Dye Sensitization and Surface Structures of Semiconductor Electrodes

Abstract

The dye-sensitization effects on the ZnO, CdS, and TiO2 electrodes in electrochemical photocells were investigated for anionic, cationic, and zwitterionic dyes. The most efficient dye-sensitized photocell was achieved by using an aluminum-doped porous ZnO sinter electrode dyed with rose bengal (an anionic dye), the energy conversion efficiency being 2.5% for incident light of 562 nm. The effect of aluminum doping was attributed to the increase of the porosity (or surface area) of the sinter and the decrease of the electrical resistance. The effect of pH and the added salts in the solution as well as the effect of crystal face were extensively investigated. It turned out that these effects mainly influence the adsorptivity of the electrode surfaces for the sensitizing dyes, not the intrinsic current quantum efficiency. From these results, the structures of the dyes on the semiconductor surfaces were discussed in relation with the mechanism of photoinjection of electrons. The merits of dye-sensitized photoelecrtodes as a photoenergy converter were discussed. © 1980, American Chemical Society. All rights reserved.