Structural, optical and electrical properties of Cu2ZnSnS4 films prepared from a non-toxic DMSO-based sol-gel and synthesized in low vacuum

This paper reports a complex analysis of structural, optical and electrical properties of Cu2ZnSnS4 (CZTS) films, prepared by spin-coating of a sol-gel based on the low-cost and environmentally friendly solvent dimethyl sulfoxide (DMSO) and synthesized in low vacuum (0.1 Pa). The effect of a short-term low-temperature treatment in air and final annealing under low vacuum (0.1 Pa) on the synthesis of CZTS films was tested and analyzed. XRD and Raman spectra have shown the polycrystalline nature of obtained CZTS films with almost a pure kesterite phase content. The average size of crystallites D~60 nm in the films was estimated. The value of the band gap Eg≈1.53 eV was determined from the analysis of optical characteristics. The analysis of electrical characteristics was carried out in the scope of the model of current transport in polycrystalline materials with electrically active grain boundaries. The determined values of the specific resistance ρ≈2.38 Ω cm, the hole density p0≈4.2×1018 cm−3 and the effective mobility μp≈0.63 cm2/(V s) demonstrate that the CZTS films under investigation are prospective for the fabrication of highly efficient solar cells.