Influence Of The Cdcl2 Solution Concentration On The Properties Of Cdte Thin Films

This work presents the influence of the concentration of CdCl2-treatment-solution on the microstructural, morphological, and optical properties of CdTe thin films The CdTe films were deposited on CdS coated borosilicate glass by Close-Spaced Sublimation (CSS) technique using a standard recipe. The CdS films were grown by RF magnetron sputtering. The deposited CdTe films were treated with CdC12 solution of 0.20 M, 0.25 M, 0.30 M, 0.35 M, and 0.40 M concentration at 395 degrees C for 25 minutes. All the films exhibit polycrystalline nature with a predominant (111) Bragg peak of cubic CdTe. The highest crystallite size and smallest micro-strain and dislocation density are found for the treatment solution of 0.35M concentration. The results present that the treatment concentration enhances the S diffusion into the CdTe layer up to a certain limit of molar concentration. The highest S concentration (similar to 2%) among the investigated samples is found for 0.35 M concentration. The SEM micrographs of the as-grown and treated films reveal that the grain size follows an increasing trend with the solution concentration up to 0.35 M. The optical bandgap of all samples is found to be in the range of 1.42 - 1.45 eV estimated from the UV-Vis-NIR transmission data. The lowest bandgap of 1.42 eV is found for the sample treated with 0.35 M solution due to the highest crystallinity among the samples investigated evident from both XRD and SEM results.