Synthesis and study of structure and phase composition in Cu_2–xS, Sn_xS_y, ZnS, Cu_xSnS_y and CuZnSnS pellets

Abstract

Synthesis of pure single-phase Cu₂ZnSnS₄ (CZTS) has attracted much attention of some laboratories and investigation centers around the world. This is important in order to eliminate secondary phases which are detrimental to the final conversion efficiency of the CZTS solar cells. Pseudo-ternary phase diagram showed the formation of pure CZTS using the mixture of Cu₂S, SnS₂ and ZnS binary sulfides; nevertheless, the gap is very narrow. An additional problem lies in the effective determination of the CZTS purity, because some secondary phases display similar X-ray diffraction and Raman spectra as those of CZTS. The present work addresses a simple, fast and economical synthesis method for the preparation of some binary, ternary and CZTS pellets, which were prepared from their corresponding co-precipitated powders. These tablets can be used not only as a sputtering target but also as a precursor in a solid-state reaction. Among the various prepared compounds, Cu_2−xS–Sn_xS_y–ZnS and Cu_xSnS_y are included and characterized to identify their presence in the CZTS pellets. From the obtained results, the usefulness of co-precipitation as a method to produce highly pure single-phase CZTS is discussed.