蓝色有机发光材料LiBq4的合成及其发光特性

蓝色有机发光材料的开发对于实现有机发光二极管(OLED)的全彩色化具有十分重要的意义.报道了蓝色有机发光材料8-羟基喹啉硼化锂(LiBq₄)的合成及提纯,研究了LiBq₄的光致发光特性,并用LiBq₄作为发光材料制备了蓝色有机发光器件,研究了电子传输层Alq₃的厚度及空穴缓冲层CuPc对器件电流-电压和亮度-电压特性的影响.结果表明,LiBq₄的光致发光峰值波长为452nm,器件ITO/PVK:TPD/LiBq₄/Alq₃/Al的电致发光光谱峰值波长位于475nm处,在25V工作电压下其最高亮度约为430cd/m².但CuPc的加入加剧了器件中载流子的不平衡注入,导致器件性能恶化.通过调整Alq₃的厚度,同时在Alq₃和Al阴极之间加入LiF薄膜以提高电子注入效率,获得了较为理想的实验结果.     

掺杂型红色有机电致发光显示器件

全色显示是有机电致发光显示(OLED)器件发展的目标,而高性能红色发光器件一直是制约全彩色OLED器件实用化的瓶颈,也是目前有机电致发光显示研究的热点。制作了掺杂DCJTB和不同浓度的rubrene两种荧光染料的红色有机电致发光显示器件,以NPB和Alq₃分别作为空穴传输层和电子传输层,发现器件性能与只掺杂DCJTB的器件相比有明显提高,发光效率提高到2～3倍。通过Frster理论和能带理论分析了器件的能量转移机理,研究发现Frster能量转移不是掺杂器件能量转移的主要形式,载流子俘获机制才是器件效率提高的主要原因;rubrene的引入使得能量能够更有效地从Alq₃转移到DCJTB,从而显著地提高了器件的发光效率和性能。     

超薄层BCP对有机电致发光器件性能的影响

采用真空热蒸镀的方法,在常规的双层器件结构的基础上,设计了三层双异质结有机电致发光器件(OLED):indium-tin oxide(ITO)/N,N′-diphenyl-N,N′-bis(1-naphthyl)(1,1′-biphenyl)-4,4′-diamine(NPB)/2,9-dimethyl-4,7-diphenyl-1,10-phenan throline(BCP)/8-hydroxyquinoline aluminum(Alq3)/Mg∶Ag。通过对器件的电致发光(EL)光谱及器件性能的表征,研究了不同超薄层BCP的厚度对OLED器件性能的影响。结果表明,当超薄层BCP的厚度从0.1nm逐渐增加到4.0nm时,器件的EL光谱实现了绿光→蓝绿光→蓝光的变化;BCP层有效地调节了载流子的复合区域,改变了器件的发光颜色,提高了器件的亮度和发光效率。     

Density functional theory analysis of a mixed‐ligand iridium compound for multi‐color organic light‐emitting diodes

Electronic states and their energies are calculated for a mixed‐ligand Ir(III) compound, (5‐chloro‐8‐hydroxyquinoline) bis(2‐phenylpyridyl) iridium (called IrQ(ppy)₂‐5Cl) using time‐dependent density functional theory (TDDFT) calculations and are compared with the experimental result. A good agreement is obtained between the calculated and measured absorption spectra. The d‐π_Q* molecular orbital transition gives the lowest‐energy triplet state absorption band. Its energy is estimated as 1.84 eV (671 nm), which is close to the absorption band position of 1.86 eV (666 nm) observed for IrQ(ppy)₂‐5Cl doped in 4,4′‐N,N′‐dicarbazole‐biphenyl (CBP) host and of 1.88 eV (660 nm) observed for IrQ(ppy)₂‐5Cl doped in polystyrene (PS). The second triplet state absorption band is caused by d‐π_ppy transition. Its position is calculated as 2.51 eV (494 nm). The dipole moment is estimated as 3.45 D, which is lower than the dipole moment of fac‐Ir(ppy)₃. This is understood by a reduced charge transfer between Ir(III) and quinoline ligand. Copyright © 2008 John Wiley & Sons, Ltd.     

Zn(BTZ)2白色有机电致发光材料的合成及其器件制备

以PCl₃为脱水剂,将邻氨基硫酚与水杨酸脱水环化合成出2-(2-羟基苯基)苯并噻唑,并进一步将所得产物与乙酸锌反应合成出2-(2-羟基苯基)苯并噻唑螯合锌(Zn(BTZ)₂)材料。以该配合物作为发光层制备出结构为ITO/PVK:TPD/Zn(BTZ)₂/Al近白色电致发光器件,其色坐标位于白场之内(x=0.242,y=0.359),在驱动电压为16V时,亮度达3200cdm²,对应的量子效率为0.32%。进一步在Zn(BTZ)₂中掺入橙红色染料Rubrene,制成ITO/PVK:TPD/Zn(BTZ)₂:Rubrene/Al结构器件,实现了纯白色发光(色坐标值:x=0.324,y=0.343),非常接近于白色等能点,且量子效率达0.47%。最后对上述器件的发光和电学性能进行了深入的研究和探讨。     

Synthesis of nonplanar bipyridyls bridged by disilane and disiloxane and their phosphorescent copper complexes

