Research promises cheaper flat-panel displays

Posted by Emma Woollacott

UCLA researchers have developed a new, single-step method for producing transparent conductors, which may herald cheaper, more powerful electronic devices and flexible solar cells that could be incorporated into drapes.

LOS ANGELES, CALIFORNIA - UCLA researchers have developed a new, single-step method for producing transparent conductors, which may herald cheaper, more powerful electronic devices and flexible solar cells that could be incorporated into drapes.

The current gold standard for transparent conductors - used in flat-panel televisions, plasma displays and touch panels, as well as solar cells - is indium tin oxide (ITO). But this is expensive, both because of production costs and a relative scarcity of indium. It is also rigid and fragile.

The new way of producing hybrid graphene–carbon nanotubes, or G-CNTs, could lead to lower-cost and much more flexible alternatives.

G-CNTs are ideal candidates for use as electrodes in polymer solar cells, say the developers. One of the benefits of polymer, or plastic, solar cells is that plastic is flexible. But until an alternative to ITOs, which lose efficiency upon flexing, can be found, this potential cannot be exploited. G-CNTs retain efficiency when flexed and also are compatible with plastics. Flexible solar cells could be used in a variety of materials, including the drapes of homes, the researchers suggest.

Graphene is an excellent electrical conductor, and carbon nanotubes are good candidates for transparent conductors because they provide conduction of electricity using very little material. The new single-step method for combining the two is claimed to be easy, inexpensive, scalable and compatible with flexible applications. G-CNTs produced this way already provide comparable performance to current ITOs used in flexible applications.

The development builds on the researchers' previous work, which introduced a method for producing graphene - a single layer of carbon atoms - by soaking graphite oxide in a hydrazine solution. The researchers have now found that placing both graphite oxide and carbon nanotubes in a hydrazine solution produces not only graphene but a hybrid layer of graphene and carbon nanotubes.

"To our knowledge this is the first report of dispersing CNTs in anhydrous hydrazine," said Yang Yang, a professor of materials science and engineering at the UCLA Henry Samueli School of Engineering and Applied Science and a member of UCLA's California NanoSystems Institute (CNSI). "This is important because our method does not require the use of surfactants, which have traditionally been used in these solution processes and can degrade intrinsic electronic and mechanical properties."

The authors outline their new processing method in Nano Letters, a journal of the American Chemical Society.