H₂S Concentration Dependence of Properties of Cu₂ZnSnS₄ Thin Film Prepared under Nonvacuum Condition

Cu₂ZnSnS₄ (CZTS) thin films were prepared by a sol–gel sulfurization method. Sulfurization was carried out in H₂S of various concentrations and the properties of the films were investigated. The CZTS thin films sulfurized at 500 °C for 1 h in 0.5 and 3% H₂S atmospheres had large grains compared with the film sulfurized in 1% H₂S atmosphere. From the X-ray diffraction analysis, the CZTS thin film sulfurized for 1 h in 0.5% H₂S atmosphere included a small amount of Cu_xS as a secondary phase. The films sulfurized for 1 h in 1 and 3% H₂S atmospheres were composed of a CZTS phase without Cu_xS. Owing to the long sulfurization process, the Cu_xS phase was eliminated and the optical properties of the films were improved. The size of the grains sulfurized in 1% H₂S increased with increasing sulfurization time from 2 to 3 h.