Influence of cadmium precursor concentration on the material and electronic properties of electrochemically grown cadmium telluride
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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.
The main author would like to thank the Materials and Engineering Research Institute (MERI), Sheffield Hallam University (SHU), UK, for the facilities made available for the work reported in this paper. The authors would like to acknowledge Prof. Dharmadasa and other members of the SHU Solar Energy Group for their contributions. The main author wishes to also thank Ekiti State University (EKSU), Ado Ekiti, Nigeria, for their support.
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