What is the best current efficiency of silicon solar cells?

Question

Read somewhere that there was a solar cell with an efficiency of over 40% but is that one a silicon solar cell?

http://www.iea-pvps.org/pv/materials.htm
Forgot to add this. Mentions about conversion efficiency of silicon based solar cells. IMHO a bit outdated, since it was written in 2002.

@tlbs101: and that is a silicon based solar cell?

Answer 1

http://www.gizmag.com/go/6563/picture/29635/

The 40% is not Si, but it is multi-junction, to capture a broader frequency spectrum of sunlight. The picture in the link is hard to read, but I believe there is Ge and GaAs as well as other materials. Also, this is a concentrator type cell, achieved by SpectroLab in Dec 2006.

For Si single crystal, I believe the highest efficiency is in the 22% range, by Sanyo.

http://www.renewableenergyaccess.com/rea/partner/story?id=49043

Answer 2

Those 40% cells are multi-junction cells using different semiconductor materials, and are still in the experimental stage, and still very, very expensive (plus they use Fresnel lens concentrators).

What is actually flying on the International Space Station are production triple junction cells that are about 28.5% efficient. Those would be the most efficient 'production' cells in use.
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