Bright Blue PHOLEDs Almost Ready for TV

Deep blue lights could make smartphones, flat panel displays more energy effficient

2 min read
Bright Blue PHOLEDs Almost Ready for TV
Photo: University of Michigan/University of Southern California

A new energy-efficient organic LED (OLED) that glows a deep blue is finally close to meeting the most stringent U.S. video display brightness requirements, researchers say.

OLEDs have enabled a new generation of bright, high-quality, low-cost, power-efficient, flexible, lightweight flat panel displays. Each pixel in an OLED display typically consists of red, green, and blue OLEDs that shine with different brightnesses to produce any desired color.

Phosphorescent OLEDs (PHOLEDs) use only one quarter the energy of conventional OLEDs. Green and red PHOLEDs are already used in smartphones and TVs, leading to longer battery lives and lower electricity bills, but developing the kind of bright deep blue PHOLEDs needed for video displays has proven challenging.

Now scientists have developed what they say are the brightest deep blue PHOLEDs reported so far, work sponsored by Universal Display Corporation and the U.S. Air Force. The researchers added their new lights nearly meet the most stringent requirements of the National Television Systems Committee (NTSC), the video standards used across most of the Americas.

"There have been previous works that reported PHOLEDs having similar color as ours, but their brightnesses were very dim, about 10 times less," says study lead author Jaesang Lee, an electrical engineer at the University of Michigan, Ann Arbor. "A combination of high brightness and deep blue color is quite revolutionary."

The new PHOLEDs are based on a kind of molecule known as a N-heterocyclic carbene iridium-III complex, which emits deep blue light very brightly. This compound also emits light efficiently because its design reduces the chances that light-emitting excitons—electrons bound to their positively charged counterparts, holes—will either get lost as heat or destroy the compound itself, Lee says.

Unfortunately, this new PHOLED has a brief operational lifetime, just like many other blue PHOLEDs, Lee says. Future research will focus on stabilizing the molecule at the heart of this new PHOLED to create a longer-lasting version of the device.

Lee, along with IEEE Fellow Stephen Forrest and their colleagues, detailed the device in the journal Nature Materials.

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3D-Stacked CMOS Takes Moore’s Law to New Heights

When transistors can’t get any smaller, the only direction is up

10 min read
An image of stacked squares with yellow flat bars through them.
Emily Cooper
Green

Perhaps the most far-reaching technological achievement over the last 50 years has been the steady march toward ever smaller transistors, fitting them more tightly together, and reducing their power consumption. And yet, ever since the two of us started our careers at Intel more than 20 years ago, we’ve been hearing the alarms that the descent into the infinitesimal was about to end. Yet year after year, brilliant new innovations continue to propel the semiconductor industry further.

Along this journey, we engineers had to change the transistor’s architecture as we continued to scale down area and power consumption while boosting performance. The “planar” transistor designs that took us through the last half of the 20th century gave way to 3D fin-shaped devices by the first half of the 2010s. Now, these too have an end date in sight, with a new gate-all-around (GAA) structure rolling into production soon. But we have to look even further ahead because our ability to scale down even this new transistor architecture, which we call RibbonFET, has its limits.

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