Abstract
How to control the dipole orientation of organic emitters is a challenge in the field of organic light-emitting diodes (OLEDs). Herein, a linear thermally activated delayed fluorescence (TADF) molecule, PhNAI-PMSBA, bearing a 1,8-naphthalimide-acridine framework was designed by a double-site long-axis extension strategy to actively control the dipole orientation. The horizontal ratio of emitting dipole orientation of PhNAI-PMSBA reaches 95%, substantially higher than that of isotropic emitters (67%). This unique feature is associated with the intrinsically horizontal molecular orientation of PhNAI-PMSBA and the good agreement between its transition dipole moment direction and molecular long axis. The PhNAI-PMSBA-based OLED achieves an ultrahigh optical outcoupling efficiency of 43.2% and thus affords one of the highest red electroluminescence with an external quantum efficiency of 22.3% and the Commission International de l’Eclairage 1931 coordinates at around (0.60, 0.40).
摘要
如何实现发光材料跃迁偶极矩取向的调控一直是有机发光 二极管(OLEDs)领域的巨大挑战之一. 本文中, 我们基于双位点长 轴延伸策略, 设计合成了一种线型的热活化延迟荧光(TADF)分子, PhNAI-PMSBA, 实现了对跃迁偶极矩取向的选择性调控. 由于 PhNAI-PMSBA具有显著的水平分子取向, 且其分子长轴与跃迁偶 极矩取向高度统一, PhNAI-PMSBA在掺杂发光薄膜中获得的跃迁 偶极矩水平取向度高达95%, 远高于各向同性发光分子67%的跃迁 偶极矩水平取向度. 因此, 基于PhNAI-PMSBA的红光OLED的光耦 合输出效率可达43.2%, 最大外量子效率达到22.3%, 其CIE1931色 坐标位于(0.60, 0.40).
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Acknowledgements
This work is dedicated to the Heroic City of Wuhan. Gong S, Zhong C and Yang C gratefully acknowledge the financial support from the National Natural Science Foundation of China (51873158, 51573141, 91833304 and 91433201), the National Key R&D Program of China (2016YFB0401002), Shenzhen Science and Technolgy Program (KQTD20170330110107046 and JCYJ20190808151209557), the Key Technological Innovation Program of Hubei Province (2018AAA013), and the Natural Science Foundation for Distinguished Young Scholars of Hubei Province (2017CFA033). Wu CC acknowledges the support from the Ministry of Science and Technology of Taiwan (MOST 107-2221-E-002-160-MY3 and 108-2221-E-002-148-MY3). Lee WK acknowledges the post-doctoral fellowship from the Ministry of Education (MOE) of Taiwan. The numerical calculations in this paper have been done on the supercomputing system in the Supercomputing Center of Wuhan University.
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Contributions
Zeng W, Gong S and Yang C conceived the original idea for investigation. Zeng X, Huang YH, Gong S, Wu CC and Yang C wrote the manuscript. Zeng X, Yin X, Xiao X, Zhang Y, and Dong XQ synthesized the compounds. Zeng X and Huang YH measured photophysical, thermal and electrochemical properties of the compounds. Huang YH, Lee WK, Lu CH, and Lee CC fabricated and characterized the devices. Gong S, Wu CC and Yang C supervised this research. Zhong C performed the quantum chemical calculations and molecular dynamics simulation. All authors discussed the progress of research and reviewed the manuscript.
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The authors declare no conflict of interest.
Xuan Zeng is a PhD student of Hubei Key Lab on Organic and Polymeric Optoelectronic Materials at Wuhan University. His research is focused on the optoelectronic materials and devices, mainly in the design, synthesis, and characterization of thermally activated delayed fluorescent materials with preferentially horizontal dipole orientation and high efficiency.
Yu-Hsin Huang received his BSc degree from the Department of Photonics, Sun Yat-San University (Kaohsiung) in 2015. Currently, he is in his PhD program in Graduate Institute of Electronics Engineering, Taiwan University. His research interest is in OLEDs, transparent conducting oxides and display technologies.
Shaolong Gong received his BSc and PhD from Wuhan University in 2007 and 2012, respectively. After working at the University of Toronto as a postdoctoral fellow, he joined the faculty of Wuhan University as an associate professor in 2014. His current research interests focus on the development of organic/polymeric optoelectronic materials and devices.
Chung-Chih Wu received his PhD degree in electrical engineering from Princeton University in 1997. He is currently the Micron Technology Chair Professor and Chairman of Electrical Engineering Department, Taiwan University. He has conducted researches and published widely in OLEDs, organic semiconductors and optoelectronics, oxide semiconductors and TFTs, and displays.
Chuluo Yang received his PhD degree in organic chemistry from Wuhan University in 1997. From 1999 to 2002, he was a postdoctoral fellow at the Hong Kong University of Science and Technology, University of New Orleans, and University of Rochester. From 2003 to 2018, he has been a full professor at Wuhan University. Since 2019, he has been a full professor at Shenzhen University. His research interests cover the synthesis, structure, property and device of organic/polymeric optoelectronic materials.
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Rational design of perfectly oriented thermally activated delayed fluorescence emitter for efficient red electroluminescence
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Zeng, X., Huang, YH., Gong, S. et al. Rational design of perfectly oriented thermally activated delayed fluorescence emitter for efficient red electroluminescence. Sci. China Mater. 64, 920–930 (2021). https://doi.org/10.1007/s40843-020-1501-1
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DOI: https://doi.org/10.1007/s40843-020-1501-1