Abstract

Composite systems consisting of fullerenes and conjugated polymers have shown promising properties for optoelectronic applications like e.g. photodetectors and solar cells. In these materials charge carrier generation is considerably enhanced as compared to single component systems due to a photoinduced electron transfer that occurs after photoexciting the conjugated polymer. The dynamics of this process is determined by different microscopic properties, i.e. the delocalization of the initially excited state, diffusion of the neutral excitation and the dissociation process itself. We apply femtosecond transient absorption spectroscopy to unravel the various mechanisms during the transition from a neutral photoexcitation to a pair of charge carriers. The neutral photoexcitation leads to a stimulated emission while the charged excitations cause a transmission change of opposite sign. Thus we can directly monitor (with subpicosecond time resolution) the dissociation process by detecting the transient quenching of the stimulated emission.

© 1998 IEEE