Electroluminescent zinc(II) bis(8-hydroxyquinoline): structural effects on electronic states and device performance

We present direct evidence for stable oligomers in vacuum-deposited thin films of zinc(II) bis(8-hydroxyquinoline) (Znq(2)). The tetramer [(Znq(2))(4)] is the energetically favored configuration in both the single crystal and the vacuum-deposited thin film. Oligomerization leads to distinct, symmetry-driven differences between the electronic states in Znq(2) and those in the archetypal organic electroluminescent molecule tris(8-hydroxyquinoline) aluminum (Alq(3)). In the case of the Znq(2) tetramer, symmetry leads to an extended network of overlapping pyridyl and phenolato moieties in the solid film. Analysis of the electronic structure of (Znq(2))(4) calculated by ab initio Hartree-Fock (HF) methods reveals a localization and energy shift of high-lying occupied and low-lying unoccupied states on symmetry related ligands located on opposite sides of the supramolecular structure resulting in a dipole moment for (Znq(2))(4) tetramer close to zero. The optimal pi-overlap pathways, altered charge distributions, and extended electronic states of tetrameric Znq(2) may be expected to enable low operating voltage organic light-emitting devices (OLEDs) based on Znq(2). We present preliminary evidence that the operating voltage of (Znq(2))(4)-based OLEDs is indeed lower than that of identical devices made with Alq(3). Strategic substitution of 8-hydroxyquinoline ligands and control of the structural symmetry of the corresponding metal chelates may offer a route to high efficiency and low operating voltage small molecule OLEDs.     

含有Alq3和Znq2的可交联聚合物的合成与表征

合成了溶解性优良、带有可聚合链段的8-羟基喹啉金属螯合物(Alq3和Znq2)单体,在室温下通过紫外光照射,形成热力学性能稳定、8-羟基喹啉金属螯合物含量高(50(wt)%以上)的交联聚合物.这种材料可以解决使用旋涂的方法制备器件带来的底层溶解的问题,从而实现大面积、多层电致发光器件的制备,还可以通过光刻手段实现器件涂层图案化,是器件实现全彩色、超像素方法之一.其光致发光和电致发光性质证明这种材料本身以及其加工性能在有机/高分子平面显示技术领域有一定应用价值.     

High-efficiency tris(8-hydroxyquinoline)aluminum (Alq3) complexes for organic white-light-emitting diodes and solid-state lighting

Combinations of electron-withdrawing and -donating substituents on the 8-hydroxyquinoline ligand of the tris(8-hydroxyquinoline)aluminum (Alq(3)) complexes allow for control of the HOMO and LUMO energies and the HOMO-LUMO gap responsible for emission from the complexes. Here, we present a systematic study on tuning the emission and electroluminescence (EL) from Alq(3) complexes from the green to blue region. In this study, we explored the combination of electron-donating substituents on C4 and C6. Compounds 1-6 displayed the emission tuning between 478 and 526 nm, and fluorescence quantum yield between 0.15 and 0.57. The compounds 2-6 were used as emitters and hosts in organic light-emitting diodes (OLEDs). The highest OLED external quantum efficiency (EQE) observed was 4.6%, which is among the highest observed for Alq(3) complexes. Also, the compounds 3-5 were used as hosts for red phosphorescent dopants to obtain white light-emitting diodes (WOLED). The WOLEDs displayed high efficiency (EQE up to 19%) and high white color purity (color rendering index (CRI≈85).     

Optimization of high-performance blue organic light-emitting diodes containing tetraphenylsilane molecular glass materials

