The US team used a three emission layer (EML) structure to obtain a peak power efficiency of 64±3 lm/W at a luminance of 1000 cd/m2 and CRI of 81. Typical CRI values for WOLEDs are between 75-80. (Applied Physics Letters 91 263503) “The power efficiency we obtained is one of the highest values among WOLEDs reported so far,” Yiru Sun, a researcher at Princeton University, told Optics.org. “What’s more, we have made no compromise in CRI for high power efficiency as we have also achieved a good quality of white colour balance.”
The 3-EML structure offers the additional advantage of allowing the color intensity to be adjusted. “We can produce a balanced white color by changing the thickness and doping concentration of the RGB emission region,” added Sun.
Although lifetimes of the device were not measured, the team recognizes that this is one of the major issues facing OLEDs and plans to address this in the future. “We will investigate more advanced dopant/ host materials that can be incorporated into this structure to achieve higher efficiency and longer lifetime,” concluded Sun