NuvoSun Hits 11.8 Efficiency With CIGS

05 August of 2009 by

When NuvoSun needs factory equipment, it goes to eBay. The Palo Alto, Calif.-based startup – which wants to make copper indium gallium selenide (CIGS)solar cells on thin metal substrates – purchased one of its vacuumchambers in its prototyping facility from a military base through theauction site, said Dave Pearce, the CEO and founder. Another piece ofproduction equipment was pieced together through components. One ofNuvoSun’s employees actually designed that machinery two decades ago soputting it together was somewhat straightforward.

The backyard ambiance in a lot of ways reflects the state of the solar union. Investors have plunked over $2.3 billion into CIGScompanies alone. CIGS, though, accounts for less than 3 percent of theworld solar market and most companies aren’t even in production. Solarprices, meanwhile, have crashed.  With a wave of acquisitions all butinevitable, cheap will be king.

195 Logo4 NuvoSun Hits 11.8 Efficiency With CIGS "The days of free money in solar are gone, so you have to have aprocess that is more capital efficient," Pearce said. "You have toassume that $100 million is not available."

On the plus side, the past few years of CIGS experimentation andaccumulated knowledge has made it easier to move quickly. The companywas formed in January 2008. In July 2008, it had its first cell.

"It was 2 percent efficient," he said. "We said, ‘Wow, it’s photoactive.’ "

Ten months later, it produced a small "champion" cell that exhibited11.8 percent efficiency. That’s in range of what other, more heavilyfunded CIGS companies have achieved. HelioVolt,which has raised $101 million, last year talked about efficiencies inthe 10 to 12 percent range.  Nanosolar, which has raised a few hundredmillion, has talked about producing 14.5 percent CIGS cells.

Ascent Solar, which makes novel CIGS-on-plastic modules, has hit 10.4 percent efficiency in a solar panel in its 1.5 megawatt pilot plant and produces panels with an 8 percent to 9 percent average efficiency.

Again, NuvoSun only produced a small test cell about the size of athumbnail, and 11.8 percent efficiency is only a baseline achievement,but Pearce argues that it demonstrates that the company has come upwith what could be a core of a workable manufacturing process.

"We’re not trying to say we did a module. The important part is that we are delivering on viable reaction pathways," he said.

By the first half of next year, NuvoSun should be able todemonstrate a complete CIGS module exhibiting ten to 11 percentefficiency.

Technically speaking, CIGS has great promise. CIGS cells in labshave come close to 20 percent efficiency, or higher than the 16.5percent efficiency of the best cadmium telluride lab cells. CIGS canalso be deposited on foil, cheaper to process and transport than theglass substrates required for crystalline silicon or cadmium telluridecells. NuvoSun, in fact, will only make CIGS cells on sheet metal.

Mass producing CIGS modules, however, is sort of like trying to pulloff a Van Halen reunion. The four elements do not work well together,which dampens efficiencies and lowers yields in mass production. Miasole,Pearce’s first CIGS company, experienced both of those problems intrying to move to mass production. The company hopes to be in massproduction next year. (Similarly, HelioVolt and SoloPower have swappedmanagement teams and experienced delays.)

Pearce, for his part, agrees. CIGS makers will have to reduce theirraw material costs for solar cells to 25 to 30 cents a watt. Finishedmodules will have to cost 70 to 75 cents a watt.

"Ultimately, modules will have to approach 50 cents a watt. At that,you can comfortably sell in the range of $1 a watt," Pearce said.

Not everyone is going to be able to do it. Some CIGS makers aretalking about 30 and 40 megawatt factories that cost close to $100million.

Efficiency will have to improve too.

"It is fairly straightforward to get to 10 to 11 percent, but youwill separate the men from the boys when you go to 12, 13, 14 and 15percent," he said. "It is deceptively simple to make small devices. Thescaling has been the challenge."

So what is NuvoSun doing that might set it apart? The company has aprecursor, post-selenization process that it combines with chemicalplating. In this, the copper, indium and gallium are deposited in afairly cold process. Selenium is added in a later high temperatureprocess. Nanosolar has a two stage process that it combines withprinting.

"The two-step process gives you more individual control. CIGS is allabout determining the right reaction pathways," he said. "You can formall sorts of subspecies you don’t want."

Some other companies use a reactive process in which all of theelements are added in a hot process. It’s like trying to mix the cakebatter and bake it all at the same time.

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