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Unveiling the TADF Emitters with Apparent Negative Singlet-Triplet Gaps: Implications for Exciton Harvesting and OLED Performance
Advanced Optical Materials ( IF 8.0 ) Pub Date : 2023-09-28 , DOI: 10.1002/adom.202301784
Xinrui Chen 1 , Sergey Bagnich 2 , Robert Pollice 3, 4 , Bing Li 1 , Yuanyuan Zhu 1 , Rishabh Saxena 2 , Yixiao Yin 1 , Weiguo Zhu 1 , Alan Aspuru‐Guzik 3, 4, 5, 6 , Eli Zysman‐Colman 7 , Anna Köhler 2 , Yafei Wang 1
Advanced Optical Materials ( IF 8.0 ) Pub Date : 2023-09-28 , DOI: 10.1002/adom.202301784
Xinrui Chen 1 , Sergey Bagnich 2 , Robert Pollice 3, 4 , Bing Li 1 , Yuanyuan Zhu 1 , Rishabh Saxena 2 , Yixiao Yin 1 , Weiguo Zhu 1 , Alan Aspuru‐Guzik 3, 4, 5, 6 , Eli Zysman‐Colman 7 , Anna Köhler 2 , Yafei Wang 1
Affiliation
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Intramolecular through-space charge transfer thermally activated delayed fluorescence (TSCT-TADF) has attracted much attention recently as it can achieve both small energy splitting and high emission efficiency. However, the relationship of excited states between TSCT and through-bond charge transfer (TBCT) remains a challenge in the TSCT-TADF molecules. Herein, three compounds DPS-m-bAc, DPS-p-bAc, and DPS-OAc that possess emissive TSCT and/or TBCT states are prepared. Interestingly, a so-called inverted energy gap is found for both DPS-m-bAc and DPS-p-bAc in toluene solution, which results from the different charge transfer states of ICThigh and ICTlow, as proved by the detailed transient photoluminescence and calculated results. Intense emission from blue to yellow associated with high photoluminescence quantum yields of 70–100% are measured in doped polymethyl(methacrylate) (PMMA) films. Notably, compound DPS-m-bAc achieves the highest reverse intersystem crossing rate constant (kRISC) of over 107 s−1 in a PMMA film, benefiting from close-lying TSCT and TBCT states. The solution-processed device with DPS-m-bAc displays a maximum external quantum efficiency of 21.7% and a relatively small efficiency roll-off (EQE of 20.2% @ 100 cd m−2). Overall, this work demonstrates how with judicious emitter engineering, a synergy between different charge transfer excited states, can be achieved, providing an avenue to achieve highly efficient solution-processed OLEDs.
中文翻译：
揭开具有明显负单线态-三线态间隙的 TADF 发射器：对激子收集和 OLED 性能的影响
分子内穿空间电荷转移热激活延迟荧光（TSCT-TADF）因其能够实现小能量分裂和高发射效率而备受关注。然而，TSCT 和键通电荷转移 (TBCT) 之间的激发态关系仍然是 TSCT-TADF 分子中的一个挑战。本文中，制备了具有发射TSCT和/或TBCT状态的三种化合物DPS- m -bAc、DPS- p -bAc和DPS-OAc。有趣的是，在甲苯溶液中，DPS- m -bAc 和 DPS- p -bAc都发现了所谓的倒置能隙，这是由 ICT high和 ICT low的不同电荷转移态引起的，正如详细的瞬态光致发光所证明的那样并计算结果。在掺杂聚甲基丙烯酸甲酯 (PMMA) 薄膜中测量到与 70-100% 的高光致发光量子产率相关的从蓝色到黄色的强发射。值得注意的是，得益于紧密的 TSCT 和 TBCT 态，化合物 DPS- m -bAc 在 PMMA 薄膜中实现了超过 10 7 s -1的最高反向系间窜越率常数 ( k RISC ) 。采用 DPS- m -bAc进行溶液处理的器件显示出 21.7% 的最大外量子效率和相对较小的效率滚降（EQE为 20.2% @ 100 cd m -2）。总体而言，这项工作展示了如何通过明智的发射极工程，实现不同电荷转移激发态之间的协同作用，从而为实现高效溶液加工 OLED 提供了途径。
更新日期：2023-09-28
中文翻译：
揭开具有明显负单线态-三线态间隙的 TADF 发射器：对激子收集和 OLED 性能的影响
分子内穿空间电荷转移热激活延迟荧光（TSCT-TADF）因其能够实现小能量分裂和高发射效率而备受关注。然而，TSCT 和键通电荷转移 (TBCT) 之间的激发态关系仍然是 TSCT-TADF 分子中的一个挑战。本文中，制备了具有发射TSCT和/或TBCT状态的三种化合物DPS- m -bAc、DPS- p -bAc和DPS-OAc。有趣的是，在甲苯溶液中，DPS- m -bAc 和 DPS- p -bAc都发现了所谓的倒置能隙，这是由 ICT high和 ICT low的不同电荷转移态引起的，正如详细的瞬态光致发光所证明的那样并计算结果。在掺杂聚甲基丙烯酸甲酯 (PMMA) 薄膜中测量到与 70-100% 的高光致发光量子产率相关的从蓝色到黄色的强发射。值得注意的是，得益于紧密的 TSCT 和 TBCT 态，化合物 DPS- m -bAc 在 PMMA 薄膜中实现了超过 10 7 s -1的最高反向系间窜越率常数 ( k RISC ) 。采用 DPS- m -bAc进行溶液处理的器件显示出 21.7% 的最大外量子效率和相对较小的效率滚降（EQE为 20.2% @ 100 cd m -2）。总体而言，这项工作展示了如何通过明智的发射极工程，实现不同电荷转移激发态之间的协同作用，从而为实现高效溶液加工 OLED 提供了途径。
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