Solution-Processed Highly Efficient Bluish-Green Thermally Activated Delayed Fluorescence Emitter Bearing an Asymmetric Oxadiazole-Difluoroboron Double Acceptor
Solution-Processed Highly Efficient Bluish-Green Thermally Activated Delayed Fluorescence Emitter Bearing an Asymmetric Oxadiazole-Difluoroboron Double Acceptor
复制标题
带有不对称恶二唑-二氟硼双受体的溶液加工高效蓝绿热激活延迟荧光发射体
DOI：
10.1021/acsami.9b07511
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发表时间：
2019
影响因子：
9.5
通讯作者：
Wang Yafei
中科院分区：
文献类型：
--
作者：
Zhou Di;Liu Denghui;Gong Xu;Ma Huili;Qian Gaowei;Gong Shaolong;Xie Guohua;Zhu Weiguo;Wang Yafei
含二氟硼（BF 2）的染料由于其极高的发光效率和良好的吸电子性能而引起了人们极大的兴趣。然而，只有少数报道二氟硼基热激活延迟荧光（TADF）已解决。本文合成了一种新型的含BF 2的TADF分子BFOXD，它含有两个受体片段恶二唑（oxadiazole，OXD）和BF 2，以及一个供体单元9，9-二甲基吖啶。为了比较，还研究了带有一个受体单元的OHOXD的前体。这两种分子在溶液和薄膜状态下都清楚地显示出具有天蓝色发射的TADF特性。此外，OHOXD经历激发态分子内质子转移耦合的分子内电荷转移过程。以9-（4-叔丁基苯基）-3，6-双（三苯基硅基）-9H-咔唑（CzSi）为基质，采用溶液法制备的有机电致发光器件的最大外量子效率（EQE）分别为2.98%和13.8%。虽然双极TADF主机的10-使用（4-（（4-（9 H-咔唑-9-基）苯基）磺酰基）苯基）-9，9-二甲基-9，10-二氢吖啶（CzAcSF）代替CzSi，基于OHOXD和BFOXD的器件表现出更好的性能，最大EQE分别为12.1%和20.1%，这使得基于BF 2的TADF分子有史以来报道的最有效和最蓝的发射。该研究表明，在TADF分子中引入多一个受体单元可以对发射效率产生积极影响，这为设计高效TADF分子开辟了一条新途径。
Difluoroboron (BF2)-containing dyes have attracted great interest owing to their exceptionally high luminescence efficiency and good electron-withdrawing properties. However, only a few reports on difluoroboron-based thermally activated delayed fluorescence (TADF) have been addressed. In this contribution, a novel BF2-containing TADF molecule of BFOXD, which contains two acceptor fragments of oxadiazole (OXD) and BF2and one donor unit of 9,9-dimethylacridine, was synthesized and characterized. For comparison, the precursor of OHOXD bearing one acceptor unit was also investigated. Both molecules clearly show TADF characteristics with sky-blue emission in solution and film state. Additionally, OHOXD undergoes excited-state intramolecular proton transfer-coupled intramolecular charge transfer processes. Using 9-(4-tert-butylphenyl)-3,6-bis(triphenylsilyl)-9H-carbazole (CzSi) as the host, the organic light-emitting diodes fabricated via a solution process show maximum external quantum efficiency (EQE) of 2.98 and 13.8% for OHOXD- and BFOXD-based devices, respectively. While the bipolar TADF host of 10-(4-((4-(9H-carbazol-9-yl)phenyl)sulfonyl)phenyl)-9,9-dimethyl-9,10-dihydroacridine (CzAcSF) is utilized instead of CzSi, the OHOXD- and BFOXD-based devices exhibit better performances with the maximum EQEs of 12.1 and 20.1%, respectively, which render the most efficient and the bluest emission ever reported for the BF2-based TADF molecules. This research demonstrates that introduction of one more acceptor unit into the TADF molecule could have a positive effect on emission efficiency, which opens a new way to design high-efficiency TADF molecules.