Zhang Chen, Lu Yang, Liu Ziyang, Zhang Yuewei, Wang Xuewen, Zhang Dongdong, Duan Lian
Key Lab of Organic Optoelectronics and Molecular Engineering of Ministry of Education, Department of Chemistry, Tsinghua University, Beijing, 100084, P. R. China.
Foshan Xianhu Laboratory of the Advanced Energy Science and Technology Guangdong Laboratory, Xianhu Hydrogen Valley, Foshan, 528200, P. R. China.
Adv Mater. 2020 Oct;32(42):e2004040. doi: 10.1002/adma.202004040. Epub 2020 Sep 6.
Exciplex-forming hosts with thermally activated delayed fluorescence (TADF) provide a viable opportunity to unlock the full potential of the yet-to-be improved power efficiencies (PEs) and stabilities of all-fluorescent white organic light-emitting diodes (WOLEDs), but this, however, is hindered by the lack of stable blue exciplexes. Here, an advanced exciplex system is proposed by incorporating bipolar charge-transport π-spacers into both the electron-donor (D) and the electron-accepter (A) to increase their distance for hypsochromic-shifted emission while maintaining the superior transporting ability. By using spirofluorene as the π-spacer, 3,3'-bicarbazole as the D-unit, and 2,4,6-triphenyl-1,3,5-triazine as the A-unit, a π-D and π-A exciplex with sky-blue emission and fast reverse intersystem crossing process is thereof constructed. Combining this exciplex-forming host, a blue TADF-sensitizer, and a yellow conventional fluorescent dopant in a single-emissive-layer, the fabricated warm-white-emissive device simultaneously exhibits a low driving voltage of 3.08 V, an external quantum efficiency of 21.4%, and a remarkable T80 (time to 80% of the initial luminance) of >8200 h at 1000 cd m , accompanied by a new benchmark PE of 69.6 lm W among all-fluorescent WOLEDs.
具有热激活延迟荧光（TADF）的激基复合物形成主体为充分挖掘全荧光白色有机发光二极管（WOLED）尚未得到充分提升的功率效率（PE）和稳定性提供了可行的机会，但这受到缺乏稳定蓝色激基复合物的阻碍。在此，通过将双极性电荷传输π间隔基分别引入电子供体（D）和电子受体（A）中，提出了一种先进的激基复合物体系，以增加它们之间的距离，实现蓝移发射，同时保持优异的传输能力。以螺芴为π间隔基，3,3'-联咔唑为D单元，2,4,6-三苯基-1,3,5-三嗪为A单元，构建了一种具有天蓝色发射和快速反向系间窜越过程的π-D和π-A激基复合物。将这种激基复合物形成主体、蓝色TADF敏化剂和黄色传统荧光掺杂剂结合在单一发射层中，制备出的暖白色发光器件同时具有3.08 V的低驱动电压、21.4%的外量子效率以及在1000 cd m-²下大于8200 h的显著T80（初始亮度降至80%所需时间），在全荧光WOLED中还达到了69.6 lm W-¹的新基准功率效率。
