Electronic excitations of the fullerene–thiophene-derived dyads

The electronic absorption spectra of fullerene–thiophene-derived dyads in the UV–vis range have been investigated and discussed taking into account the results of time-dependent density functional theory (TD-DFT) calculations. It was found that the strongest excitations in the dyads are mainly related to the excitations of the fullerene part with some influences from the thiophene-derived part and intramolecular charge transfer processes. The 3T–F dyad significantly differs from the others — the calculated HOMO–LUMO gap in this molecule is significantly lower than in other dyads. This difference is caused by the length of the oligomer and probably by the electron delocalization connected with that length.