Thermal Precursor Approach to Pristine Fullerene Film as Electron Selective Layer in Perovskite Solar Cells

Abstract

In perovskite solar cells (PSCs), electron selective layers (ESLs) assume a crucial role in blocking holes and transporting electrons for high performances. To achieve low-temperature solution processing of PSCs, organic n-type materials such as fullerene-based molecules have recently been employed to replace a typical TiO2 ESL that requires high temperature (>450°C) for fabrication. Herein, soluble C60–9-methylanthracene mono-adduct (C60(9MA)) is used as a thermal precursor to the C60 ESL in planar PSCs. The best performing PSC device shows a power conversion efficiency of 15.0% under the simulated AM 1.5G one sun illumination, which is superior to that of the device with compact TiO2 as an ESL (12.9%). Remarkably, a fill factor of the C60-based PSC (0.723) is enhanced compared to that of the TiO2-based one (0.671) owing to the low charge-transfer resistance at the interface of C60–perovskite. These results suggest that the thermal precursor approach to pristine fullerene films is a promising approach for fabricating ESL in high-performance PSCs with relatively low fabrication temperature (<140°C).