Photoinduced Electrochemical Properties of Organized Assembly of Amphiphilic Redox Polymers by Langmuir-Blodgett Technique

Spatial arrangement of the ruthenium dipyridyl complex and ferrocene derivative in hetero-deposited redox polymer Langmuir-Blodgett (LB) films was carried out for direction control of photocurrent flow produced by photoinduced electron transfer reaction and for high quantum efficiency. Two hetero-deposited structures were obtained by varying the deposition order of the redox polymer monolayers by the LB technique. Cyclic voltammograms of hetero-deposited redox polymer LB films exhibited current rectifying and charge storage properties. Light irradiation led to anodic photocurrent of hetero-deposited redox polymer LB films consisting of Ru copolymer LB film as an inner layer and Fc copolymer LB film as an outer layer on the ITO (Fc/Ru/ITO) electrodes. On the other hand, cathodic current was observed at the reverse layered structure (Ru/Fc/ITO) electrodes. The direction of photocurrent flow depended on the deposition order of redox polymer LB films on the ITO electrode. Photocurrent quantum efficiency of 5.9% of the hetero-deposited redox polymer LB film was achieved. High photocurrent conversion efficiency is explained by inhibition of recombination of photoinduced charge separation due to hetero-deposited LB film structures.