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2016-4-7

An international joint research group led by Associate Professor TAKEDA Youhei and OKAZAKI Masato (graduate student) of the Division of Applied Chemistry, Graduate School of Engineering, Osaka University and Dr. Przemyslaw Data and Prof. Andrew P. Monkman of the Department of Physics, Durham University succeeded in developing a new thermally activated delayed fluorescence (TADF) material which displays emission of light in colors from green to deep-red.

Through a detailed optical property investigation of this material, this group also confirmed that TADF was achieved through intersystem crossing (ISC) from the singlet excited state (1CT) to the triplet excited state (3LEA), a world first.

In addition, the external quantum efficiency (EQE) of the organic EL devices manufactured by using these newly developed TADF materials in their emitting layer reached 16%, greatly surpassing 5%, the limiting value obtained by conventional fluorescent materials.

These research results will contribute to the research and development of white TADF light emitting devices for indoor- and outdoor-use through combination with TADF materials that emit light in shorter wavelengths (deep blue ~ yellow) which are currently being developed all over the world.

Abstract

A new family of thermally activated delayed fluorescence (TADF) emitters based on U-shaped D-A-D architecture with a novel accepting unit has been developed. All investigated compounds have small singlet-triplet energy splitting (ΔEST) ranging from 0.02 to 0.20 eV and showed efficient TADF properties. The lowest triplet state of the acceptor unit plays the key role in the TADF mechanism. OLEDs fabricated with these TADF emitters achieved excellent efficiencies up to 16% external quantum efficiency (EQE).

This research was published in the electronic version of Angewandte Chemie International Edition on April 6, 2016 (Germany time).

OLED device emitting bright orange light

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Figure 2a

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Figure 2b

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Figure 2c

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To learn more about this research, please view the full research report entitled "Dibenzo[a,j]phenazine-Cored Donor–Acceptor–Donor Compounds as Green-to-Red/NIR Thermally Activated Delayed Fluorescence Organic Light Emitters" at this page of the Angewandte Chemie International Edition website.


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