Chen Xiang, Zhang Hao, Tan Hong-Ji, Yang Liu, Qin Peng, Zheng Xu-Hui, Tang Shan-Shun, Liu Yu, Tong Qing-Xiao
Department of Chemistry, Key Laboratory for Preparation and Application of Ordered Structural, Material of Guangdong Province, Shantou University, Guangdong, 515063, P. R. China.
State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun, Jilin, 130012, P. R. China.
Chemistry. 2021 May 3;27(25):7275-7282. doi: 10.1002/chem.202005214. Epub 2021 Mar 18.
High-performance deep-blue emitters with external quantum efficiencies (EQEs) exceeding 5 % are still scarce in organic light-emitting diodes (OLEDs). In this work, by introducing a [1,2,4]triazolo[1,5-a] pyridine (TP) unit at the N1 position of phenanthroimidazole (PI), two luminescent materials, PTPTPA and PTPTPA, were obtained. Systematic photophysical analysis showed that the TP block is suitable for constructing hybridized local and charge-transfer (HLCT) emitters. Its moderate electron-withdrawing ability and rigid planar structure can enhance the CT component while ensuring color purity. In addition, compared with PTPTPA, the additional phenyl ring of PTPBPTA not only increased the oscillator strength, but also decreased the Stokes shift. TDDFT calculations pointed out facile reverse intersystem crossing processes in PTPTPA from high-lying triplet states to the singlet excited state. A nondoped device based on PTPTPA as emitter showed impressive performance with EQE of 7.11 % and CIE coordinates of (0.15, 0.09). At the same time, it was also an efficient host for yellow and red phosphorescent OLEDs. By doping yellow (PPYBA) and red (BTPG) phosphorescent dyes into PTPTPA, a white OLED with a high EQE of 23.85 % was achieved. The successful design of PTPTPA not only provided an optimization choice for OLED emitters, but also demonstrated the empirical rules for the design of multifunctional deep-blue emitters.
在有机发光二极管（OLED）中，外量子效率（EQE）超过5%的高性能深蓝色发光体仍然稀缺。在这项工作中，通过在菲咯咪唑（PI）的N1位置引入一个[1,2,4]三唑并[1,5-a]吡啶（TP）单元，获得了两种发光材料PTPTPA和PTPTPA。系统的光物理分析表明，TP嵌段适合构建杂化局域和电荷转移（HLCT）发光体。其适度的吸电子能力和刚性平面结构可以增强电荷转移成分，同时确保颜色纯度。此外，与PTPTPA相比，PTPBPTA额外的苯环不仅增加了振子强度，还减小了斯托克斯位移。含时密度泛函理论（TDDFT）计算指出，PTPTPA中存在从高能三重态到单重激发态的容易的反向系间窜越过程。基于PTPTPA作为发光体的非掺杂器件表现出令人印象深刻的性能，EQE为7.11%，CIE坐标为（0.15, 0.09）。同时，它也是黄色和红色磷光OLED的有效主体材料。通过将黄色（PPYBA）和红色（BTPG）磷光染料掺杂到PTPTPA中，实现了EQE高达23.85%的白色OLED。PTPTPA的成功设计不仅为OLED发光体提供了一种优化选择，还展示了多功能深蓝色发光体设计的经验规则。
