Li Jie, Gong Heqi, Zhang Jincheng, Zhou Shiyi, Tao Li, Jiang Lihua, Guo Qiang
College of Optoelectronic Technology, Chengdu University of Information Technology, Chengdu, China.
College of Electrical Engineering & New Energy, Hubei Provincial Engineering Technology Research Center for Power Transmission Line, China Three Gorges University, Yichang, China.
Front Chem. 2021 May 13;9:693813. doi: 10.3389/fchem.2021.693813. eCollection 2021.
Heptazine derivatives have attracted much attention over the past decade by virtue of intriguing optical, photocatalytic as well as electronic properties in the fields of hydrogen evolution, organic optoelectronic technologies and so forth. Here, we report a simple -conjugated heptazine derivative (HAP-3DF) possessing an n→* transition character which exhibits enhanced electroluminescence by exploiting thermally activated delayed fluorescence (TADF). Green-emitting HAP-3DF shows relatively low photoluminescence quantum efficiencies ( ) of 0.08 in toluene and 0.16 in doped film with bis(2-(diphenylphosphino)phenyl) ether oxide (DPEPO) as the matrix. Interestingly, the organic light-emitting diode (OLED) incorporating 8 wt% HAP-3DF:DPEPO as an emitting layer achieved a high external quantum efficiency (EQE) of 3.0% in view of the fairly low of 0.16, indicating the presence of TADF stemming from n→* transitions. As the matrix changing from DPEPO to 1,3-di (9-carbazol-9-yl)benzene (mCP), a much higher of 0.56 was found in doped film accompanying yellow emission. More importantly, enhanced electroluminescence was observed from the OLED containing 8 wt% HAP-3DF:mCP as an emitting layer, and a rather high EQE of 10.8% along with a low roll-off was realized, which should be ascribed to the TADF process deriving from exciplex formation.
在过去十年中，七嗪衍生物因其在析氢、有机光电子技术等领域具有引人入胜的光学、光催化以及电子特性而备受关注。在此，我们报道了一种具有n→*跃迁特性的简单共轭七嗪衍生物（HAP-3DF），它通过利用热激活延迟荧光（TADF）展现出增强的电致发光。发出绿色光的HAP-3DF在甲苯中的光致发光量子效率（）相对较低，为0.08，在以双（2-（二苯基膦基）苯基）醚氧化物（DPEPO）为基质的掺杂薄膜中为0.16。有趣的是，鉴于相当低的0.16，以8 wt% HAP-3DF:DPEPO作为发光层的有机发光二极管（OLED）实现了3.0%的高外量子效率（EQE），这表明存在源于n→*跃迁的TADF。当基质从DPEPO变为1,3-二（9-咔唑-9-基）苯（mCP）时 在掺杂薄膜中发现伴随黄色发射的光致发光量子效率更高，为0.56。更重要的是，从以8 wt% HAP-3DF:mCP作为发光层的OLED中观察到了增强的电致发光，并且实现了10.8%的相当高的EQE以及低滚降，这应归因于源自激基复合物形成的TADF过程。
