1,3,4-oxadiazole-based deep-blue thermally activated delayed fluorescence emitters for organic light emitting diodes
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A series of four 1,3,4-oxadiazole-based thermally activated delayed fluorescence (TADF) derivatives are reported as emitters for organic light emitting diodes (OLEDs). As a function of the nature of the substituent on the weak 1,3,4-oxadiazole acceptor their emission color could be tuned from green-blue to blue. The highly twisted conformation between carbazoles and oxadiazoles results in effective separation of the HOMO and the LUMO resulting in a small singlet-triplet splitting. The corresponding singlet-triplet energy gaps (∆EST) range from 0.22 to 0.28 eV resulting in an efficient reverse intersystem crossing (RISC) process and moderate to high photoluminescence quantum yields (ΦPL), ranging from 35 to 70% in a DPEPO matrix. Organic light-emitting diodes (OLEDs) based on i-2CzdOXD4CF3Ph achieve maximum external quantum efficiency (EQEmax) of up to 12.3% with a sky-blue emission at CIE of (0.18, 0.28) while the device based on i-2CzdOXDMe shows blue emission at CIE of (0.17, 0.17) with a maximum EQE of 11.8%.
Li , Z , Li , W , Keum , C , Archer , E , Zhao , B , Slawin , A M Z , Huang , W , Gather , M C , Samuel , I D W & Zysman-Colman , E 2019 , ' 1,3,4-oxadiazole-based deep-blue thermally activated delayed fluorescence emitters for organic light emitting diodes ' , Journal of Physical Chemistry , vol. 123 , no. 40 , pp. 24772-24785 . https://doi.org/10.1021/acs.jpcc.9b08479
Journal of Physical Chemistry
Copyright © 2019 American Chemical Society. This work has been made available online in accordance with publisher policies or with permission. Permission for further reuse of this content should be sought from the publisher or the rights holder. This is the author created accepted manuscript following peer review and may differ slightly from the final published version. The final published version of this work is available at https://doi.org/10.1021/acs.jpcc.9b08479
DescriptionWe are grateful to the EPSRC for financial support (grants EP/P010482/1, EP/J01771X, EP/J00916 and EP/R035164/1). We gratefully acknowledge funding through the EPSRC NSF- CBET lead agency agreement (EP/R010595/1, 1706207) and a Leverhulme Trust Research Grant (RPG-2017-231). We thank the EPSRC UK National Mass Spectrometry Facility at Swansea University for analytical services. Z.L. and W. L. thank the China Scholarship Council (grant numbers 201703780004 and 201708060003)
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