

” Copper Nanowires can now be ‘grown’ in bulk and then ‘printed’ on a surface to transparently conduct current! ”

– Benjamin Wiley, Duke Chemistry

Most people probably don’t realize that thin film solar panels and flat screen TV’s share alot in common, since they both rely heavily on the technologies of ‘thin-film dialectrics’ (TFD) to produce the substrates (electrode layers) that control either the emission or absorption of light. So obviously, any advances made in the manufacturing processes for these films could create both cost and technical efficiencies that would enable TFD’s to either consume less power, or generate more energy on an even cost basis for a given amount of light. This would be no small achievement if you consider the growing demand for efficient display screens, and the persistent cost barriers to all the solar panels that people are hoping to install in the very near Future. The exciting Science News here is that new discoveries in copper-based ‘Nano Tech’ are offering the first cheaper and efficient alternatives to existing methods that we’ve seen in quite awhile, and could genuinely change the surface of playing field if Cu-based nanotech can continue to overcome the hurdles of establishing a brand new TFD process.

Currently the status quo of TFD manufacturing is based in a predominance of electrode films made from Indium Tin Oxide (ITO), and this rather expensive method still has quite a few nagging drawbacks. First of all, ITO is pricey to process, it’s also brittle and thus fragile; so its production process remains highly inefficient; and it’s already an expensive technology that’s becoming even more costly because of the dual increases in market demand (scarcity) for both raw materials and the finished product. Currently the only alternatives we see on the horizon are coming from nano technology that uses either silver or carbon nano-tubes – which both remain highly cost prohibitive and difficult to produce. However a research team at Duke University have recently announced that they’ve perfected a method to grow nanowires from Copper, which promises to dramatically reduce not only the manufacturing demands for these thin films, but also allow for them to be much more flexible, durable, and cost efficient – Especially since copper is an abundant resource who’s price can’t be as easily cornered and manipulated by merchants and market forces…



Benjamin Wiley, an assistant professor of chemistry at Duke University, and his students, PhD candidate Aaron Rathmell and undergraduate Stephen Bergin, grew the copper nanowires in a water-based solution that promises to radically change the manufacturing process for transparent TFD’s. “By adding different chemicals to the solution, you can control the assembly of atoms into different nanostructures,” Wiley said. In this case, when the copper crystallizes, it first forms tiny “seeds,” and then a single nanowire sprouts from each seed. It’s a mechanism of crystal growth that has never been observed before.

Because the copper nanowires are flexible and in an aqueous solution, the Duke team envisions them being manufactured in a roll-to-roll system similar to newspaper printing, which would be a dramatic simplification over current methods. The particles are also so small, that they will be transparent to light sources, which makes them ideal for display screens and photo-voltaic solar films.

“If we are going to have these ubiquitous electronics and solar cells,” Wiley said, “we need to use materials that are abundant in the earth’s crust and don’t take much energy to extract.” There are very few materials that are both conductive and transparent, which is why Indium based materials are still the standard. However copper nanotubes stand poised to change all that with the new “growth’ process that is being perfected at Duke, and is already in the process of being patented.

In order to scale the carbon tube process up to commercial production levels though, the team still needs to find a method of preventing the nanowires from clumping as they grow, which reduces transparency, and also preventing the copper from oxidizing, which decreases their conductivity. Once this is accomplished, will have a TFD material that will be much cheaper to both produce, and work with than Indium or Silver based dielectrics, while producing results at the same level of performance.

The trick here, according to some experts and pundits, will be getting to a high aspect ratio on the wires (ie. realllly long wires). At this stage, they can get only get ~65% transparency, which is already pretty consistent in the 400-1000nm wavelength range. If they could replicate the transparency of Silver (Ag nanotech) they’d really have something impressive to boast about. Estimates are made that this CU nanotech could lop off 0.10-0.30$/W. Which is pretty dramatic when you consider that Solar is currently sitting at about 0.80$/W.

So with copper being a thousand times more abundant than Indium, and 100 times cheaper to work with, there’s no doubt that the existing investors in silver nanotube technologies, could soon be seeing some of the light that copper is promising to produce in the near future.

SOURCES:

http://www.dukenews.duke.edu/2010/05/put_slug_here.html

http://www.nanitenews.com/research/Copper_nanowires_grown_by_new_process_create_long-lasting_displays.asp