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Highly efficient natural dye-sensitized photoelectrochemical solar cells based on Cu-doped zinc oxide thin film electrodes

M. D. Tyonaa, R. U. Osujib, F. I. Ezemab, S. B. Jamburec and C. D. Lokhandec

The current work under studied the photosensitizing action of a natural dye obtained from Indigofera arrecta plant (a herbicious plant) on nanocrystalline Cu-doped zinc oxide (CZO) thin film electrodes synthesized by chemical bath deposition (CBD) technique. This dye, having 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 photo-excited dye molecules into the conduction band of CZO was evidenced by electrochemical impedance lowering of the dye-capped CZO electrode at optimum Cu impurity level of 3 at.% which facilitates fast charge carrier transport in the semiconductor. On irradiation of the dye-capped CZO thin film electrodes with white light of intensity 80 mW/cm2, power conversion efficiency (η) of the (CZO electrode/Indigofera arrecta plant dyecontaining electrolyte/platinum electrode) cell was found to be 4.16 % with fill factor of 0.54. The values of short circuit photocurrent Isc, and open-circuit photovoltage Voc, measured to be6.8 mA/cm2 and 0.91 V show the applicability of the natural dye in solar cells