Browsing by Author "Sakalani, Adam Mwarabu"

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    Effect of purified natural dyes on dye-sensitized solar cell performance
    (The University of Dodoma, 2020) Sakalani, Adam Mwarabu
    In this study, natural dye-sensitized solar cells (NDSSCs) were fabricated using crude and purified natural dye extracts aimed at investigating the effect of purified natural dyes on the dye-sensitized solar cell (DSSC) performance. Ethanol and methanol solvents were used to extract natural dyes from Senna singueana flowers, Senna singueana leaves, Ximenia caffra fruits, and Bougainvillea glabra bracts. Liquid-liquid extraction (LLE) method was used to purify the ethanol and methanol natural dye extracts. Ultraviolet-visible (UV-VIS) characterization of the extracted natural dyes revealed that two Senna singueana flower, six Senna singueana leaf, two Ximenia caffra fruit, and five Bougainvillea glabra bract extracts attained lightharvesting efficiency (LHE)of more than 73 % and energy bandgap (Eg) lower than 2.92 eV. In order to find out the effect of purification on the DSSC performance parameters and stability, NDSSCs were fabricated using Senna singueana leaf ethanol (SLE), Senna singueana leaf petroleum ether separate (SL1), Senna singueana leaf chloroform separate (SL2), Senna singueana leaf ethyl acetate separate (SL3), Senna singueana leaf n-butanol separate (SL4), Bougainvillea glabra bract ethanol (BBE), Bougainvillea glabra bract chloroform separate (BB2), and Bougainvillea glabra bract aqueous separate (BB5) extracts. The power conversion efficiency (η) of the fabricated NDSSCs were as follows: SLE (0.68 %), SL1 (0.02 %), SL2 (0.51 %), SL3 (0.41 %), SL4 (0.04 %), BBE (0.45 %), BB2 (0.02 %), and BB5 (0.04 %). Therefore, the η and stability due to aging of the NDSSCs using purified natural dyes were found to be lower than those using crude natural dyes. This means that, the natural dyes exhibited a synergetic effect. In this study, it was concluded that purification of ethanol extracts from Senna singueana leaves and Bougainvillea glabra bracts resulted a negative effect on the DSSC performance parameters (especially the η)and stability.