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

The quaternary chalcogenide Cu 2 ZnSnS 4 (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 °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 × 10 −2 Torr without using the traditional toxic, corrosive and flammable H 2 S gas. Significant improvement in CZTS crystallinity was achieved through annealing at temperatures up to 450°C. However, traces of Cu 2 S in CZTS were found after annealing at 500 °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 Ω·cm.