M. D. Tyona, R. U. Osuji, F. I. Ezema, S. B. Jambure and C. D. Lokhande
A study has been successfully carried out on the photosensitizing action of a natural dye obtained from Indigofera arrecta plant (a herbicious plant) on nanocrystalline Al-doped zinc oxide (AZO) thin film electrodes synthesized by chemical bath deposition (CBD) technique. The porous nanostructures of the AZO enhanced dye-sensitized solar cell performance. This dye with strong absorption in the visible range with almost constant absorption peak, was found to convert visible light in the range of 300–750 nm into electrical energy. The electron injection by photoexcited dye molecules into the conduction band of AZO was evidenced by electrochemical impedance lowering of the dye-capped AZO electrode at optimum Al impurity level of 2 at % which facilitate fast charge carrier transport in the conduction band of the semiconductor. On irradiation of the dye-capped AZO thin film electrodes with white light of intensity 80 mW/cm2, power conversion efficiency (η) of the (AZO electrode/Indigofera arrecta plant dyecontaining electrolyte/platinum electrode) cell was found to be 0.51 % with fill factor of 0.47. The values of short circuit photocurrent Isc, and open-circuit photovoltage Voc, measured as 1.35 mA/cm2 and 0.643 V confirmed the applicability of the natural dye in solar cells.
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