Synthesis of Cu2ZnSnS4 thin film absorbers by sulfurizing dip-coated precursors

Cu2ZnSnS4 (CZTS) thin films, a potential candidate for the absorber layers of solar cells, were successfully deposited on soda lime glass substrates by sulfurizing dip-coated precursors. This is a simple and low-cost process. In this method, the precursor films were obtained by several cycles of dipping and air-jet cutting to rinse the film and make it flat, followed by drying at 200 ο C for 15 minutes. The solutions that were used in the dipping process contained copper (II) acetate monohydrate, zinc (II) acetate dehydrate, tin (II) chloride dehydrate and thiourea, dissolved in a solution of water and ethanol (30% vol). By sulfurizing the precursors in Ar + H2S (5%) gas to prevent oxidation, a CZTS single phase can be obtained with a ratio of Cu/[Zn + Sn] = 0.89, Zn/Sn = 1.03 and S/metal = 1.01. The films had a band gap of about 1.5 eV and the absorption coefficient was higher than 10 4 cm -1 . The electrical properties of the films were shown to be p-type semiconductors with a carrier concentration of 10 18 cm -3 . The films can be applied as the absorber layers in solar cells.