The paper of Prof. Chihaya Adachi (Principal Investigator, Hydrogen Production Research Division, I²CNER / Project Leader, Center for Organic Photonics and Electronics Research (OPERA) ) was published in “Nature Photonics” on March 2, 2014.
■ Summary
Organic light-emitting diodes (OLEDs) employing thermally activated delayed fluorescence (TADF) have emerged as cheaper alternatives to high-performance phosphorescent OLEDs with noble-metal-based dopants. However, the efficiencies of blue TADF OLEDs are still low at high luminance, limiting full-colour display. Here, we report a blue OLED containing a 9,10-dihydroacridine/diphenylsulphone derivative that has a comparable performance to today’s best phosphorescent OLEDs. The device offers an external quantum efficiency of 19.5% and reduced efficiency roll-off characteristics at high luminance. Through computational simulation, we identified six pretwisted intramolecular charge-transfer (CT) molecules with small singlet–triplet CT state splitting but different energy relationships between 3CT and locally excited triplet (3LE) states. Systematic comparison of their excited-state dynamics revealed that CT molecules with a large twist angle can emit efficient and short-lifetime (a few microseconds) TADF when the emission peak energy is high enough and the 3LE state is higher than the 3CT state.
■ Paper
Title: Efficient blue organic light-emitting diodes employing thermally activated delayed fluorescence
Authors:Qisheng Zhang, Bo Li, Shuping Huang, Hiroko Nomura, Hiroyuki Tanaka and Chihaya Adachi
Journal: Nature Photonics