INVESTIGATION OF THE PHOTO-VOLTAICPROPERTIES OF SOME NATURAL DYES

Abstract

The dye-sensitized solar cell (DSSC) is a photochemical electric cell, which consists of the photo electrode, the dye, the electrolyte, and the counter electrode. DSSCs are distinct relative to the other types of solar cells because it utilizes dye to generate electricity. Investigation of the photo-voltaic properties of some natural dyes belonging to carotenoid (Annatto – from the Bixa orellana plant),anthraquinone (Cochineal and Madder – both from the Dactylopius coccus insects and Rubia tinctorum root respectively) & neoflavonoid (Brazilwood – from the heartwood of the Caesalpinia echinata plant) was carried out. DSSCs was made using the Doctor-blade technique in preparing thin film components FTO (Fluorine-doped Tin Oxide, a type of transparent conducting oxide-TCO) in the order - glass/TiO2 / Natural Dye / Electrolyte / Carbon / FTO glass. The Doctor-blade technique involves the addition of TiO2 paste to the top edge of the FTO glass between three pieces of tape used in holding down the glass, with the use of a glass rod, the paste was spread across the plate, thus, the gap between the strips of tape is now filled with a layer of reasonably homogenous TiO2 paste.The cell performance parameters obtained after testing the cells were extracted from the I-V curves, they are: Short circuit current (Isc) – current when the voltage is zero, Open circuit voltage (Voc) – maximum voltage available from a solar cell & this occurs at zero current, Fill factor (FF) – a ratio of the actual power output (Imax x Vmax) to the ‘dummy’ power output (Isc x Voc ). The performance parameters of DSSCs prepared using each dye are as listed: Madder dye (Isc = 0.059mA, Voc = 0.127, FF = 37.9%); Brazilwood dye (Isc = 0.048mA, Voc= 0.165 FF = 37.5%); Annatto dye (Isc = 0.095mA, Voc= 0.40 FF = 44.2%); Cochineal dye (Isc = 0.085mA, Voc= 0.222 , FF = 41.0%). The DSSC prepared using dye extracted from Annatto seeds as photo-sensitizer showed the better photovoltaic performance compared with other dyes. Keywords: Dye-sensitized solar cells; Natural dyes; TiO2; Carotenoid; Anthraquinone; Neoflavonoid; Photo-sensitizer.