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The rapid shortage of petrochemical energy has led to the great demand in developing clean and renewable energy sources; such as solar cells in these years. The first commercially available photovoltaic cell (PV) by using solar energy is silicon-based solar cell however with high production cost and high energy payback time. This limited the usage and agitated vigorous studies on the next-generation solar cells in order to reduce cost and increase efficiency. It was until 1991, dye-sensitized solar cells (DSSCs) have attracted increasing interests by the pioneering work of O’Regan and Gratzel. They used a Ru-based dye to achieve higher conversion efficiency in a cell made of titania (TiO2) as the active layer. Recent development of solar cells in dye-sensitized type devices is one great step forward in the field. The DSSCs take advantages in simple fabrication technique and low production costs in contrast to those conventional silicon-based solar cells. The DSSC device (Fig. 1) is basically comprised of two facing electrodes: a transparent photoanode, consisting of a mesoporous large band gap semiconductor as an active layer, modified with a monolayer of dye molecules and a Pt counter electrode, both deposited on conductive glass substrates, for example: indium tin oxide (ITO) glass. An appropriate medium containing the redox couple (usually I−/I3−) is placed between the two electrodes to transfer the charges. Among other semiconductors employed as the active layer of the DSSCs, titania known to have wide energy band gap, can absorb dye and is capable of generating electron-hole pairs via photovoltaic effect. DSSCs based on mesoporous titania, which exhibits very high specific surface area (and better dye-absorbing) has been drawn much attention over the past few years. A number of surface modification techniques have been reported to produce nanostructural TiO2 layer. Moreover, researchers suggested that one dimensional nanostructural TiO2 such as nano-rods, nano-wires or nano-tubes is an alternative approach for higher PV efficiency due to straightforward diffusion path of the free electron once being generated. For these reasons, we use several cost-effective manufacturing methods to develop the nanostructural TiO2 electrode at near room |
