The One Percent Solution: How Innovalight’s Silicon Ink Makes Solar Panels Slightly More Efficient, and Why That’s a Huge Deal
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form silicon dioxide, i.e. quartz or sand, which is useless for photovoltaic cells. Preventing that was “a major achievement we made in the company,” says Burke. “I can tell you, there were some very dark moments in the early stages where we sat around the room saying ‘It can’t be done, physics is against us.’ But after a lot of hard work and effort you start to figure out some really innovative ways to do it.”
Innovalight needed the particles of silicon to be pure so that they’d add to the efficiency of electron exchange inside photovoltaic wafers. It needed them to be tiny because the next step in the company’s process, once it’s produced the nanocrystal powder, is to mix it with a solvent. “You don’t want to have the particles falling out of solution, so having particles of that size allows you to turn them into an ink—a new species of silicon,” says Burke.
Using standard screen printing equipment already found on all solar cell fabrication lines, manufacturers can then put a thin layer of the ink on top of a silicon solar cell, directly beneath the areas where contact fingers will be attached. In effect, the silicon ink acts as a doping agent in these areas, decreasing the electric resistance of the bulk silicon and allowing the contact wires to extract more of the free electrons knocked loose by the sun’s photons.
There are other ways to eke efficiency improvements from photovoltaic cells, of course, but many of them require exotic materials or deposition methods, says Burke. “The problem facing most of these ideas is that they are not manufacturable,” he says. “You have to be able to process 1,600 wafers an hour at 99.5 percent yields, and that is a pretty extraordinary task. So the fewer steps you have to add, the better. In our case, it’s just one, and the material is completely benign.” (As another example of a company taking an innovative apprach to improving solar cell efficiency, I’d point to Boston-area startup 1366 Technologies. There, engineers simply make the contact fingers narrower, so they don’t block as much sunlight from hitting the wafer.)
But while Innovalight fared better with silicon ink than it had with lighting, the company has still had its share of recent twists and turns. For several years after the 2005 re-launch, Burke was pushing for the company to become a full-fledged solar panel manufacturer. Innovalight even built its own demonstration solar cell manufacturing line—a very costly investment. But by 2008 he had decided that manufacturing “was probably not the best route for us,” Burke says. “And that has turned out to be correct. All of this [solar manufacturing] has gone offshore. You have unprecedented scale in China, and the capital required to build those factories is just enormous. We figured, why not deploy our technology into that huge infrastructure—and that has turned out to be the smartest thing we’ve ever done.”
This year Innovalight announced the first two customers for its silicon ink, Yingli Solar (NYSE: YGE) in Baoding, China, and JA Solar (NASDAQ: JASO) in Shanghai. There are “many other” customers, but Innovalight isn’t contractually allowed to … Next Page »
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