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

Hematite, alpha-Fe2O3, is arising as a promising electron-extraction material in perovskite solar cells, yet present alpha-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 alpha-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 alpha-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 alpha-Fe2O3/PCBM ETL showed a competitive power conversion efficiency of 14.2%, which is 20% higher than that of pristine alpha-Fe2O3-based solar cells. Moreover, alpha-Fe2O3/PCBM-based perovskite solar cells exhibited improved stability compared to the pristine alpha-Fe2O3-based devices, retaining over 95% of their initial values after 45days storage in dark in humid air.