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Achieving 21% external quantum efficiency for nondoped solution-processed sky-blue thermally activated delayed fluorescence OLEDs by means of multi-donor/acceptor emitter with through-space/-bond charge transfer.

Zheng, Xujun and Huang, Rongjuan and Zhong, Cheng and Xie, Guohua and Ning, Weimin and Huang, Manli and Ni, Fan and Dias, Fernando B. and Yang, Chuluo (2020) 'Achieving 21% external quantum efficiency for nondoped solution-processed sky-blue thermally activated delayed fluorescence OLEDs by means of multi-donor/acceptor emitter with through-space/-bond charge transfer.', Advanced science., 7 (7). p. 1902087.

Abstract

Although numerous thermally activated delayed fluorescence (TADF) organic light-emitting diodes (OLEDs) have been demonstrated, the efficient blue or even sky-blue TADF-based non-doped solution-processed devices are still very rare. Herein, we skilfully incorporate through-space charge transfer (TSCT) and through-bond charge transfer (TBCT) effect, as well as the multi-(donor/acceptor) characteristic into one molecule. The former allows this material to show small singlet-triplet energy splitting (ΔEST) and high transition dipole moment. The latter, on one hand, further lights up multi-channel reverse intersystem crossing (RISC) to increase triplet exciton utilization via degenerating molecular orbitals. On the other hand, the nature of the molecular twisted structure effectively suppresses intermolecular packing to obtain high PLQY in neat flims. Consequently, using this design strategy, T-CNDF-T-tCz containing three donor and three acceptor units, successfully realizes an extremely small ΔEST (~ 0.03 eV) and a high PLQY (~ 0.76) at the same time, hence the non-doped solution-processed sky-blue TADF-OLED displays record-breaking efficiency among the solution processes-based non-doped sky-blue OLEDs, with high brightness over 5200 cd m−2 , current efficiency up to 46.4 cd A−1 , and external quantum efficiency up to 21.0%.

Item Type:Article
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Status:Peer-reviewed
Publisher Web site:https://doi.org/10.1002/advs.201902087
Publisher statement:© 2020 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Date accepted:08 January 2020
Date deposited:15 January 2020
Date of first online publication:08 February 2020
Date first made open access:11 February 2020

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