Organic electroluminescent device with an aromatic amine-containing polymer as a hole transport layer (I): Poly[N-[p-N′ -phenyl-N′-[1,1′-biphenyl-4′-[N″-phenyl-N″-(2-methylphenyl)amino]-4-amino]]phenyl methacrylamide]

Electroluminescent devices were fabricated using a holetransporting polymer, poly[N-[p-N′ -phenyl-N′-[1,1′-biphenyl-4′-[N″-phenyl-N″-(2-methylphenyl)amino]-4-amino]]phenyl methacrylamide] (PTPDMA), and tris(8-quinolinolato)aluminum(III) complex, Alq, as the hole transport layer and the emitter layer, respectively. A device structure of glass substrate/indium–tin–oxide/PTPDMA/Alq/Mg:Ag was employed. Hole injection from the electrode through the PTPDMA layer to the Alq layer and concomitant electroluminescence from the Alq layer were observed. Bright green luminescence with a luminance of 20,000 cd/m² was obtained at a drive voltage of 14 V.     

Plasma-polymerized carbon disulfide films as a hole transport layer in organic electroluminescent devices

Electroluminescent devices were fabricated using plasma-polymerized carbon disulfide films, poly(CS₂), and tris(8-quinolinolato)aluminum(III) complex, Alq, as the hole transport layer and the emitting layer, respectively. A cell structure of glass substrate/indium–tin–oxide/poly(CS₂/Alq/Mg/Ag) was employed. Smooth hole injection from the electrode through the poly(CS₂) layer and concomitant electroluminescence from the Alq layer were observed. Green emission with a luminance of 250 cd/m² was achieved at a drive voltage of 14 V.     

吡唑啉衍生物作为空穴传输层在电致发光材料中的应用

我们曾报道过有关1,3二苯基吡唑啉衍生物的光谱和光物理行为^[1,2],并详细地研究了它们在受激发后的辐射和非辐射衰变过程.该类化合物作为一种良好的光致发光材料,由于存在着分子内共轭的电荷转移结构,因此表现出较强的光诱导分子极化能力,可用作为有机非线性光学材料^[3]、光折变材料等.此外,还发现该类化合物在组合型光导器件中可用作空穴传输层材料.既然这类化合物兼具光致发光和空穴传输功能,很自然的会考虑到,它是否也能用作为一种有机的电致发光(EL)材料.有机电致发光材料的重要性自不待言,特别近年来许多科学家致力于此,因此进展很快.但寻找新的高效材料,不论是用作主要的发光层或其它的辅助性化合物,仍在继续.本简报即是对上述化合物用作EL材料的初步研究.     

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...     

氧化石墨烯掺杂PEDOT:PSS作为空穴注入层对有机发光二极管发光性能的影响

研究了氧化石墨烯(GO)掺杂聚(3,4-亚乙二氧基噻吩):聚(苯乙烯磺酸) (PEDOT:PSS)作为空穴注入层对有机发光二极管发光性能的影响. 在PEDOT:PSS水溶液中掺入GO, 经过湿法旋涂和退火成膜后, 不仅提高了空穴注入层的空穴注入能力和导电率, 透光率也得到了相应的提高, 从而使得有机发光二极管(OLED)器件的发光性能得到了提升. 通过优化GO掺杂量发现, 当GO掺杂量为0.8%(质量分数)时, 空穴注入层的透光率达到最大值(96.8%), 此时获得的OLED器件性能最佳, 其最大发光亮度和最大发光效率分别达到17939 cd·m^-2和3.74 cd·A^-1. 与PEDOT:PSS 作为空穴注入层的器件相比, 掺杂GO后器件的最大发光亮度和最大发光效率分别提高了46.6%和67.6%.     

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.     

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.     

Approaching charge balance in organic light-emitting diodes by tuning charge injection barriers with mixed monolayers

Self-assembled monolayers (SAMs) of binary mixtures of 1-butylphosphonic acid and the trifluoromethyl-terminated analogue (4,4,4-trifluoro-1-butylphosphonic acid) were formed on ITO surfaces to tune the work function of ITO over a range of 5.0 to 5.75 eV by varying the mixing ratio of the two adsorbents. The mixed SAM-modified ITO surfaces were used as the anode in the fabrication of OLED devices with a configuration of ITO/SAM/HTL/Alq3/MX/Al, where HTL was the NPB or BPAPF hole-transporting layer and MX was the LiF or Cs(2)CO(3) injection layer. It was shown that, depending on the HTL or MX used, the maximum device current and the maximum luminance efficiency occurred with anodes of different modifications because of a shift in the point of hole/electron carrier balance. This provides information on the charge balance in the device and points to the direction to improve the performance.     

