Improving the grain size of \(\text {Cu}_{2}\text {ZnSnS}_{4}\) thin films by annealing thermally evaporated Cu–ZnS–Sn–S precursors

In this study, \(\text {Cu}_{2}\text {ZnSnS}_{4}\) (CZTS) thin films were grown on Mo-coated glass substrates by thermal evaporation of the precursor layers followed by annealing in a graphite box. The effect of annealing on the grain growth and morphology of the CZTS thin films was investigated at two different temperatures and \(\text {S}_{2}\) partial pressures. X-ray diffraction and Raman spectroscopy analyses confirmed the formation of CZTS films with a kesterite structure with (112) preferred orientation. The grain growth was significantly enhanced by annealing the stacks at \(550\,^\circ {\text{C}}\) for 30 min at a \(\text {S}_{2}\) partial pressure of \(1.2 \times 10^{4}\,\text{Pa}\). The grain size was found to be in the range of \(1.0{-}2.0\,\upmu \text {m}\). The same grain size was obtained by carrying out the annealing at \(580\,^\circ {\text{C}}\) and a \(\text {S}_{2}\) partial pressure of \(1.96 \times 10^{4}\,\text{Pa}\) just for 10 min. This grain size was much larger than the grain size of CZTS films obtained from annealing the stacks in two-zone tubular furnaces.