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

Abstract A new fullerene derivative, PC 61 BNI, was designed and synthesized in which [6,6]-phenyl C 61 -butyric acid methyl ester (PC 61 BM) 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 PC 61 BNI as an electron transport material (ETM) and its performance was compared with that of the device fabricated using PC 61 BM. Optical and electrochemical properties of the PC 61 BNI 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 PC 61 BNI layer. The lowest unoccupied molecular orbital (LUMO) energy level of PC 61 BNI (–3.75 eV) was found to be higher than that of PC 61 BM (–3.91 eV). The device fabricated with PC 61 BNI 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.