Solar cells high-efficiency

The uncertainties in this cost analysis arise principally from the early stage of technology development for solar concentrators, high-efficiency solar cells, and solid oxide electrolysis cells. There are many positive indications that these technologies can progress and achieve their performance and cost potentials, but additional work will be needed. 

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. 

MSP titania was also used to make electrodes, which were tested in a dye-sensitized solar cell [116]. The short-circuit photocurrent, open-circuit photovoltage and fill factor increased with increasing sintering temperature, having a performance threshold at 450 °C, showing that the more ordered structures are required for high solar cell conversion efficiencies. 

Luminescent Solar Concentrators A high efficiency Si concentrator solar cell for use with prismatic covers has been described,46 and an LSC based upon PMMA doped with U02 is reported to be suitable for use with solar cells.47 Efficiencies of 24.8% have been achieved using a GaAs-Fresnel lens concentrator solar cell.48... 

The drives toward high efficiency and low cost may intersect by the fabrication of thin film tandem cell stacks in which the thin films consist of four-and five-element alloys of the ternary semiconductors. It has already been demonstrated that thin films of such alloys can be deposited by rf-sputtering7 and chemical spray pyrolysis.8 It has also been shown that large grained specimens of these four- and five-element alloys can be used to fabricate solar cells having efficiencies in excess of 10%, i.e. these semiconductor alloys are promising photovoltaic materials. 

AQUEOUS FUEL CELL HIGH EFFICIENCY SOLAR CEU CARBON NANO TUBE LIGHTING... 

Solar cells have been used extensively and successfully to power sateUites in space since the late 1950s, where their high power-to-weight ratio and demonstrated rehabiUty are especially desirable characteristics. On earth, where electrical systems typically provide large amounts of power at reasonable costs, three principal technical limitations have thus far impeded the widespread use of photovoltaic products solar cells are expensive, sunlight has a relatively low power density, and commercially available solar cells convert sunlight to electricity with limited efficiency. Clearly, terrestrial solar cells must be reasonably efficient, affordable, and durable. International efforts are dedicated to obtaining such devices, and a number of these activities have been reviewed (1). 

Yet another alternative is the thin-film solar cell. This cannot use silicon, because the transmission of solar radiation through silicon is high enough to require relatively thick silicon layers. One current favourite is the Cu(Ga, InjSci thin-film solar cell, with an efficiency up to 17% in small experimental cells. This material has a very high light absorption and the total thickness of the active layer (on a glass substrate) is only 2 pm. 

Ultrafast photoinduced electron transfer in semiconducting polymers mixed with controlled amounts of acceptors this phenomenon has opened the way to a variety of applications including high-sensitivity plastic photodiodes, and efficient plastic solar cells ... 

Single-Crystal Silicon. Silicon is still the dominant material in photovoltaic. It has good efficiency, which is 25% in theory and 15% in actual practice. Silicon photovoltaic devices are made from wafers sliced from single crystal silicon ingots, produced in part by CVD (see Ch. 8, Sec. 5.1). However, silicon wafers are still costly, their size is limited, and they cannot be sliced to thicknesses less than 150 im. One crystalline silicon wafer yields only one solar cell, which has an output of only one watt. This means that such cells will always be expensive and can only be used where their high efficiency is essential and cost is not a major factor such as in a spacecraft applications. 

Wanlass, M., ANew Approach to High Efficiency Solar Cells, Photonic Spectra, pp. 159-165 (Nov. 1992)... 

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