Preparation Of Cu₂ZnSnS₄Thin Films By Paste Coating

Cu2ZnSnS4is one of the most promising absorber materials for thin film solar cells because of its direct band gap (1.5eV) at room temperature being close to the ideal band gap, and high optical absorption coefficient (104cm-1) for considerable conversion efficiency. In this paper, Cu2ZnSnS4thin films were prepared by paste coating. Precursor pastes were obtained by milling CuS, SnS, and ZnS. Cu2ZnSnS4thin films were successfully prepared by annealing precursor layers in an Ar atmosphere, which were coated on glass substrates using these pastes. The Cu2ZnSnS4films were characterized by Laser particle size analyzer, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and UV-vis spectrophotometer. The effects of different ratios and annealing temperatures on Cu2ZnSnS4thin films were also investigated.The results show that the Cu2ZnSnS4thin films with the ratio of Zn/Sn=1.17and Cu/(Zn+Sn)=0.96and annealing at450℃demonstrate a typical kesterite structure, preferred orientation along the (112) plane, with1.3×104cm-1of the absorption coefficient and possessing1.37eV optical band gap. The study also illustrates that the crystallization of the film becoming better, the optical band gap of the film becoming smaller and the absorption coefficient of the film becomes larger with the annealing temperature heating up.