Synthesis, characterization, and photoelectrochemical study of Cd1−xZnxS solid solution thin films deposited by spray pyrolysis for water splitting

A series of Cd1−xZnxS thin films were deposited onto indium-doped tin oxide (ITO) coated glass substrates by ultrasonic spray pyrolysis CdCl2, ZnCl2, and CS(NH2)2 aqueous solutions. The XRD patterns revealed that these films processed a wurtzite structure and a series of solid solutions of CdS and ZnS formed. The lattice constants decreased as the x value increased. From the transmittance and reflectance, the optical band gap was estimated to be between 2.45 eV and 3.72 eV, and the band gap increased as the x value increased according to a near linear relationship with the x value. The Mott-Schottky tests revealed that the flat potential shifted negatively as the x value increased. The photo responses agreed with the optical absorption of these films quite well. The current–potential measurements under chopped Xe lamp light irradiation show that the CdS deposited at 300 °C had best photoresponse. Its photoelectrochemical efficiency was estimated to be about 0.95% under 0.73 V bias from two electrodes current–potential tests.