Abstract
Although fullerene bisadducts are promising electron-transporting materials for tin halide perovskite solar cells, they are generally synthesized as a mixture of isomeric products that require a complicated separation process. Here, we introduce a phenylene-bridged bis(pyrrolidino)fullerene, Bis-PC, which forms only a single isomer due to geometrical restriction. When used in a tin perovskite solar cell with a PEA(0.15)FA(0.85)SnI(3) (PEA: phenylethylammonium and FA: formamidinium) light absorption layer, the resulting open-circuit voltage (V (OC)) was 0.78 V, a value higher than that of fullerene monoadducts and comparable to that of the commonly used indene-C(60) bisadduct (ICBA). The performance could be further improved by the composition engineering of perovskite, where the PEA(0.15)(FA(0.87)MA(0.13))(0.85)SnI(3) based device (MA: methylammonium) exhibited a photoelectric conversion efficiency of 12.3% with a V (OC) of 0.86 V. The device with single-isomer Bis-PC shows superior stability to that with mixed-isomer ICBA, retaining its initial performance after 3000 h storage under an inert atmosphere.