Abstract: A process for electrodepositing a thin layer of cadmium selenide on a suitable substrate is disclosed. The substrate is immersed in an electrolyte bath with pH ranging from 5 to 10 and having an aqueous solution of selenosulphite ions and cadmium ions complexed with nitrilotriacetic acid. The pH range shifts the chemical equilibrium of complexing the cadmium ions towards associated complexed cadmium ions. A voltage is applied to the cathode and anode in the electrolyte to reduce the selenosulphite ions to produce selenide ions at the cathode of a sufficient concentration which reacts with the complexed cadmium ions to electrodeposit thereby cadmium selenide on the cathode. The thin layer of cadmium selenide is particularly useful in a photoelectrochemical cell.