Enhancing moisture resistance in p-i-n perovskite solar cells: utilizing fullerene derivatives as advanced electron transport materials

Herein, we report on the family of fullerene derivatives F2-F6 as electron transport materials (ETMs) in inverted perovskite solar cells (PSCs). According to the results, F2 and F4 have power conversion efficiencies (PCE) of 17.2% and 16.7%, respectively, which indicates better performance than conventional ETM (PC₆₁BM). Utilizing infrared scattering scanning near-field optical microscopy (IR s-SNOM), we ascertained that F2 and F4 demonstrate exceptional uniformity and are devoid of defects. This characteristic contributes to a reduction in trap density and charge recombination in PSCs, ultimately enhancing device efficiency and mitigating hysteresis. Above all, F2 showed no signs of deterioration when the PSCs were exposed to 45 ± 5% relative humidity for 1000 h. Our research provides an innovative viewpoint on how to create novel fullerene compounds that enhance efficiency and stability of PSCs.