TY - JOUR
T1 - Improving Processability and Efficiency of Resonant TADF Emitters
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
UR - http://www.scopus.com/inward/record.url?scp=85076107915&partnerID=8YFLogxK
U2 - 10.1002/adom.201901627
DO - 10.1002/adom.201901627
M3 - Article
AN - SCOPUS:85076107915
SN - 2195-1071
VL - 8
JO - Advanced Optical Materials
JF - Advanced Optical Materials
IS - 2
M1 - 1901627
ER -