www.physorg.com/news99904887.html
Their results appear in a recent edition of Applied Physics Letters. Most conventional solar cells used in today's applications, such as for supplemental power for homes and buildings, are one-sun, single-junction silicon cells that use only the light intensity that the sun produces naturally, and have optimal efficiency for a relatively narrow range of photon energies. The Spectrolab group experimented with concentrator multijunction solar cells that use high intensities of sunlight, the equivalent of 100s of suns, concentrated by lenses or mirrors. Significantly, the multijunction cells can also use the broad range of wavelengths in sunlight much more efficiently than single-junction cells. "These results are particularly encouraging since they were achieved using a new class of metamorphic semiconductor materials, allowing much greater freedom in multijunction cell design for optimal conversion of the solar spectrum," Dr. "The excellent performance of these materials hints at still higher efficiency in future solar cells." In the design, multijunction cells divide the broad solar spectrum into three smaller sections by using three subcell band gaps. Each of the subcells can capture a different wavelength range of light, enabling each subcell to efficiently convert that light into electricity. While Spectrolab's primary business is supplying PV cells and panels to the aerospace industry (many of their solar cells are used on satellites currently in orbit), the company envisions that this breakthrough will also have applications in commercial terrestrial solar electricity generation. The research that led to the discovery of the high efficiency concentrator solar cell was funded partly by the US Department of Energy's National Renewable Energy Laboratory, and will play a significant role in the government's Solar America Initiative, which aims to make solar energy cost-competitive with conventional electricity generation by 2015. The company has said that these solar cells could help concentrator system manufacturers produce electricity at a cost that is competitive with electricity generated by conventional methods today. The Spectrolab scientists also predict that with theoretical efficiencies of 58% in cells with more than three junctions using improved materials and designs, concentrator solar cells could achieve efficiencies of more than 45% or even 50% in the future. Citation: King, R R, Law, D C, Edmondson, K M, Fetzer, C M, Kinsey, G S, Yoon, H, Sherif, R A, and Karam, N H "40% efficient metamorphic GaInP/GaInAs/Ge multijunction solar cells."
ory=Environment On 1-Jun-2007 by adoucette The exciting thing about PVs that operate at > 1 sun is the cost of the PV system isn't dictated by the cost of the PV cells themselves. Given that these cells also have much higher efficiency this is a very good day for the PV industry. As the article said QUOTE The company has said that these solar cells could help concentrator system manufacturers produce electricity at a cost that is competitive with electricity generated by conventional methods today. On 1-Jun-2007 by Enthalpy Sure, this is the right way to make PV. Less expensive per m2, thus allowing monocrystalline technology and perhaps stacked semiconductors. However, such technologies are >15 years old, even if this article forgets to tell it. But this must be compared with the price: could well be that a single Si-junction (or perhaps GaAs) makes cheaper electricity. Companies that have worked for space activities are generally unable to attain normal costs. Don't forget to cool the cells, as 100 times solar concentration is a lot, and the cooler must be cheap. And storing electricity is still very difficult at a competitive cost. No, you won't have to wait 50 years, since this doesn't belong to the semiconductor culture. And as I said, good cells exist for a long time, so what are you waiting for? On 1-Jun-2007 by googleplex Another solar article missing the $/Watt metric. Localized power generation from solar cells is currently the best temporary solution to our power needs. All of our energy ultimately comes from nuclear (either the sun or teresstrial nuke plant). Hydrocarbons and bio fuels are inefficient distribution mechanisms for this energy. Solar buys us time until we can have clean and cost effective fusion power. Put the solar cells close to where the energy is consumed (rooftops).
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