Effective Photoinduced Electron Transfer in Hetero-Deposited Redox Polymer LB Films

The spatial arrangement of the ruthenium dipyridyl complex and ferrocene derivative in heterodeposited redox polymer Langmuir−Blodgett (LB) films is used for the direction control of the photocurrent flow resulting from the photoinduced electron-transfer reaction and the high quantum efficiency. Two kinds of heterodeposited structures are constructed by varying the deposition order of these redox polymer monolayers by the LB technique. The cyclic voltammograms of the heterodeposited redox polymer LB films show current rectifying and charge storage properties. On light irradiation, the anodic photocurrent is observed at the heterodeposited 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, whereas a cathodic photocurrent is observed at the reverse layered structure (Ru/Fc/ITO) electrodes. The direction of photocurrent flow depends on the deposition order of the redox polymer LB films on the ITO electrode. A photocurrent quantum efficiency of 5.9% of the heterodeposited redox polymer LB film is achieved. The high photocurrent conversion efficiency is explained by the inhibition of the recombination of the photoinduced charge separation due to the presence of the heterodeposited LB film structures.