Full Spectrum Solar Cells

Eric Drexler in his book Nanosystems: molecular machinery, manufacturing, and computation, said that we could use moleculary nanotechnology to cheaply create solar cells that would convert as much as 90% of incoming solar energy into useable electricity. Such a development would permanently solve our energy problems on earth, and a go a long way towards closing the materials loop and returning the earth into a greener place.

In the meantime, there continue to be tantalizing leads towards moving in this direction without nanotechnology.

From the article, An unexpected discovery could yield a full spectrum solar cell.

The serendipitous discovery means that a single system of alloys incorporating indium, gallium, and nitrogen can convert virtually the full spectrum of sunlight -- from the near infrared to the far ultraviolet -- to electrical current.

"It's as if nature designed this material on purpose to match the solar spectrum," says MSD's Wladek Walukiewicz, who led the collaborators in making the discovery.

What began as a basic research question points to a potential practical application of great value. For if solar cells can be made with this alloy, they promise to be rugged, relatively inexpensive -- and the most efficient ever created.

Two layers of indium gallium nitride, one tuned to a band gap of 1.7 eV and the other to 1.1 eV, could attain the theoretical 50 percent maximum efficiency for a two-layer multijunction cell. (Currently, no materials with these band gaps can be grown together.) Or a great many layers with only small differences in their band gaps could be stacked to approach the maximum theoretical efficiency of better than 70 percent.

"If it works, the cost should be on the same order of magnitude as traffic lights," Walukiewicz says. "Maybe less." Solar cells so efficient and so relatively cheap could revolutionize the use of solar power not just in space but on Earth.

Posted by paul at April 17, 2004 01:20 PM | TrackBack