α-DTC70 Fullerene Performs Significantly Better than β-DTC70 as Electron Transporting Material in Perovskite Solar Cells.

In this work, two new C70 isomers, α and β bis(2-(thiophen-2-yl)ethyl)-C70-fullerene mono-adducts (DTC70), were synthesized, characterized and used as electron transporting materials (ETMs) in perovskite solar cells (PSCs). Our results show that the α isomer improves both the J sc and FF values of the devices, when compared to the results for the β-isomer and to those for phenyl-C70-butyric acid methyl ester (PC71BM), used as control. Devices based on α-DTC70 achieved a power conversion efficiency (PCE) of 15.9%, which is higher than that observed with PC71BM (15.1%).