Solar cells gallium-arsenide

Gallium aluminum arsenide in solar cells Gallium arsenide phosphide in light-emitting diodes Gallium arsenide infrared detectors, lasers, and photocopiers... 

Photovoltaic (PV) solar cells, which convert incident solar radiation directly into electrical energy, today represent the most common power source for Earth-orbiting spacecraft, such as the International Space Station, where a photovoltaic engineering testbed (PET) is actually assembled on the express pallet. The solid-state photovoltaics, based on gallium arsenide, indium phosphide, or silicon, prove capable, even if to different extents and with... 

Parkinson, B.A., Heller, A., and Miller, B., Effects of cations on the performance of the photoanode in the n-gallium arsenide/potassium selenide (K2Se)-potassium diselenide (K2Se2)-potassium hydroxide/carbon semiconductor liquid junction solar cell, /. Electrochem. Soc., 126,954,1979. 

The satellite would need 50 to 100 square kilometers of collector area using 14% efficient monocrystalline silicon solar cells. More expensive triple junction gallium arsenide solar cells with an efficiency of 28% would reduce the collector area by half. In both cases the solar station s structure would be several kilometers wide, making it much larger than most manmade structures on Earth. Building structures of this size in orbit has never been attempted before. 

Gallium arsenide (Ga + As — GaAs) is electroluminscent in infrared hght and is used for telephone equipment, lasers, solar cell, and other electronic devices. 

Single crystal silicon (sc-Si), polyciystalline silicon (p-Si), and amorphous silicon (a-Si) can all be used to make solar cells, with fabrication cost and device photoconversion efficiencies decreasing as one moves from single-crystal to amorphous materials. Various properties of these materials are summarized in Table 8.1. Other relatively common solar cell materials include gallium arsenide (GaAs), copper indiirm diselenide (CIS), copper indium-gallium... 

Gallium arsenide exhibits semiconductor properties. It is used in transistors, lasers, solar cells and various high-speed microcircuits. 

Gallium arsenide solar cells advanced in the 1980s for space use because they weighed much less than silicon cells of similar output, since GaAs absorbs sunlight much more strongly than silicon. 

Solar cells based on silicon or gallium arsenide provide a way to convert the radiant energy of the sun directly into electrical work by a technology that is virtually nonpolluting (Fig. 22.26). The high capital costs of solar cells make them uncompetitive with conventional fossil fuel sources of energy at this time, but as reserves of fossil fuels dwindle, solar energy will become an important option. 

Donald Osborn, supervisor of the solar program of the Sacramento Municipal Utility District in California, says that analysts expect the price of the price of a single-crystal module to be as low as 2 per watt by 2010. Osborne says that advanced thin-film cells made of exotic materials such as gallium arsenide have shown laboratory efficiencies as high as 28 percent with concentrated sunlight.18 Some thin-film photovoltaic modules are expected to cost as little as 1.25 per watt by 2010. 

There is a problem with the widespread use of arsenic, cadmium, and selenium in electronic and photovoltaic devices. Cadmium mercury telluride is used in infrared-sensing night goggles. Cadmium sulfide, cadmium selenide, gallium arsenide, and analogues, are used in solar cells. If their use becomes widespread, then an efficient system of collecting used cells for reprocessing will be needed. Some workers feel that it will be better to use nontoxic silicon cells wherever possible. (Solar cells are discussed in Chap. 15.)... 

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