Determination of the Bandgap Energy of Dye-Sensitized Solar Cell Photoanodes Fabricated from Local Nigerian Fruits

Dye-sensitized solar cells using natural dye sensitizers extracted from locally available fruits represent a promising, low-cost approach to solar energy conversion in developing countries. This study determines the optical bandgap energy and photoelectrochemical properties of dye-sensitized titanium dioxide photoanodes fabricated using dye extracts from three Nigerian fruits: zobo leaves sourced from Sokoto State, black plum from Taraba State, and wild berry from Imo State. Dye extraction was performed by maceration in ethanol, and photoanodes were prepared by doctor-blading TiO2 paste onto fluorine-doped tin oxide glass substrates and sensitizing in dye solution. Optical transmittance spectra were measured using a UV-Vis spectrophotometer, and the Tauc plot method was applied to extract optical bandgap energies from absorption edge data. Short-circuit current density, open-circuit voltage, and power conversion efficiency were measured under simulated AM1.5 solar illumination using a source meter. Results indicate optical bandgap values of 2.3 eV to 2.7 eV for the three dye-sensitized electrodes, within the desirable range for visible light absorption. Zobo extract-sensitized cells showed the highest short-circuit current density of 1.18 mA/cm2, attributed to the strong light absorption of anthocyanin pigments. The study demonstrates the feasibility of fabricating functional dye-sensitized solar cells from widely available Nigerian agricultural byproducts and recommends further optimization of electrolyte composition. Keywords: dye-sensitized solar cell, bandgap energy, natural dye, Nigerian fruits, photoanode