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Issue 5, 2020
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Rational design of efficient orange-red to red thermally activated delayed fluorescence emitters for OLEDs with external quantum efficiency of up to 26.0% and reduced efficiency roll-off

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Abstract

The development of high efficiency orange-red/red thermally activated delayed fluorescence (TADF) organic light emitting diodes (OLEDs) with reduced efficiency roll-off remains a huge challenge. By fusing two weak electron-withdrawing benzoyl and quinoxaline units into one molecule, a strong π-accepting phenyl(quinoxalin-6-yl)methanone unit is introduced as an acceptor to develop three orange-red to red TADF emitters, (2-(4-(phenoxazin-10-yl)phenyl)quinoxalin-6-yl)phenylmethanone (PXZ-PQM), (2,3-bis(4-(phenoxazin-10-yl)phenyl)quinoxalin-6-yl)(phenyl)methanone (DPXZ-PQM) and (3,6-di(phenoxazin-10-yl)dibenzophenazin-11-yl)phenylmethanone (DPXZ-DPPM). By tuning the numbers of the donor and electron-withdrawing characteristics of the acceptor, the emission wavelength can be regulated from orange-red to red (592–642 nm). The rigid planar constituent moieties and highly twisted molecular structures induce high photoluminescence quantum yields of 61–88% in doped films and extremely small singlet–triplet energy splitting. The orange-red TADF-OLED using DPXZ-PQM as an emitter achieves a maximum external quantum efficiency (EQE) as high as 26.0% at 590 nm, which is among the highest EQE values reported for orange-red TADF-OLEDs with similar wavelengths. More importantly, a low efficiency roll-off is rendered with EQEs of 20.1 and 13.7% at a luminance of 100 and 1000 cd m−2, respectively.

Graphical abstract: Rational design of efficient orange-red to red thermally activated delayed fluorescence emitters for OLEDs with external quantum efficiency of up to 26.0% and reduced efficiency roll-off

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Supplementary files

Article information


Submitted
29 Oct 2019
Accepted
16 Dec 2019
First published
18 Dec 2019

J. Mater. Chem. C, 2020,8, 1614-1622
Article type
Paper

Rational design of efficient orange-red to red thermally activated delayed fluorescence emitters for OLEDs with external quantum efficiency of up to 26.0% and reduced efficiency roll-off

J. Liang, C. Li, Y. Cui, Z. Li, J. Wang and Y. Wang, J. Mater. Chem. C, 2020, 8, 1614
DOI: 10.1039/C9TC05892C

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