ABSTRACT
The world’s energy demands will grow with increasing standards of living and economic growth. The energy crisis has become a serious issue with the consumption of oil reserves; however, most current energy consumption from oil reserves has caused serious environmental pollution problems. To reverse this crisis, we must develop renewable energy sources that are cost-effective as well as environmentally friendly. Biomass, wind, solar, geothermal, and hydroelectric power are well-known alternative energy sources. In particular, solar radiation may be a promising source of green energy. By an electrochemical process, solar radiation can be converted into electricity through photovoltaic devices. During the last few decades, thin films of crystalline silicon and semiconductor compounds have been developed for use in solar cells [1]. However, such devices have a high production cost. In 1991, Gratzel et al. discovered dye-sensitized solar cells (DSSCs), which are considered a potentially low-cost and highly efficient photovoltaic alternative to the traditional silicon-based solar cell [2]. DSSCs rely on high specific surface area and wide-band gap semiconductor oxides as a photosensitized anode for organic or metalorganic-complex 254dye molecules adsorption. They recently emerged as promising third-generation photovoltaic cells because they are flexible, inexpensive, and easier to manufacture than silicon-based solar cells [3]. In a DSSC, photons from sunlight strike the dye molecules, which excite electrons to elevate the dye to a higher energy level. The electrons are injected into the conduction band of the porous oxide photoanode. The oxidized dye molecule is regenerated by an electrolyte containing a redox system R/R−, usually iodide/tri-iodide. Recently, a maximum conversion efficiency of approximately 11% DSSC was obtained using highly porous and nanocrystalline TiO2 films with ruthenium-based dye adsorption [4].
