Issue 6, 2023

Efficient narrowband green OLEDs with TADF sensitizers combining multiple charge-transfer pathways

Abstract

Multiple resonance (MR) thermally activated delayed fluorescence (TADF) emitters have attracted much attention for their narrow emission band and high efficiency. However, organic light-emitting devices based on MR-TADF emitters generally suffer from severe efficiency roll-off at high current density due to their relatively large singlet–triplet splitting energy. In this work, three TADF molecules are designed by an ortho-connected oligo carbazole donor and diphenyltriazine acceptor with the purpose of combining both through-bond charge transfer (TBCT) and through-space charge transfer (TSCT). Through fine tuning the proportion of intramolecular TBCT and TSCT by changing the number of carbazole units, a relatively high reverse intersystem crossing rate (kRISC) approaching 106 s−1 and radiative transition rate (kF) of over 106 s−1 are achieved. As a result, the devices using these molecules as emitters give maximum external quantum efficiency (EQE) of over 20% with extremely low efficiency roll-off of 9.9% at the practical luminance of 1000 cd m−2. Furthermore, by using these materials as assistant hosts and sensitizers and DMAc-BN as a terminal emitter, high efficiencies of 23.9% and 66.0 lm W−1 are achieved with a full width at half maximum of 46 nm, featuring slow efficiency roll-off with EQE of 17.9% at the luminance of 1000 cd m−2.

Graphical abstract: Efficient narrowband green OLEDs with TADF sensitizers combining multiple charge-transfer pathways

Supplementary files

Article information

Article type
Research Article
Submitted
28 Dec 2022
Accepted
31 Jan 2023
First published
01 Feb 2023

Mater. Chem. Front., 2023,7, 1128-1136

Efficient narrowband green OLEDs with TADF sensitizers combining multiple charge-transfer pathways

D. Li, J. Yang, J. Chen, X. Peng, W. Li, Z. Chen, W. Qiu, G. Yang, Z. Yang, M. Li, S. Jiang, D. Liu, Y. Gan, K. Liu and S. Su, Mater. Chem. Front., 2023, 7, 1128 DOI: 10.1039/D2QM01363K

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