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 PEA0.15FA0.85SnI3 (PEA: phenylethylammonium, FA: formamidinium) light absorption layer, the resulting open-circuit voltage (VOC) was 0.78 V, a value higher than fullerene monoadducts and comparable to the commonly used indene-C60 bisadduct (ICBA). The performance could be further improved by the composition engineering of perovskite, where the PEA0.15(FA0.87MA0.13)0.85SnI3 based device (MA: methylammonium) reached a photoelectric conversion efficiency of 12.3% with a VOC of 0.86 V. The device with single-isomer Bis-PC shows superior stability to mixed-isomer ICBA, maintaining the initial performance after 3,000 h storage under an inert atmosphere.

This article is Open Access

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