Photo sensitizing and electrochemical performance analysis of mixed natural dye and nanostructured ZnO based DSSC

The paper highlights the enactment of the natural dyes, like purple cabbage, spinach, turmeric and their mixture as a photo-sensitizer, with nanostructured zinc oxide (ZnO) as a photo-anode, based dye-sensitized solar cell (DSSC). The field emission scanning electron microscopic image of ZnO, prepared by chemical bath deposition process, proclaims two different types of morphology, nano-wire and nano-plate shape. The photo sensitizing properties of the natural dyes and their mixed part are explored through FTIR spectra and UV-vis light absorbance characteristics. The FTIR spectra explore the presence of different anchoring chemical groups which confirm the strong anchoring bond with ZnO and enhancement of electron mobility. The diffused reflectance spectra (DRS) of dye-loaded ZnO films incisive the absorption of dye on the mesoporous ZnO surface. The relative energy band positions of individual and mixed dye, yield stable execution of the cell that has been performed through the cyclic voltammeter. The driving force energy requirement for effortless transport of electron from the mixed dye to the conduction band of ZnO is revealed lowers (0.34 eV) as compared to individual dyes. Electrochemical impedance spectroscopy (EIS) analysis has been executed to find the charge transfer resistance, total bulk resistance, recombination loss through Nyquist plots and Bode plots. These characteristics pretense as the mixed dye has an eminent rate of electron transportation and lower recombination loss with longer electron lifetime. The photon to electrical power conversion efficiencies of purple cabbage, spinach, turmeric and their mix dyes are explored as 0.1015%, 0.1312%, 0.3045%, and 0.602%, respectively under same simulated light condition. The mixed dye reveals the stable performance of the cell with the highest conversion efficiency due to the absorption of an extensive range of the solar spectrum and wellsuited electrochemical responses. (author)