Charge separation and recombination in small band gap oligomer-fullerene triads.

Synthesis and photophysics of a series of thiophene-thienopyrazine small band gap oligomers end-capped at both ends with C-60 are presented In these triads a photoinduced electron transfer reaction occurs between the oligomer as a donor and the fullerene as an acceptor Femtosecond photoinduced absorption has been used to determine the rates for charge separation and recombination It was found that change separation takes place within approximately 10 Ps and is situated close to the Marcus optimal region Charge recombination is taster in o-dichlorobenzene (ODCB) (15-45 ps) than in toluene (90-730 ps) because in ODCB charge recombination takes place close to the optimal region In toluene the recombination is situated in the inverted region with a much higher activation barrier No signs of recombination into a triplet state were observed