Photoelectrochemical properties of ZnO/tetrasulfophthalocyanine hybrid thin films prepared by electrochemical self-assembly

Dye-loaded zinc oxide (ZnO) thin films prepared by a one-step electrochemical synthesis from aqueous mixtures of zinc nitrate and water soluble tetrasulfonated metallophthalocyanines (TSPcMt), in which Mt = Zn(II), Al(III)[OH] or Si(IV)[OH](2), have been studied photoelectrochemically. Visible light absorbed in the TSPcMt led to the sensitization of ZnO. A significantly higher conversion efficiency was found for monomeric as compared to aggregated TSPcMt adsorbed on the ZnO surface. The highest photocurrents were observed for TSPcSi. This could be explained by a strong interaction of the TSPcSi with the ZnO, leading to a highly ordered growth of the ZnO/TSPcSi films with a large fraction of TSPcSi monomers adsorbed to the ZnO surface. The strong adsorption also leads to a more efficient electron injection from the TSPcSi monomers into the conduction band of ZnO as compared to other TSPcMt.