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

The fact that fullerenes are good electron accepters has generated interest in covalently linked complexes between electron donors and fullerenes: pho toinduced charge transfer in these dyads has great potential for use in pho tovoltaic devices. In this Letter, we investigate the excited-state propert ies of a perylene-fulleropyrrolidine dyad using steady-state and femtosecon d time-resolved spectroscopies. Following photoexcitation, charge separatio n and energy transfer occur in nearly equal proportion; both processes take place on a sub-picosecond timescale. This suggests that competition betwee n energy and charge transfer is common in these molecular systems, so that the best molecules for device applications are not necessarily those with t he fastest electron transfer rates. (C) 2000 Published by Elsevier Science B.V.