Synthesis and photophysical properties of fullerene derivatives containing a C60-fluorene core

Three novel fullerene derivatives containing a C60-fluorene core and thiophenyl, terthiophenyl and tetrathiophenyl groups grafted at the 2-position of the fluorene ring, respectively, were synthesized and characterized. Their photophysical and electrochemical properties were investigated systematically. The results showed that their UV-vis absorption bands in the range of 350–500 nm were much wider and stronger than that of the traditional fullerene derivative PC61BM, and the LUMO energy levels of the synthesized fullerene derivatives were gradually up-shifted by increasing of the number of thiophene rings in the oligothiophene units.