The effect of CO32- on the structural and optical properties of CdS thin films prepared by chemical bath deposition

The objective of the present study is to provide the effect of immersion time and CO32- concentration on the structural and optical properties of CdS films. Chemical bath deposition was performed to prepare two sets of samples using two different solutions. The first set was prepared using a mixture of cadmium carbonate CdCO3, thiourea, ammonia, distilled water, and a few drops of dilute sulphuric acid. The obtained solution was milky due to the partial dissociation of cadmium carbonate. For the second set, the solution contains the same chemical composition with the difference in the amount of added acid to turn the chemical solution clear and transparent. Hexagonal CdS film structures were obtained with (002) preferred orientation for the first set of samples. The transmittance in the visible domain is between 76 and 92%, and the values of the gap energy are between 2.43 and 2.59 eV according to the deposition time. For the second set, the obtained CdS films have a cubic structure with (111) preferential orientation. The transmittance of the films was found to be between 38 and 80%, and the bandgap energy increased with immersion time from 2.18 to 2.32 eV.