基于七元环三芳胺给体的蓝光热活化延迟荧光材料的构筑

doi:10.6023/cjoc202312006

摘要/Abstract

设计合成高效发光材料对于蓝光有机发光二极管(OLED)的进一步研究和应用至关重要. 以扭曲七元环结构的9H-三苯并[b,d,f]氮杂䓬(TPA)为给体, 设计合成了两种新型蓝光发光分子TRZCz-TPA和TRZ-TPA, 并对它们的热稳定性、电化学性质、光物理性质和器件性能等进行了表征. 光谱研究表明, TRZCz-TPA和TRZ-TPA均为蓝光发射, 其甲苯溶液中的发射波长分别为455和440 nm. 和TRZ-TPA分子不同的是, TRZCz-TPA的受体邻位引入3,6-二叔丁基咔唑(tBuCz), 产生较大的空间位阻, 使得二苯基三嗪(TRZ)受体构型扭曲, 与苯环π-桥平面存在较大二面角, 从而最高占据分子轨道(HOMO)和最低未占据分子轨道(LUMO)分别转移到tBuCz给体和TRZ受体上, 其发光性质由TPA给体到TRZ受体的沿键电荷转移特性(TBCT)转变为tBuCz给体到TRZ受体的空间电荷转移特性(TSCT), 单三线态能隙(ΔE_ST)从0.53 eV显著降至0.04 eV, 具有热活化延迟荧光(TADF)性质. 此外, 大位阻的tBuCz给体可以降低聚集态下的发光猝灭现象, 因此, TRZCz-TPA掺杂薄膜的光致发光量子产率(PLQY)为42.0%, 掺杂器件的最大外量子效率(EQE_max)为10.4%, 而TRZ-TPA的PLQY和EQE_max仅为6.5%和3.7%.

关键词: 有机发光二极管, 热活化延迟荧光, 沿键电荷转移, 空间电荷转移, 七元环三芳胺给体

The development of efficient blue light-emitting materials is a crucial yet challenging task in organic light-emitting diodes (OLED). Two novel blue light-emitting molecules, TRZCz-TPA and TRZ-TPA, have been designed and synthesized based on the heptagonal 9H-tripheno[b,d,f]nitrozoafluorene (TPA) donor. Their thermal stability, electrochemical properties, photophysical properties, and device performances were characterized. TRZCz-TPA and TRZ-TPA both exhibit blue emission in toluene solution with emission peaks at 455 and 440 nm, respectively. In contrast to TRZ-TPA, which exhibits through-bond charge transfer (TBCT) from the TPA donor to the diphenyltriazine (TRZ) acceptor, TRZCz-TPA, featuring two adjacent 3,6-di-tert-butylcarbazole (tBuCz) donors near the TRZ acceptor, demonstrates through-space charge transfer (TSCT) from the tBuCz donors to the TRZ acceptor. This leads to a remarkable reduction in the singlet-triplet energy gap (ΔE_ST) from 0.53 eV to 0.04 eV, thereby displaying thermally activated delayed fluorescence (TADF) properties. Additionally, tBuCz donor with large steric hindrance effectively suppresses aggregation-induced quenching in the aggregated state. Consequently, TRZCz-TPA achieves a photoluminescence quantum yield (PLQY) of 42.0% and a maximum external quantum efficiency (EQE_max) of 10.4% in OLED devices, significantly outperforming TRZ-TPA (PLQY=6.5%, EQE_max=3.7%).

Key words: organic light-emitting diodes, thermally activated delayed fluorescence, through-bond charge transfer, through- space charge transfer, heptagonal triarylamine donor

引用此文

李治, 李祯龙, 刘俊杰, 憨卫国, 游劲松, 宾正杨. 基于七元环三芳胺给体的蓝光热活化延迟荧光材料的构筑[J]. 有机化学, 2024, 44(6): 2006-2013.

Zhi Li, Zhenlong Li, Junjie Liu, Weiguo Han, Jingsong You, Zhengyang Bin. Construction of Blue Thermally Activated Delayed Fluorescence Materials Based on the Heptagonal Triarylamine Donor[J]. Chinese Journal of Organic Chemistry, 2024, 44(6): 2006-2013.

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图/表 5

图式1. 目标化合物的合成路线

Scheme 1. Synthetic routes to the target molecules

Compd.	HOMO/ eV	LUMO^c/ eV	λ_abs^a/ nm	λ_em^a/ nm	FWHM^a/ nm	ΔE_ST^a/ eV	τ_p^b/ ns	τ_d^b/ μs	PLQY^b/ %	C₁^b/ %	C₂^b/ %	k_RISC^b/ 10⁶ s^–1	T_d/ ℃	T_m/ ℃
TRZCz-TPA	–5.52	–2.11	321	455	68	0.04	8.49	1.41	42.0	30.5	69.5	1.9	452	319
TRZ-TPA	–5.61	–2.45	363	440	80	0.53	3.09	—	6.5	—	—	—	415	307

表1. TRZCz-TPA和TRZ-TPA的主要光物理和热学性质表征数据

Table 1. Photophysical and thermal parameters of TRZCz-TPA and TRZ-TPA

图1. TRZCz-TPA和TRZ-TPA的分子结构和前线分子轨道计算

Figure1. Molecular structures and frontline molecular orbital distributions of TRZCz-TPA and TRZ-TPA

图2. 甲苯溶液中(a) TRZCz-TPA和(b) TRZ-TPA的紫外-可见吸收光谱、室温荧光光谱(298 K)和低温磷光光谱(77 K); (c)掺杂膜的室温荧光光谱(40% TRZCz-TPA或TRZ-TPA:DPEPO, 298 K); (d)掺杂膜(40% TRZCz-TPA或TRZ-TPA:DPEPO, 298 K)的瞬态荧光光谱

Figure 2. UV spectra, room-temperature fluorescence spectra (298 K) and low-temperature phosphorescence spectra (77 K) of (a) TRZCz-TPA and (b) TRZ-TPA in toluene solution; (c) room-temperature fluorescence spectra of the doped films (40% TRZCz-TPA or TRZ-TPA:DPEPO, 298 K); (d) transient photoluminescence spectra of the doped films (40% TRZCz-TPA or TRZ-TPA:DPEPO, 298 K)

图3. (a) OLED器件有机层分子结构; (b) OLED器件结构; (c) OLED器件电致发光光谱; (d) EQE-亮度曲线; (e)电流密度-电压-亮度曲线

Figure 3. (a) Molecular structures of the materials used OLED devices; (b) OLED device structure; (c) eletroluminescence spectra of OLED devices; (d) EQE-luminance curves and (e) current density-voltage-luminance curves of OLED devices

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