Effect of dye extracts on the optical properties of chemically deposited ZnS thin films

الملخص EN

The study reports on the influence of dye extracts of Naulcea latifolia (Uvuru-ilu) leaves on the optical properties of Zinc Sulphide (ZnS) thin films grown by the chemical bath deposition method.

The concentration of the ZnS thin films were varied in the range 0.1 M to 0.7 M and other deposition variables (pH, and bath temperature) were kept constant.

The films were characterised using optical spectroscopy (transmittance versus wavelength, reflectance versus wavelength, absorbance versus wavelength) to investigate the optical constants (optical absorption coefficient, energy bandgap, extinction coefficient and the optical density).

The results show that the transmittances of the dye –sensitized films were higher compared to the as-deposited layers.

The transmittance exhibited a concentration dependent behaviour for films grown without addition of the dye extracts.

The transmittance were typically < 50 % for the non dye-sensitized ZnS thin films grown at concentrations ≤ 0.3 M and > 50 % for films grown at concentrations ≥ 0.5 M.

However the presence of the dye extracts increased the transmittances significantly, independent of the different concentrations used.

The energy bandgap was direct, with values ≤ 3.60 eV for films grown at concentrations ≥ 0.5 M and 3.80 eV for films grown at lower concentrations.

These values strongly suggest the use of these films in optoelectronic applications and related device designs.