Using films made of copper nanowires could cut the cost of touch screens, LEDs and solar cells, while allowing the development of foldable electronics and improved solar cells, according to new research.
Duke University chemists have developed a technique to organize copper atoms in water to form long, thin, non-clumped nanowires. The nanowires are then transformed into transparent, conductive films and coated onto glass or plastic.
They say their copper nanowire films have the same properties as those currently used in electronic devices and solar cells, but are less expensive to manufacture.
The films currently used to connect pixels in electronic screens are made of indium tin oxide, or ITO. It’s highly transparent, which means it transmits information well. But the ITO film must be deposited from a vapor in a process that is a thousand times slower than newspaper printing, and, once the ITO is in the device, it cracks easily.
Indium is also an expensive rare earth element, costing as much as $800 per kilogram.
One alternative is to use inks containing silver nanowires – and, indeed, the first cellphone with a screen made from silver nanowires is set to hit the market this year. But silver, like indium, is still pretty 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.
Last year, Duke chemist Ben Wiley and graduate student Aaron Rathmell were able to form a layer of copper nanowires on glass to make a transparent conducting film – but found its performance wasn’t up to scratch because the wires clumped together.
But their new way of growing the copper nanowires and coating them on glass surfaces eliminates the clumping problem, they say.
The copper nanowires maintain their conductivity and form when bent back and forth 1,000 times, while ITO films lose their conduction and structure after just a few bends.
Wiley’s co-founded a company called NanoForge Corp to manufacture copper nanowires for commercial applications, and says it’s now filling orders.
He believes that copper nanowires could be in screens and solar cells in the next few years, leading to lighter and more reliable displays and making solar energy more competitive with fossil fuels.