Naphthalene-, Anthracene-, and Pyrene-Substituted Fullerene Derivatives as Electron Acceptors in Polymer-based Solar Cells

A series of aryl-substituted fullerene derivatives were prepared in which the aromatic moiety of [6,6]-phenyl C61-butyric acid methyl ester (PC61BM) was modified by replacing the monocyclic phenyl ring with bicyclic naphthalene (NC61BM), tricyclic anthracene (AC61BM), and tetracyclic pyrene (PyC61BM). The PC61BM derivatives were synthesized from C60 using tosylhydrazone and were tested as electron acceptors in poly(3-hexylthiophene) (P3HT)-based organic photovoltaic cells (OPVs). The lowest unoccupied molecular orbital (LUMO) energy level of NC61BM (−3.68 eV) was found to be slightly higher than those of PC61BM (−3.70 eV), AC61BM (−3.75 eV), and PyC61BM (−3.72 eV). The electron mobility values obtained for the P3HT:PC61BM, P3HT:NC61BM, P3HT:AC61BM, and P3HT:PyC61BM blend films were 2.39 × 10–4, 2.27 × 10–4, 1.75 × 10–4, and 2.13 × 10–4 cm2 V–1 s–1, respectively. P3HT-based bulk-heterojunction (BHJ) solar cells were fabricated using NC61BM, AC61BM, and PyC61BM as electron acceptors, and their performances were compared with that of the device fabricated using PC61BM. The highest power conversion efficiencies (PCEs) observed for devices fabricated with PC61BM, NC61BM, AC61BM, and PyC61BM were 3.80, 4.09, 1.14, and 1.95%, respectively, suggesting NC61BM as a promising electron acceptor for OPVs.