基于4-氰基嘧啶受体的热活化延迟荧光材料合成及其电致发光性能研究

doi:10.6023/A26030070

摘要/Abstract

热活化延迟荧光(TADF)材料因其成本低廉和高内量子效率(IQE)在有机发光二极管(OLED)领域有巨大的应用前景. 本工作以4-氰基嘧啶为受体, 吩噁嗪、吖啶、二苯胺和咔唑为给体, 将给体和受体通过苯环桥连设计合成了4种给体-受体(D-A)型热活化延迟荧光材料PhPX-CN、PhAd-CN、PhDPA-CN和PhCz-CN, 制备了4种D-A型分子均有扭曲的结构. 最高占据分子轨道(HOMO)和最低未占分子轨道(LUMO)分别位于给体和受体分子上, 实现了HOMO与LUMO空间上的分离, 4种分子展现出较小的单线态与三线态的能极差(ΔE_ST<0.3 eV)和明显的TADF性质. 同时, 通过改变给体的给电子能力实现了对ΔE_ST的调控. 以PhDPA-CN为客体材料制备的绿色OLED器件的最大外量子效率(EQE)为6.85%, 以PhCz-CN为客体材料制备的蓝光OLED器件的最大EQE为3.04%.

关键词: 4-氰基嘧啶受体, D-A结构, 能级调控, 热活化延迟荧光, 有机发光二极管

Organic light-emitting diodes (OLEDs) have advantages such as low driving voltage, high brightness, high color purity, flexible display capabilities, lightweight construction, and fast response times, which position them as promising next-generation display materials. Thermally activated delayed fluorescence (TADF) materials can achieve 100% exciton utilization through the reverse intersystem crossing (RICS) process and are known as the third-generation luminescent materials. TADF molecules achieve a small singlet-triplet energy gap (ΔE_ST) by separating the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) through a donor-acceptor (D-A) twisted structure, thereby enhancing the RISC rate. Currently, many donor molecules have been developed, while acceptor molecules have not been fully explored. In this study, 4-cyanopyrimidine was used as the acceptor, and phenoxazine, diphenylamine, carbazole, and acridine were used as donors. The donors and acceptors were connected through a benzene ring bridge by the Suzuki- Miyaura and Buchwald-Hartwig coupling reactions, and four D-A type TADF materials, PhPX-CN, PhDPA-CN, PhCz-CN, and PhAd-CN, were synthesized. The four prepared TADF molecules all have a twisted D-A structure, with the HOMO and LUMO located on the donor and acceptor fragments, respectively, achieving spatial separation of HOMO and LUMO. Therefore, the four TADF molecules exhibit small singlet-triplet energy gaps (<0.3 eV). As the electron-donating ability of the donors decreases in sequence, the maximum emission spectra of the fluorescent materials PhPX-CN, PhAd-CN, PhDPA-CN, and PhCz-CN gradually blue-shift from 513 nm to 502, 496, and 440 nm. When PhDPA-CN and PhCz-CN were respectively used as guest materials and doped in the host materials 4,4′-di(N-carbazolyl)-1,1′-biphenyl (CBP) and 1,3-bis(carbazol-9-yl) benzene (mCP), the maximum external quantum efficiencies (EQE) of the OLED devices are 6.85% and 3.04%, respectively, achieving green and blue emissions. 4-Cyanopyrimidine has excellent electron-withdrawing ability and can be used to prepare TADF materials with common donor molecules. Moreover, the emission wavelength can be precisely controlled by changing the electron-donating ability of the donors.

Key words: 4-cyanopyrimidine acceptor, donor-acceptor (D-A) structure, energy level regulation, thermally activated delayed fluorescence (TADF), organic light-emitting diodes (OLEDs)

引用此文

陶骏飞, 许世攀, 杜旭洋, 尹赫, 闫安, 杭怀腾, 陈亮, 周桂江, 孙源慧, 杨晓龙. 基于4-氰基嘧啶受体的热活化延迟荧光材料合成及其电致发光性能研究[J]. 化学学报, 2026, 84(7): 1040-1048.

