Effect of calcination on the structural, morphological and optical properties of earth abundant Cu2FeSnS4 powders prepared by solid-state reaction

In this paper, we investigate the effect of calcination on the properties of Cu2FeSnS4 (CFTS) prepared by solidstate reaction. As fabricated, the polycrystalline sample was crushed and the powders was calcined at different temperatures (TC = 800, 900 and 1000 degrees C). A Rietveld analysis shows that the calcined powders have predominately the stannite phase with a nearly stoichiometric composition, with the presence of a small amount of SnS, supported by Raman scattering. Energy dispersive spectroscopy confirms the homogeneity of the CFTS materials. Moreover, the analysis of the surfaces of CFTS pellets using scanning electron microscopy showed a more compact and dense morphology as the calcination temperature increases, thus enhanced photosensitivity. From optical studies, we found that the bandgap energy decreases from 1.40 to 1.18 eV with increasing calcination temperature. Calcination can be a tool to engineer the optical band gap.