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-thi ophene-2,5-diyl-vinylene) using the pump and probe technique. Transien t photoinduced bleaching has been measured both in chloroform solution and in film. A complete and fast absorption recovery after photoexcit ation 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 c ontribution of the vinyl group to the backbone rigidity. The observed excited state dynamics is interpreted in terms of polaron-exciton reco mbination on deformation centers whose concentration and distribution depend on the supermolecular organization of the sample.