Effects of annealing on elemental composition and quality of CZTSSe thin films obtained by spray pyrolysis

Abstract

The spray pyrolysis was used for the deposition of Cu₂ZnSn(S, Se)₄ (CZTSSe) kesterite thin films. The basic spray pyrolysis solution was prepared from two precursor solutions containing thiourea and cooled to a temperature near 1°C, which leads to minimizing the number of insoluble hydrates of copper chloride. The optimal substrate temperature was 350°C and the distance from the sprayer nozzle 30 cm. The as-deposited Cu₂ZnSnS₄ layers were annealed in S₂ atmosphere for the compensation of the sulfur deficiency and with the addition of Sn in order to avoid tin loss. Cu₂ZnSn(S, Se)₄ thin films were obtained after the annealing of as-deposited films in the (S₂ + Se₂) atmosphere. The surface morphology and composition of obtained thin films were investigated using the energy dispersive X-ray (EDX) microanalysis and Raman spectroscopy measurements. The structural characterization by the grazing incidence X-ray diffraction (GIXRD) showed the presence of Cu_2–xS phases in all of the annealed thin films. For the Se/(S + Se) ratio of the thin films annealed in the (S + Se) atmosphere was established from EDX measurements and analysis of GIXRD data, the results are in satisfactory agreement.