IMRE, U-M Develop True Blue OLED

Researchers from the Institute of Materials Research and Engineering (IMRE), a research institute of Singapore’s Agency for Science, Technology and Research (A*STAR), and the University of Michigan (U-M) have developed a blue organic light emitting diode (OLED) with an efficiency reaching 9.4 percent, double that of the maximum theoretical efficiency limit. This paves the way for longer-lasting, more efficient and vivid OLED displays for the consumer market.

The researchers discovered that by changing the thickness of the light emitting layer and optimising the concentration of light emitting material in the same layer they could double the OLED efficiency from the current maximum 5 percent EQE.

The achievement allows manufacturers of full color OLED displays to use the new fluorescent materials to make devices that have significantly longer lifetime, consume less power and more importantly, can emit pure, and brighter blue light that will give more life-like colors to OLED displays compared to liquid crystal displays (LCDs) and light emitting diode displays (LEDs). The material is also solution-processable making it easy to manufacture and cost-effective. This could greatly enhance the attractiveness of OLED displays in the consumer market.

“One of the reasons why current OLED displays are not as popular as LCD and LED displays is that the blue emitters have short lifetime and poor color quality,” said Dr. Chen Zhikuan, an IMRE Senior Scientist and one of the principal researchers behind the fluorescent OLED development. “With our breakthrough, OLED TVs could well be the next wave in consumer displays and may soon appear in your homes.” Blue light emitters are also used in a wide array of other devices such as TVs and monitors as well as in LED lighting.

Current OLED displays are either phosphorescent or fluorescent materials displays. Though phosphorescent OLEDs have efficiencies that reach 11 percent, they are less stable, have shorter lifetimes and produce poor color quality with their light blue color emissions. Blue light has a wider band gap that requires higher energy for effective blue light emission, and inherently has lower efficiency and a shorter lifetime. By employing unique materials design and computer simulations the researchers were able to create a new OLED device that emitted fluorescent pure blue light with an amazing 9.4 percent EQE. Fluorescent materials are more stable compared to phosphorescent materials and have longer lifetimes. The developed blue emitters are solution processed, which mean they can be easily manufactured and made into huge size displays using low cost printing methods.

IMRE

A*STAR