBM‐based perovskite solar cells exhibited improved stability compared to the pristine α‐Fe2O3‐based devices, retaining over 95 % of their initial values after 45 days storage in dark in humid air.