Facile synthesis and optical properties of pure and Ni2+, Co2+, Bi3+, Sb3+ substituted Cu3SnS4

Abstract

Cu₃SnS₄ in an orthorhombic symmetry has been stabilized by a simple and one pot synthesis involving the reaction of thiourea complexes of copper and tin. The obtained product has been characterized thoroughly using high resolution powder X-ray diffraction (PXRD), SEM-EDX, Raman, UV-vis-NIR, and photoluminescence spectroscopy measurements. The presence of bands at 282, 317, 333 and 346 cm⁻¹ in the Raman spectrum conclusively confirmed the orthorhombic symmetry of Cu₃SnS₄. Adopting this synthetic strategy, quaternary compositions consisting of nickel, cobalt, antimony and bismuth have been synthesized and characterized by all physico-chemical techniques. Of all these, compositions containing bismuth and antimony in place of tin are quite original and are reported for the first time. While the nickel substitution retained the orthorhombic symmetry, cobalt substitution resulted in tetragonal symmetry for the quaternary composition. Similarly, the presence of bismuth ions in the lattice preserved the orthorhombic symmetry and the PXRD pattern of the product containing Sb³⁺-ions could be indexed to tetragonal symmetry. The homogeneous distribution of all these elements in the samples was verified from a scanning TEM technique. The band gaps of the pure and Ni²⁺, Co²⁺, Bi³⁺ and Sb³⁺substituted Cu₃SnS₄ compositions, determined from the UV-vis-NIR absorbance data, were in the range of 0.9–1.46 eV. This is ideally suited for the use of these materials in photovoltaic cells.