Photosensitization of nanocrystalline TiO₂ films by anthocyanin dyes

Reasonably high stable photocurrents, with quantum yields up to Φ = 0.52 are observed using TiO₂ photosensitized by adsorbed anthocyanin dyes with iodide/iodine in water at pH 1. The respective yields in pure ethanol are usually somewhat lower, up to Φ = 0.33. Open circuit photovoltage up to 0.47 V in ethanol and 0.38 in water are obtained. The effects of changing charge carrier concentrations and pH, as well as the photocurrent spectra and yields under various conditions are reported. These simple systems show relatively high quantum yields of the photocurrents, as well as good stability when acidic aqueous solutions of the charge carriers are employed. Comparable yields are obtained in ethanol solutions, although some of the dyes quickly deteriorate.