Photoinduced absorption of poly(3-alkylthiophens)

We report a study of the photoinduced absorption of a series of poly-3-decylthiophene (P3DT) samples with different supermolecular organization, such a cast films, good and bad solvent solutions. Both solid state samples and solutions exhibit two photoinduced absorption bands but their origin is rather different. In solutions there is an indication for an intra-chain mechanism leading to photoexcited states. Their nature is thus different from that of the bipolaronic states typical of non degenerate conjugated polymers. In the cast films there is evidence that photoexcited states are mainly due to interchain hopping bringing thus further support to the bipolaronic assignement in the solid state.