氟化吡唑啉蓝色电致发光器件的制备

自从Tang等[1]首次报道了多层有机电致发光器件以来, 人们研究了大量的新型材料[2,3], 其中较吸引人的方法是将高量子产率的荧光染料掺杂于传输层中制备电致发光器件[4～9]. 三芳基吡唑啉化合物具有较高的荧光产率和蓝色发射特性. 这些化合物具有分子内电荷传输性能, 在激发状态下分子可发生扭曲形成电子给体-受体结构[10], 因此在EL器件制备过程中既可以作为载流子传输材料, 又可以作为发光材料来应用. 虽然吡唑啉类化合物在固态下具有空穴传输特性[11], 也有较高的荧光产率, 但它们的玻璃转化转变温度较低, 在制备EL器件时, 如单独作为传输层或发射层时, 该类材料易于结晶, 从而使得器件的性能快速衰减. 如果将它们分散于聚合物等主体中, 就会避免重结晶问题. 我们在三苯基吡唑啉中引入强吸电子基团CF3, 导致分子的刚性增强和荧光强度增加, 熔点升高. 将氟化三苯基吡唑啉(FTPP)作为发光中心制作了两类EL器件, 均获得蓝光发射. FTPP分子结构见图1.     

基于N-乙基咔唑-2-乙烯基-8-羟基喹啉锌的黄绿色有机电致发光器件的性能

通过用一种既具有空穴传输特性又具有发光特性的新型荧光染料N-乙基咔唑-2-乙烯基-8-羟基喹啉锌((E)-2-(2-(9-ethyl-9H-carbazol-3-yl)vinyl) quinolato-zinc, CzHQZn)作为受主, 制备了结构为ITO/2T-NATA (30 nm)/CBP: 6%Ir(ppy)3:wCzHQZn(20 nm)/Alq3(50 nm)/LiF/Al(ITO: indium-tin oxide, 2T-NATA: 4,4',4'-{N,N-(2-naphthyl)-N-phenylamino}-triphenylamine, CBP: 4,4-N,N'-dicarbazole-biphenyl, Ir(ppy)3: factris (2-phenylpyridine) iridium, Alq3: tris(8-quinolinolato) aluminum; w 是CzHQZn 的质量分数)的黄绿色有机电致发光器件(OLEDs). 研究了掺杂体系在不同掺杂浓度(w=5%、10%、12%、15%)时的电致发光(EL)特性. 结果表明, CzHQZn 掺杂浓度为10%的器件在11 V 电压下实现了黄绿光发射, 色坐标为(0.4045, 0.5113), 最大发光亮度为16110 cd·m-2; 而在7 V电压下的最大发光效率为2.19 cd·A-1, 最大外量子效率为0.775%.     

Performance Improvement of Organic Light Emitting Diodes Using Poly(N-vinylcarbazole) (PVK) as a Blocking Layer

High efficiency organic light‐emitting‐devices (OLED) have been fabricated by incorporation of a polymeric layer as a controller of the unbalanced charge. In device configuration of ITO/PEDOT:PSS/PVK/Alq₃/LiF:Al, poly(N‐vinylcarbazole) (PVK) was selected as a block‐ing layer (BL) because it has a hole transporting property and a higher band gap, especially a lower LUMO level than the emitting layer (Alq₃) and a higher HOMO level than the hole injection layer (PEDOT: PSS). As a result, the optimal structure with this bl layer showed a peak efficiency of 6.89 cd/A and 2.30 lm/W compared to the device without the PVK layer of 1.08 cd/A, 0.27 lm/W. This result shows that the PVK layer could effec‐tively block the electrons from metal cathode and confine them in the emitting layer and accomplish the charge balance, which leads to enhanced hole‐electron balance for achieving high recombination efficiency.     

Organic electroluminescent devices using europium complex‐doped poly(N‐vinylcarbazole)

Electroluminescence (EL) properties of europium (Eu) complex‐doped poly(N‐vinylcarbazole) (PVK) were investigated. A device structure of glass substrate/indium‐tin oxide/hole‐injection layer/Eu complex‐doped PVK/hole‐blocking layer/electron transport layer/electron‐injection layer/Al was employed. Red emission originating from Eu complex was observed. Relatively high luminance of 50 cd/m² and an efficiency of 0.2% were obtained. Copyright © 2004 John Wiley & Sons, Ltd.     

