Study on the effects of different sulfur vaporization temperature on the properties of CuInS2 thin films

Abstract

CuInS2 (CIS) absorber thin films were prepared by sulfurization of In/Cu metallic stacked precursor. The precursor thin films were sulfurized using a commercial furnace system in the S-2 (s) + Ar atmosphere at 425 degrees C for 1 h. Effects of different S vapor temperature from 150 to 400 degrees C on the structural, morphological, compositional and optical properties of CIS thin films were investigated. X-ray diffraction and Raman studies showed that the sulfurized thin films with S vaporization temperature below 300 degrees C exhibited CIS tetragonal structure with secondary phases such as CuxSy, CuIn5S8, and InxSy. The sulfurized thin films with S vaporization temperature over 350 degrees C showed a single CIS tetragonal structure. Compositional ratio of CIS thin films showed that Cu/ In and S/(Cu + In) ratio in the CIS thin films with S vaporization temperature over 350 degrees C were 1.0-1.2 and 0.9-1.1, respectively, while compositional ratio deviated from stoichiometry when the sulfurized thin films below S vaporization temperature of 350 degrees C. Optical study showed that the band gap energy and the absorption coefficient of CIS thin films were estimated from 1.18 eV to 1.5 eV and over 10(4) cm(-1), respectively. (c) 2013 Elsevier B.V. All rights reserved.