Solar DSSC

The DSSC differs substantially from the p-n-junction solar cell because electrons are injected from the photosensitiser into the CB of the semiconductor and no holes are formed in the VB of the semiconductor. 

Scientific interest in nanocarbon hybrid materials to enhance the properties of photocatalysts and photoactive electrodes has been growing rapidly [1-8]. The worldwide effort to find new efficient and sustainable solutions to use renewable energy sources has pushed the need to develop new and/or improved materials able to capture and convert solar energy, for example in advanced dye-sensitized solar cells - DSSC (where the need to improve the photovoltaic performance has caused interest in using nanocarbons for a better cell design [9,10]) or in advanced cells for producing solar fuels [11-13]. 

Previous sections have demonstrated how nanocarbon-semiconductor hybrid materials provide a number of potential advantages for the development of advanced devices for a sustainable use of renewable energy. Two of the more relevant areas are (i) to improve the performances of DSSCs and (ii) to develop novel cells for producing solar fuels. 

Fig. 17.5 Scheme of basic processes occurring in DSSCs (a) and organic solar cells (c). (b) Band bending for an n-type semiconductor and a p-type semiconductor in equilibrium with an electrolyte. 

Methods have been developed for fabrication of the highly-ordered titania nanotuhe arrays from titanium thin films atop a substrate compatible with photolithographic processing, notably silicon or FTO coated glass [104]. The resulting transparent nanotuhe array structure, illustrated in Fig. 5.16, is promising for applications such as anti-reflection coatings and dye sensitized solar cells (DSSCs). Fig. 5.17 shows the typical anodization behavior of a 400 nm Ti thin film anodized at 10 V in an HE based electrolyte. Eor a fixed HE concentration, the dimensions of the tube vary with respect to... 

Fig. 8.6a Schematic representation of a dye-sensitized solar cell (DSSC).

DSSC-based Tandem Cell for Solar Hydrogen Production... 

The dye-sensitised solar cell (DSSC) is constructed as a sandwich of two conducting glass electrodes filled with a redox electrolyte. One of the electrodes is coated, using a colloidal preparation of monodispersed TiOj particles, to a depth of a few microns. The layer is heat treated to rednce resistivity and then soaked in a solution of the dye until a monomolecnlar dispersion of the dye on the TiO is obtained. The dye-coated electrode (photoanode) is then placed next to a connter electrode covered with a conducting oxide layer that has been platinised , in order to catalyse the reduction of the mediator. The gap between the two electrodes is filled with an electrolyte containing the mediator, an iodide/triodide conple in acetonitrile. The structure is shown schematically in Fignre 4.29. 

Fig. 31 (a) Schematic design of a dye-sensitized solar cell, (b) Energy band diagram of DSSC. (Reprinted with permission from [265])... 

Dye-sensitized solar cells (DSSCs) are photoelectrochemical solar devices, currently subject of intense research in the framework of renewable energies as a low-cost photovoltaic device. DSSCs are based upon the sensitization of mesoporous nanocrystalline metal oxide films to visible light by the adsorption of molecular dyes.5"7 Photoinduced electron injection from the sensitizer dye (D) into the metal oxide conduction band initiates charge separation. Subsequently, the injected electrons are transported through the metal oxide film to a transparent electrode, while a redox-active electrolyte, such as I /I , is employed to reduce the dye cation and transport the resulting positive charge to a counter electrode (Fig. 17.4). 

DSSCs efficiencies up to 10.4%8 have been reported for devices employing nanocrystalline Ti02 films. Several studies have addressed the use of alternative metal oxides including SnCU,9 10 ZnO,11,12 and Nb205.13 The performance of dye-sensitized solar cells can be understood in view of the kinetic competition among the various redox processes involved in the conversion of light into electricity. Ultrafast electron injection (k2) has been observed in the femtosecond-picosecond (10 l5-... 

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