Designing interfaces that function to facilitate charge injection in organic light-emitting diodes

Layer-by-layer (LbL) assembly of triarylamine (TAA)-containing polymers has been applied for anode functionalizations in organic light-emitting diodes (OLEDs). Surface work function of the ITO electrodes was significantly altered with the functionalizations, and the values changed depending on electron affinity of the substituents (X) on the TAA units. When the functionalized ITO electrodes were utilized for the conventional TPD/Alq OLED, the multilayers of P1 (X = 4-OMe) and P2 (X = none) were found to promote better energy matching at the ITO/TPD interface to reduce the hole injection barrier. Furthermore, the multilayers having heterodeposited structure of several TAA polymers provided stepped and graded electronic profiles to facilitate hole mobility from ITO to TPD, so that the resulting OLED devices can exhibit appreciably reduced turn-on voltage and higher luminous intensities.     

Organic electroluminescent devices using organosilicon polymers containing phenylene or diethynylanthracene units

Double‐layer electroluminescent (EL) devices composed of an alternating polymer with mono‐, di‐, or tri‐silanylene and phenylene units, [(Si R) _m (C₆H₄)] _n (R = alkyl, m = 1–3) as a hole‐transporting layer, and tris(8‐quinolinolato)­aluminium(III) complex (Alq) as an electron‐transporting–emitting layer were fabricated. The longer silanylene chain lengths in the polymer, on going from m = 1 to m = 2 and 3, result in better electrical properties for the EL devices, implying that the σ–π conjugation in the polymers plays an important role in the hole‐transporting properties, including the hole‐injection efficiency from an anode. This is in marked contrast to the improved hole‐transporting properties that occur in response to reducing the silanylene chain length of silanylene‐diethynylanthracene polymers previously reported. The UV absorption maxima of silanylene‐phenylene polymers shift to longer wavelengths with increasing m, and their oxidation peak potentials in cyclic voltammograms shift to lower potential with increasing m, in accordance with the improved electrical properties of the device that are observed with the polymers containing the longer silanylene chain. A triple‐layer EL device with a hole‐transporting layer of monosilanylene‐diethynylanthracene polymer, an electron‐transporting–emitting layer of Alq, and an electron‐blocking layer of N,N′‐diphenyl‐N,N′‐bis(3‐methylphenyl)‐1,1′‐biphenyl‐4,4′‐diamine (TPD) exhibited a maximum efficiency of 1.0 lm W⁻¹ and a maximum luminance of 14750 cd m⁻², both of which are much higher than the values obtained from a conventional EL device with TPD/Alq. Copyright © 1999 John Wiley & Sons, Ltd.     

Influence of Poly(methylmethacrylate) on 8-hydroxyquinoline Derivative-Metal Complexes Electroluminescence

A new method is presented of enhancing the organic electroluminescent(EL) efficiency by using poly (methylmethacrylaie) (PMMA) as barrier layers which play the role of controlling the electron-hole recombination in the organic EL materials. The organic EL device with one layer of 8-hydroxyquinoline derivalive-metal complexes-(Alq3, Znq2) as the EL-emitting layers, and two layers of EL emitting materials deposited on PMMA Langmuir-Blodgett films (PMMA/Alq3, PMMA/Znq2) sandwiched between indium/tin oxide (ITO) and aluminum electrodes have been fabricated, respectively. The evidence reveals that the LB film takes an importance to raising the 8-hydroxyquinoline derivative-metal complexes EL efficiency.     

Bright White Organic Light-emitting Device Based on 1,2,3,4,5,6-Hexakis（9,9-diethyl-9H-fluoren-2-yl）benzene

Organic light-emitting devices(OLEDs) with the structure of indium-tin-oxide(ITO)/N,N'-bis-(1-naphthyl)-N,N'-diphenyl-(1,1'-biphenyl)-4,4'-diamine(NPB)/2,9-dimenthyl-4,7-diphenyl-1,10-phenanthroline(BCP)/tris(8-hydroxyquinoline)aluminum(Alq3)/Mg:Ag or that of ITO/NPB/1,2,3,4,5,6-hexakis(9,9-diethyl-9H-fluoren-2-yl)benzene(HKEthFLYPh)/Alq3/Mg:Ag were studied.White light emission was achieved with the two devices when the thicknesses of BCP and HKEthFLYPh were 1.5 nm(device B) and 5 nm(device II),respectively...     

