Single phase polycrystalline Cu2ZnSnS4 grown by vertical gradient freeze technique

Abstract We report on the growth of high quality single phase Cu 2 ZnSnS 4 (CZTS) solar absorber material grown by the vertical gradient freeze (VGF) method for the first time. Polycrystalline CZTS ingot was grown in a vacuum sealed quartz ampoule. Structural and compositional analysis of the grown ingot was carried out by X-ray diffraction (XRD), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). XRD pattern revealed a highly crystalline tetragonal structure with lattice parameters of a =5.429 A and c =10.847 A corresponding to kesterite CZTS crystal. Raman spectra confirmed the existence of single phase CZTS without any secondary phases. Energy dispersive X-ray spectroscopy (EDS) and EDS mapping were performed over a large area of the ingot to evaluate the elemental distribution on multiple polycrystals. The grown crystal was nearly stoichiometric with an atomic ratio of Zn/Sn=1.03 and Cu/(Zn+Sn)=0.964. EDS mapping showed a uniform elemental distribution over the polycrystals and a slight Cu-rich and Zn-poor composition at the grain boundaries.