Two cyclohexanofullerenes used as electron transport materials in perovskite solar cells

Abstract

Two fullerene C60 derivatives, 2-(3-ethoxycarbonylpropyloxy)-(5,8)-dihydronaphthyl-(6,7)-[6,6]-C60 (EDNC) and 2-benzyloxy-(5,8)-dihydronaphthyl-(6,7)-[6,6]-C60 (BDNC), are introduced into p-i-n type planar heterojunction perovskite solar cells as electron transport materials (ETMs) to investigate electrochemical, charge-transporting, and film-forming properties of fullerene ETMs and the resulting photovoltaic performance in comparison with [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM). Due to better surface morphology, the EDNC-involving device shows better performance (12.64%) than that of BDNC-based device (7.36%) despite of their similar LUMO energy level, electron mobility, optical properties, and electrochemical properties. Higher power conversion efficiency (PCE) of 15.04% is achieved using PC61BM as the ETM, the electronic mobility of PC61BM is approximately one order of magnitude higher than that of EDNC, which leads to slightly higher short-circuit current density and fill factor for PC61BM-based device. This work demonstrates that factors such as electron mobility and surface morphology should be envisaged in searching for fullerene derivatives as efficient ETM in perovskite solar cells.