ULTRAFAST EXCITON DYNAMICS IN A POLYMERIC HETEROSTRUCTURE BASED ON THIENYLENE-PHENYLENE SEQUENCES

We have investigated by femtosecond pump-and-probe measurements the ex citon dynamics in a novel conjugated polymeric heterostructure consist ing of regularly alternated thienylenic and phenylenic segments. A fas t initial relaxation followed by a power law decay has been observed. The initial part of the decay is consistent with the self-trapped exci ton relaxation process. The power law decay has been interpreted in te rms of the modulation of the energy band gap along the polymeric chain s. We have also studied the optical properties of a thienylene-based o ligomer with the same well-barrier-well structure of the polymer in or der to investigate the role of disorder on the polymer relaxation dyna mics.