Cyanocarbazole-based bipolar host materials for efficient phosphorescent and thermally activated delayed fluorescence OLEDs†

IF 2.7 3区 化学 Q2 CHEMISTRY, MULTIDISCIPLINARY
Yeting Tao, Yaotian Zhang, Shiying Hu, Jian Wang, Yuying Wu, Wenbo Yuan, Wei Yao and Youtian Tao
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Abstract

The investigation of suitable organic host materials is crucial for the development of high-efficiency triplet exciton-based organic light emitting diodes (OLEDs). In this study, two isomeric carbazole/1,3,5-triazine hybrid bipolar-transport host materials o-3CN-TRZ and o-4CN-TRZ are developed. The alteration of cyano substitution from the 3- to the 4-position of carbazole resulted in a slight reduction in the HOMO levels from −5.80 to −5.87 eV, accompanied by a gentle decline in the singlet/triplet energy levels. This was evidenced by a shift in the fluorescence emission peak from 450 to 474 nm and the observation of relatively high triplet energies of 2.79 and 2.77 eV for o-3CN-TRZ and o-4CN-TRZ, respectively. Notably, compared to the bare carbazole-based model compound o-Cz-TRZ, the introduction of a cyano group at either the 3- or the 4-position led to a notable enhancement in the electron-transport properties. However, the hole-transport behavior of o-3CN-TRZ was evidently inferior to that of o-4CN-TRZ. Therefore, when employed as host materials for both phosphorescence and thermally activated delayed fluorescence OLEDs, o-4CN-TRZ hosted devices all exhibited higher efficiencies than o-3CN-TRZ. Maximum external quantum efficiencies of 20.5, 16.8 and 16.9% versus 19.6, 12.5 and 13.8% were achieved for green phosphorescent (ppy)2Ir(acac), greenish-yellow TADF 4tCzDOXD and 4tCzCNPy-based devices, respectively.

Abstract Image

用于高效磷光和热激活延迟荧光oled的基于氰咔唑的双极性主体材料
研究合适的有机主体材料是开发高效三态激子基有机发光二极管的关键。本研究制备了两种异构体咔唑/1,3,5-三嗪杂化双极性输运宿主材料o-3CN-TRZ和o-4CN-TRZ。氰基取代从咔唑的3-位到4-位的改变导致HOMO能级从−5.80 eV轻微降低到−5.87 eV,同时伴有单重态和三重态能级的轻微下降。荧光发射峰从450 nm移至474 nm, o-3CN-TRZ和o-4CN-TRZ的三重态能量相对较高,分别为2.79和2.77 eV。值得注意的是,与裸咔唑模型化合物o-Cz-TRZ相比,在3-或4-位置引入氰基导致电子输运性质显著增强。但o-3CN-TRZ的空穴输运行为明显不如o-4CN-TRZ。因此,当用作磷光和热激活延迟荧光oled的宿主材料时,o-4CN-TRZ宿主器件都比o-3CN-TRZ表现出更高的效率。基于绿色磷光(ppy)2Ir(acac)、绿黄色TADF 4tCzDOXD和4tczcnpy器件的最大外量子效率分别为20.5%、16.8%和16.9%,而基于绿色磷光(ppy)2Ir(acac)器件的最大外量子效率分别为19.6%、12.5和13.8%。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
New Journal of Chemistry
New Journal of Chemistry 化学-化学综合
CiteScore
5.30
自引率
6.10%
发文量
1832
审稿时长
2 months
期刊介绍: A journal for new directions in chemistry
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