Intramolecular Exciton Diffusion in Poly(3-hexylthiophene)

Emission quenching by fullerenes covalently attached to both ends of a series of size-selected regioregular poly(3-hexylthiophene) samples was quantified and used to determine the intrachain exciton diffusion length. The diffusion length was found to be L-D = 7.0 +/- 0.8 nm. When the distance dependence of the quenching mechanism is considered, this is the same value that has been reported for emissive excitons in thin films. This result indicates that intrachain exciton transport is more facile for excitons localized to single chains than that for excitons that are delocalized between chains. In the context of solar cells, the result indicates additional complexity and the potential for competing issues when considering morphological design of the film to enhance both exciton and charge transport.