Tetrabenzo[a,c]phenazine Backbone for Highly Efficient Orange-Red Thermally Activated Delayed Fluorescence with Completely Horizontal Molecular Orientation
Tetrabenzo[a,c]phenazine Backbone for Highly Efficient Orange-Red Thermally Activated Delayed Fluorescence with Completely Horizontal Molecular Orientation
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DOI：
10.1002/anie.202106570
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发表时间：
2021-07-21
影响因子：
16.6
通讯作者：
Adachi, Chihaya
中科院分区：
文献类型：
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作者：
Balijapalli, Umamahesh;Lee, Yi-Ting;Adachi, Chihaya
设计并表征了三种热激活延迟荧光(TADF)分子，即PQ1、PQ2和PQ3，它们分别由电子受体(A)四苯并[a，c]吩嗪(TBPZ)和电子供体(D)吩恶嗪(PXZ)单元组成。平面受主操纵和D和A单元之间的高空间位阻的综合作用赋予了高分子刚性，通过提高光致发光量子产率(PLQY)来抑制激子的非辐射衰减。特别是，PQ3中包含单态和三态电荷转移激发态和局域激发三重态的有序激发态以较短的延迟寿命(tau(D))提高了反向系间交叉速率常数(k(RISC))。基于PQ3的橙红色OLED显示出最大的外部电致发光量子效率(EQE)为27.4%，并且由于薄膜状态下跃迁偶极矩的完全水平取向，很好地抑制了EL效率的滚降。
Three thermally activated delayed fluorescence (TADF) molecules, namely PQ1, PQ2, and PQ3, are composed of electron-accepting (A) tetrabenzo[a,c]phenazine (TBPZ) and electron-donating (D) phenoxazine (PXZ) units are designed and characterized. The combined effects of planar acceptor manipulation and high steric hindrance between D and A units endow high molecular rigidity that suppresses nonradiative decay of the excitons with improved photoluminescence quantum yields (PLQYs). Particularly, the well-aligned excited states involving a singlet and a triplet charge-transfer excited states and a localized excited triplet state in PQ3 enhances the reverse intersystem crossing rate constant (k(RISC)) with a short delay lifetime (tau(d)). The orange-red OLED based on PQ3 displays a maximum external EL quantum efficiency (EQE) of 27.4% with a well-suppressed EL efficiency roll-off owing to a completely horizontal orientation of the transition dipole moment in the film state.