XRD STUDY OF COPPER-TIN SULPHIDE FILMS ON FTO GLASS

Various tin sulfides are chalcogenide semiconductor materials that have attracted great interest due to their abundant, inexpensive, and non-toxic elements, as well as their suitable optical and electrical properties for use as photovoltaic absorbers [1]. The ternary Cu-Sn-S system includes stable compounds such as Cu₂SnS₃, Cu₃SnS₄, and Cu₄SnS₄ [1]. Cu₂SnS₃ is the most studied compound in this system and has been successfully applied in thin-film solar cells. Additionally, Cu₄SnS₄ has demonstrated photovoltaic properties in thin-film devices with an efficiency of 2.34% [1]. The aim of this work was to synthesize copper-tin sulphide films on FTO glass by sequential ion adsorption and reaction (SILAR) method and characterize the films using XRD analysis. For the deposition of tin sulphide films, each sample was prepared in the following steps: firstly, the cleaned FTO substrate was immersed into a cationic precursor (0.1 M SnCl₂ and citric acid solution) for 30s and the tin ions on the top of the substrate were adsorbed, secondly, a sample was immersed in an anionic precursor (0.1 M Na₂S solution) for 30s. During this step sulphide ions react with tin ions adsorbed on the top and form tin sulphide films. To remove loosely bound ions, the samples were washed in distilled water for 20s after immersions in the cationic and anionic precursors. In this study 20, 30,40 SILAR cycles were carried out. Then the samples were modified with solutions (0.1 M) of copper (II) and copper (II/I) ions, carried out with solutions of copper (II) sulphate or copper(II) sulphate with hydroquinone, for different durations (10; 20; 30 minutes). Then, the samples were annealed at 200 °C to increase the crystallinity of obtained films. X-ray diffraction analysis of the copper-tin sulphide films on the FTO glass slides was carried out using a Bruker AXS D8 Advance X-ray diffractometer. The X-ray diffractograms of the films were analysed using the Search Match software package. X-ray diffraction analysis identified SnS, Sn₂S₃, Sn₃S₄, anilite, djurleite, digenite and mixed copper tin sulphide phases Cu₄SnS₄ and Cu₂Sn₃S₈. From the RSDA analysis it can be concluded that the number of cycles, the duration of treatment with copper (II) salt solution and the use of hydroquinone, and annealing temperature affects the deposited layers.