New Multi-Junction Cell Could Offer a Big Leap for Solar

There remain many people who are skeptical of solar energy.

They insist it can't scale. They question whether utilities will buy, or can buy, such unreliable power. They question whether the exponential “Moore's Law” improvements I've written about are even possible.

Then there are days like today that blow the skeptics away.

Researchers at the Lawrence Berkelely Lab have figured out a way to create high-efficiency multi-junction cells from a single semiconductor material, rather than layers of multiple materials.

What's most impressive about the latest Berkeley Lab breakthrough isn't the claim of 50% efficiency (against today's 15%). It's the possibility that the new cell could be made cheaply, on fairly standard semiconductor production lines.

What the team headed by Wladek Walukiewicz and Kin Man Yu of the Solar Energy Material Sciences Division (MSD) of Berkeley Lab, found is is that by a mix of indium and gallium can be made sensitive to different solar wavelengths by altering the mix, and with three different compounds layered on a single substrate using a standard metalorganic chemical vapor depositions (MOCVD) process you can create a cell that captures the whole spectrum.

multi-junction cells have been around for a while, but they have required a wide variety of materials that were either hard to make or hard to manufacture. These cells can be made in conventional ways, and the materials they're made of are all compatible, variations on a theme.

There are still some technical problems but the lab is already working with two serious commercial partners, Rose Street Labs Energy  of Phoenix and Sumika Electronic Materials, a unit of Japan's Sumitomo. The Berkeley technology could appear in both flat panel and thin film formats.

That's the supply side. I'm just as as impressed by what is happening on the demand side. Georgia Power, which as I've noted before drives hard bargains on solar projects, buying cheap and selling dear, has nevertheless signed its second 1 MW contract in two months, this time for a facility in Dalton, Georgia to be built by United Renewable Energy on land owned by a local utility company. The local utility will advertise “green energy,” Georgia Power will own the plant and act as wholesaler, United Renewable will build it.

It's a straightforward, simple business deal, the kind made every day. What it says to me is there is enormous demand around the country for current technology.

What will there be for systems that are three times more efficient?