The Chinese Solar Machine Layer by Layer Fire in the Library The Mystery Behind Anesthesia
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Abasifreke Ebong, assistant director of Georgia Tech's Photovoltaic Research Center, says to confirm that this is happening, the next step is to study the oxygen content of the solar wafers after they're removed from the firing furnace. If the oxygen is lower, the theory holds. "That's the data we're waiting for," he says.
According to Mike Davies, senior vice president at Sixtron, every 0.1 percentage of net efficiency spared from light-induced degradation results, on average, in a $600,000 gain in profit margin for each 60-megawatt cell production line.
Sixtron's system eliminates the silane gas hazard, relying instead on a proprietary solid polymer material that contains silicon and carbon. Using heat and pressure, the solid is converted to a less dangerous methyl silane gas during the cell-coating process. The solid-to-gas conversion takes place inside the company's gas-handling cabinet system, called SunBox, which has been designed to plug directly into industry-standard systems that exist on most cell-production lines.
Joshua Pearce, a professor of advanced materials at Queen's University in Kingston, Ontario, says Sixtron may be overstating the risks of using silane in a photovoltaic cell plant. "There are standard safety procedures that make working in a photovoltaic factory very safe," he says. Still, he adds, "anything to drop the cost of photovoltaic, even if by a small amount, is a great contribution."
Sixtron says it is already working with the top three providers of photovoltaic cell manufacturing equipment in Germany, and has interest from several others. The company plans to rent out the system at a cost roughly the same as using a silane-based system. Importantly, it avoids the need to use other light-induced degradation reduction strategies, based on alternative manufacturing methods or the use of higher-cost wafers doped with gallium.
Manufacturing in the United States is in trouble. That's bad news not just for the country's economy but for the future of innovation.
aunderdown
77 Comments
Solar cell efficiency and manufacturing safety
The short timescale efficiency drop mentioned in the article is attributed to the combination of boron (p dopant) atoms with oxygen present in the solar cell material. I was wondering if this degradation mechanism was previously known, or if it was discovered by the Georgia Tech research group. If it was previously known, have there been any efforts to introduce oxygen scavenging substances into the solar cell material to protect the boron?
As for the dangers of silane gas: Even if the danger is manageable, it would be better to eliminate the source of the danger (change the chemistry of the system, thus eliminating the root cause) rather than to rely on "downstream" protection measures. The Sixtron process looks like it can accomplish this.
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junegie
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Re: Solar cell efficiency and manufacturing safety
There are serious errors concerning ownership of the discovery in the original article. The article should be: LID reduction by Silexium silicon carbon nitride coating was first discovered by Dr. Junegie Hong (CTO of Sixtron) last year and solar cell benchmark activities were done with GATech. More result and mechanism behind will be presented in the coming European PVSEC 2010 Valencia in September. In order to anwer your question, Silexium coating partly plays a role in scavenging oxygen in the Cz Si wafer depending on the nature of Cz wafers, namely oxygen and boron content.
by Dr. Junegie Hong, CTO of Sixtron Advanced Materials (www.sixtron.com)
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