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

Hematite, α‐Fe 2 O 3 , is arising as a promising electron‐extraction material in perovskite solar cells, yet present α‐Fe 2 O 3 ‐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‐Fe 2 O 3 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‐Fe 2 O 3 ETL improved the crystallinity of CH 3 NH 3 PbI 3 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‐Fe 2 O 3 /PCBM ETL showed a competitive power conversion efficiency of 14.2 %, which is 20 % higher than that of pristine α‐Fe 2 O 3 ‐based solar cells. Moreover, α‐Fe 2 O 3 /PCBM‐based perovskite solar cells exhibited improved stability compared to the pristine α‐Fe 2 O 3 ‐based devices, retaining over 95 % of their initial values after 45 days storage in dark in humid air.