Cu₂ZnSn(S,Se)₄ absorber layer formation and characterization using solution dip coating and selenization method

In the present study, Cu 2 ZnSn(S,Se) 4 popularly known as CZTSSe (Copper Zinc Tin Sulfo-Selenide) film is prepared from the low cost, nontoxic solution by mixing of CuCl 2 (Copper Chloride), ZnS(Zinc Sulfide), SnCl 2 (Tin Chloride), thioacetamide in ethylene glycol to form a precursor solution. Here, we have used for the first time the ZnS compound as a zinc source in place of conventional ZnCl 2 as its binding energy with other constituents is more. The results imply that high quality of CZTSSe film could be feasible by infusing selenium during annealing of the film in selenium atmosphere in the temperature range of 500 °C−520 °C. The formed film shows perfect kesterite structure with a balanced interplanar spacing at the above-mentioned environment. The one-step annealing with selenisation of the as-deposited film shows improved crystallite size, microstrain, and lattice parameters. From the compositional analysis results, the infusion of selenium on annealing at high temperature shows the decrease in Cu/(Zn + Sn) ratio and an increase in Zn/Sn ratio as compared to as-deposited films confirming the required stoichiometric ratio for photovoltaic applications. The SEM image confirms the formation of a compact regular surface when the film is subjected to the annealing process. The bandgap of the film was calculated from UV–vis spectrophotometer and there is an increase in conductivity and mobility of the annealed absorber layer is found from the Hall measurement system.