Decrease of Recombination Losses in Bicomponent  WO 3 / TiO2 Films Photosensitized with Cresyl Violet and Thionine

Abstract

The recombination of photoinjected electrons in semiconducting metal oxide films, photosensitized with cresyl violet and thionine, has been investigated. A comparative analysis of photoresponse characteristics for single‐component photoelectrodes, and , and bicomponent heterogeneous photoelectrodes, was performed for front and back side illumination of the films. A considerably higher photoresponse was observed for bicomponent films in comparison to single‐component films. Employing a porous matrix layer with high open surface area as the substrate for a very thin nanoparticulate overlayer is beneficial for efficient photogeneration for two reasons. First, a lower lying conduction band of the matrix layer provides the escape path for photoinjected electrons from the conduction band of the film to the external circuit and prevents the recombination at the /electrolyte interface. Second, the recombination losses during the electron transport through grain boundaries in film decrease strongly due to the small film thickness. It has been shown that by employing the back side illumination, further decrease in recombination losses of photoinjected electrons can be achieved.