Copper nanowire to help drive solar cell production costs down

30. September 2011 | Products, Research & Development, Industry & Suppliers | By:  Cheryl W. Kaften

A new high-performance, flexible copper nanowire, first developed at Duke University in the U.S. last year and now being commercialized at a spin-off company called NanoForge Corporation, may drive down the cost of solar cell production.

Flexible copper nanowire

Having determined the advantages of copper nanowire, Wiley decided to take the next step: commercialization. Image: Ben Wiley/Duke University.

Furthermore, the copper nanowire could replace the current transparent conductive coating of choice for liquid crystal displays and flat panel displays - indium tin oxide (ITO) -  on the screens of cell phones, e-readers, and iPads. And it could help engineers to build foldable electronics.

Assistant Professor of Chemistry Benjamin J. Wiley, Ph.D., and graduate student  Aaron Rathmell have found a technique that "organizes" copper atoms in water to form long, thin, non-clumped nanowires. The nanowires are then transformed into transparent, conductive films, which can be quickly and easily coated onto glass or plastic by a manufacturer.


While indium tin oxide is highly transparent, which transmits the information well, the ITO film must come from a vapor in a process 1,000 times slower than newspaper printing; and, once the ITO is in the device, it cracks very easily. Wiley and Rathmell created the new copper nanowires to maintain their conductivity and form when bent back and forth 1,000 times, so it has much greater flexibility.

Indium is also an expensive rare earth element, costing as much as $800 per kilogram. These problems have driven worldwide efforts to find less expensive materials that can coat or print like ink at much faster speeds to make low-cost, transparent conducting films, according to Wiley.

One alternative to an ITO film is to use inks containing silver nanowires. Interestingly enough, Wiley worked on the development of silver nanowires when he was a graduate research fellow at the University of Washington (2003-2007), advised by Professor Younan Xia.

"The first project I worked on," he explained in an exclusive interview with pv magazine, "was to make the synthesis of silver nanowires highly reproducible, because, depending on the source of ethylene glycol we used, we got totally different results. I found that the contaminants in the ethylene glycol, iron, and chloride ions were critical to formation of silver nanowires.  The subsequent patent was licensed by Cambrios [a Sunnyvale, California –based company that develops electronic materials for the display industry]."

The first cell phone with a screen made from silver nanowires will be on the market this year. But silver, like indium, is still expensive at $1,400 per kilogram. Copper, on the other hand, is a thousand times more abundant than indium or silver, and about 100 times less expensive, costing only $9 per kilogram.

Having determined the advantages of copper nanowire, Wiley decided to take the next step: commercialization.

He co-founded a company called NanoForge Corp, located not far from Duke University in Durham, North Carolina, in November 2010 to manufacture copper nanowires for commercial applications.

"I was introduced to Steven Warwick [now, Chief Executive Officer of NanoForge] by Henry Berger in Duke’s Office of Licensing and Ventures. We met over lunch and decided to work together. Going from a laboratory technology to selling product in one year would not have been possible, if it had not been for Steven’s complete commitment to the success of NanoForge," says Wiley.

Warwick is not a newcomer to business management: He has 15 years of senior executive leadership experience in three startup companies - one leading to a $1.2 billion IPO, another sold for $180 million - and 15 years of corporate experience at Agilent and Harris Corp. He also has extensive experience in team building and management, technology development, high technology marketing, and strategic partnerships; and has helped raise more than $300 million in equity financing.

In early 2011, NanoForge received a $45,000 North Carolina IDEA grant for refinement and scale-up of the manufacturing process of copper nanowires, and it is now filling orders.

Wiley, who has taken the title chief scientific officer in the privately held company, says, "We are selling to major multinational entities that are well-known in the electronics industry, but do not have any publicly announced relationships at this time."

Does Wiley think his discovery will revolutionize the solar industry?  "We have no aspirations to completely displace current technologies," he comments. "If we can replace one percent of transparent conducting materials within five years, we will be extremely successful."


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