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Improving Processability and Efficiency of Resonant TADF Emitters: A Design Strategy
Advanced Optical Materials ( IF 8.0 ) Pub Date : 2019-12-03 , DOI: 10.1002/adom.201901627 David Hall 1, 2 , Subeesh Madayanad Suresh 1 , Paloma L. dos Santos 3 , Eimantas Duda 4 , Sergey Bagnich 4 , Anton Pershin 2 , Pachaiyappan Rajamalli 1, 3 , David B. Cordes 1 , Alexandra M. Z. Slawin 1 , David Beljonne 2 , Anna Köhler 4 , Ifor D. W. Samuel 3 , Yoann Olivier 2, 5 , Eli Zysman‐Colman 1
Advanced Optical Materials ( IF 8.0 ) Pub Date : 2019-12-03 , DOI: 10.1002/adom.201901627 David Hall 1, 2 , Subeesh Madayanad Suresh 1 , Paloma L. dos Santos 3 , Eimantas Duda 4 , Sergey Bagnich 4 , Anton Pershin 2 , Pachaiyappan Rajamalli 1, 3 , David B. Cordes 1 , Alexandra M. Z. Slawin 1 , David Beljonne 2 , Anna Köhler 4 , Ifor D. W. Samuel 3 , Yoann Olivier 2, 5 , Eli Zysman‐Colman 1
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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.
中文翻译：
提高谐振TADF发射器的可加工性和效率：一种设计策略
引入了一种新的设计策略来解决共振热激活延迟荧光（R-TADF）发射器的持续性缺陷，以减少聚集引起的猝灭效应，这被认为是关键限制因素之一。Mes 3 DiKTa发射体的光致发光量子产率提高了80％，而在3.5 wt％的1,3-双（N-咔唑基）苯中，参考DiKTa的发射率为75％。重要的是，即使在高掺杂浓度下，也可以消除聚集体的发射，并大大减少了聚集体引起的猝灭。对于这两个分子，三重态在电致发光中几乎被定量地上转换为单重态，尽管单重态-三重态的能隙（ΔE很大（≈0.21 eV）ST），符合相关的量子化学计算和缓慢的反向系统间穿越。据推测，负责窄的荧光和磷光发射光谱的晶格刚度还保护三元组免于非辐射衰变。与母体DiKTa（14.7％）相比，Mes 3 DIKTa的最大外部量子效率（EQE max）提高了21.1％，并且与文献中的共振TADF有机发光二极管（OLED）相比，重要的是降低了效率下降。该设计策略对OLED应用的R‐TADF发射器的未来设计的承诺。
更新日期：2020-01-17
中文翻译：
提高谐振TADF发射器的可加工性和效率：一种设计策略
引入了一种新的设计策略来解决共振热激活延迟荧光（R-TADF）发射器的持续性缺陷，以减少聚集引起的猝灭效应，这被认为是关键限制因素之一。Mes 3 DiKTa发射体的光致发光量子产率提高了80％，而在3.5 wt％的1,3-双（N-咔唑基）苯中，参考DiKTa的发射率为75％。重要的是，即使在高掺杂浓度下，也可以消除聚集体的发射，并大大减少了聚集体引起的猝灭。对于这两个分子，三重态在电致发光中几乎被定量地上转换为单重态，尽管单重态-三重态的能隙（ΔE很大（≈0.21 eV）ST），符合相关的量子化学计算和缓慢的反向系统间穿越。据推测，负责窄的荧光和磷光发射光谱的晶格刚度还保护三元组免于非辐射衰变。与母体DiKTa（14.7％）相比，Mes 3 DIKTa的最大外部量子效率（EQE max）提高了21.1％，并且与文献中的共振TADF有机发光二极管（OLED）相比，重要的是降低了效率下降。该设计策略对OLED应用的R‐TADF发射器的未来设计的承诺。
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