Molecular glass material (4-(5-(4-(diphenylamino)phenyl)-2-oxadiazolyl)phenyl)triphenylsilane (Ph(3)Si(PhTPAOXD)) was used as the blue light-emitting material in the fabrication of high-performance organic light-emitting diodes (OLEDs). In the optimization of performance, five types of OLEDs were constructed from Ph(3)Si(PhTPAOXD): device I, ITO/NPB/Ph(3)Si(PhTPAOXD)/Alq(3)/Mg:Ag, where NPB and Alq(3) are 1,4-bis(1-naphylphenylamino)biphenyl and tris(8-hydroxyquinoline)aluminum, respectively; device II, ITO/NPB/Ph(3)Si(PhTPAOXD)/TPBI/Mg:Ag, where TPBI is 1,3,5-tris(N-phenylbenzimidazol-2-yl)benzene; device III, ITO/Ph(2)Si(Ph(NPA)(2))(2)/Ph(3)Si(PhTPAOXD)/TPBI/Mg:Ag, where Ph(2)Si(Ph(NPA)(2))(2) is bis(3,5-bis(1-naphylphenylamino)phenyl)-diphenylsilane, a newly synthesized tetraphenylsilane-containing triarylamine as hole-transporting material; device IV, ITO/Ph(2)Si(Ph(NPA)(2))(2)/NPB/Ph(3)Si(PhTPAOXD)/TPBI/Mg:Ag; device V, ITO/CuPc/NPB /Ph(3)Si(PhTPAOXD)/Alq(3)/LiF/Al, where CuPc is Cu(II) phthalocyanine. Device performances, including blue color purity, electroluminescence (EL) intensity, current density, and efficiency, vary drastically by changing the device thickness (100-600 A of the light-emitting layer) and materials for hole-transporting layer (NPB and/or Ph(2)Si(Ph(NPA)(2))(2)) or electron-transporting material (Alq(3) or TPBI). One of the superior OLEDs is device IV, showing maximum EL near 19 000 cd/m(2) with relatively low current density of 674 mA/cm(2) (or near 3000 cd/m(2) at 100 mA/cm(2)) and high external quantum efficiency of 2.4% (1.1 lm/W or 3.1 cd/A). The device possesses good blue color purity with EL emission maximum (lambda(max)(EL)) at 460 nm, corresponding to (0.16, 0.18) of blue color chromaticity on CIE coordinates. In addition, the device is reasonably stable and sustains heating over 100 degrees C with no loss of luminance on the basis of the annealing data for device V. Formation of the exciplex at the interface of NPB and Ph(3)Si(PhTPAOXD) layers is verified by EL and photoluminescence (PL) spectra studies on the devices with a combination of different charge transporting materials. The EL due to the exciplex (lambda(max)(EL) at 490-510 nm) can be properly avoided by using a 200 A layer of Ph(3)Si(PhTPAOXD) in device I, which limits the charge-recombination zone away from the interface area.     

8-巯基喹啉阴离子的锌配合物及其衍生物的电子光谱性质的含时密度泛函理论研究

采用从头算(ab initio)和密度泛函理论(DFT B3LYP)方法, 对配合物8-巯基喹啉锌Zn(tq)₂及其5种衍生物基态结构进行优化, 用含时密度泛函理论(TD-DFT/B3LYP)及6-31＋G(d)基组计算吸收光谱; 同时用ab initio HF 单激发组态相互作用(CIS)法在6-31G(d)基组上优化其最低激发单重态几何结构, 用含时密度泛函理论计算发射光谱. 结果表明, 电子在基态与激发态间的跃迁, 主要是在配体8-巯基喹啉(tq)环内的电荷转移, 电子从含S的苯硫酚环转移至含N的吡啶环上; 吸收光谱和发射光谱的计算值与实验值基本符合. 该类配合物都是优良的电子传输材料, 改变金属离子和取代基均可以调控发光材料的光谱波段.     

超薄层在白色有机电致发光器件中的应用

以DCJTB为掺杂剂, 以BCP为空穴阻挡层, 研究了两种结构的有机电致发光器件ITO/NPB/BCP/Alq3:DCJTB/Alq3/Al(结构A)和ITO/NPB/BCP/Alq3/Alq3:DCJTB/Alq3/Al(结构B)的电致发光光谱. 实验结果显示, 在结构A器件的电致发光光谱中, 绿光的相对发光强度较弱,增加Alq3层的厚度对绿光的相对发光强度的影响也很小; 而在结构B器件的电致发光光谱中, BCP层与掺杂层(Alq3:DCJTB)之间的Alq3薄层对绿光的相对发光强度影响显著, 用很薄的Alq3层就可以得到强的绿光发射. 进一步改变器件结构, 利用有机超薄层就可以得到稳定的白光器件ITO/NPB(50 nm)/BCP(3 nm)/Alq3(3 nm)/Alq3:DCJTB(1%(w))(5 nm)/Alq3(7 nm)/Al. 随着电压的增加(14-18 V), 该器件的色坐标基本保持在(0.33, 0.37)处不动; 在432 mA·cm-2的电流密度下, 该器件的发光亮度可达11521 cd·m-2.     

