Discussion on the purity and the crystallization of CZTS compound

Cu2ZnSnS4 is a new material with low extraction cost. It belongs to Cu-Zn-Sn-S quaternary system and has recently attracted great attention as promising photovoltaic material. Due to its interesting properties such as a band-gap around 1.5 eV and a large absorption coefficient in the order of 104 cm−1. This compound is considered as ideal for effective phonon absorption and photo-generation. Since the sulfur is an important element in the stoichiometric composition, the effect of its content on the purity, the stability and the crystallization of this material has been taken in account. High purity Cu2ZnSnS4 single phase compound, with an excess sulfur starting concentration lying in the range 3-20 wt%, could be obtained. In these conditions, Cu2ZnSnS4 alloy has been synthesized and vertically well textured along the melt flow. Depending on the additional sulfur amount at the starting charge, it was possible to control both the solidification conditions and the morphology of Cu2ZnSnS4 phase. As a result, the solidification process allowed us to control the as grown crystal under stationary stable regime.