Excitation Energy Shuttling in Oligothiophene–Diketopyrrolopyrrole–Fullerene Triads

Abstract

The photophysical properties of a thiophene-diketopyrrolopyrrole oligomer linked to two fullerene units via alkyl linkers of different lengths have been investigated in solution. The molecules exhibit excitation energy shuttling between the singlet and triplet photoexcited states. Photoexcitation of the oligomer is followed by singlet energy transfer to the fullerene, intersystem crossing to the triplet state, and then triplet energy transfer back to the oligomer. Competing electron transfer reactions, followed by recombination to the triplet state, are energetically possible and cannot be ruled out but were not observed and seem to have a small contribution in solution.