Ultrafast competition between energy and charge transfer in a functionalized electron donor/fullerene derivative

The fact that fullerenes are good electron acceptors has generated interest in covalently linked complexes between electron donors and fullerenes; photoinduced charge transfer in these dyads has great potential for use in photovoltaic devices. In this Letter, we investigate the excited-state properties of a perylene–fulleropyrrolidine dyad using steady-state and femtosecond time-resolved spectroscopies. Following photoexcitation, charge separation and energy transfer occur in nearly equal proportion; both processes take place on a sub-picosecond timescale. This suggests that competition between energy and charge transfer is common in these molecular systems, so that the best molecules for device applications are not necessarily those with the fastest electron transfer rates.