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

We report the morphology and photoelectrochemical (PEC) behaviour of CdSe/Z nO composite coatings prepared by the screen-printing and sintering techniq ue. Precipitates of two different chemical baths were used for the screen-p rinting process. Atomic force microscopy images show that the topography of the composite coatings depends on the precipitate. Superior PEC performanc e 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 lar ger values of photocurrent. Under short circuit conditions, photocurrent os cillations were observed in the stability curves of fresh specimens, in bot h composites. They are attributed to the complex solution chemistry of Zn c ompounds, formed during the sintering step by incomplete oxidation and ther mal decomposition of the ZnCl2 flux. The hexagonal character of CdSe, enhan ced 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.