Robust Electron Transport Layers via In Situ Cross-Linking of Perylene Diimide and Fullerene for Perovskite Solar Cells

While employing charge transport layers (CTLs) in optoelectronic devices including hybrid perovskite solar cells is essential for high performance, using solution-processed organic semiconductor-based CTLs poses challenges for device fabrication. Cross-linking the organic semiconductor is a viable approach, but cross-linked CTLs require additional development for practical application. Here a facile in situ strategy to prepare a cross-linked electron transport layer (ETL) is demonstrated by employing a semiconducting cross-linker composed of perylenediimide-diazide, together with the fullerene (C₆₀) derivative coded as PCBM. Varying the PCBM ratio the cross-linking conditions affords a tunable ETL that exhibits solvent tolerance, suitable electron mobility (>10^–4 cm² V^–1 s^–1), and hydrophobicity at cross-linking temperatures as low as 120 °C. In both the n–i–p structure and the p–i–n perovskite solar cells employing our ETL, stable power generation and hysteresis-free performance are achieved. Optimized p–i–n devices with our cross-linked ETL gave power conversion efficiency of over 12% (active area of 1.07 cm²). These results suggest that robust n-type semiconducting films obtained with our cross-linking method are promising as ETLs in practical optoelectronic applications.