Charge Transfer in Fullerene-Conducting Polymer Compositex: Electronic and Excitonic Properties

Abstract

C60 doping into conducting polymer with highly extended π-electron system in the main chain induces remarkable quenching of photoluminescence in conducting polymer and drastic enhancement of photoconductivity. These results can be explained in terms of photo-induced charge transfer between conducting polymer and C60. That is, photoexcited excitons or exciton-polarons on conducting polymer are effectively dissociated at C60 molecules transferring electrons to C60. Photoexcitation of C60 results in the transfer of hole from C60 to conducting polymer. These novel C60 doping effects have been observed not only in conducting polymers with non-degenerated ground state structures but also those with degenerated ground state structure such as di-substituted acetylene polymers with solitonic electronic systems. Highly effective photo-induced charge transfer has been also observed in conducting polymer/C60 heterojunctions, which are interpreted as donor (D)-acceptor (A) photocell. Based on this finding we have demonstrated an organic photovoltaic cell with D-A double heterojunction, Al/C60/OEP/conducting polymer/TTO, in which OEP is octaethylporphine as an light absorbing antenna molecule. Novel characteristics have also been observed in various other junction devices utilizing C60 doped conducting polymer. Granular and multiphase superconductivity has been found in C60-conducting polymer-alkali metal composites. Effect of other type of fullerenes such as C70, modified C60 and C60 polymers, and also effect of C60 doping in polysilanes and their derivatives have also been studied.