POLYMERIC FILMS CONTAINING ACCEPTOR DONOR ASSEMBLIES - PHOTOELECTRODES BASED ON IRRADIATION OF INTERMOLECULAR AND INTRAMOLECULAR CHARGE-TRANSFER COMPLEXES

The behavior under visible irradiation of optically transparent electrodes (OTE) modified by thin films of polypyrrole containing several kinds of electron acceptor-donor assemblies has been investigated. Photolysis of electrodes coated by thin films of polypyrrole substituted by a reversible electron acceptor (viologen) in the presence of an irreversible electron donor (benzilate anion) in acetonitrile gives appreciable photocurrents. The photoresponse results from the photoinduced charge separation of the charge-transfer complex created at the interface. The measured photocurrents are markedly larger (up to 5 times) with films of polypyrrole substituted by a reversible electron acceptor (viologen) covalently linked with a donor (phenothiazine, triphenylamine, or benzidine) than with the former ones under similar experimental conditions. The greater efficiency of these materials is attributed to the formation of an intramolecular charge-transfer complex occurring inside films between the two molecular entities. Markedly weaker photocurrents are obtained with polypyrrole films based on bilayers of the two independent components than with films of unimolecular design while films based on copolymers arrangements give moderately weaker photoresponses.