Photocurrent Generation Properties of Half-Photocell Consisting of Electropolymerized Hierarchical Polythiophene Thin Films as Photoexciting Electron Donor and C60 as Electron Acceptor

Abstract

Polybithiophene/poly(3,4-ethylenedioxythiophene)/indium-tin-oxide coated transparent glass electrodes were prepared by sequential electrochemical polymerization with cyclic voltammetry. The thickness of polybithiophene films was varied by the scan rate of applied potentials during polymerization. Obtained hierarchical polythiophene films were characterized by absorption spectra, fluorescence spectra, scanning electron microscopy, laser microscopy, and atomic force microscopy. Half-photocell properties of the hierarchical polythiophene thin films were evaluated by a three-electrode electrochemical cell in CH _2 Cl _2 solution of electrolyte and C _60 as a sacrificial electron acceptor under irradiation of monochromatic light. The thickness and absorbance of hierarchical polythiophene thin films increased by decreasing of scan rate of applied potentials during the polymerization of polybithiophene. While, maximum peaks of fluorescence intensity and internal quantum yield of cathodic photocurrent were observed at 20 nm thickness of polythiophene film under irradiation from the glass side of the transparent electrode. Almost maximum external quantum efficiencies of cathodic photocurrent were observed from 20 nm to 1.5 μ m thicknesses of polythiophene films. These tendencies suggest that CH _2 Cl _2 solution of C _60 and electrolyte penetrate into the polybithiophene layer up to 1.5 μ m.