Innovation promises flexible solar cells, transistors, displays
May 28, 2013
Purdue University researchers have created a new type of transparent electrode that might find uses in solar cells, flexible displays for computers and consumer electronics, and future optoelectronic circuits for sensors and information processing.
The electrode is made of silver nanowires covered with graphene, an extremely thin layer of carbon. The hybrid material shows promise as a possible replacement for indium tin oxide, or ITO, used in transparent electrodes for touch-screen monitors, cell-phone displays and flat-screen televisions.
ITO is relatively expensive due to limited abundance of indium, inflexible (cracks when bent), and degrades over time, becoming brittle and hindering performance.
Hybrid transparent material can be bent, conducts current well
The hybrid material could represent a step toward several innovations, including flexible solar cells and color monitors, flexible “heads-up” displays in car windshieldsm and information displays on eyeglasses and visors.
“The key innovation is a material that is transparent, yet electrically conductive and flexible,” said David Janes, a professor of electrical and computer engineering. Such hybrid structures could enable researchers to overcome the “electron-transport bottleneck” of extremely thin films (“two-dimensional” materials).
Combining graphene and silver nanowires in a hybrid material overcomes drawbacks of each material individually: both the graphene and silver nanowires conduct electricity with too much resistance to be practical for transparent electrodes.
Findings show the material has a low “sheet resistance,” or the electrical resistance in very thin layers of material, which is measured in units called “squares.” At 22 ohms per square, it is five times better than ITO, which has a sheet resistance of 100 ohms per square.
The hybrid structure was also found to have little resistance change when bent, while ITO shows dramatic increases in resistance when bent.