Disilane- and disiloxane-bridged bipyridyls ( DSBPy and DSOBPy ) were prepared and their optical properties were investigated in comparison with those of previously reported monosilane- and monogermane-bridged counterparts. The UV–visible absorption and photoluminescence bands of DSBPy and DSOBPy were blue-shifted as a result of elongation of the bridging units from monosilane and monogermane to disilane and disiloxane, likely due to the enhanced twisting of the bipyridyl units. Phosphorescent complexes DSBPy–Cu and DSOBPy–Cu were prepared by the interaction of DSBPy and DSOBPy with Cu₂I₂(PPh₃)₂. X-ray diffraction studies of their single-crystal structures revealed polymeric structures composed of repeat units of DSBPy or DSOBPy and [Cu^II(PPh₃)]₂. Organic light-emitting diodes with the ITO/PEDOT:PSS/ DSBPy–Cu or DSOBPy–Cu :PCTSQ/TAZ/Al structure were fabricated to examine the applications of the complexes as electroluminescent materials. The devices emitted yellow light with emission maxima at approximately 600 nm, and maximal luminance reached 120 and 190 cd m⁻² for devices based on DSBPy–Cu and DSOBPy–Cu , respectively. The performance of the DSOBPy–Cu -based device was improved by using TAZ as the dopant of the emissive layer, and luminance was increased to 390 cd m⁻².     

Phosphorescent κ3-(N^C^C)-Gold(III) Complexes: Synthesis,Photophysics, Computational Studies and Application to Solution-Processable OLEDs

Efficient OLED devices have been fabricated using organometallic complexes of platinum group metals. Still, the high material cost and low stability represent central challenges for their application in commercial display technologies. Based on its innate stability, gold(III) complexes are emerging as promising candidates for high-performance OLEDs. Here, a series of alkynyl-, N-heterocyclic carbene (NHC)- and aryl-gold(III) complexes stabilized by a κ³-(N^C^C) template have been prepared and their photophysical properties have been characterized in detail. These compounds exhibit good photoluminescence quantum efficiency (η_PL) of up to 33 %. The PL emission can be tuned from sky-blue to yellowish green colors by variations on both the ancillary ligands as well as on the pincer template. Further, solution-processable OLED devices based on some of these complexes display remarkable emissive properties (η_CE 46.6 cd.A⁻¹ and η_ext 14.0 %), thus showcasing the potential of these motifs for the low-cost fabrication of display and illumination technologies.     

Photophysics and Electrochemistry of some Thione Far-Red/Near-IR Triplet Emitters

The photophysics and cyclic voltammetry of two novel phosphorescent thiones, 2,2-dimethyl-indan-1-one-3-thione (DMIKT) and 2,2-dimethyl-indan-1,3-dithione (DMIDT), and three known phosphorescent thiones, 4H-pyran-4-thione (PT), 4H-1-benzopyran-4-thione (BPT) and 2,2-dimethylindan-1-thione (DMIT), have been characterised and compared. The phosphorescence emission of DMIT, DMIKT and DMIDT extends from the red into the near-IR spectral region. The additional carbonyl or thione group of DMIKT and DMIDT causes a significant shift in the emission maxima to 680 nm compared to that of DMIT, at 637 nm, in perfluorinated hydrocarbons. In acetonitrile the emission maxima of DMIKT and DMIDT are at 696 and 706 nm, respectively, and the spectra show vibronic bands which extend out beyond 850 nm. There is a significant reduction in triplet lifetime along this series (from 44 (±2) μs (DMIT) to 10 ((±0.8) μs (DMIKT) in perfluorinated solvents, and 8.6 (±0.5) (DMIT), 1.3 (±0.5) (DMIKT) and 0.35 (±0.07) μs (DMIDT) in acetonitrile), as well as a reduction in the rate constant for ground-state quenching of the triplet, (from 9.8 ((±0.9) to 3.5 ((±0.6) and 1.3 ((±0.2) × 10⁹ mol⁻¹ dm³ s⁻¹ for the same compounds). The addition of the C=O or C=S groups also causes a decrease in phosphorescence quantum yield with the highest emission quantum yield obtained for DMIT (Φ _P = 0.149 (±0.015)). Electrochemical studies show that while PT and BPT exhibit irreversible redox behaviour, DMIT, DMIKT and DMIDT all show at least one reversible reduction wave attributed to a one-electron process centred on the C=S moiety. The suitability of these lumophores for use in OLEDs is discussed.     

有机薄膜器件负电阻特性的影响因素

研究了影响有机染料掺杂聚合物薄膜器件负电阻特性的因素，为探索有机负电阻的机理提供实验依据。实验中制备了多种有机染料掺杂聚合物薄膜器件，研究了有机小分子染料、聚合物基体、薄膜组成及厚度、ITO和聚苯胺阳极等对有机染料掺杂聚合物薄膜器件负电阻特性的影响。在室温、大气环境下，所制备的多种有机染料掺杂聚合物器件在所加电压为3～4V时，观察到明显的负电阻特性，电流峰谷比最大约为8。负电阻现象及峰谷比的大小受膜厚和器件的结构、制备工艺等影响。提出用负电阻和二极管并联组成的等效电路模型解释影响负电阻特性的因素，认为负电阻特性与载流子的不平衡注入有关。在此基础上设计、合成了主链含唔二唑电子传输基团的可溶性聚对苯撑乙烯衍生物，该聚合物兼具空穴和电子传输功能，在空气中具有较稳定的N型负电阻特性。进一步控制相关材料和工艺条件，有可能得到易于控制的负阻效应，开发出新型的有机负电阻器件。