Effect of H2S annealing for Sb-doped CuInS2 thin films prepared from ternary compound

Full text : Among ternary chalcopyrite semiconductors, CuInS2 may be the most promising material for photovoltaic applications due to the band gap energy of 1.53 eV, which perfectly matches the solar spectrum for energy conversion. Furthermore, since the material does not contain toxic Se atom, these may have an advantage in comparison with the frequently studied CuInSe2 and Cu(In,Ga)Se. In the previous papers, Sb-doped CuInS2 films have been prepared on glass substrates using the single-source thermal evaporation method, and the films were subsequently annealed from 250 to 500 degrees Celsium in air atmosphere. It is reported that the polycrystalline CuInS2 thin films were successfully grown at annealing of 400 degrees Celsium by X-ray diffraction (XRD) measurement and the CuInS2 thin films was stable for annealing at high temperature. In this paper, it is reported on effect of H2S annealing for Sb-doped CuInS2 thin films prepared by the single-source thermal evaporation method using Sbdoped CuInS2 powder. Cu-In-S thin films were deposited on glass substrates by the single-source thermal evaporation using Sb-doped ternary compound as starting materials. Polycrystalline Sb-doped CuInS2 powder that were grown at 700 degrees Celsium for 1 hour under high pressure at 25 MPa by HP method from the mixed Cu2S and In2S3 powders with Sb powder was employed as a starting material. After the evaporation, the films were annealed in H2S atmosphere from 250 to 500 degrees Celsium for 60 min. The thickness of the films was about 1.4∼2.0 μm. It has been shown that X-ray diffraction (XRD) patterns of the Sb-doped films annealed in H2S. XRD patterns indicated that these films appeared CuS phase with CuInS2 phase by annealing at 250 degrees Celsium as same as the undoped films. The composition ratios of Cu, In and S atoms of the Sb-doped films are close to stoichiometry at the lower temperature than those of the undoped films. The grain size of the crystals in the Sb-doped films annealed at 400 degrees Celsium is approximately 1.0 μm. The grain size of the crystals in the Sb-doped films becomes large with increasing the temperature