Dye-sensitized cells

Preliminary measurements with space-resolved PMC techniques have shown that PMC images can be obtained from nanostructured dye sensitization cells. They showed a chaotic distribution of PMC intensities that indicate that local inhomogeneities in the preparation of the nanostructured layer affect photoinduced electron injection. A comparison of photocurrent maps taken at different electrode potentials with corresponding PMC maps promises new insight into the function of this unconventional solar cell type. 

Due to its direct relation to Section VI, we begin with a cell in which mainly the hole transporting properties of molecular glasses are used the solid-state dye sensitized cell. 

EPFL (Switzerland) nano-crystal dye sensitized cell... 

The difference between the two illumination geometries is much less marked when the penetration depth of the light is comparable with the film thickness, as is usually the case for dye sensitized cells. As Fig. 8.30 shows, the characteristic frequency is quite similar in both cases since carriers are generated throughout the whole of the film. 

Fig. 8.32. Bode plot showing experimental data and best and fit to the short circuit IMPS response of a dye sensitized cell. Dc photocurrent 6.3 mA. The upper solid line in each plot shows the fitted response in the absence of RC attenuation. Note the limiting high frequency phase shift is 45°, which is characteristic of diffusion control. The lower line illustrates the improved fit obtained by including the influence of r n. R = lOfl, C = 5 x 10 F.

Similarly, the search for a stable dye material and better electrolyte material in dye-sensitized cells (Gratzel cells) has a potential to lead to lower-cost solar cells. There is a need to increase the stable efficiency of such cells a stable efficiency of about 10 percent could be quite useful. 

In a conventional single crystal or polycrystalline photoelectrochemical cells, the difference between the Fermi level of the semiconductor electrode and the counter electrode is expected to follow a logarithmic relationship with the light intensity described by the diode equation [160]. An analog of the diode equation for dye-sensitized cells can be obtained by equating the recombination rate to the injection flux under open-circuit conditions, Eq. 34 ... 

Apart from recapture of the injected electrons by the oxidized dye, there is an additional loss channel in the nanocrystalline dye-sensitized cell which involves reduction of triiodide ions in the electrolyte present within the mesoporous network ... 

The diversification of energy sources tailored to the requirements and resources of each country using nature s renewable resources such as the sun (photovoltaics), wind power, geothermal energy and biomass is a definite requirement. If solar cells are chosen to provide an alternative to fossil fuels, significant research work is needed (i) to develop new routes for the production of crystalline silicon, (ii) in the development of amorphous silicon hybrid materials that could result in enhanced efficiencies, (iii) for further development of thin-layer technology, (iv) in concerted efforts for cheaper and more stable dyes, (v) in improving the efficiency of the dye-sensitized cells and (vi) in process development to deliver enhanced device performances, ensure sustainability and reduce production costs on an industrial scale. 

Dye-Sensitized Cells Dye-sensitized solar cells (DSSCs) are slightly more complex than bilayer and bulk heterojunction cells, but as was the case for bilayer cells, the increase in device complexity reduces the number of functions that must be performed by each of the materials. A schematic drawing of a dye-sensitized solar cell is shown in Fig. 8.8. A layer of sintered, interconnected TiC>2 nanoparticles, which serves as the electron transport material (ETM), is coated by a thin layer of light absorbing dye. The remaining pores in the dye-coated TiC>2 layer are then filled with a... 

The overall conversion efficiency of the dye-sensitized cell is determined by the photocurrent density measured at short circuit (/sc)> the open-circuit photo-voltage (Toe), the fill factor of the cell (FF) and the intensity of the incident light (/g). 

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