Improved Performance and Stability of Inverted Planar Perovskite Solar Cells Using Fulleropyrrolidine Layers.

Inverted planar structure perovskite solar cells (PSCs), due to their low-temperature precessing and lack of hysteretic problems, are attracting increased attention by researchers around the world. Fullerene derivatives are the most widely used electron transport materials (ETMs) in inverted planar perovskite solar cells, especially [6,6]-phenyl-C61-butyric acid methylester (PC61BM), which exhibits very good performance. However, to the best of our knowledge, the influence of adducts on fullerene-based PSCs performance has not been fully explored to date. In this work, two fullerene derivatives, 2,5-(dimethyl ester) C60 fulleropyrrolidine (DMEC60) and the analogous C70 derivative (DMEC70), were synthesized in high yield via a 1,3-dipolar cycloaddition reaction at room temperature and incorporated into CH3NH3PbI3 perovskite solar cells as electron transport materials. Possibly because the attached pyrrolidine ester groups are able to coordinate with the perovskite layer, the devices based on DMEC60 and DMEC70 achieved power conversion efficiencies (PCE) of 15.2% and 16.4%, respectively. Not only were both devices' efficiencies higher than those based on PC61BM and PC71BM, but their stabilities were also higher than those for PCBM-based devices. The results suggest that DMEC60 and DMEC70 are better alternatives than PC61BM and PC71BM for the ETMs in PSCs.