Photo-electrochemical properties of ZnO and TiO2 layers in ionic liquid environment

Abstract

Photoinduced electrochemical functionality of uniform TiO2 and ZnO films prepared by sol–gel method, in the former case in the reverse micelle environment, was studied using a specific type of ionic liquids as electrolytes. The coating part was arranged as piezoelectric ink-jet printing. Ionic liquids could be regarded as nanostructured fluids with two distinctive kinds of spatial domain: one ionic, the other non-polar. The driving force for the segregation of the nonpolar chains is energetic. They are excluded from the cohesive network of positive and negative charges that is formed by the charged groups of the ions in close contact. If side-chains are too short they do not disturb the ionic network significantly and, they do not possess enough conformational freedom to adopt low energy configuration. By increasing the chain-length the role of its spatial arrangement becomes important. Such features must be reflected in their specific behaviour as electrolytes in the contact with photoactive semiconducting thin films. Attention was also paid to the correlation of the values of generated photocurrent densities in layers with the fluidity and conductivity of the used ionic liquids.