Molecular control of charge and energy transfer in self-assembled polymer films: toward improved ultrafast holographic materials

摘要

Abstract: We report on the optical characterization of a series of multi-layered organic superlattices made by polyelectrolyte self-assembly. Using a high molecular weight, water-soluble, anionic form of poly-phenylene vinylene, self-assembled films can be formed which show high photoluminescence quantum efficiency (QE). A dramatic red shift of the luminescence and increase in QE is observed as additional PPV layers are added. We attribute the red shift and increasing QE to a changing conformation of the polymer chains as the superstructure is assembled, together with efficient Frster energy transfer in a preferred direction away from the substrate toward layers with longer effective conjugation length. Upon adding a C$-60$/ top layer, the luminescence spectrum is strongly quenched. We attribute this to charge transfer of from the top-most polymer layer to the C$-60$/ layer. We discuss the possibilities of exploiting this directional charge transfer in an ultrafast holographic device along with other optics for increasing the temporal diffraction efficiency of polymer-based mediums. !9