不同电子传输层的蓝光有机电致发光器件的性能研究

自从Tang等^[1]首次报道多层有机电致发光器件（OLED）以来,其在亮度和效率上有了质的飞跃,表明器件的结构对提高发光亮度和发光效率起着至关重要的作用,单层器件虽然具有制作简单的优点,但却存在明显缺点：（1）复合发光区靠近金属电极,该处缺陷很多,非辐射复合几率大,导致器件效率降低;（2）由于两种载流子注入不平衡,载流子的复合几率较低,因而影响器件的发光效率,要使发光层中具有高的载流子辐射复合效率,两种载流子的注入及传输能力应相当,否则传输快的一方就会直接穿过发光层到达对电极被猝灭,平衡电子和空穴的注入与传输可通过在电极和发光层之间加入载流子输运层或限制层制作多层器件的途径来实现,基于上述考虑,我们以PPCP为发光层（PPCP是一种荧光效率较高的蓝光材料^[2-4],对其进行深入研究尚未见有文献报道＿,设计了4种不同电子传输层（ETL)的三层 结构的OLED,为研究电子传输层对器件性能的影响,我们还制备了不含电子传输层的双层器件,结果表明,通过选择合适的ETL,OLED的发光亮度及发光效率会有很大程度的改善。     

White and Red Organic Light Emitting Materials

Derivatives of 2,3-(1,4-dialkoxyaceno)norbornadiene underwent ring-opening metathesis polymerization (ROMP) upon the catalysis of a ruthenium complex to afford the corresponding polymers. The polymeric materials containing anthracene chromophores emit white electro-luminescence, which can be fabricated into light-emitting diodes (LED). The broad emission band is composed of a blue emission from anthracene and a red emission from aggregates. A single layer device, ITO/polymer/Ca/Al, can be turned on at 7V and exhibits maximum intensity 427 cd/m2 at 15 V. A double layer device, ITO/polymer/TPBI/Mg:Ag (TPBI = (2,2′,2"-(1,3,5-benzenetriyl)-tris(1-phenyl-1H-benzimidazole)) displayed blue light with turn-on voltage 6 V and maximal intensity 930 cd/m2 at 15 V.Derivatives of bisindolylmaleimide were found to form amorphous solid films which exhibit intensive red luminescence. The property of forming glasses can be ascribed to the nonplanar geometry of these molecules. LED devices were fabricated by a layer of pure dye sandwiched between two charge transporting films. The yellow emission spectrum of the devices utilizing Alq (tris(8-hydoxyquinolinato)aluminum) contains a green component from Alq. Pure red emissions can be achieved by replacing Alq with TPBI. Typical devices can be turned on at ～3 V with maximal intensity 2000 cd/m2. White color devices are under current investigation, in which the green Alq layer is replaced by its blue derivative (bis(2-methyl-8-hydoxyquinolinato)(phenolato)aluminum).     

Electronic and chemical properties of tin-doped indium oxide (ITO) surfaces and ITO/ZnPc interfaces studied in-situ by photoelectron spectroscopy

The chemical and electronic properties of tin-doped indium oxide (ITO) surfaces and its interface with zinc phthalocyanine (ZnPc) were investigated using photoelectron spectroscopy partly excited by synchrotron radiation from the BESSY II storage ring. Preparation and analysis of ITO and ITO/ZnPc layer sequences were performed in-situ without breaking vacuum. The Fermi level position at the ITO surface varies strongly with oxygen content in the sputter gas, which is attributed to an increase of surface band bending as a consequence of the passivation of the metallic surface states of ITO. The shift of the Fermi level is accompanied by a parallel increase of the work function from 4.4 to approximately 5.2 eV. No changes in the surface dipole are observed with an ionization potential of I(P) = 7.65 +/- 0.1 eV. The barrier height for hole injection at the ITO/ZnPc interface does not vary with initial ITO work function, which can be related to different chemical reactivities at the interface.     

输运层厚度对双层有机器件复合发光的影响

采用ITO/PVK/Alq/Al双层电致发光(EL)结构,制备了三种载流子输运层厚度分别为30、 60、 120 nm,发光层厚度均为300 nm的有机薄膜EL器件,测试其EL谱及J-V特性曲线.根据有机EL器件中载流子的产生和输运过程导出了载流子复合几率及电子和空穴密度分布表示式,用以解释其发光强度随输运层厚度的变化关系,用一维无序结构载流子随机跃迁模型讨论输运层厚度对器件电流密度及启动电压的影响,探讨了载流子在薄膜中的输运过程,其理论与实验符合得很好.