Fluorine-induced improvement of structural and optical properties of CdTe thin films for solar cell efficiency enhancement

CdTe thin films of different thicknesses were electrodeposited and annealed in air after different chemical treatments to study the effects of thickness and the different chemical treatments on these films for photovoltaic applications. The thicknesses of the samples range from 1.1 to 2.1 μm and the annealing process was carried out after prior CdCl₂ treatment and CdCl₂ + CdF₂ treatment as well as without any chemical treatment. Detailed optical and structural characterisation of the as-deposited and annealed CdTe thin films using UV–Vis spectrophotometry and X-ray diffraction reveal that incorporating fluorine in the well-known CdCl₂ treatment of CdTe produces remarkable improvement in the optical and structural properties of the materials. This CdCl₂ + CdF₂ treatment produced solar cell with efficiency of 8.3% compared to CdCl₂ treatment, with efficiency of 3.3%. The results reveal an alternative method of post-deposition chemical treatment of CdTe which can lead to the production of CdTe-based solar cells with enhanced photovoltaic conversion efficiencies compared to the use of only CdCl₂.