Buckminsterfullerene derivatives bearing a fluoroalkyl group for use in organic photovoltaic cells

Six novel fluoroalkylpyrrolidine-substituted [60]fullerene derivatives were synthesized and their ability to perform as new n-type organic photovoltaic materials was evaluated. The fullerene derivatives were soluble in common organic solvents, affording good processability properties for the fabrication of photovoltaic cells, and showed an absorption range and molar extinctions similar to those of [6,6]-phenyl C61 butyric acid methyl ester. Bulk-heterojunction photovoltaic cells using poly(3-hexylthiophene):fullerene derivative blends as the photovoltaic active layers were fabricated and characterized. The performances of the photovoltaic cells were notably affected by the substituents on the fullerene derivatives. Short fluoroalkyl (C4F9) chains on pyrrolidine-linked phenyl groups were suitable substituents for the photovoltaic materials in the current study. This fullerene derivative bearing a C4F9-phenyl group showed a moderate power conversion efficiency of 0.53% during simulated AM 1.5 G solar irradiation at 100 mW/cm2. This is so far the first report of the use of fluoroalkyl fullerene derivatives as the active materials in organic photovoltaic cells.