Study of the thermal decomposition of Cu2ZnSnS4 (CZTS) in different atmospheres: effect of annealing on its structural and optical properties

The objectives of this study were twofold: firstly, to study the thermal decomposition of Cu2ZnSnS4 (CZTS) in the air or inert atmosphere, and secondly, to study the impact on the structural and optical properties of pure CZTS nanoparticles annealing in an air atmosphere at temperatures of 300 and, 400 degrees C. CZTS nanoparticles were synthesized at 200 degrees C through a hydrothermal-microwave technique. CZTS nanoparticles were characterized by TGA, XRD, Raman, SEM, HR-TEM, and UV-Vis techniques to analyze decomposition temperature, crystalline structure, vibrational transitions, morphology, d-spaces, and optical properties, respectively. The assynthesized particles at 200 degrees C showed 6 nm size and were annealed at 300, 400, and 500 degrees C in an air atmosphere. TGA analysis shows CZTS nanoparticles remain stable inside the air atmosphere until 400 degrees C. However, this material is stable in the inert atmosphere until 600 degrees C. XRD pattern confirmed the decomposition of CZTS in an air atmosphere at 500 degrees C to Cu2S, SnO2, Zn(SO4), Cu(SO4), and Cu-2(SO4)O. CZTS nanoparticles were stable up to 400 degrees C, showing a better optical property in the crystal size and structure. The band gap value of CZTS nanoparticles decreases with the heat treatment, which gives a better advantage to light absorption in the visible range for better opto-electronic applications.