Structural, optical and photoelectrochemical properties of screen-printed and sintered (CdS) x(ZnS) 1− x (0< x<1) films

Sulfides of zinc and cadmium have been used effectively in various optolectronic devices and recently as photocatalysts in the production of molecular hydrogen in photoelectrochemical processes. We have prepared sintered CdZnS films by the screen printing method without the presence of the typical flux material. The formation of crystalline ternary compounds is inferred from the X-ray diffraction pattern of these films. Their structural and optical properties are studied by reflection spectra in a wavelength range of 300–600 nm. The films have a direct band gap, which varies from 3.7 eV for zinc sulfide to 2.45 eV for cadmium sulfide. Films with a narrow range of composition were found to be stable in Na 2SO 3 solution under cathodic or anodic polarization in dark and illuminated conditions. This potential interval allowed to determine the flat band potentials from capacity measurements in the dark, which indicated strong contribution of double layer capacitance, surfaces states, and non-uniform doping concentration. Electrochemical impedance measurements where further performed, giving detailed information about the relevance of these factors and the optimum composition of coupled semiconductor films for photocatalytic purposes.