Near IR photoluminescence in mixed films of conjugated polymers and fullerenes

The photoinduced electron transfer between conjugated polymers and a series of functionalized fullerenes was studied. A new photoluminescence signal was observed in the near IR (∼1.4 eV). This weak IR photoluminescence does not result from direct excitation of the fullerene, but from radiative electron-hole recombination between the fullerene excited state and the polymer ground state. The intensity of this recombination luminescence depends on the electrochemical nature of the functional group; it is observed only for fullerenes with first reduction potential higher than that of C60.