Characterization of CuInS2 Films Prepared by Electroplating and Sulfurization

Abstract

As a ternary compound, CuInS2 with band gap about 1.5 eV, has chalcopyrite crystal structure, high absorption coefficient and low toxicity of sulfur, therefore, CuInS2 is a promising absorbing layer used in solar cells with thin films. Electroplating method has many advantages of low cost and easy operation etc. CuInS2 precursor samples were prepared by electroplating with raw materials of CuCl2·2H2O, InCl3 and Na2S2O3·5H2O etc., and the precursor films were heat treated in sulfur atmosphere. The phases of product samples were determined by X-ray diffraction (XRD) and the surface morphology was observed by scanning electron microscopy (SEM), and the elemental content of the film was analyzed by energy dispersive spectroscopy (EDS). Results show that uniform and dense CuInS2 precursor films can be obtained under conditions of CuCl2·2H2O, InCl3, Na2S2O3·5H2O and C6H5Na3O7·2H2O with contents of 10 mmol/L, 10 mmol/L, 100 mmol/L and 1.25 mmol/L respectively, pH 3.5 and deposition potential –1.0 V. CuInS2 film with good crystallinity was obtained by sulfurizing precursor film at 350 oC for 6h, has different XRD peaks for (112), (024/220) and (116/132) crystal planes respectively. Many lumps with uniform size are found, and there are little holes distributing on the surface after heat treatment. The precursor and sulfurized films were all found containing copper, indium and sulfur elements. It is found that the sulfur content in the films was obviously increased after sulfurizing.