Influence of cadmium precursor concentration on the material and electronic properties of electrochemically grown cadmium telluride

The structural, optical, morphological, compositional and electronic properties of a two-electrode electroplated cadmium telluride (CdTe) deposited from electrolytic baths with different Cd-precursor concentrations was investigated. The XRD shows the formation of dominant cubic (111) CdTe at 2θ = ~24.0°. The presence of hexagonal (101)Te was observed for the as-deposited layer grown from the 0.5 M Cd-precursor electrolyte. Improvement in the crystallite size, micro-strain and dislocation density was recorded with increasing Cd-precursor which peaks at 1.5 M Cd-precursor concentration. Further improvement was also recorded after CdCl₂ post-growth treatment. The bandgap energy of the films increased from (1.20 to 1.52) eV with an increase in the Cd-precursor concentration. The energy bandgap of the films tend towards the ideal bulk CdTe bandgap of 1.45 eV after CdCl₂-treatment. Topologically, the SEM micrographs reveal that beyond 0.5 M Cd-precursor concentration, the underlying substrate becomes fully covered with CdTe thin-films and the formation of curly floral-like agglomerations is exhibited. The electrical properties of the deposited CdTe thin films were correlated to the Cd-precursor concentration, as a transition from p-type to n-type electrical conduction were recorded with increasing Cd-precursor concentration from 0.5 M.