Synthesis and properties of a thiophene-substituted diaza[7]helicene for application as a blue emitter in organic light-emitting diodes

Carbazole-based diaza[7]helicene substituted by thiophene groups, 2,12-dithiophene-5,15-dihexyl-5,15-diaza[7]helicene (6), was synthesised successfully and confirmed by ¹H NMR, ¹³C NMR, High Resolution Mass Spectrometry, Time of Flight Mass Spectrometry. Compound 6 exhibited good solubility and excellent thermal stability with no melting point and a high decomposition temperature of 453.64 °C. A doped device with a structure of ITO/NPB (50 nm)/CBP: 10% 6 (30 nm)/Bphen (20 nm)/Mg:Ag (150 nm)/Ag (50 nm) emitted the blue light at 460 nm with Commission Internationale de LEclairage (CIE) coordinate of (0.176, 0.26). The maximum brightness and external quantum efficiency (EQE) were 2306 cd m^?2 and 0.41%, respectively.     

Novel liquid crystalline organic semiconducting oligomers incorporating N-heterocyclic carbazole moieties for fluorescent OLEDs

A novel class of nematic liquid crystalline organic semiconducting oligomers incorporating N-heterocyclic carbazole moieties has been synthesised using simple and highly efficient reaction pathways. The electroluminescent colour of these novel oligomers can be varied in a controlled manner by molecular design. The values of the ionisation potential and the electron affinity of these electroluminescent oligomers can also be matched by structural design to the Highest Occupied Molecular Orbital (HOMO) energy level of the electron-blocking layer and the Lowest Unoccupied Molecular Orbital (LUMO) energy level of electron-transporting layer in the Organic light emitting diodes to create low charge-injection barriers for electrons and holes, respectively leading to electroluminescence with an efficacy up to 4.1 cd A^?1.     

Density functional study on electronic structures and reactivity in methyl‐substituted chelates used in organic light‐emitting diodes

The electronic structure and reactivity trends of a set of tris‐(n‐methyl‐8‐quinolinolato) metal (III) (n = 0, 3, 4, 5; metal = Al⁺³, Ga⁺³) used as electron‐transport layer in organic light‐emitting diodes were studied and compared. All geometries were optimized at B3LYP/6‐31G(d,p) level of theory. The geometries of the ground state (S₀) of unsubstituted molecules AlQ3 and GaQ3 were found to be slightly affected by the methyl group, which is in agreement with previous works. Methyl‐derivatives conserve largely the electronic structures of AlQ3 and GaQ3. The energies of the frontier orbitals highest occupied and lowest unoccupied molecular orbital are raised by the electron‐releasing effect of methyl group. Molecular orbital contribution analysis reveals that the orbital population is essentially the same for both MQ3 and their derivatives. Analyses of the ionization potential and electron affinity showed that MQ3 tend to be better hole‐blockers than methylated analogues and 5Me‐MQ3 have higher hole‐injection capability than the other methyl‐substituted derivatives. The global reactivity analysis showed that the electrophilicity index can be an indicator of electron‐injection capability in these complexes. Local reactivity analysis showed that atomic sites that are prone to nucleophilic/electrophilic attack are atoms C‐4 in L3/C‐5 in L1. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010     

Modular Synthesis of Polybenzo[b]silole Compounds for Hole‐Blocking Material in Phosphorescent Organic Light Emitting Diodes

A diversity‐oriented synthetic strategy allowed us to design a series of conjugated molecules containing multiple benzosilole units that can be utilized as efficient hole‐blocking materials for phosphorescent organic light emitting diodes (OLEDs). Some of these compounds showed a performance surpassing that of the current standard, bathocuproine. The new compounds were easily synthesized in a modular fashion from a previously reported 3‐stannyl benzosilole building unit. Studies on the properties of these compounds in solution and in the solid state indicate that they possess high electron affinity, high ionization potential, and form stable amorphous films that show high electron‐drift mobility. The correlation between their molecular properties and the efficiency of the OLED device performance is also investigated.     

High efficiency top-emitting white organic light-emitting devices with a (metal/organic)2 cathode

White top-emitting organic light-emitting devices (TEOLEDs) were fabricated on a glass substrate with metal/organic multilayer of (Ag/Alq₃)₂ (Alq₃ is tris-(8-hydroxyquinoline) aluminum) as cathode. White TEOLEDs with high efficiency were obtained due to the microcavity effects. And the (Ag/Alq₃)₂ cathode, which adjusted the optical characteristics of the devices, played an important role. In addition, Alq₃–Ag–Alq₃ multilayer could work as a buffer layer, which would simplify the process of encapsulation for devices. We also calculated the electroluminescence spectrum of devices encapsulated with Al₂O₃ (150 nm) and Al₂O₃(75 nm)/ZrO₂(75 nm). And the results indicated that the CIE coordinates is almost the same between with and without encapsulating.     

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。     

红色磷光喹喔啉铂(II)配合物及其有机电致发光器件的制备

利用2,3-二苯基喹喔啉和氯亚铂酸钾(K2PtCl4)反应,合成了一种新型喹喔啉铂的配合物(DPQ)Pt(acac),通过元素分析,1HNMR测定对配合物结构进行了表征,结果显示得到的是目标化合物.利用紫外光谱和荧光光谱对配合物进行了研究.利用该材料作为磷光染料制备了结构为ITO/NPB(21nm)/NPB∶7%(DPQ)Pt(acac)(17.5nm)/BCP(7nm)/Alq3(21nm)/Mg∶Ag(10∶1)(120nm)/Ag(10nm)的有机电致发光器件(OLED).结果表明,该配合物在442和485nm处存在单重态1MLCT(金属到配体的电荷跃迁)和三重态3MLCT的吸收峰;在632nm处有较强的金属配合物三重态的磷光发射;该器件的启动电压是5.0V,器件的最大亮度为1516cd·m-2,外量子效率为0.66%,流明效率为0.26lm·W-1,是一种红色磷光材料.     

OLED器件新型应用研究进展

有机发光二极管(organic light-emitting diodes,OLED)具有可柔性制备、低驱动电压、低功耗等优点,近年来技术上的突飞猛进及其广泛的应用前景,使之成为平板显示、新型照明、可穿戴,以及智能电子产品开发中最热门的研究课题之一.作为新一代的显示及照明技术,小尺寸OLED显示器已实现商业化,大尺寸O...     

可溶液加工蓝色聚集诱导发光小分子的合成及其器件性能

利用四苯基甲烷中碳原子特殊的sp³轨道杂化结构来打断并控制分子内共轭程度,并采用硅原子替换四苯基甲烷中的碳原子合成四苯基硅烷.将这两种结构作为核,在其四周以四苯乙烯（TPE）或三苯乙烯（triPE）修饰,设计并合成了六个具有聚集诱导发光（AIE）效应的小分子.这些分子均可以溶解在常见有机溶剂中并具有良好的热稳定性.通过溶液旋涂法将其应用到有机电致发光器件（OLED）中,得到最好的器件效率为亮度最大值（L_max）1730 cd·m^-2,电流效率最大值（L_max）2.21 cd·A^-1,功率最大值（η_p,max）0.77 lm·W^-1,外量子效率最大值（η_ext,max）1.01%.