Characteristic Of CdTe Polycrystalline Thin Films And Study Of CdS/CdTe Interface

The pure and Dy-doped CdTe thin films are prepared by vacuum evaporation on substrates of CdS thin films and glasses. The characteristics of samples are tested by X-ray diffraction、Atomic Force Microscopy、X-ray photoelectron spectrograph、 Ultraviolet-Visible spectrophotometer and Scanning Electron Microscopy. According to the results, the effects of heat temperature、Cl-treaded、Dy-doped and substrates to CdTe thin films has been studied systematically, the changing of CdS/CdTe interface has also been explored.The experimental results show that the best condition of heat treatment is20min at375℃.After treating the thin films are cube sphalerite structural CdTe with [111] preferred orientation, the lattice constant of CdTe thin films are6.4688A. The optical bandgap is1.510eV.Experiment find that the crystalline structure of CdTe thin films do not change after doping, but make the XRD results more identical with the standard PDF card. Dy doping increase the lattice constant,crystal cell volume of CdTe thin films, and reduce the average grain size. There are less CdO and TeO2in Dy-doped CdTe thin films, Dy doping restrain the combination of CdO and TeO2and make the thin films approach standard chemical ratio. The optical bandgap of Dy-doped CdTe thin films increase to1.516eV.After Cl-treated the crystalline structure of CdTe thin films are still cube sphalerite structure with [111] preferred orientation. C1-treated let the lattice constant,crystal cell volume and average grain size decrease. Meanwhile Cl-treated make the surface of CdTe thin films more flat, and have better grain size uniformity. There is a few of Cl in CdTe thin films after Cl-treated and make the thin films approach standard chemical ratio. Dy-doped increase the optical absorption in visible wavelengths, widen the absorption spectra, decrease the optical bandgap and make that better for the solar cell.CdTe thin films on CdS substrates has stronger [111] preferred orientation. Higher substrate temperature and Cl-treated can boost the diffuses between CdS and CdTe thin films. At the same time, the CdTe thin films on CdS substrates strengthened optical absorption in near-infrared wavelengths.