Effect of Volume of Zn2+ Solution on the Optical Properties of Spray-Deposited H.Sabdariffa(Zobo) Dye-Doped ZnS Thin Films

This work presents the successful deposition of H. Sabdariffa(Zobo) dye-doped ZnS thin films with different volumes of Zn2+ solutions on cleaned glass substrate slides using inexpensive chemical spray-pyrolysis technique with the substrates kept at a constant temperature of 200oC. The final spray solution for the growth of the films contained aqueous solutions of ZnSO4.7H2O, SC(NH2)2, and H.Sabdariffa dye extracts. ZnSO4.7H2O and SC(NH2)2 served as precursors for Zn2+ and S2- respectively while H.Sabdariffa was used as dye. The sprayed film properties were characterized for optical properties using a HINOTEK 756S UV-VIS spectrophotometer. From the absorbance’s spectral analysis, other optical parameters such as transmittance, reflectance, absorption coefficient, band gap energy and optical density were calculated. The films indicated high absorbance in the UV region and high transmittance in the VIS – NIR regions, whereas reflectance is generally low. The films indicated direct band gap energy range of 2.10eV to 2.62eV. The optical density indicated range of 0.5 to 6.16. Based on relatively low reflection, strong absorption in UV region, high transmission and wide band gap indicated by the films. Therefore, it can be concluded that the films are suitable for the fabrication of solar cells. Also, the films are good for anti-dazzling coatings and thermal control coatings in automotive and architectural industries respectively.