Wednesday, November 03, 2010

When Fool´s gold becomes smarts´gold

Today, most solar cells are made of silicon, but they are expensive: though silicon is abundant, turning it into photovoltaics requires extensive, energy-intensive processing.
So a study of possible solar-cell materials, examining not only their chemistry and physics but also their availability produced as a result fool’s gold (pyrite or iron sulfide): it is abundant and cheap, and it has optical properties that allow it to efficiently convert sunlight into electricity.
The theoretical efficiency of iron sulfide is 31 percent.
That’s as good as silicon.
What’s more, 20 nanometers of pyrite can absorb as much light as 300 micro meters of silicon.
Because it absorbs so much more light, it can be made into thinner cells, which require less raw material.
Previous efforts to build solar cells with pyrite produced devices that, at best, converted only 2.8 percent of sunlight into electricity.
The low efficiency was due to inconsistencies in the crystal structure of the pyrite.
Making pyrite nanoparticles will produce pyrite crystals with a uniform, favorable structure .
The resulting material will outperform conventional pyrite in solar cells.
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