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Thin films of CdTe/CdS were prepared using the thermal evaporation technique with pressure 2 × 10−5 mbar on substrate from glass. The thickness of CdCl2 layer around 150 nm was deposited making as-deposited CdTe/CdS films. The films covered by cadmium chloride (CdCl2) layer were annealed in atmosphere of (O2 + Ar) at different temperatures of 400 °C, 450 °C and 480 °C for 15 min. The effect of CdCl2 as a top layer on morphological, structural and optical properties was studied, and the results were compared with as-deposited films and also with (O2 + Ar) annealing process. The refractive index in whole wavelength and film thickness was estimated by Cauchy dispersion relation and Swanepoel's envelope method, respectively. Furthermore, many optical parameters such as transmittance, absorbance, reflectance, and optical band gap, Urbach energy, film thickness, electronic polarizability, lattice dielectric constant were calculated also in this study. The heat treatment of our films with depositing CdCl2 layer in (O2 + Ar) flow lowered the energy gap which led CdTe/CdS films to be a candidate to work in thin-film solar cells as an absorber layer. [ABSTRACT FROM AUTHOR]

Abstract: Polymeric films composed of mixture of ethyl cellulose (EC) and hydroxypropyl cellulose (HPC) are prepared from casting combined solvent (methylene chloride and methanol in 1:1 ratio) containing 8% weight/volume of both polymers (EC to HPC in 1:3 weight ratio). The structural and optical studies of the films are carried out by X-ray diffraction and UV–vis spectrophotometer. The films are polycrystalline structure with an average grain size from 23.15 to 10.79nm. The possible optical transition in these films is found to be allowed direct transition. The optical band gap energy (E g ) is estimated to be 5.02eV for HPC–EC plain film and then decreases with increasing the filler content reaching to 4.24eV for the film filled with maximum Se80Te14Sn6 content of 1w%. This suggests that Se80Te14Sn6, as filler, is a good choice to control the optical properties of HPC–EC blend film. [Copyright &y& Elsevier]