Photoelectrochemical Conversion of Solar Energy

The most important advantage of photoelectrochemical cells with semiconductor electrodes, as compared to, for example, solid-state semiconductor solar cells, is a relatively low sensitivity of their characteristics to the crystalline perfection of the semiconductor and the degree of its purification. Polycrystalline semiconductor electrodes in electrochemical solar cells exhibit both high absolute and high relative (as compared to single-crystal electrodes) conversion efficiency. This opens, at least in principle, the way of 

The mechanism of operation of photoelectrochemical cells and the characteristics of particular systems have been considered in detail in review articles and in a monography therefore, these topics are beyond the scope of the present review. It seems reasonable, however, to concentrate here on the most important problems, which are to be solved before photoelectrochemical cells find extensive practical application. 

The main obstacle to creating liquid junction solar cells is photocorrosion of semiconductor electrodes, which reduces considerably their lifetime. In order to prevent, for example, anodic photocorrosion, a well-reversible redox couple is introduced into an electrolyte solution, so that the reaction of oxidation of the red component competes for photoholes with the reaction of photodecomposition of the electrode material (see Section IV.2). With the aid of this method, photocorrosion has been practically prevented in certain types of photocells and the duration of their continuous operation has been increased up to about one year. Yet, there are other, more subtle mechanisms of electrode degra-dation, which has hitherto prevented the lifetime of photoelectrochemical cells from becoming comparable with the 20-year lifetime of solid-state solar cells. 

Realization of the process in the photostimulated electrolysis regime. In this case, the main fraction of quanta of solar radiation is utilized to generate a photoelectrochemical reaction, and the deficient (for the necessary 2 eV) energy is supplied with the aid of an external voltage source. The greatest progress in this direction has been reached in Reference 76. 

Realization of a two-quantum type process. Combining two semiconductor photoelectrodes (an n-type anode and a p-type cathode) in a single photoelectrochemical cell and choosing appropriately the characteristics of both electrodes, we can obtain an effective summation of photopotentials developed across each of the electrodes and produce the energy sufficient for photoelectrolysis of water/  

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Gratzel M (2007) Photovoltaic and photoelectrochemical conversion of solar energy. Phil Trans R Soc A 365 993-1005... 

Nakato Y, Tsumura A, Tsubomura H (1982) Efficient photoelectrochemical conversion of solar energy with n-type silicon semiconductor electrodes surface doped with IIIA elements. Chem Lett 1071-1074... 

Pleskov Yu. V., Photoelectrochemical Conversion of Solar Energy, Nauka, Moscow (1990) (in Russian). 

Several excellent books have been published since these years for example, Energy Resources through Photochemistry and Catalysis, by M. Gratzel (1983), Photocatalysis Fundamentals and Applications, by N. Serpone and E. Pelizzetti (1989), Photoelectrochemical Conversion of Solar Energy, by Yu. V. Pleskov (1990), Photochemical Conversion and Storage of Solar Energy, by E. Pelizzetti and M. Schiavello (1991) and Photocatalytic Purification and Treatment of Water and Air, by D. F. Ollis and H. Al-Ekabi (1993). Nevertheless, in these books no attempt was made to approach this research area from the point of view of classical chemical physics. 

Tailoring of Interfaces for the Photoelectrochemical Conversion of Solar Energy... 

Scaife DE (1980) Oxide semiconductors in photoelectrochemical conversion of solar energy. Solar Energy 25 41-54... 

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