Photoexcitation dynamics in conjugated polymeric heterostructures

Summary form only given. In the last few years the interest in organic quantum wells has grown very rapidly due to their potential applications in NLO electronics etc. Aimed at obtaining regularly spaced wells along the polymeric chain axis, we have designed and prepared a novel class of conjugated polymers consisting of regularly alternating low gap thienylenic (T) and high gap phenylenic (B) mojeties of various length corresponding to the general formula (T/sub x/B/sub y/)/sub n/. With the intent of understanding the effects of the presence of energy barriers and the role of interchain transfers on the formation and decay of selftrapped excitations, we have studied the photoexcitation dynamics of these conjugated regular block copolymers by measuring the femtosecond bleaching decay and the photoluminescence picosecond decay of (T/sub 3/B/sub 2/)n and (T/sub 6/B/sub2/)/sub n/ in films, pellets and solutions..While the ferntosecond transient transmission changes are sensistive to the intrachain processes involving the formation of the exciton-polaron, the decay in the picosecond-nanosecond range is controlled by the interchain hopping of the excitons towards recombination sites and is therefore dependent on the sample supermolecular organization. The effect of the presence of the barriers is discussed by comparing the decay behaviour of the copolymer with those of the homopolymer.