Experimental Investigation on the use of Vernonia Amygdalina-Mucuna Pruriens Dye Mixture as Sensitizer in Dye-Sensitized Solar Cell

Dye-sensitized solar cells (DSSCs) have the advantages of low cost, flexibility, simple method of assemblage, and performance under low intensity of light. The pigments are responsible for the release of the electrons into the wide band gap semiconductor like TiO
2
where the charge separation and transport take place. This study focuses on investigation into locally available plant pigments in Nigeria with sufficient photon-harvesting potential for dye sensitized solar cell production. Dye pigment extracts from two plants; Vernonia amygdalina and Mucuna pruriens, which are commonly found in the western region of Nigeria were used in this study. The UV-Vis absorption spectral of the pigments shows Vernonia amygdalina absorbed over a wavelength range of 450-680 nm with the wavelengths of absorption maximum at 535, 615, and 665 nm. Mucuna pruriens absorbed at a wavelength range of 500-710 nm and wavelengths of maximum absorption are 507, 540, 610, and 663 nm. The two pigments were mixed at different ratios and the UV-Vis absorption spectra obtained. The most significant plots, ratios 2:3, 1:1 & 3:2 were studied and it was found that ratio 3:2 yielded seven dyes, Vernonia amygdalina - Mucuna pruriens dye mixture at ratio 3:2 also yielded the best result in terms of photo-absorption strength over a wider range of wavelength covering 320-730 nm. Therefore Vernonia amygdalina - Mucuna pruriens dye mixture at ratio 3:2 was selected for use in a DSSC fabrication where its performance was compared with those sensitized with Vernonia amygdalina and Mucuna Pruriens seperately. The dye mixture was used to sensitize TiO
2
based DSSC with 0.88 and 2.45% obtained as fill factor and efficiency respectively. The results of this work have shown that the mixture of Vernonia amygdalina and Mucuna pruriens is potential dye blend for DSSC that perform best at a ratio 3:2 mixture.