Graphene-based thin films may lead to flexible displays

August 3, 2011

Graphene thin-film grid (credit: Tour Lab/Rice University)

Researchers at Rice University have created thin films that could revolutionize touch-screen displays, solar panels, and LED lighting — a strong candidate to replace indium tin oxide (ITO).

ITO is a commercial product widely used as a transparent, conductive coating. It’s the essential element in virtually all flat-panel displays, including touch screens on smart phones and iPads, and is part of organic light-emitting diodes (OLEDs) and solar cells.

ITO works well in all of these applications, but has several disadvantages. The element indium is increasingly rare and expensive, and requires fragile glass. It’s also brittle. Both of these factors heighten the risk of a screen cracking when a smart phone is dropped and further rule ITO out as the basis for flexible displays.

An electron microscope image of a hybrid electrode shows solid connections after 500 bends. The transparent material combines single-atom-thick sheets of graphene and a fine mesh of aluminum nanowire on a flexible substrate (credit: Tour Lab/Rice University)

The researcher’s new thin film combines a single-layer sheet of highly conductive graphene with a fine grid of metal nanowire. The researchers claim the material easily outperforms ITO and other competing materials, with better transparency and lower resistance to electric current. The metal grid strengthens the graphene, and the graphene fills all the empty spaces between the grid.

The researchers found a grid of five-micron nanowires made of inexpensive, lightweight aluminum did not detract from the material’s transparency.

In tests, the researchers found the hybrid film’s conductivity decreases by 20 to 30 percent with the initial 50 bends, but after that, the material stabilizes. There were no significant variations up to 500 bending cycles, the researchers said.

The researchers said the breakthrough could lead to computers that wrap around the wrist and solar cells that wrap around just about anything.

Ref.: Yu Zhu, et al., Rational Design of Hybrid Graphene Films for High-Performance Transparent Electrodes, ACS Nano, 2011; : 110729133414013 [DOI: 10.1021/nn201696g]