Performance of Some Selected Natural Dye and Their Mixture as Photosensitizers in the Fabrication of DSSCs

Performance of some selected natural dye and their mixture as photosensitizer in the fabrication of dye sensitize solar cell (DSSC) was examined. Six different cells of DSSC was fabricated using natural dye extracts from; Bush or Wild mango leaf (WM), Mucuna pruriens (MS) leaf, Sand cherry (SC) leaf and African velvet tamarinds (AV) leaf. The dyes of Mucuna pruriens and sand cherry (Co-MS) were co-sensitized and also four of the sample dyes were co-sensitized, (AV, SC, MP and WP) (Co-All) as photosensitizers. These natural dyes were extracted using ethanol and Doctor Blade’s technique was used for the deposition of the TiO2 on a transparent Fluorine-doped Tin Oxide (FTO) coated glass substrates. The deposited TiO2 thin film were subjected to XRD, UV-Vis spectroscopy and I-V characterization to determine their structural, optical and solar cell parameter. Films structural analysis from XRD pattern of the samples showed prominent polycrystalline films with sharp and narrow diffraction peak intensities observed at (200), (210) and (310), (511) respectively corresponding to 2θ value of 25.61o-65.68o for AV,WM and Co-All, 25.56o-38.02o for SC, MP and Co-MS with an oriented growth of hexagonal structures, respectively. AV dye has the highest absorbance and reflectance value of 0.99 a.u and 0.21 a.u while Co-All has the peak transmittance value of 0.85a.u in the UV-Vis region of the electromagnetic spectrum. AV dye has the least band gap value of 2.32eV. The I-V characteristics of the fabricated films were analyzed under light illumination intensity of 100W/cm2 and dark illumination. The result showed that the efficiency of DSSC under light illumination is higher than that under dark illumination.MP single dye produced the highest efficiency value of 0.14%. The efficiency of the single dye MP was found to be higher than that of the co-sensitized dyes. Co-All has a slight higher conversion efficiency value of 0.029% under standard light illumination when compared to the Co-MS with value of 0.025%. Though the conversion efficiency of the dyes were not improved by co-sensitization, the dyes showed a promising applications in solar cells as light havesting material.