Junfei Tao, Shipan Xu, Xuyang Du, He Yin, An Yan, Huaiteng Hang, Liang Chen, Guijiang Zhou, Yuanhui Sun, Xiaolong Yang. Synthesis and Electroluminescence Performance of Thermally Activated Delayed Fluorescence Materials Based on 4-Cyanopyrimidine Acceptor[J]. Acta Chimica Sinica, 2026, 84(7): 1040-1048.

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图/表 12

图式1. PhAd-CN、PhCz-CN、PhPX-CN和PhDPA-CN的合成

Scheme 1. Syntheses of PhAd-CN、PhCz-CN、PhPX-CN and PhDPA-CN

图1. TGA曲线图

Figure 1. TGA Curve Graph

图2. 室温下甲苯溶液中紫外-可见吸收光谱和荧光发射光谱图

Figure 2. Ultraviolet-visible absorption spectra and fluorescence emission spectra at room temperature in toluene solution

Compound	λ_abs^a/nm	λ_PL solution ^b/film ^c (nm)	FWHM solution ^b/film ^c (nm)	τ_PF^d/τ_DF^e (ns/μs)	E_HOMO^f/E_LUMO^g (eV)	E_g^h/eV	PLQYⁱ/%
PhPX-CN	284, 324, 396	513/518	89/91	8.11/9.50	－5.22/－2.98	2.24	67
PhAd-CN	385	502/522	80/90	29.52/9.11	－5.05/－2.78	2.28	52
PhDPA-CN	294, 376	496/510	83/85	14.01/10.95	－5.30/－2.97	2.33	59
PhCz-CN	288, 356	440/470	75/94	19.74/9.60	－5.66/－2.98	2.68	45

表1. 光物理性能

Table 1. Summary of optical properties

图3. 掺杂浓度为15% (w)的CBP薄膜的发光光谱

Figure 3. Emission spectra doped in CBP films at a concentration of 15% (w)

图4. 掺杂浓度为15% (w)的CBP薄膜的光致发光瞬态衰减曲线

Figure 4. Transient PL decay curve of 15% (w) doped CBP film

图5. 循环伏安曲线

Figure 5. Cyclic voltammetry graph

图6. 基于优化S0几何构型构建的四种TADF分子的HOMO/LUMO分布、能级分布、能隙分布以及S1/T1能级图谱

Figure 6. The four TADF molecules based on the optimized S0 geometric configuration, the distribution of HOMO/LUMO, energy levels, energy gaps, and the energy level diagram of S1/T1

图7. 基于优化S1的S0→S1 NTO分布图和S0态下给体受体之间的扭转角

Figure 7. The NTO distribution map of S0→S1 based on the optimized S1 configuration and the S0 geometry showing the twisting angle between donor and acceptor

图8. 器件结构及功能层材料的分子结构式与能级图

Figure 8. Molecular structural formulas and energy level diagrams of device structures and functional layer materials

图9. A3和B3的(a) EL光谱图, (b)电流密度-电压-亮度特性曲线, (c) EQE与亮度特性曲线和(d) CE、PE与亮度特性曲线

Figure 9. (a) EL spectra, (b) current density-voltage-luminance curves, (c) EQE-L curves of devices and (d) current efficiency-luminance characteristics, and power efficiency-luminance characteristics of A3 and B3

Device	V_on^a/V	L_max^b/ (cd•m⁻²)	EQE_max^c/%	CE_max^d/ (cd•A⁻¹)	PE_max^e/ (lm•W⁻¹)	λ_EL^f/ nm	FWHM/nm
A1	5.5	1106	6.52	18.03	9.44	500	84
A2	5.0	1253	6.85	19.85	11.34	508	86
A3	5.0	1503	6.83	20.13	11.50	512	87
B1	7.0	340	1.14	1.32	0.59	464	96
B2	6.0	426	1.72	2.11	1.11	468	85
B3	6.0	712	3.04	6.26	3.27	476	112

表2. 基于PhDPA-CN和PhCz-CN器件的电致发光性能

Table 2. Electroluminescent performance of devices based on PhDPA-CN and PhCz-CN

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