Abstract
A new design strategy is introduced to address a persistent weakness with resonance thermally activated delayed fluorescence (R-TADF) emitters to reduce aggregation-caused quenching effects, which are identified as one of the key limiting factors. The emitter Mes3DiKTa shows an improved photoluminescence quantum yield of 80% compared to 75% for the reference DiKTa in 3.5 wt% 1,3-bis(N-carbazolyl)benzene. Importantly, emission from aggregates, even at high doping concentrations, is eliminated and aggregation-caused quenching is strongly curtailed. For both molecules, triplets are almost quantitatively upconverted into singlets in electroluminescence, despite a significant (≈0.21 eV) singlet-triplet energy gap (ΔEST), in line with correlated quantum-chemical calculations, and a slow reverse intersystem crossing. It is speculated that the lattice stiffness responsible for the narrow fluorescence and phosphorescence emission spectra also protects the triplets against nonradiative decay. An improved maximum external quantum efficiencies (EQEmax) of 21.1% for Mes3DIKTa compared to the parent DiKTa (14.7%) and, importantly, reduced efficiency roll-off compared to literature resonance TADF organic light-emitting diodes (OLEDs), shows the promise of this design strategy for future design of R-TADF emitters for OLED applications.
Original language | English |
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Article number | 1901627 |
Number of pages | 10 |
Journal | Advanced Optical Materials |
Volume | 8 |
Issue number | 2 |
DOIs | |
Publication status | Published - 1 Jan 2020 |
Funding
This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sk?odowska Curie grant agreement No. 838885 (NarrowbandSSL). S.S. acknowledges support from the Marie Sk?odowska-Curie Individual Fellowship. This work was funded by the EC through the Horizon 2020 Marie Sklodowska-Curie ITN project TADFlife (grant #: 812872). The St Andrews team would also like to thank the Leverhulme Trust (RPG-2016-047) and EPSRC (EP/P010482/1) for financial support. Computational resources were provided by the Consortium des ?quipements de Calcul Intensif (C?CI), funded by the Fonds de la Recherche Scientifiques de Belgique (F.R.S.-FNRS) under Grant No. 2.5020.11, as well as the Tier-1 supercomputer of the F?d?ration Wallonie-Bruxelles, infrastructure funded by the Walloon Region under the Grant Agreement No. 1117545. A.P. acknowledges the financial support from the Marie Curie Fellowship (MILORD project, No. 748042). D.B. is a FNRS Research Director. The authors thank Franck-Julian Kahle for support with data analysis. Y.O. acknowledges fruitful discussions with Prof. Juan-Carlos Sancho-Garcia from the University of Alicante and Prof. Luca Muccioli from the University of Bologna.
Funders | Funder number |
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Fonds de la Recherche Scientifiques de Belgique | 2.5020.11 |
Horizon 2020 Marie Sklodowska-Curie | |
Universidad de Alicante | |
Horizon 2020 Framework Programme | 748042, 812872 |
H2020 Marie Skłodowska-Curie Actions | |
Waalse Gewest | 1117545 |
Engineering and Physical Sciences Research Council | EP/P010482/1 |
Leverhulme Trust | RPG-2016-047 |
European Commission | 838885 |
Fonds De La Recherche Scientifique - FNRS | |
Fédération Wallonie-Bruxelles | |
Università di Bologna |
Keywords
- blue emission
- multiresonance thermally activated delayed fluorescence
- organic light emitting diodes
- SCS-CC2 approach
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