Fabrication, Doping and Characterization of Polyaniline and Metal Oxides: Dye Sensitized Solar Cells

Abstract

The photoelectrochemical devices like dye sensitized solar cell (DSSCs) are the promising photovoltaic device for the utilization of solar into electricity energy by converting solar radiation through the generation of photogenerated carriers. DSSCs possess the benign properties of low cost, high conversion efficiency and ease of fabrication (Gratzel, 2005, 2004 & Frank, et al., 2004). Several significant advantages are associated to DSSCs such as the semiconductor-electrolyte interface (SEI) is easy to manufacture and it is cost effective for production, non sensitive to the defects, the two functions of light harvesting and chargecarrier transport are remain separated and favours the direct energy transfer from photons to chemical energy. Although, DSSCs are the promising photovoltaic technology for achieving reasonably high conversion efficiency but the improvements are still demanded to develop a high potential technology. A typical DSSC is comprised of a dye-coated mesoporous nanocrystalline metal oxide semiconductor, machinated between two the conductive transparent electrodes as shown in Fig. 1. A liquid iodide/tri-iodide redox couple as an electrolyte is introduced to fill the pores of the film and to improve the contact between the nanoparticles (Gratzel, 2000). Upon photo excitation of the dye, the electrons are injected into the conduction band of the nanocrystalline metal oxide semiconductor and the original state of the dye is restored by the electron donation from the hole conductor. The regeneration of the sensitizer by the hole conductor intercepts the recapture of the conduction band electron by the oxidized dye and the hole conductor is regenerated at the counter-electrode. The circuit is completed via electron migration through the external load. Nanocrystalline metal oxide semiconductor like TiO2, ZnO and SnO2 etc have been accepted as the effective photoanode materials for DSSCs due to their good optical and electronic properties. Till date, DSSCs constructed from TiO2 nanocrystalline metal oxide electrodes has presented the highest solar to electricity conversion efficiency of 11.4%. These nanocrystalline metal oxide semiconductors possess high surface to volume ratio required