Cu2ZnSnS4 crystal growth using an SnCl2 based flux†
The stoichiometry and phase homogeneity of the kesterite type compound Cu2ZnSnS4 play a key role in its efficiency in solar cells. In this work, CuCl2, ZnCl2 and SnCl2 were applied as solvents in the Cu2ZnSnS4 crystal 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 SnCl2 presented a single-phase Zn-rich kesterite with composition Cu1.94Zn1.06SnS4 and unit cell parameters of a = 5.4324(3) and c = 10.8383(2) Å. The crystal structure of Cu1.94Zn1.06SnS4 was determined by single crystal X-ray diffraction analysis. The integral phase purity of the crystals grown with the use of the SnCl2 solvent was verified by powder X-ray diffraction analysis and Raman measurements. In the Raman spectrum, the FWHM value of the 337 cm−1 line was as low as 9.6 cm−1 that indicates the minimal lattice disorder.