Cu₂ZnSnS₄crystal growth using an SnCl₂based flux

The stoichiometry and phase homogeneity of the kesterite type compound Cu₂ZnSnS₄play a key role in its efficiency in solar cells. In this work, CuCl₂, ZnCl₂and SnCl₂were applied as solvents in the Cu₂ZnSnS₄crystal growth for the first time. The multiphase ingot was obtained by direct fusion of the stoichiometric batch composed of constituent elements. Compared to that, the material recrystallized in SnCl₂presented a single-phase Zn-rich kesterite with composition Cu_1.94Zn_1.06SnS₄and unit cell parameters ofa= 5.4324(3) andc= 10.8383(2) Å. The crystal structure of Cu_1.94Zn_1.06SnS₄was determined by single crystal X-ray diffraction analysis. The integral phase purity of the crystals grown with the use of the SnCl₂solvent was verified by powder X-ray diffraction analysis and Raman measurements. In the Raman spectrum, the FWHM value of the 337 cm⁻¹line was as low as 9.6 cm⁻¹that indicates the minimal lattice disorder.