Sn/Cu/ZnS precursor were deposited by evaporation on soda lime glass at room temperature,and then polycrystalline thin films of Cu2ZnSnS4（CZTS） were produced by sulfurizing the precursors in a sulfur atmosphere at a temperature of 550℃for 3 h.Fabricated CZTS thin films were characterized by X-ray diffraction,energy dispersive X-ray spectroscopy,ultraviolet-visible-near infrared spectrophotometry,the Hall effect system,and 3D optical microscopy.The experimental results show that,when the ratios of[Cu]/（[Zn]+[Sn]） and[Zn]/[Sn]in the CZTS are 0.83 and 1.15,the CZTS thin films possess an absorption coefficient of larger than 4.0 x 104 cm-1 in the energy range 1.5-3.5 eV,and a direct band gap of about 1.47 eV.The carrier concentration,resistivity and mobility of the CZTS film are 6.98 x 1016 cm-3,6.96Ω-cm,and 12.9 cm2/（V-s）,respectively and the conduction type is p-type.Therefore,the CZTS thin films are suitable for absorption layers of solar cells.
Ag- and Sn-doped In2S3 thin films were deposited on glass substrates using the thermal evaporation technique. The doping was realized by thermal diffusion. The influences of Ag and Sn impurities on the electrical, structural, morphological, and optical properties of the In2S3 films were investigated. In all deposited samples, the x-ray diffraction spectra revealed the formation of cubic In2S3 phase. A significant increase in the crystallite size was observed after Ag doping,while the doping of Sn slightly decreased the crystallite size. The x-ray photoelectron spectroscopy verified the diffusion of Ag and Sn into the In2S3 films after annealing. The optical study illustrated that Ag doping resulted in a reduction of the optical band gap while Sn doping led to a widening of the gap. Optical properties were investigated to determine the optical constants. Besides, it was found that the resistivity decreases significantly either after Ag or Sn incorporation. The study demonstrates that the Sn-doped In2S3 thin films are more suitable for buffer layer application in solar cells than the Ag-doped In2S3 thin films.
