Synthesis and characterization of a novel fullerene derivative containing carbazole group for use in organic solar cells

A novel carbazole-group-containing fullerene derivative (CBZ-C60) with good solubility in common organic solvents was synthesized. This derivative was analyzed by using many techniques such as NMR, FAB-MS, FTIR and UV–vis absorption spectroscopy. Further, bulk heterojunction photovoltaic devices were fabricated. Since the LUMO energy level of CBZ-C60 was higher than that of fullerene, the open-circuit voltage (Voc) of devices based on CBZ-C60 was higher than that of devices based on fullerene. The power-conversion efficiency was highest for devices with composite thin films that have P3HT/CBZ-C60 composition ratios of 1:1 and were annealed at 150 °C for 10 min. The maximum Voc, short-circuit current density, and PCE of the best device were 0.64 V, 2.32 mA/cm2, and 0.48%, respectively.