Blue OLEDs Improved

By setting an efficiency record for blue organic LEDs (OLEDs), researchers say they are closer to flipping the switch on cheaper, richer LED-type room lighting.

University of Florida materials science engineers have announced a record for blue OLEDs. Because blue is essential to white light, the advance helps overcome a hurdle to creating a lighting source that is much more efficient than compact fluorescents but that can produce high-quality light similar to that given off by standard incandescent bulbs.

“The quality of the light is really the advantage,” said Franky So, an associate professor of materials science and engineering at the university and lead investigator on the project. He collaborated with materials science engineering professor Paul Holloway and assistant professor Jiangeng Xue.

OLEDs, each about 2 mm², display a blue hue in this device created by University of Florida materials science and engineering researchers, who have achieved an efficiency record for blue OLEDs. Because blue is essential to white light, the advance helps overcome a hurdle to producing a light source that is much more efficient than compact fluorescents but that emits high-quality light similar to that of standard incandescent bulbs (photo courtesy of the University of Florida).

OLEDs are similar to inorganic LEDs but are built with organic semiconductors on large-area glass substrates rather than with inorganic semiconductor wafers. When used in display screen computer monitors, OLEDs have higher efficiency, better color saturation and a larger viewing angle. OLED displays also are used in cell phones, cameras and personal digital assistants. OLED flat panel TVs recently were introduced by Sony.

So and his team’s blue OLED achieved a peak efficiency of 50 lm — a lumen is a measure of brightness as perceived by human eyes — per watt. That’s a significant step toward the goal of his project: to achieve white light with efficiency higher than 100 lm/W.

So said the fact that OLEDs are highly “tunable” — each OLED is an individual light, which means differently colored OLEDs can be combined to produce different shades of light — puts warm, rich light easily within reach.

“The quality of the light generated can easily be tuned by using different color emitters,” he said. “You can make it red, green, blue or white.”

The US Department of Energy, which funded the research, reported the results on its Web site. Papers about it appeared earlier this year in the journal Applied Physics Letters.

For more information, visit: www.ufl.edu