Category SOLAR CELLS – DYE-SENSITIZED DEVICES

5. Outlook

The quest and demand for clean and economical energy sources have increased interest in the development of solar applications. DSSCs have proved to be an alternative approach to the conventional silicon based solar cells. Research on DSSCs has grown rapidly in the recent years due to the several attractive figures of this interesting field: The international awareness of the necessity to develop new technologies in Renewable Energy Resources; The need of easy and inexpensive procedures for fabricating Solar cells; The fact that DSSCs can be transparent so that they can be integrated into mobile or immobile constructions as Photovoltaic Windows. All these features are carried by DSSCs and for this reason they are popular and they are expected to be even more popular in the near future...

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Parallel-module

A simple fabrication procedure of making DSSC modules is parallel connection. According to this structure small cells in the form of long stripes are connected in parallel.

Fig. 8. (a) W-Module (b) Z-Module DSSC (Seo et al., 2009)

In this structure parallel grids utilizing conductive fingers to collect current are printed on the two electrodes of the cells. The printing method of current collectors is quite similar to that applied in conventional photovoltaics based on silicon. Common metals used as current collectors reducing the distance of electron transfer and internal resistance of FTO glass are: Ag, Cu, Ni, Ti. The solar cell efficiency is considerably reduced when it is converted to module despite the high unit cell efficiency...

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W-module

It also concerns a series connection of the cells while inner-connections are avoided. Unlike the z-module and monolith module that are manufactured in the same direction to the adjacent cell, the W-module secures a structure that are in an opposite direction of the adjacent cell. Hence, it does not require direct wiring or bus electrode and realizes high reliability since the inner-cell contact occurs directly on the substrate. It also secures a structure to maximize the available area to record relatively high conversion efficiency. It is able to simultaneously manufacture multiple cells and can also manufacture cell and module at the same time...

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Monolith module

The monolith modules have similar structure to amorphous silicon modules that are currently used in the market. Monolith modules use a single sheet of conductive glass (FTO) where successive layers of TiO2 are formed on the substrate. Prior films deposition the glass is scribed by a laser in order to isolate one cell from the other. Direct wiring is not needed in this type of modules. It records relatively broad available area and high conversion efficiency, and enables simultaneous production of multiple cells (Wang et al., 2010). Usually, the TiO2 stripes are formed according to screen printing method...

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Manufacturing of Dye sensitized solar cells

While many research groups investigate the working principles of DSSCs and new developments have been achieved concerning their efficiency and large scale applications, new companies founded in the meanwhile try to carry DSSC technology in market place evaluating all process steps are needed for industrial production. Experimental results for small size solar cells cannot directly applied in large scale DSSCs as the efficiencies measured for small size solar cells cannot be repeated in large scale (Spath et al., 2003). This is caused by the high internal resistance of FTO substrates which eliminates their efficiency and it is found to be drastically decreased. Below are referred some of the main issues which have to be taken into account before DSSCs go to a production line:

• Large area d...

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Positive electrode (catalysts)

The counter electrode is one of the most important components in the dye-sensitized solar cell. The major role of the counter electrode in addition to the cell finalization is the reduction of the redox species used as a mediator in regenerating the sensitizer after electron injection, or collection of the holes from the hole conducting material in a solid-state DSSC. Counter electrodes of dye-sensitized solar cells can be prepared with different materials and methods. Platinum, graphite, activated carbon, carbon black, single-wall carbon nanotubes, poly(3,4-ethylenedioxythiophene) (PEDOT), polypyrrole, and polyaniline can be used as catalysts for the reduction of triiodide...

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Quasi-solid electrolytes

In some cases the very viscous ionic liquids but in most cases the composite organic/inorganic materials are referred as quasi-solid electrolytes. Nanocomposite organic/inorganic materials are constituted of two interpenetrating subphases which are mixed in nanoscale. The organic subphase is usually consisted of few surfactants or polyether chains and the inorganic subphase is made of an inorganic network which typically is silicon dioxide or titanium dioxide. Such nanocomposite gels can accommodate appropriate solvents within the organic subphase (that is within the pores left by the inorganic network) so that ionic conductivity can be raised to a satisfactory degree...

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Solid electrolytes

When it is referred the use of solid electrolytes it is generally accepted that people mean the use of p-type semiconducting materials either organic or inorganic. In the case of organic materials the most popular is spiro-MeOTAD which initially proposed by Gratzel and co­workers (Kruger et al., 2002). The recorded efficiency was about 4% while new organic semiconductors were appeared in the meanwhile. Polymer based solid electrolytes are usually referred as efficient alternatives to liquid based electrolytes but the efficiency is still poor. Polymer usually containing polyether units can be used as solid electrolytes in DSSCs...

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