FEMTOSECOND TRANSIENT BLEACHING DECAY IN POLY(ALKYL-THIOPHENE-VINYLENE)S IN SOLUTION AND IN FILM

We report on ultrafast absorption measurements on poly(3,4-dibutyl-thiophene-2,5-diyl-vinylene) using the pump and probe technique. Transient photoinduced bleaching has been measured both in chloroform solution and in film. A complete and fast absorption recovery after photoexcitation occurs in solution, while a long-lived component is observed in film. The comparison of the temporal behavior of the initial transient bleaching decay between solution and film allows us to evaluate the contribution of the vinyl group to the backbone rigidity. The observed excited state dynamics is interpreted in terms of polaron-exciton recombination on deformation centers whose concentration and distribution depend on the supermolecular organization of the sample.