Fast spin-flip enables efficient and stable organic electroluminescence from charge-transfer states
Fast spin-flip enables efficient and stable organic electroluminescence from charge-transfer states
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DOI：
10.1038/s41566-020-0668-z
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发表时间：
2020-08-03
期刊：
影响因子：
35
通讯作者：
Friend, Richard H.
中科院分区：
文献类型：
--
作者：
Cui, Lin-Song;Gillett, Alexander J.;Friend, Richard H.
从三重态到单重态激发态的自旋翻转，即反向系间穿越（RISC），是用于改善有机发光二极管中的光发射的有吸引力的途径，如使用热激活延迟荧光（TADF）的器件所示。然而，器件稳定性和效率滚降仍然是源于低RISC速率（k（RISC））的具有挑战性的问题。在这里，我们报告了一个TADF分子与多个供体单元，形成电荷共振型混合三重态，导致一个小的单重态-三重态的能量分裂，大的自旋轨道耦合，和一个密集的歧管的三重态能量接近的单线态。我们的TADF分子中的Thek（RISC）快达1.5 × 10（7）s（-1），比典型的TADF发射器高出两个数量级。基于该分子的有机电致发光器件表现出良好的稳定性（1，000 cd m（-2）的T（90）约为600 h）、高的最大外量子效率（>29.3%）和低的效率衰减（
A spin-flip from a triplet to a singlet excited state, that is, reverse intersystem crossing (RISC), is an attractive route for improving light emission in organic light-emitting diodes, as shown by devices using thermally activated delayed fluorescence (TADF). However, device stability and efficiency roll-off remain challenging issues that originate from a slow RISC rate (k(RISC)). Here, we report a TADF molecule with multiple donor units that form charge-resonance-type hybrid triplet states leading to a small singlet-triplet energy splitting, large spin-orbit couplings, and a dense manifold of triplet states energetically close to the singlets. Thek(RISC)in our TADF molecule is as fast as 1.5 x 10(7) s(-1), a value some two orders of magnitude higher than typical TADF emitters. Organic light-emitting diodes based on this molecule exhibit good stability (estimatedT(90)about 600 h for 1,000 cd m(-2)), high maximum external quantum efficiency (>29.3%) and low efficiency roll-off (