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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, Advance Article
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, Advance Article , DOI: 10.1039/C9TC05892C

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