Dramatic Solar Efficiency Possible?

November 9, 2003 – Vol.8 No.33

DRAMATIC SOLAR EFFICIENCY POSSIBLE?

Multiband Solar Cells - with more research, that’s a term you might be hearing more often in a few years.

Solar cells are limited in their efficiency by the band gap of light waves that will effectively knock loose electrons and create the flow of electric current inside a solar cell. With typical solar cells some light is absorbed and converted to electricity, but most isn’t.

Multijunction cells have the best efficiency at about 30 percent by utilizing a number of layers or junctions. Light that passes through one layer might get caught up in the next and so on. But with the efficiency increase comes complexity and the cost of the cell goes up.

If a single junction solar cell were created that could absorb multiple band gaps of light energy - a wider spectrum of solar energy - then efficiency would go up, and possibly price in relation to efficiency could go down.

The way to increase efficiency dramatically is to develop new types of semiconductors designed to absorb multiple band gaps of light, say a team of researchers from the Lawrence Berkeley National Labs, University of California at Berkeley and the Massachusetts Institute of Technology. They claim that using crystals of made of a combination of zinc, manganese and tellurium (ZnMnTe) with added oxygen impurities, semiconductors could be made for single junction solar cells that would have efficiencies of up to 56 percent.

At this stage no one is talking price, and no cells appear to have been made. Ultimately the cost of production would affect the viability of the cells. Scientists used pulsed laser melting and a novel technique to add the oxygen impurities to make the ZnMnTe semiconductor. For the research paper: http://arxiv.org/ftp/cond-mat/papers/0309/0309477.pdf