Extremely condensing triplet states of DPEPO-type hosts through constitutional isomerization for high-efficiency deep-blue thermally activated delayed fluorescence diodes.
Extremely condensing triplet states of DPEPO-type hosts through constitutional isomerization for high-efficiency deep-blue thermally activated delayed fluorescence diodes.
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通过结构异构化实现 DPEPO 型主体的极度凝聚三重态，用于高效深蓝色热激活延迟荧光二极管
DOI：
10.1039/c5sc04848f
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发表时间：
2016-04-01
期刊：
影响因子：
8.4
通讯作者：
Xu H
中科院分区：
文献类型：
--
作者：
Zhang J;Ding D;Wei Y;Xu H
热激活延迟荧光(TADF)主体DPEPO的不对称组成异构体，称为24‘DPEPO，赋予深蓝TADF二极管最先进的性能，包括超过20%的外部量子效率。热激活延迟荧光(TADF)染料与其主体作为纯有机分子的相似性使得主体在分子间相互作用中占据主导地位，对TADF二极管中激子的获取和利用至关重要。DPEPO是最常用的具有空间邻位取代二苯基氧膦(DPPO)基团的高能隙蓝TADF基质，用于抑制分子间相互作用，但由于其电活性较弱，存在严重的效率衰减问题。相反，对位取代的DPPO具有较小的空间位阻，在分子内电子耦合方面表现出更好的性能。在这项工作中，DPEPO的四个结构异构体被构建为二苯醚(DPE)，其中2或4位分别取代了两个二苯基氧膦(DPPO)，即22‘DPEPO(即DPEPO)、24DPEPO、24’DPEPO和44‘DPEPO。在分离构型的基础上，邻位和对位取代的DPPO的空间效应和电活性被成功地整合到24‘DPEPO中，同时由于其不对称的构型，分子间的相互作用显著减弱。与其同类化合物相比，24‘DPEPO具有刚性结构和类似于22’DPEPO的局域激发态，在相互作用抑制方面和在电荷通量平衡方面可与44‘DPEPO相比改善电荷迁移率。值得注意的是，由于邻位DPPO在T1位上的主要取向效应，它的T1态非常紧密地凝聚在一个苯基上，其剩余的五个苯基最大限度地保护了它免受分子间相互作用的影响。因此，24‘DPEPO使其基于DMAC-DPS的深蓝器件具有最先进的性能，包括色度坐标为(0.16，0.17)的高颜色纯度，外量子效率(EQE)超过20%，在1000cdm-2时的EQE滚降低至32%。结果表明，24’DPEPO的器件性能远远超过22‘DPEPO和44’DPEPO的简单集成，验证了主机优化的意义。
An asymmetric constitutional isomer of the thermally activated delayed fluorescence (TADF) host DPEPO, named 24′DPEPO, endowed deep-blue TADF diodes with state-of-the-art performance, including external quantum efficiency beyond 20%. The similarity of thermally activated delayed fluorescence (TADF) dyes and their hosts as pure organic molecules makes hosts predominant in intermolecular interactions and crucial to exciton harvesting and utilization in TADF diodes. DPEPO is the most popular high-energy-gap blue TADF host with steric ortho-substituted diphenylphosphine oxide (DPPO) groups for intermolecular interaction suppression, but suffers from serious efficiency roll-off due to its weak electroactivity. On the contrary, para-substituted DPPO with small steric hindrance is superior in intramolecular electronic coupling. In this work, four constitutional isomers of DPEPO are constructed as diphenylether (DPE) with two diphenylphosphine oxide (DPPO) groups substituted at either the 2 or 4 position, namely 22′DPEPO (viz.DPEPO), 24DPEPO, 24′DPEPO and 44′DPEPO, respectively. On the basis of separation configuration, the steric effect and electroactivity of ortho- and para-substituted DPPOs are successfully integrated in 24′DPEPO, accompanied by remarkably reduced intermolecular interactions due to its unsymmetrical configuration. Compared to its congeners, 24′DPEPO has a rigid structure and locally excited states similar to 22′DPEPO for interaction suppression and improved charge mobility comparable to 44′DPEPO for charge flux balance. Significantly, by virtue of the predominant orientation effect of ortho-DPPO on the T1 location, its T1 state is extremely condensed onto a single phenyl, protected from intermolecular interactions by its remaining five phenyls at its maximum extent. Consequently, 24′DPEPO endowed its DMAC-DPS-based deep-blue devices with state-of-the-art performance, including high color purity with chromaticity coordinates of (0.16, 0.17), external quantum efficiency (EQE) beyond 20% and EQE roll-off as low as 32% at 1000 cd m–2. It is shown that the device performance of 24′DPEPO was far beyond simple integration of those of 22′DPEPO and 44′DPEPO, verifying the significance of host optimization.
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影响因子：
4.4
作者：
BECKE, AD
通讯作者：
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影响因子：
4.4
作者：
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