Improving Processability and Efficiency of Resonant TADF Emitters: A Design Strategy

David Hall; Subeesh Madayanad Suresh; Paloma L. dos Santos; Eimantas Duda; Sergey Bagnich; Anton Pershin; Pachaiyappan Rajamalli; David B. Cordes; Alexandra M.Z. Slawin; David Beljonne; Anna Köhler; Ifor D.W. Samuel; Yoann Olivier; Eli Zysman-Colman

doi:10.1002/adom.201901627

Improving Processability and Efficiency of Resonant TADF Emitters: A Design Strategy

David Hall, Subeesh Madayanad Suresh, Paloma L. dos Santos, Eimantas Duda, Sergey Bagnich, Anton Pershin, Pachaiyappan Rajamalli, David B. Cordes, Alexandra M.Z. Slawin, David Beljonne, Anna Köhler, Ifor D.W. Samuel, Yoann Olivier, Eli Zysman-Colman

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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 (ΔE_ST), 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 (EQE_max) 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
Article number	1901627
Number of pages	10
Journal	Advanced Optical Materials
Volume	8
Issue number	2
DOIs	https://doi.org/10.1002/adom.201901627
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
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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10.1002/adom.201901627

2020_OlivierY_articleFinal published version, 2.69 MB

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Hall, D., Suresh, S. M., dos Santos, P. L., Duda, E., Bagnich, S., Pershin, A., Rajamalli, P., Cordes, D. B., Slawin, A. M. Z., Beljonne, D., Köhler, A., Samuel, I. D. W., Olivier, Y., & Zysman-Colman, E. (2020). Improving Processability and Efficiency of Resonant TADF Emitters: A Design Strategy. Advanced Optical Materials, 8(2), Article 1901627. https://doi.org/10.1002/adom.201901627

@article{a0c7dc6e39b74a22ac2cb5de876f4755,

title = "Improving Processability and Efficiency of Resonant TADF Emitters: A Design Strategy",

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.",

keywords = "blue emission, multiresonance thermally activated delayed fluorescence, organic light emitting diodes, SCS-CC2 approach",

author = "David Hall and Suresh, {Subeesh Madayanad} and {dos Santos}, {Paloma L.} and Eimantas Duda and Sergey Bagnich and Anton Pershin and Pachaiyappan Rajamalli and Cordes, {David B.} and Slawin, {Alexandra M.Z.} and David Beljonne and Anna K{\"o}hler and Samuel, {Ifor D.W.} and Yoann Olivier and Eli Zysman-Colman",

note = "Funding Information: This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sk{\l}odowska Curie grant agreement No. 838885 (NarrowbandSSL). S.S. acknowledges support from the Marie Sk{\l}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 {\'E}quipements de Calcul Intensif (C{\'E}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{\'e}d{\'e}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. Publisher Copyright: {\textcopyright} 2019 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim",

year = "2020",

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doi = "10.1002/adom.201901627",

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T2 - A Design Strategy

AU - Hall, David

AU - Suresh, Subeesh Madayanad

AU - dos Santos, Paloma L.

AU - Duda, Eimantas

AU - Bagnich, Sergey

AU - Pershin, Anton

AU - Rajamalli, Pachaiyappan

AU - Cordes, David B.

AU - Slawin, Alexandra M.Z.

AU - Beljonne, David

AU - Köhler, Anna

AU - Samuel, Ifor D.W.

AU - Olivier, Yoann

AU - Zysman-Colman, Eli

N1 - Funding Information: This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska Curie grant agreement No. 838885 (NarrowbandSSL). S.S. acknowledges support from the Marie Skłodowska-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 Équipements de Calcul Intensif (CÉCI), 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 Fédération 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. Publisher Copyright: © 2019 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

PY - 2020/1/1

Y1 - 2020/1/1

N2 - 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.

AB - 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.

KW - blue emission

KW - multiresonance thermally activated delayed fluorescence

KW - organic light emitting diodes

KW - SCS-CC2 approach

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ER -

Improving Processability and Efficiency of Resonant TADF Emitters: A Design Strategy

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Improving Processability and Efficiency of Resonant TADF Emitters: A Design Strategy

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