A substrate-supported photoelectrode, which includes an essentially two-dimensional transparent conductive oxide (TCO) film supported by a substrate, wherein the film is doped with at least one element of Group III, and one or more single crystal essentially one-dimensional nanostructures that are integral with the film and grown upwardly therefrom without a boundary layer therebetween, wherein the film and the nanostructures are essentially identical in composition and include zinc oxide or a zinc oxide alloy. Methods for preparing the substrate-supported photoelectrode and solar cells incorporating the substrate-supported photoelectrode are also provided.