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Tunable polymers could make truly white OLED

Posted: 16 Sep 2013     Print Version  Bookmark and Share

Keywords:University of Utah  polymer  platinum  organic light-emitting diodes 

Researchers at University of Utah were able to "tune" the plastic-like polymer to emit light of different colours by inserting platinum atoms into an organic semiconductor.

"These new, platinum-rich polymers hold promise for white organic light-emitting diodes and new kinds of more efficient solar cells," says University of Utah physicist Z. Valy Vardeny, who led a study.

Certain existing white light bulbs use LEDs, or light-emitting diodes, and some phone displays use organic LEDs, or OLEDs. Neither are truly white LEDs, but instead use LEDs made of different materials that each emit a different colour, then combine or convert those colours to create white light.

In the new study, Vardeny and his team explained how they inserted platinum metal atoms at different intervals along a chain-like organic polymer, and thus were able to adjust or tune the colours emitted.

"That is a step towards a truly white OLED generated by multiple colours from a single polymer."

Existing white OLED displays – like those in recent cell phones – use different organic polymers that emit different colours, which are arranged in pixels of red, green and blue and then combined to make white light, says Vardeny, a distinguished professor of physics. "This new polymer has all those colours simultaneously, so no need for small pixels and complicated engineering to create them."

"This polymer emits light in the blue and red spectral range, and can be tuned to cover the whole visible spectrum," he adds. "As such, it can serve as the active [or working] layer in white OLEDs that are predicted to replace regular light bulbs."

The new polymer also could be used in a new type of solar power cell in which the platinum would help the polymer convert sunlight to electricity more efficiently. And because the platinum-rich polymer would allow physicists to "read" the information stored in electrons' "spins" or intrinsic angular momentum, the new polymers also have potential uses for computer memory.

In the new study, the researchers made the new platinum-rich polymers and then used various optical methods to characterise their properties and show how they light up when stimulated by light.

The polymers in the new study aren't quite OLEDs because they emit light when stimulated by other light. An OLED is a polymer that emits light when stimulated by electrical current.

"We haven't yet fabricated an OLED with it. The paper shows we get multiple colours simultaneously from one polymer," making it possible to develop an OLED in which single pixels emit white light."

Vardeny predicts about one year until design of a "platinum-rich pi-conjugated polymer" that is tuned to emit white light when stimulated by light, and about two years until development of true white organic LEDs.





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