Solar-energy conversion photovoltaic cells

Gratzel, M. (2005) Solar energy conversion by dye-sensitized photovoltaic cells. Inorganic Chemistry, 44 (20), 6841-6851. 

J. Yang, A. Banerjee, K. Lord, S. Guha, Correlation of component cells with high efficiency amorphous silicon alloy triple junction solar cells and modules. Office for Offidal Publications of the European Communities, Luxembourg, Proceedings of the 2nd World Conference on Photovoltaic Solar Energy Conversion, Vienna, July 6-10, 1998,... 

While the application of photovoltaic cells has been dominated by solid-state junction devices principally made from silicon, recent work in this field offers the prospect of efficient solar-energy conversion by novel methods. 

Adapted from M. Gratzel, Solar Energy Conversion by Dye-Sensitized Photovoltaic Cells , Inorganic Chemistry, Volume 44 (20), 2005 American Chemical Society... 

For reviews of photovoltaic principles and applications, consult Merrigan, J.A., "Sunlight to Electricity - Prospects for Solar Energy Conversion by Photovoltaics", MIT Press, Cambridge, Mass., 1975 "Solar Cells", C.E. Backus, ed.,... 

Solar energy conversion and photovoltaic devices encompass one of the most active applied topics of research in this area191. Thus, photoelectrochemical cells based on electrodes (Sn02, Pt) coated with tetrapyrroles have been studied for a long time191-194. Most studies were performed with phthalocyanines due to their stability and wide range of redox... 

Fahrenbruch, A. L. Bube, R. H. Fundamentals of Solar Cells. Photovoltaic Solar Energy Conversion-, Academic Press New York, 1983. 

This volume, based on the symposium Photoeffects at Semiconductor-Electrolyte Interfaces, consists of 25 invited and contributed papers. Although the emphasis of the symposium was on the more basic aspects of research in photoelectrochemistry, the covered topics included applied research on photoelectrochemical cells. This is natural since it is clear that the driving force for the intense current interest and activity in photoelectrochemistry is the potential development of photoelectrochemical cells for solar energy conversion. These versatile cells can be designed either to produce electricity (electrochemical photovoltaic cells) or to produce fuels and chemicals (photoelectrosynthetic cells). 

A.L. Fahrenbruch, R.H. Bube Fundamentals of Solar Cells Photovoltaic Solar Energy Conversion (Academic Press, New York 1983)... 

Moore compared the technological branch of solar energy conversion, essentially photovoltaics, with the biological branch. He explained how a standard fuel cell that operates on oxygen and hydrogen produces water and electromotive force. A typical human-engineered fuel cell operates at 50-60 percent power conversion efficiency and uses platinum or other noble metals as catalysts. 

This type of device has been contrasted489 with a series connection of a photovoltaic p-n junction solar cell and a water electrolyzer. Unlike the latter which is a majority carrier system (i.e., the n-side of the junction is the cathode and the p-side becomes the anode), in a photochemical diode, minority carriers (holes for the n-type and electrons for the p-type) are injected into the electrolyte. This distinction translates to certain advantages in terms of the overall energetics of the solar energy conversion system (see Ref. 489). 

However, the last few years have also seen a growing awareness of the problems inherent in using the semiconductor-electrolyte interface as a means of solar-energy conversion. Very long-term stability may not be possible in aqueous electrolytes and no oxide material has been identified that has properties suitable for use as a photoanode in a photoelectrolysis cell. Highly efficient photovoltaic cells are known, both in aqueous and non-aqueous solutions, but it is far from clear that the additional engineering complexity, over and above that required for the dry p-n junction photovoltaic device, will ever allow the "wet photovoltaic cells to be competitive. These, and other problems, have led to something of a pause in the flood of papers on semiconductor electrochemistry in the last two years and the current review is therefore timely. I have tried to indicate what is, and is not, known at present and where future lines of development may lie. Individual semiconductors are not treated in detail, but it is hoped that most of the theoretical strands apparent in the last few years are discussed. 

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