Asymmetric intramolecular charge transfer enables highly efficient red thermally activated delayed fluorescent emitters
Asymmetric intramolecular charge transfer enables highly efficient red thermally activated delayed fluorescent emitters
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不对称分子内电荷转移可实现高效的红色热激活延迟荧光发射器
DOI：
10.1016/j.cej.2022.141061
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发表时间：
2022
影响因子：
15.1
通讯作者：
Hui Xu
中科院分区：
文献类型：
--
作者：
Chao Qu;Huiqin Wang;Yi Man;Zhe Li;Peng Ma;Peng Chang;Xin Li;Chunmiao Han;Yudong Pang;Hui Xu
为了提高红色热激活延迟荧光（TADF）发射体的光致发光（PL）和电致发光（EL）性能，提出了一种可行的非对称给体-受体-秒受体（D-A-A）结构策略。以三苯胺（TPA）、二噻吩[2,3-a:3 ',2 ' -c]非那嗪（DTPZ）和二苯基氧化膦（DPPO）分别为供体、受体和第二受体，设计合成了四种新型TADF发射体D-A-A结构otpapo - dtpz和ptpapo - dtpz和D-A-D型peodtpa - dtpz和pdtpa -DTPZ。结果表明，不对称化合物在TPA给体和DPPO受体之间形成了大量的c单键h···O氢键，有效地促进了分子内和分子间的电荷转移。此外，DPPO基团的位阻有效地抑制了浓度猝灭。因此，不对称d - a结构dotpapo - dtpz和ptpapo - dtpz具有较高的PL量子产率和较低的非辐射率，从而具有较好的电致发光性能。其中，基于ptpapo - dtpz2的器件在632 nm处的最大亮度为19360 cd m−2，外量子效率为11.4%，分别是基于pdtpa - dtpz2器件的2.3倍和1.5倍。
A feasible strategy of asymmetric donor–acceptor-second acceptor (D-A-A) structure is proposed for improving the photoluminecense (PL) and electroluminescence (EL) performance of red thermally activated delayed fluorescence (TADF) emitters. As a concept, four newly TADF emitters are designed and synthesized, D-A-A structureoTPAPO-DTPZandpTPAPO-DTPZand D-A-D typeoDTPA-DTPZandpDTPA-DTPZ, by using triphenylamine (TPA), dithieno[2,3-a:3′,2′-c]phenazine (DTPZ) and diphenylphosphine oxide (DPPO) groups as the donor, acceptor and second acceptor, respectively. It is demonstrated that abound intra- and inter-molecular Csingle bondH···O hydrogen bonds are forming between TPA donor and DPPO acceptor for the asymmetric compounds, which effectively promote the intra- and inter-molecular charge transfer. Moreover, the steric hindrance of DPPO group availably suppresses the concentration quenching. As a consequence, the asymmetric D-A-A structuredoTPAPO-DTPZandpTPAPO-DTPZexhibit relatively higher PL quantum yields and lower nonradiation rates, and thus better EL performance. In particular, device based onpTPAPO-DTPZachieves the maximum luminance of 19360 cd m−2and external quantum efficiency of 11.4 % at 632 nm, which are 2.3 and 1.5 times the values ofpDTPA-DTPZbased device.