Priyanka Chawla

Enhancement in Conversion Efficiency by Surface Modification of Photoanode for Natural Dye-Sensitized Solar Cell

To avoid the negative effects of current energy systems on environmental pollution and global warming, research have been focused on renewable energy sources for the future. Among the renewable energy sources, solar cells have attracted a great interest as a solution to this problem. As a result, the conversion of solar energy into different forms has been the core of research for the past few years. The conventional solid state silicon-based solar cells, though highly efficient, are yet to become popular for mass applications as they are highly expensive. Therefore, developing low-cost devices for harvesting solar energy is most desirable. Dye-sensitized solar cells (DSSCs) have been considered as one of the most promising photovoltaic technologies because they are generally made from inexpensive components and have a simple designed structure. Numerous metal complexes and organic dyes have been utilized as sensitizers so far; the highest efficiency of DSSCs sensitized by ruthenium complex and osmium complex compounds absorbed on nanocrystalline TiO2 reached 11–12 %. The major drawbacks of ruthenium are its rarity, high cost and the complicated synthesis of ruthenium complexes. The natural dyes anthocyanin/betacyanin obtained from fruits, flowers and leaves can be easily extracted by simple procedures and their cost-effectiveness, non-toxicity and complete biodegradation; therefore, the use of natural dyes in DSSCs has been a major focus of research. Among various wide-bandgap semiconducting oxides, nanocrystalline TiO2 (ns-TiO2) is the most suitable material for the photoanode of DSSC but TiO2 can utilize only 6 % of the total solar irradiation in photocatalysis. Doping with metal oxides has been considered a promising way for improving the photocatalytic efficiency of ns-TiO2. The increased photoactivity of CuO–TiO2 may be attributed to the improvement of the light absorption properties and the slowdown of the recombination between the photoexcited electrons and holes during the photoreaction. We have studied the performance of DSSCs sensitized with anthocyanin pigments extracted from black grapes. The solar cell was assembled using CuO–TiO2 thin film on ITO-coated glass with anthocyanin dye, liquid electrolyte system with LiI: I2 as a redox couple. The obtained solar conversion efficiency was 4.8 % using an irradiation of 100 mW/cm2.

Surface Modification and Optimization of Semiconductor ns-TiO2–WO3 Admixed Photoelectrode in Regard to Solar Hydrogen Production

To minimize the harmful effects of commercial energies like fossil fuel and nuclear energy on our environment, research is going on to find clean and renewable sources of energy. The main efforts of researchers nowadays is to harness solar energy for the production of clean hydrogen fuels by a photoelectrochemical (PEC) cell which represents a very attractive but challenging alternative. Some strategies have been developed to improve PEC performances of the photoelectrode materials, including doping for enhancing visible light absorption in the wide bandgap semiconductor or promoting charge transport in the narrow bandgap semiconductor, respectively. This chapter deals with the investigation on the optimization of ns-WO3–TiO2 admixed/Ti with respect to optimum photoelectrode area for semiconductor septum (SC-SEP) PEC solar cell. The motivation of the present work was to prepare an electrode having high-effective surface area and hence better quantum yield and improved PEC activity. Several attempts have been made to bring spectral response of TiO2 into visible or near visible region. It is known that the spectral response of the TiO2 films can be improved through admixing with appropriate oxides. The surface morphology, structural, and PEC characterization of the bare TiO2 as well as the TiO2 overlaid with WO3 thin film admixtures have been investigated in relation to hydrogen production through SC-SEP PEC solar cell. The PEC response of ns-WO3–TiO2 photo electrodes for four different electrode areas has been measured to explore the effect of electrode area on the output power in a chemical fuel (i.e., H2) produced by SC-SEP PEC cell. This was done for determining the electrode area for optimum electrical output and hydrogen production. The PEC cell having ns-WO3–TiO2 admixed/Ti photoanode of several geometric areas like 0.5, 1.0, 1.5, 2.0, and 2.5 cm2 were fabricated and characterized. It has been found that the photoanode area corresponding to optimum electrical output and hydrogen production rate corresponds to 1.0 cm2. The ns-WO3–TiO2 exhibited a high photocurrent and photovoltage of 15.6 mA cm–2, 960 mV, respectively. The ns-WO3–TiO2 electrode exhibited a higher hydrogen gas evolution rate of 13.8 l h–1 m−2.

Natural photosensitizers for solid-state dye sensitized solar cell

Natural dye sensitized solar cells (DSSC) have been widely investigated as a next generation solar cell because of their simple structure and low manufacturing cost. In the present work betacyanin dye responsible for the red color of many fruits and leaves having favorable absorption spectra with the solar spectrum has been used in fabrication of solid state dye sensitized solar cell. A Nanocomposite polymer electrolyte consisting of Poly vinyl alcohol (PVA), Lithium acetate, Ethylene carbonate (EC) and Propylene carbonate (PC) with TiO2 filler was used as a solid state thin film electrolyte for betacynin based Dye Sensitized Solar cell. The nanocomposite polymer was complexed with ammonium iodide and iodine crystals were added to the polymer electrolyte. The DSSC with the nanocomposite polymer electrolyte showed good photovoltaic performnance including short circuit photocurrent density (Jsc) 9.8 mA cm-2, the opencircuit volyage (Voc) 0.435 V, the fill factor (ff) of 52% and the conversion effeciency (η) of 2.2% under AM 1.5.