STRUCTURAL, OPTICAL CONSTANTS AND ENERGY GAP TUNABILITY WHEN INCORPORATING Te INTO CdSe THIN FILM FOR SOLAR CELLS

In the present work, polycrystalline materials of CdSe1-xTex with (x = 0, 0.2, 0.4, 0.6, 0.8 and 1 at. %) were prepared by a conventional solid-state reaction method. Thin films of CdSe1-xTex of about 0.5 µm have been produced using evaporation method. The prepared thin films were characterized by using EDAX and X-ray diffractometer. The Xray diffraction studies shows that the films are polycrystalline in nature, and well oriented along a preferred direction of (002) for hexagonal and along (111) for cubic crystal structure. Both of optical constants (n, k) and film thickness have been determined precisely in terms of envelop method. Analysis of the optical absorption data showed that the transition mechanism takes place by a direct transition. The band gap decreases from 1.677 eV (CdSe) with an increase in Te concentration passing through a minimum of 1.412 eV for CdSe0.4Te0.6 (x = 0.6) and then for higher Te concentration band gap increases to 1.486 eV corresponds to pure CdTe. The importance of CdSe1-xTex compound is the tunability of band gap when incorporating Te into the CdSe. The dispersion of the refractive index is described using the Wimple–DiDomenico (WDD) single oscillator model. The non-linear refractive index has been discussed.