On Dec 6, 2006, at 8:36 AM, Harold Hallikainen wrote:

> It looks like the efficiency increase is due to the multi-layer
> cell instead of the concentrator. Each layer absorbs a different
> portion of the spectrum, converting it to electricity instead of
> heat. The concentrator allows a small cell to capture light from
> a large area. This, of course, could be done with conventional
> cells, but there are cooling problems.40.7% looks really nice
>
Multi-layer cells aren't new, but the 40.7% number is a significant
improvement over the typical triple-junction cell (which IIRC hovers
around 27%)  The layers aren't as easy as you might think; each junction
is going to be optimal at a particular wavelength, so three junctions
implies using pretty exotic semiconductors...

BillW
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