位阻诱导扭曲结构的蓝光材料合成及其在蓝色有机发光二极管(OLED)中的应用

doi:10.6023/A25060223

摘要/Abstract

有机电致发光技术已广泛应用于全彩柔性显示和固态照明领域. 蓝色作为三原色之一, 蓝光材料是有机发光二极管(OLED)应用领域的研究重点. 将3,6-二叔丁基咔唑引入至联吡啶氮原子的邻、间和对位, 构建了三种不同的发光材料. 该材料中咔唑取代基与联吡啶核心发生强烈的扭曲, 形成位阻诱导的扭曲结构. 这种分子结构有效限制分子共轭体系的长度, 并抑制分子内振动对能量的消耗, 从而确保了蓝光具有很高的色纯度. 2,2'-双(3,6-二叔丁基-9H-咔唑-9-基)-3,3'-联吡啶(2TCzOBPy)和4,4'-双(3,6-二叔丁基-9H-咔唑-9-基)-3,3'-联吡啶(2TCzPBPy)器件的CIE坐标分别为(0.152, 0.063)和(0.172, 0.098), 它们的色度坐标y值均小于0.1, 属于高色纯度的深蓝光. 此外, 3,3'-双(3,6-二叔丁基-9H-咔唑-9-基)-4,4'-联吡啶(2TCzMBPy)器件获得的最大外量子效率(EQE)为3.6%, 获得最大亮度为5423 cd•m⁻².

关键词: 有机发光二极管, 扭曲结构, 联吡啶, 蓝光, 高色纯度

Organic light-emitting diode (OLED) technology has been widely applied in the fields of full-color flexible displays and solid-state lighting. As one of the three primary colors, blue light plays a crucial role in OLED technology, making blue-emitting materials a focal point of research in this domain. To achieve blue light emission with high color purity, blue-emitting materials need to emit light within a narrow wavelength range. However, this narrow-band emission often comes at the cost of reduced luminescence efficiency, as precise regulation of molecular energy levels to realize narrow-band emission is highly challenging in practical material design. Considering this, this work proposes an innovative molecular design strategy. Through the Suzuki-Miyaura coupling reaction of pyridine units with corresponding boronate esters, three bipyridine derivatives with different substitution sites were successfully synthesized. Subsequently, 3,6-di-tert-butylcarbazole groups were introduced to the ortho, meta, and para positions of the pyridine nitrogen atoms in the bipyridine core via C—N coupling reactions, yielding three target compounds with distinct twisted structures. In these materials, the 3,6-di-tert-butyl- carbazole unit acts as the donor and the pyridine unit as the acceptor. A significant dihedral angle exists between the carbazole substituents and the bipyridine core. This steric-induced twisted structure effectively restricts the extension of the molecular conjugated system and suppresses the energy loss due to intramolecular vibrations, thereby ensuring high color purity of blue light. Thermogravimetric analysis indicates that all three materials exhibit excellent thermal stability, with decomposition temperatures exceeding 310 ℃. Photophysical tests reveal that 2,2'-bis(3,6-di-tert-butyl-9H-carbazol-9-yl)-3,3'-bipyridine (2TCzOBPy) and 4,4'-bis(3,6-di-tert-butyl-9H-carbazol-9-yl)-3,3'-bipyridine (2TCzPBPy) show deep blue light emission at 440 nm and 422 nm, respectively, in doped films. OLED devices fabricated with these two compounds as the emissive layers have CIE coordinates of (0.152, 0.063) and (0.172, 0.098), respectively, with y values of the color coordinates both less than 0.1, indicating deep blue light emission with high color purity. Additionally, devices based on 3,3'-bis(3,6-di-tert-butyl- 9H-carbazol-9-yl)-4,4'-bipyridine (2TCzMBPy) exhibit blue-green light emission, achieving a maximum external quantum efficiency (EQE) of 3.6% and a maximum brightness of 5423 cd•m⁻².

Key words: organic light-emitting diode (OLED), twisted structure, bipyridine, blue light, high color purity

引用此文

闫安, 许世攀, 杜旭洋, 刘文平, 赵堃翔, 李胜利, 钟道昆, 周桂江, 杨晓龙, 孙源慧. 位阻诱导扭曲结构的蓝光材料合成及其在蓝色有机发光二极管(OLED)中的应用[J]. 化学学报, 2025, 83(11): 1317-1323.

Yan An, Xu Shipan, Du Xuyang, Liu Wenping, Zhao Kunxiang, Li Shengli, Zhong Daokun, Zhou Guijiang, Yang Xiaolong, Sun Yuanhui. Synthesis of Blue-Emitting Materials with Sterically Induced Twisted Structures and Their Application in Blue Organic Light-Emitting Diode (OLED)[J]. Acta Chimica Sinica, 2025, 83(11): 1317-1323.

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图/表 9

图式1. 三种化合物的合成路线

Scheme 1. Synthetic routes of the three compounds

图1. 三种化合物的TGA曲线

Figure 1. TGA curves of the three compounds

Compound	Absorption^a/nm	Emission^b/nm	τ^b/ns	PLQY^b/%	T_d/℃
2TCzOBPy	243, 295, 328, 342	440	2.8	50.7	337
2TCzMBPy	239, 297, 345, 391	487	11.6	94.4	317
2TCzPBPy	241, 296, 344	422	3.2	38.0	340

表1. 三种化合物的光物理性能数据

Table 1. Photophysical properties data of the three compounds

图2. 二氯甲烷中的紫外-可见吸收光谱曲线

Figure 2. UV-Vis absorption spectra in dichloromethane solution

图3. 薄膜状态下荧光发射光谱

Figure 3. Fluorescence emission spectra in films

图4. 三种化合物优化后的分子结构以及前沿分子轨道分布

Figure 4. Optimized molecular structures and frontier molecular orbital distributions of the three compounds

图5. 实验中所用有机材料分子的化学结构式和器件的结构图

Figure 5. Chemical structures of organic materials and simplified configuration of OLED device

图6. 基于三种材料的(a) EL光谱和CIE坐标图、(b)电流密度-电压-亮度曲线、(c)最大外量子效率-亮度曲线及(d)电流效率-亮度-功率效率曲线

Figure 6. (a) EL spectra and CIE coordinate diagram, (b) current density-voltage-luminance curves, (c) maximum external quantum efficiency-luminance curves, and (d) current efficiency-luminance-power efficiency curves based on the three materials

Device	V_on^a/V	L_max^b/(cd•m⁻²)	EQE^c/%	CE^d/(cd•A⁻¹)	PE^e/(lm•W⁻¹)	λ_EL/nm	CIE (x, y)
2TCzOBPy	4.5	2888	2.4/2.3	5.4	2.9	437	(0.172, 0.098)
2TCzMBPy	4.6	5423	3.6/2.4	11.2	6.3	496	(0.224, 0.399)
2TCzPBPy	5.4	71	0.5/—	0.3	0.2	416	(0.152, 0.063)

表2. 三种材料的电致发光性能

Table 2. Electroluminescence properties of three materials

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