Ai Qi, Chai Jingshan, Lou Weiwei, Liu Tiangeng, Wang Dan, Deng Chao, Wang Chao, Li Guijie, Liu Xiaogang, Liu Zugang, Zhang Qisheng
MOE Key Laboratory of Macromolecular Synthesis and Functionalization, Department of Polymer Science and Engineering , Zhejiang University , Hangzhou 310027 , China.
College of Optical and Electronic Technology , China Jiliang University , Hangzhou 310018 , China.
ACS Appl Mater Interfaces. 2020 Feb 5;12(5):6127-6136. doi: 10.1021/acsami.9b19474. Epub 2020 Jan 22.
Triplet excitons can be effectively harvested in organic light-emitting diodes employing thermally activated delayed fluorescence (TADF) molecules as the emitter and host. A design strategy for blue and green emitters with small S-T splitting (Δ) is to construct a donor-acceptor (D-A) type molecule with moieties combining a high T level with a strong electron-donating/withdrawing character. Here, we report a new kind of TADF emitter with an indolo[2,3-]indole (IDID) donor. In comparison to other reported indolocarbazole and indoloindole donors, IDID has a higher T level, which is comparable to that of the classical donor 9,9-dimethyl-9,10-dihydroacridine (DMAC) for blue TADF emitters. The sky-blue and green TADF emitters based on the IDID donor and a phenyltriazine acceptor exhibit high photoluminescence quantum yields (0.78-0.92) and short TADF lifetimes (1.1-1.7 μs) in doped films. Devices employing these IDID-based emitters offer an external quantum efficiency of 19.2%, which is comparable to that obtained for a device employing an analogous compound with a DMAC donor, while the stability of the former is higher than that of the latter owing to the just-right D-A twisting angles (∼59°) in the IDID-based emitters leading to a balance between Δ and the fluorescence rate. The utilization of host materials with a similar polarity to the emitter is found to be an effective strategy to improve device stability.
在采用热激活延迟荧光（TADF）分子作为发光体和主体的有机发光二极管中，三线态激子能够被有效地捕获。设计具有小的S-T分裂（Δ）的蓝色和绿色发光体的策略是构建一种供体-受体（D-A）型分子，其部分基团兼具高T能级和强给电子/吸电子特性。在此，我们报道了一种新型的含吲哚并[2,3-]吲哚（IDID）供体的TADF发光体。与其他已报道的吲哚咔唑和吲哚吲哚供体相比，IDID具有更高的T能级，这与用于蓝色TADF发光体的经典供体9,9-二甲基-9,10-二氢吖啶（DMAC）相当。基于IDID供体和苯基三嗪受体的天蓝色和绿色TADF发光体在掺杂薄膜中表现出高光致发光量子产率（0.78 - 0.92）和短的TADF寿命（1.1 - 1.7 μs）。采用这些基于IDID的发光体的器件具有19.2%的外量子效率，这与采用具有DMAC供体的类似化合物的器件相当，而前者的稳定性高于后者，这是由于基于IDID的发光体中恰到好处的D-A扭转角（约59°）导致了Δ与荧光速率之间的平衡。发现利用与发光体极性相似的主体材料是提高器件稳定性的有效策略。
