Thin polymer to extend OLED display life?

May 16, 2012

A polymer discovered at Georgia Tech could allow air-stable electrodes to be used in OLED displays.

At the moment, efficient OLED displays need to have low 'work function' metals as internal electrodes, which are all reactive metals like calcium, magnesium or lithium that are corroded by air.

It is partly for the protection of these electrodes that there is so much research into barrier layers to keep oxygen and water out of flexible OLED displays.

Georgia Tech researchers have introduced "what appears to be a universal technique to reduce the work function of a conductor", said the university. "They spread a layer of a polymer approximately 1-10nm thick on the conductor's surface to create a strong surface dipole."

The polymers containing aliphatic amine groups that "substantially", according to the university, reduce the work function of conductors including metals, transparent conductive metal oxides, conducting polymers, and graphene.

Which means, claims Georgia, that the polymers can convert an air-stable high work function metal into low work function electrode inside a display.

"The reduction arises from physisorption of the neutral polymer, which turns the modified conductors into efficient electron-selective electrodes," the research team told the journal Science.

The polymers can be processed in air from solutions in solvents such as water and methoxyethanol.

"These polymers are inexpensive, environmentally friendly and compatible with existent roll-to-roll mass production techniques," said Professor Bernard Kippelen of Georgia Tech. "Replacing the reactive metals with stable conductors, including conducting polymers, completely changes the requirements of how electronics are manufactured and protected. Their use can pave the way for lower cost and more flexible devices."

To illustrate the new method, Kippelen and his peers evaluated the polymers' performance in organic thin-film transistors and OLEDs. They've also built a prototype, claimed to be the first-ever completely plastic solar cell.