Novel four-pyridylbenzene-armed biphenyls as electron-transport materials for phosphorescent OLEDs

A series of four-pyridylbenzene-armed biphenyl derivatives were designed and synthesized as an electron-transport and exciton- and hole-block layer for the fac-tris(2-phenylpyridine)iridium (Ir(PPy)3)-based green phosphorescent organic light-emitting devices (OLEDs), giving improved efficiency in comparison to that with both the electron-transport layer of tris(8-hydroxyquinoline)aluminum (Alq3) and the exciton- and hole-block layer of 2,9-dimethyl-4,7-diphenylphenathroline (BCP).     

中位四(1-苯基吡唑-4-基)卟啉掺杂空穴传输材料的红色有机电致发光器件(英文)

使用中位-四(1-苯基吡唑-4-基)卟啉(TPPyPH2)掺杂空穴传输材料N,N′-二苯基-N,N′-双(4-甲苯基)-1,1′-二苯基-4,4′-二胺(TPD)制备了红色有机电致发光器件.因为TPD的发射光谱与TPPyPH2的吸收光谱具有更大的光谱重叠,为了得到更为有效的从主体材料TPD向红光染料TPPyPH2的能量传递,我们使用TPD代替传统的8-羟基喹啉铝(Alq3)作为主体发光材料.器件在680nm处具有纯的红光发射峰;通过使用Alq3电子传输层以及使用Alq3共掺杂发光层的方法,使器件的发光性能得到了改善,结构为ITO/Alq3+TPPyPH2+TPD(50nm)/Alq3(30nm)/Al的器件的最大发光亮度为177cd/m2.     

Interface modification of 8-hydroxyquinoline aluminium with combined effects in quasi-solid dye-sensitized solar cells

In this paper, 8-hydroxyquinoline aluminium (Alq(3)) was used in interface modification of dye-sensitized solar cells (DSCs). Alq(3) was the first discovered interface modification material with combined effects of retarding charge recombination and F?rster resonant energy transfer (FRET). Results of dark current curve and AC impedance showed that Alq(3) could retard charge recombination in DSCs. I-V curves showed that conversion efficiency increased with Alq(3) modification. Besides the interface modification effect, it was discovered that Alq(3) also acted as energy relay dye with the FRET effect between itself and N3, which increased photoresponse and electron injection. The application of Alq(3) with combined effects opened a new door to explore more novel multi-functional interface modification materials to improve the performance of DSCs.     

Highly luminescent zinc(II)-bis(8-hydroxyquinoline) complex nanorods: sonochemical synthesis, characterizations, and protein sensing

Highly luminescent zinc(II)-bis(8-hydroxyquinoline) (Znq(2)) complex nanorods have been synthesized via a sonochemical route from the microemulsion containing zinc acetate and 8-hydroxyquinoline. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images showed that the products were rod-like morphology with a diameter of about 200-450 nm and a length of about 1-3 microm. A possible mechanism for the formation of Znq(2) nanorods is proposed that the ultrasound wave might urge the collision and fusion of initial Znq(2) nuclei to form nanorods. The photoluminescence (PL) and resonance light scattering (RLS) of the products were also investigated. The Znq(2) nanorods were found to be sensitive to several proteins, such as human serum albumin (HSA), bovine serum albumin (BSA), bovine hemoglobin (Hb), and egg albumin (EA), displaying an increase in intensities of both PL and RLS. The protein-concentration dependence of the PL and RLS intensities can be well described as a Langmuir-type binding isotherm. This is the first report on the enhancement of PL and RLS intensities of Znq(2) nanorods by proteins. On the basis of enhanced PL and RLS intensities, the protein could be detected at the nanogram per milliliter level. The experimental results clearly showed that the Znq(2) nanorods were good protein probes for easy and highly sensitive detection.     

