Design, synthesis and characterization of 1,8-naphthalimide based fullerene derivative as electron transport material for inverted perovskite solar cells

A new fullerene derivative, PC61BNI, was designed and synthesized in which [6,6]-phenyl C-61-butyric acid methyl ester (PC61BM) was modified by replacing the methyl group with 1,8-naphthalimide (NI) to investigate the molecular structure modification effect on perovskite solar cell performance. Inverted perovskite solar cells were fabricated employing PC61BNI as an electron transport material (ETM) and its performance was compared with that of the device fabricated using PC61BM. Optical and electrochemical properties of the PC61BNI were characterized, and how NI substitution affects the solar cells performance was investigated. The photoluminescence quenching experiments confirmed efficient electron injection from perovskite film into PC61BNI layer. The lowest unoccupied molecular orbital (LUMO) energy level of PC61BNI (-3.75 eV) was found to be higher than that of PC61BM (-3.91 eV). The device fabricated with PC61BNI exhibited a power conversion efficiency (PCE) of 10.79% with photocurrent density (Jsc) of 20.23 mA/cm(2), open-circuit voltage (Voc) of 1.078 V and fill factor (FF) of 0.497.