Photoelectrochemical cells sensitizer systems

As already mentioned in the introduction, various fundamental and many empirical results have been published. Although photoelectrochemical cells are easily made, many problems concerning the stability of semiconductors and the function of catalysts still remain to be solved. There are few other approaches such as for instance sensitization (see e.g.) which are not treated here. In addition it should be mentioned that photoelectrochemical systems have been used for light induced synthesis of organic compounds (see e.g.) which could also not be considered in this article. 

Figure 6. Schematic diagram of a photoelectrochemical cell based on a sensitized semiconductor electrode. M = metal-polypyridine sensitizer, R = reversible electron-relay system, e.g. h/lj -...

The ability of porous photoelectrochemical systems to separate effectively electrons and holes is widely known since the presentation of the dye-sensitized particulate Ti02 solar cell [16, 105, 130-137]. In this system, the photocurrent quantum yield (the number of electrons counted in the external circuit as photocurrent divided by the number of absorbed photons) is close to unity. This means that electron-hole pair recombination is essentially absent. Efficient separation of photogenerated electrons and holes was demonstrated with several other photoelectrochemical systems [105, 130-137]. Photovoltaic devices based on permeated hole-conducting and... 

The combination of different analytical techniques will allow the development of novel approaches to sensing. In particular, the coupling between optics and electrochemistry seems to be very promising. In this respect, only few examples of light addressable electrodes and photoelectrochemical sensors have been reported. " Finally, increase of the sensitivity of the sensing system has been achieved by irradiating the electrochemical cell with microwaves or ultrasounds. 

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