Effect of growth techniques on the properties of CdTe thin films for photovoltaic application

Cadmium Telluride thin films have been deposited on FTO coated glass substrates by using the sputtering and thermal evaporation technique. CdTe thin film was firstly grown by sputtering at a substrate temperature 300°C, as well as CdTe thin film was also deposited by thermal evaporation technique. The grown films from both processes were annealed in a vacuum furnace of nitrogen ambient at pressure 250-300 mTorr. A comparative study of structural and optical properties and surface morphology analysis of these films was carried out by means of XRD, AFM and UV-Vis spectrometry. The XRD patterns reveal that the grown films in both processes are crystalline in nature having the (111) preferential orientation around 2θ=23.8°. Surface roughness and topography were observed from the AFM images. The sputtered grown CdTe thin films exhibit higher values of average and root mean square of the roughness (RMS) as it was observed by AFM analysis. The transmission and absorption spectra was analyzed for wavelengths range of 350 nm to 1100 nm. From the UV analysis, it is observed that the films are very suitable for photovoltaic applications because it allows passing 80% along the whole range. The band gap has been found 1.49 eV and 1.41 eV for the films deposited from sputtering and thermal evaporation, respectively.