Morphology and photoelectrochemical behaviour of CdSe/ZnO composites obtained by the screen printing technique

Abstract

We report the morphology and photoelectrochemical (PEC) behaviour of CdSe/ZnO composite coatings prepared by the screen-printing and sintering technique. Precipitates of two different chemical baths were used for the screen-printing process. Atomic force microscopy images show that the topography of the composite coatings depends on the precipitate. Superior PEC performance and stability are obtained for the composite based on the precipitate of a dimethyl selenourea bath, which has a well formed polycrystalline surface with a narrow distribution of cluster sizes. The lower diffuse reflectance and smoother topography of these coatings, when compared to the composite based on the precipitate of a selenosulphate bath, can be correlated to larger values of photocurrent. Under short circuit conditions, photocurrent oscillations were observed in the stability curves of fresh specimens, in both composites. They are attributed to the complex solution chemistry of Zn compounds, formed during the sintering step by incomplete oxidation and thermal decomposition of the flux. The hexagonal character of CdSe, enhanced in the precipitate of the dimethyl selenourea bath, is expected to have an important role in determining the quality of the composite coating and its PEC performance.