Study on preparation and fluorescence characteristic of the (Alqx)/Al2O3 nano colloids

Alumina 8-hydroxyquinoline complexes (Alqx)/Al2O3 nano colloids have been successfully prepared by focused, pulsed laser ablation at the interface of solid Al2O3 and a flowing liquid containing 8-hydroxyquinoline (Q) and one of two polymers (polystyrene, PS, and polymethyl methacrylate, PMMA). Three factors influenced the luminescence of the (Alqx)/Al2O3 nano colloids. The first factor was whether the 8-hydroxyquinoline was added before or after laser ablation. The second factor was if the reaction medium consisted of (1) Q dissolved in ethanol, (2) Q dissolved in cyclohexane containing PS, or (3) Q dissolved in ethyl acetate containing PMMA. The third factor affecting luminescence was the age of the colloids. The (Alqx)/Al2O3 nano colloid product was characterized by transmission electron microscopy (TEM), ultraviolet visible spectroscopy (UV-vis), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and fluorescence spectroscopy. The product from all three-reaction media luminesced when irradiated with ultraviolet light. The product formed in cyclohexane containing PS gave the greatest luminescence, followed by the product formed in ethanol, and the product formed in ethyl acetate containing PMMA gave the smallest luminescence. The luminescence mechanism is similar to that of Alq3.     

Photochemical production of electroluminescent image

A polymer containing donorN-epoxypropylcarbazolyl groups and the acceptor tris(8-quinolinolato) aluminum (Alq₃) was shown to form a light-sensitive, acid-producing polymeric composition. The acid in the presence of 8-quinolinol (8-hydroxyquinoline) ensured photochemical dissolution of aluminum in the polyeric layer, yielding additionally organic aluminum complexes, such as Alq₃, Alq²⁺, and Alq ₂ ⁺ , and Alq₃-con-taining polymers. This led to a emergence of electroluminescence (EL) upon application of a potential difference to a sandwich diode representing transparent anode/exposed polymer layer/aluminum cathode. Electroluminescence did not appear at an Alq₃ concentration of 6 wt % and less in the composition, and only partial dissolution of the aluminum film after its deposition on the exposed polymeric layer provided the emergence of EL whose intensity increased with increasing the dose absorbed by the polymer. The addition of the chemical sensitizer dimethylaminobenzaldehyde to the composition triggered the conventional process of chemical amplification which consists in thermal buildup of the acid in exposed area. This provided a significant increase in concentration of organoaluminum complexes and enhancement of EL intensity.     

Nondoped-type White Organic Light-Emitting Diode Using Star-Shaped Hexafluorenylbenzene as an Energy Transfer Layer

White organic light-emitting diodes (WOLEDs) with a structure of indium-tin-oxide (ITO)/N,N'-bis-(1-naphthyl)-N,N'-diphenyl-(1,1'-biphenyl)-4,4'-diamine (NPB)/1,2,3,4,5,6-hexakis(9,9-diethyl-9H-fluoren-2-yl)benzene (HKEthFLYPh)/5,6,11,12 -tetraphenylnaphtacene (rubrene)/tris(8-hydroxyquinoline) aluminum (Alq3)/Mg:Ag were fabricated by vacuum deposition method, in which a novel star-shaped hexafluorenylbenzene HKEthFLYPh was used as an energy transfer layer, and an ultrathin layer of rubrene was inserted between HKEthFLYPh and Alq3 layers as a yellow light-emitting layer instead of using a time-consuming doping process. A fairly pure WOLED with Commissions Internationale De L'Eclairage (CIE) coordinates of (0.32, 0.33) was obtained when the thickness of rubrene was 0.3 nm, and the spectrum was insensitive to the applied voltage. The device yielded a maximum luminance of 4816 cd/m2 at 18 V.     

以N,N-四(间联苯基)-4,4-联苯二胺为正孔传送材料的有机电致发光器件(英文)

用新的路径成功地合成了N,N -四(间联苯基)-4,4 -联苯二胺(m TBPBz).以m TBPBz作为正孔传送材料,探讨了它在有机电致发光器件中的应用.制作了结构为玻璃基板／ITO阳极(130nm)／m TBPBz(40nm)／Alq(60nm)／LiF(0.5nm)／Al阴极(100nm)的器件.结果显示:该有机电致发光器件的绿色发光来源于Alq层.10V时,它的最大亮度为9486cd／m2.证明了m TBPBz具有正孔传送性能,可作为电致发光材料使用.     

