Current OLED displays have a challenge when it comes to blue light sources. While there are red and green organic light emitting diodes with high performance, there is a lack of availability of similarly powerful blue light sources. Researchers in Japan have used a new combination of emitter molecules and demonstrated a new approach that can address this challenge.
The pure blue OLED divides the energy conversion and emission processes between two different molecules. Using this approach, the researchers could produce a high-efficiency, high-blue emission that can maintain brightness for a relatively long time. The device does not use expensive metal atoms.
Researchers say that while there are a growing number of options for red and green OLEDs, devices that emit high-energy blue light have been challenging. Compromises have always been made with efficiency, color purity, cost and service life. Blue emitters generally have a shorter lifespan and use expensive metals such as iridium or platinum.
Researchers at the Kyushu University’s Center for Organic Photonics and Electronics Research (OPERA) developed molecules that emit light based on the process of thermally activated delayed fluorescence. The process can achieve efficiency without a metal atom and often has an emission that includes a wide range of colors.
The researchers used a two-molecule approach called hyperfluorescence. With this approach, the team achieved longer operating lifetimes at higher brightness than previously reported for highly efficient OLEDs with similar color purity. Their approach essentially stacks two devices on top of each other to effectively double emissions for the same electrical current. The result was a lifespan that almost doubled at high brightness. Researchers estimate that the device can maintain 50 percent of its brightness for over 10,000 hours at moderate intensity. The team hopes that in the future their OLED will replace the current blue OLEDs used in displays.
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