Study of Electro-Optical Performance and Interfacial Charge Transfer Dynamics of Dye Sensitized Solar Cells Based on ZnO Nanostructures and Natural Dyes

The present work reports comparative assessment of optical and electrical properties of DSSCs fabricated using vertically aligned ZnO nanorods synthesized using low cost Sol-Gel spin coating technique on ITO coated glass substrate and ZnO nanopowder and their application in the fabrication of natural dye based Dye Sensitized Solar Cells. Natural dyes extracted from pomegranate and turmeric are used sensitizers. The surface morphology and crystal structure have been investigated by scanning electron microscopy and X-ray diffraction techniques. Optical absorption properties of the dyes were studied using UV-VIS spectroscopy. Photovoltaic parameters like Open Circuit voltage (V-OC), Short Circuit current (I-SC), fill factor (FF), Energy Conversion efficiency (eta) were calculated to study the performances of the cells. Cell parameters like series resistance (R-s) and shunt Resistance (R-sh) were calculated from the I-V curve. Electrochemical impedance spectroscopy (EIS) was employed for detail investigation of the charge carrier recombination properties and the charge transfer mechanism at different interfaces of the DSSC devices. Various cell parameters were determined by fitting the experimental EIS curves with the appropriate equivalent circuit. The electron lifetimes were determined using bode plot of EIS measurement for the ZnO nanorod and ZnO nanoparticle photo electrodes sensitized using curcumin dye from turmeric and anthocyanin dye from pomegranate juice. The ZnO nanorod sensitized with curcumin cell emerged out as the best performing cell among the four cells which can be attributed to the highest electron lifetime, higher recombination resistance resulting in lower charge carrier recombination in the ZnO/Dye/Electrolyte interface. Many researchers have studied sensitizing effect of curcumin dye with different nanostructures of ZnO but we are the first to study the sensitizing effect of curcumin dye on ZnO nanorod like structure.