混合蓝色和绿色发射的高亮度白色有机电致发光器件

使用星形六苯芴类新材料1,2,3,4,5,6-hexakis(9,9-diethyl-9H-fluoren-2-yl)benzene (HKEthFLYPh)分别制备了三种不同结构的有机电致发光器件. 在结构为indium-tin oxide (ITO)/NPB (40 nm)/HKEthFLYPh (10 nm)/Alq3(50 nm)/Mg:Ag (200 nm)的器件中, 获得了两个电致发光谱峰分别位于435 和530 nm处的明亮白光. HKEth-FLYPh是能量传输层; N,N’-bis-(1-naphthyl)-N,N’-diphenyl-(1,1’-biphenyl)-4,4’-diamine (NPB)是空穴传输层和蓝色发光层; tris(8-hydroxyquinoline)aluminum (Alq3)是电子传输层和绿色发光层. 结果表明, 当驱动电压为15 V时, 器件的最大亮度达到8523 cd·m-2; 在5.5 V时, 器件达到最大流明效率为1.0 lm·W-1. 在电压为9 V时, CIE色坐标为(0.29, 0.34). 此外, 通过改变HKEthFLYPh层的厚度, 发现蓝色发射的相对强度随着HKEthFLYPh层厚度的增加而增强.     

Triarylboron-functionalized 8-hydroxyquinolines and their aluminium(III) complexes

The first examples of triarylboron-functionalized 8-hydroxyquinoline ligands and their aluminium complexes have been synthesized. These luminescent derivatives of the well-known electron transport material tris(8-hydroxyquinoline)aluminium (Alq(3)) display enhanced electron-accepting ability relative to Alq(3), and can also be used as an indicator for small F(-) and CN(-) anions.     

可溶性聚合物电致发光材料PDHPV的合成及单、双层发光二极管器件的发光性能比较

可溶性聚合物电致发光材料ＰＤＨＰＶ的合成及单、双层发光二极管器件的发光性能比较李晨曦，尹春，黄文强，印寿根，张会旗，何炳林，郑军，华玉林（南开大学高分子化学研究所，天津，３０００７１）（天津理工学院材料物理研究所）关键词ＰＤＨＰＶ共轭聚合物；电致发光...     

侧链含8-羟基喹啉铝配合物的聚苯乙烯的合成与发光性能研究

通过高分子反应法研究制备了高分子化的8-羟基喹啉铝发光材料.首先使用自制的氯甲基化试剂1,4-二氯甲氧基丁烷(BCMB),制备了5-氯甲基-8-羟基喹啉(CHQ);通过聚苯乙烯(PS)与CHQ之间的Friedel-Crafts烷基化反应,制得侧链键合有8-羟基喹啉(HQ)的改性聚苯乙烯HQ-PS;再使HQ-PS与二配体...     

Theoretical study on the effects of nitrogen and methyl substitution on tris-(8-hydroxyquinoline) aluminum: an efficient exciton blocking layer for organic photovoltaic cells

We studied the effect of nitrogen and methyl substitution on tris-(8-hydroxyquinoline) aluminum (Alq(3)) with density functional theory, which has been adopted as an exciton blocking layer (EBL) in organic photovoltaic cells (OPVCs). The substitution of electron withdrawing nitrogen on the phenoxide moiety of Alq(3) lowers the highest molecular orbital (HOMO) level, thus photogenerated excitons can be effectively blocked in OPVC. Additional substitution of methyl on the pyridine moiety makes that Alq(3) has a smaller electron reorganization energy, which results in higher electron mobility with keeping HOMO level almost intact. Therefore, nitrogen and methyl simultaneous substitution shows high performance both in exciton blocking and electron mobility. This is the origins of the short circuit current enhancement in OPVC with 4-hydroxy-8-methyl-1,5-naphthyridine aluminum chelate (Alq(3) with the substitution of both nitrogen and methyl group) EBL.     

Wire-on-wire growth of fluorescent organic heterojunctions

Dendritic organic heterojunctions with aluminum tris(8-hydroxyquinoline) (Alq(3)) microwire trunks and 1,5-diaminoanthraquinone (DAAQ) nanowire branches were prepared by a two-step growth process. The prefabricated Alq(3) microwires act as nucleation centers for site-specific secondary vapor growth of DAAQ nanowires, resulting in the unique dendritic heterostructures. When the trunk was excited with a focused laser beam, emitted light of various colors was simultaneously channeled from the branched nanowires via both waveguiding and energy transfer. The intensity of the out-coupled emissions was modulated effectively by changing the polarization of the incident light.