Oligomer-Fullerene Dyads:Photophysics and Performance as Active Layer Material in Photovoltaic Cells

摘要

The photophysics of a homologous series of oligo(p-phenylene vinylene)-fulleropyrrolidine (OPVn-C60, n = 1 to 4, with n the number of phenyl rings) donor-acceptor dyads and the corresponding single moiety model compounds were studied. Fast intramolecular singlet-energy transfer occurs after photoexcitation of the OPVn moiety in an apolar solvent. Photoexcitation in a polar solvent results in electron transfer for OPV3-C60, OPV4-C60, and to some extent for OPV2-C60, but not for OPV1-C60. These results are compared to the results obtained for mixtures of the single moiety model compounds in the same solvents. In these dyads electron transfer is likely to occur via a two-step process, i.e. a very fast singlet-energy transfer prior to charge separation. In thin films of OPV3-C60 and OPV4-C60, a long-lived charge-separated state is formed after photoexcitation. This long lifetime is attributed to the migration of charges to different molecules. A flexible photovoltaic device, prepared from OPV4-C60, is presented.