Electro-Plating and Characterisation of CdTe Thin Films Using CdCl2 as the Cadmium Source

Cadmium telluride ( CdTe) thin films have been successfully prepared from an aqueous electrolyte bath containing cadmium chloride ( CdCl2) center dot H2O and tellurium dioxide ( TeO2) using an electrodeposition technique. The structural, electrical, morphological and optical properties of these thin films have been characterised using X-ray diffraction ( XRD), Raman spectroscopy, optical profilometry, DC current- voltage ( I- V) measurements, photoelectrochemical ( PEC) cell measurement, scanning electron microscopy ( SEM), atomic force microscopy ( AFM) and UV- Vis spectrophotometry. It is observed that the best cathodic potential is 698 mV with respect to standard calomel electrode ( SCE) in a three electrode system. Structural analysis using XRD shows polycrystalline crystal structure in the as- deposited CdTe thin films and the peaks intensity increase after CdCl2 treatment. PEC cell measurements show the possibility of growing p-, i- and n- type CdTe layers by varying the growth potential during electrodeposition. The electrical resistivity of the as- deposited layers are in the order of 104 Omega center dot cm. SEM and AFM show that the CdCl2 treated samples are more roughness and have larger grain size when compared to CdTe grown by CdSO4 precursor. Results obtained from the optical absorption reveal that the bandgap of as- deposited CdTe ( 1.48- 1.52) eV reduce to ( 1.45- 1.49) eV after CdCl2 treatment. Full characterisation of this material is providing new information on crucial CdCl2 treatment of CdTe thin films due to its built-in CdCl2 treatment during the material growth. The work is progressing to fabricate solar cells with this material and compare with CdTe thin films grown by conventional sulphate precursors.