Influence of calcination on the structural properties of earth abundant Cu2ZnSnS4

Abstract

In the present work, we report on the synthesis of nano-crystalline kesterite copper zinc tin sulfide (CZTS) in powder form and the post-annealing process at high temperatures (calcination), and study their physical properties. We have successfully synthesized CZTS by direct fusion, and the resulting material was crushed to obtain a fine powder. Then, the resulting powder was calcined at high temperatures: 800–1000 ∘C. The calcined samples have been characterized with a number of different structural: X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and optical techniques: photoluminescence (PL), Raman and diffuse reflectance spectroscopy (DRS). From the XRD analysis we grant that the material presents mainly the kesterite structure and it is polycrystalline, with a preferential orientation along the [112] direction. From XRD, SEM, EDX and Raman spectroscopy, we conclude that the best crystallinity and stoichiometry was obtained for a calcination temperature of 900 ∘C. From te PL and DRS results we deduce that the sample with smaller emission and an energy gap close to 1.5 is that calcined at 900∘. In summary, we can confirm from the present study made with a number structural and optical techniques, that the CZTS has grown in the kesterite structure and the sample calcined at 900∘C has the best crystallinity and the optimum band gap to be used as an absorber in solar cell devices.