Substitution effects on a new pyridylbenzimidazole acceptor for thermally activated delayed fluorescence and their use in organic light-emitting diodes
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In this work a new acceptor is used for use in thermally activated delayed fluorescence (TADF) emitters, pyridylbenzimidazole, which when coupled with phenoxazine allows efficient TADF to occur. N-functionalization of the benzimidazole using methyl, phenyl, and tert-butyl groups permits color tuning and suppression of aggregation-caused quenching (ACQ) with minimal impact on the TADF efficiency. The functionalized derivatives support a higher doping of 7 wt% before a fall-off in photoluminescence quantum yields is observed, in contrast with the parent compound, which undergoes ACQ at doping concentrations greater than 1 wt%. Complex conformational dynamics, reflected in the time-resolved decay profile, is found. The singlet−triplet energy gap, ΔEST, is modulated by N-substituents of the benzimidazole and ranges of between 0.22 and 0.32 eV in doped films. Vacuum-deposited organic light-emitting diodes, prepared using three of the four analogs, show maximum external quantum efficiencies, EQEmax, of 23.9%, 22.2%, and 18.6% for BIm(Me)PyPXZ , BIm(Ph)PyPXZ , and BImPyPXZ , respectively, with a correlated and modest efficiency roll-off at 100 cd m–2 of 19% 13%, and 24% of the EQEmax, respectively.
Hall , D , Rajamalli , P , Duda , E , Madayanad Suresh , S , Rodella , F , Bagnich , S , Carpenter-Warren , C L , Cordes , D B , Slawin , A M Z , Strohriegl , P , Beljonne , D , Köhler , A , Olivier , Y & Zysman-Colman , E 2021 , ' Substitution effects on a new pyridylbenzimidazole acceptor for thermally activated delayed fluorescence and their use in organic light-emitting diodes ' , Advanced Optical Materials , vol. 9 , no. 20 , 2100846 . https://doi.org/10.1002/adom.202100846
Advanced Optical Materials
Copyright © 2021 The Authors. Advanced Optical Materials published by Wiley-VCH GmbH. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.