The photochemical deposition of a p-type semiconducting copper(I) oxide (Cu2O) layer by irradiating visible light in an aqueous solution containing a lactic acid and copper sulfate hydrate is presented. The p-Cu2O layer was photochemically stacked on a chemically deposited n-type semiconducting ZnO layer/quartz glass substrate, and the photovoltaic device was constructed by forming a Au top electrode using a sputtering technique. The Au/p-Cu2O/n-ZnO photovoltaic device showed an electrical rectification and the performance of 46 mV in open-circuit voltage (V-oc) and 75 mu A cm(-2) in short-circuit current density (J(sc)) under an Air Mass 1.5 illumination. (c) 2006 The Electrochemical Society.