Zinc oxide is a wide band gap semiconductor with wide application in thin film devices such as n-type window layers for thin film solar cells, piezoelectric and luminescent devices, and for catalytic applications. We have cathodically electrodeposited films of ZnO by reduction of dissolved oxygen in a non-aqueous solution (dimethylsulfoxide) containing a Zn salt. This method allows a large deposition potential window and gives films with high transparency, good crystallinity and adherence. The ZnO was electrodeposited on Cu(In,Ga)Se-2 as a buffer layer. The resulting solar cells gave higher light-to-electricity conversion efficiencies (> 11%) than those made with conventional r.f. sputtered insulating ZnO.