Saturday, April 14, 2007

40% Efficient Solar Cells: They Are Being Used Back On Earth

The usual efficiency for solar panels is 10-20%. Efficiency is the conversion rate of capture, comparing the potential energy that strikes an area of ground with the energy (electricity) captured by the solar panel. This relatively low efficiency is one reason why solar electricity hasn't caught on. In December last year, a company called Spectrolab has achieved a new world record in solar cell efficiency. By using concentrated sunlight, Spectrolab demonstrated the ability of a photovoltaic cell to convert 40.7% of the sun’s energy into electricity. Multijunction cells perform at higher efficiencies than conventional single-junction silicon solar cells, because they convert more of the solar spectrum into energy by breaking it up into chunks. For example, the first layer of Spectrolab's record-breaking triple-junction cell is composed of gallium indium phosphide, which converts short-wavelength portions of the spectrum, such as blue and UV. The second layer, made of gallium arsenide, captures the middle part of the spectrum. The third germanium layer does a good job with IR light.

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