Effect of Titanium Oxide (TiO₂) on Natural Dyes for the Fabrication of Dye-Sensitized Solar Cells

Abstract

Titanium oxide (TiO2) is the most widely used white pigment because of its brightness and very high reflective index, traits surpassed by only a few other materials; it has gained adequate ground in the fabrication of solar cells due to its wide band gap of 3.32 eV. Various natural dyes such as laali plant dye, zobo leaf dye and tomato seed dye act as sensitizers. This research intends to explore the effect of this titanium oxide on enhancing sensitivity in light harvesting by using dye-sensitized solar cell fabrication. Indium tin oxide, one of the transparent, conducting optical glasses, was chosen for the photoanode, on which the prepared titanium powder and the extracted dye were coated using the screen printing method. TiO2 was screen printed over the TCO (ITO) or plain glass slide and annealed at 4000 °C for 3 min; then, the dyes were injected drop by drop and analysis was carried out for XRD and UV–optical. From the XRD results obtained for the laali dye, the XRD showed no prominent peaks and when improved by introducing titanium oxide, it showed the peaks as having a rutile nature which enhances light harvesting. The optical properties showed a transmittance edge at 350 nm which gradually increased as the wavelength increased with no visibility on the absorbance graph. For the tomato dye, a visible peak was observed and this increased with the addition of titanium oxide, while transmittance rose at 380 nm and fell at 550 nm, with no absorbance. The zobo dye showed no evidence of visible peaks and little change in the peak visibility with the addition of TiO2 was observed, with the transmittance edge at 350 nm, maximum at 390 nm and constant with TiO2 enhancement, and showing no visible absorbance properties. Laali and zobo are good transmittance materials, unlike the tomato dye which is a good absorbance material. Conclusively, TiO2 is effective in dye-sensitized solar cell fabrication since there were visible changes within the scientific environment which further enhanced light harvesting.

Keywords

• adhesion
• annealed
• dyes
• fabrication
• titanium oxide
• light harvesting