New pure-blue OLED could overcome current challenges for OLED displays

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, the availability of similarly performing blue light sources is lacking. Researchers in Japan have used a new combination of emitter molecules and demonstrated a new approach that may overcome this challenge.

The pure-blue OLED splits the energy conversion and emission processes between two different molecules. Using this approach, the researchers could produce a pure-blue emission with high-efficiency that can maintain brightness for relatively long times. The device doesn't use any expensive metal atoms.

Researchers say that while there are a growing number of options for red and green OLEDs, devices emitting high-energy blue light have been a challenge. Trade-offs have always occurred with efficiency, color purity, cost, and lifetime. Blue emitters generally have shorter operational lifetimes and use expensive metals like iridium or platinum.

Researchers from 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 exhibits emission containing a wide range of colors.

The researchers used a two-molecule approach termed hyperfluorescence. Using that approach, the team achieved longer operational lifetimes at a 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 the emission for the same electrical current. The result was a lifespan that nearly doubled at high brightness. Researchers estimate the device could maintain 50 percent of its brightness for over 10,000 hours at more moderate intensity. The team hopes their OLED will replace current blue OLEDs used in displays in the future.