Band gap tunable and improved microstructure characteristics of Cu2ZnSn(S1-x,Sex)4 thin films by annealing under atmosphere containing S and Se

Cu2ZnSn(SxS1-x)(4) (CZTSSe) thin films were prepared by annealing a stacked precursor prepared on Mo coated glass substrates by the sputtering technique. The stacked precursor thin films were prepared from Cu, SnS2, and ZnS targets at room temperature with stacking orders of Cu/SnS2/ZnS. The stacked precursor thin films were annealed using a tubular two zone furnace system under a mixed N-2 (95%) + H2S (5%) + Se vaporization atmosphere at 580 degrees C for 2 h. The effects of different Se vaporization temperature from 250 degrees C to 500 degrees C on the structural, morphological, chemical, and optical properties of the CZTSSe thin films were investigated. X-ray diffraction patterns, Raman spectroscopy, and X-ray photoelectron spectroscopy results showed that the annealed thin films had a single kesterite crystal structure without a secondary phase. The 2 theta angle position for the peaks from the (112) plane in the annealed thin films decreased with increasing Se vaporization temperature. Energy dispersive X-ray results showed that the presence of Se in annealed thin films increased from 0 at% to 42.7 at% with increasing Se vaporization temperatures. UV-VIS spectroscopy results showed that the absorption coefficient of all the annealed thin films was over 10(4) cm(-1) and that the optical band gap energy decreased from 1.5 eV to 1.05 eV with increasing Se vaporization temperature. (C) 2013 Elsevier B. V. All rights reserved.