Low Temperature Synthesized Quaternary Chalcogenide Cu2ZnSnS4 from Nano-Crystallite Binary Sulfides

The quaternary chalcogenide Cu2ZnSnS4 (CZTS) is known to be a potential cost-effective absorber material in solar cells. In this study, CZTS has been successfully synthesized by low temperature annealing of binary sulfides of CuS, ZnS and SnS nano-crystallites which were produced by a simple chemical bath deposition technique. The achieved formation temperature of CZTS was 300 degrees C, which was significantly lower than reported values. The formation of CZTS was investigated through characterization techniques - x-ray diffraction (XRD), Raman spectroscopy and elemental mapping in scanning transmission electron microscopy (STEM). Sample annealing was performed in a Quartz tube under 1.0 x 10(-2) Torr without using the traditional toxic, corrosive and flammable H2S gas. Significant improvement in CZTS crystallinity was achieved through annealing at temperatures up to 450 degrees C. However, traces of Cu2S in CZTS were found after annealing at 500 degrees C. The optical and electrical properties of CZTS were also investigated. The CZTS sample showed a direct band gap of 1.47 eV, p-type conduction and a resistivity of 1.06 Omega.cm. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3598168] All rights reserved.