Microstructural-dependent photovoltaic properties of polymer solar cells based on different fullerene derivatives

Chlorobenzene, o-dichlorobenzene, and 1,2,4-trichlorobenzene were used as solvents to fabricate active layers of poly(3-hexylthiophene) (P3HT) and fullerene derivatives for polymer solar cells. The fullerene derivatives employed in this study include indene-C₆₀ bisadduct (ICBA) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM). The microstructural features of P3HT:ICBA and P3HT:PCBM thin films were studied using spectroscopy methods. Results show that an overgrowth of P3HT crystallites and the longer effective conjugation length of P3HT chains in thin films can reduce the power conversion efficiency of devices. The presence of ICBA in thin films can limit the growth of P3HT crystallites, which results in a higher fill factor of the ICBA-based devices compared with PCBM-based devices.