Organic Electroluminescent Thin Film Using 8—hydroxyquinoline Zinc as Emitting Layer

Organic electroluminescent thin film using Znq2(Znq2) as the emitting layer material with structure of glass/ITO/Znq2/Al(cell) was fabricated.The V-I curve ,V-B curve and electroluminescent spectra of the cell were measured.Meanwhile the fluorescent spectra, excited spectra and absorption spectra of Znq2 with power and film states were also measured.     

Efficient Organic Multi—quantum Well Electroluminescent Devices Using Aluminum as Cathodes

Organic green light emitting devices(LEDs)with multi-quantum well(MQW)structure were fabricated.Aromatic diamine(TPD)was used as holetransporting layer and potential barrier layer;Tris(8-hydroxyquinoline)aluminunum(Alq3)was acted as electron-transporting emitter and MQW green emitter.Airstable aluinum(Al)was used as electron-injection contact.The influence of the thickness of potential barrier layer and the number of quantum well on the electroluminescent(EL)efficiencies of the devices was investigated.The organic LEDs with two quantum wells showed enhanced EL efficiencies.Maximum external quantum efficiency and brightness were 1.04% and 7000cd/m^2,respectively.     

Control of the Interface between Tris(8-quinolinolato) Aluminum and Aluminum Layers in an Organic Electroluminescent devices

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双层电极有机电致发光器件

主要讨论了在有机双层电致发光器件 Ｉ Ｔ Ｏ／ Ｔ Ｐ Ｄ／ Ａｌｑ３／ Ａｌ 的 Ａｌｑ３／ Ａｌ 界面处引入绝缘材料 Ａｌ２ Ｏ３ 薄层对器件性能的影响。实验发现具有双层电极 Ａｌ２ Ｏ３／ Ａｌ 的器件发光效率比单层电极 Ａｌ 的器件效率提高了六倍多,这是由于 Ａｌ２ Ｏ３ 薄层的引入,降低了界面的表面态密度,提高电子的注入能力,有效地提高了激子的辐射复合几率所致     

Eu3+配合物红色有机电致发光器件

合成了一种新型的Ｅｕ＾３＋配合物－Ｅｕ（ＢＡ）２（ＭＡＡ）（Ｐｈｅｎ）,并将其作为红光发射材料制备了结构为Ｇｌａｓｓ／ＩＴＯ／Ｅｕ（ＢＡ）２（ＭＡＡ）（Ｐｈｅｎ）／Ａ１ｒ的有机电致发光薄膜器件。这种材料具有很强的荧光和很好的单色性且比较强的电致发光。器件的开戾电压为１２Ｖ。在电压为２６Ｖ的正向驱动下,器件的亮度为１５ｃｄ／ｍ＾２,发光效率为０．２５１ｍ／Ｗ。结合测量粉末、薄膜状态下的荧光光谱、激发     

基于TPD:PO-T2T的黄光激基复合物发光性能研究

通过多源有机分子气相沉积系统(LN-386SA)制备结构为ITO/HAT-CN/TPD/TPD:PO-T2T/PO-T2T(x=10,20,30,40,50,60,70 nm)/LiF/Al的有机发光器件,研究了电子传输层(PO-T2T)厚度对TPD:PO-T2T黄光激基复合物发光性能的影响。PO-T2T厚度对其电致发光(electroluminescence, EL)光谱几乎没有影响,但对电流密度(current density, CD)、亮度、效率等性能有较大影响。由于金属铝扩散至发光层中会形成淬灭中心降低发光效率,当PO-T2T越厚时,扩散至发光层的铝原子越少,因此发光效率随PO-T2T厚度增加而增加。当PO-T2T厚度为70 nm时,获得最大电流效率(current efficiency, CE)和功率效率(power efficiency, PE),分别为2.16 cd/A、2.12 lm/W。此外,瞬态EL性能表明TPD:PO-T2T的发光来自TPD和PO-T2T分别对载流子的直接捕获,没有发光瞬时过冲或者深陷阱中载流子逃逸复合发光的现象。     

单异质结蓝色有机电致发光器件

为了增加电子注入,蓝色有机电致发光器件中通常包含一层由发绿光的Alq组成的电子传输层,因此器件的发光常常不可避免地要出现Alq本身的发光从而影响器件的发光色纯度.在以胺类衍生物(N,N'- diphenyl-N,N'-bis(3-methylphenyl)-1,1'biphenyl-4,4'diamine,TPD)为空穴传输层,DSA衍生物(4,4'-bis (2,2-diphenylvinyl)-1,1'-biphenyl, DPVBi)为发光层,当用Liq为电子注入层与Al结合构成复合电极时所制备的双层单异质结蓝色有机电致发光器件中由于去除了Alq而得到色度纯正的DPVBi的发光,同时又保持了较高的发光效率.     

Synthesis of polymers for hole and electron transport materials inorganic electroluminescent devices

Styrene-type polymers having tetraphenylbenzidine (TPD) or tetraphenylphenyldiaminobenzene unit (PDA) and a oxadiazole unit (PBD) on the side chain were prepared as hole and electron transport materials, respectively, of an electroluminescent (EL) device. The device structures employed were [indium-tin-oxide (ITO)/hole transport layer (HTL)/Al] (type I), or [ITO/hole transport layer (HTL)/electron transport layer (ETL)/Al] (type II). Type I devices provided current density higher than 100 mA/cm² but no luminescence was observed. Type II devices emitted luminescence of about 10 cd/m² at the current density of about 170 mA/cm². The emission maximums of these devices were 460 and 530 nm for the device using TPD and PDA, respectively     

有机电致发光薄膜的电流输运机理的分析

用TPD作空穴传输层、8－羟基喹啉锌作发光层,制备了有机薄膜器件,测量了其电致发光特性。分析了该器件的电流输运机理,认为该有机薄膜器件在电致发光时流过器件的电流受热电子注入效应、空间电荷限制效应、隧穿效及器件电阻效应的影响。     

用ZnS薄膜作为空穴缓冲层的高效率有机发光二极管

用磁控溅射方法制备的ZnS薄膜作为有机发光器件(OLEDs)的空穴缓冲层,使典型结构的 OLEDs(ITO/TPD/Alq/LiF/Al) 的发光性能得到改善.ZnS 缓冲层厚度对器件性能影响的实验结果表明,当ZnS缓冲层厚度为 5 nm 时,器件的亮度增加了2倍多;当ZnS缓冲层厚度为5、10 nm时,器件的发光电流效率增加40%.研究结果表明 ZnS 薄膜是一种好的缓冲层材料,它能够提高器件的发光效率,改善器件的稳定性.     

Effect of different processing methods for the hole transporting layer on the performance of double layer organic light-emitting devices

The hole transporting layer （HTL） of organic light-emitting device （OLED） was processed by vacuum deposition and spin coating method, respectively, where N,N＇-biphenyl-N, N＇-bis（3-methylphenyl）- 1, l＇-biphenyl-4,4＇ -diamine （TPD） and poly （vinylcarbazole） （PVK） acted as the hole-transport materials. Tris-（8-hydroxyquinoline）- aluminum （Alq3） was utilized as both the light-emitting layer and the electron transporting layer. The basic structure of the device cell was： indium-tin-oxide （1TO）/PVK ： TPD/Alq3/Mg：Ag. The electroluminescent （EL） characteristics of devices were characterized. The results showed that the peak of EL spectra was located at 530 nm, which conformed to the characterizing spectrum of Alq3. Compared with using vacuum deposition method, the green emission with a maximum luminance up to 26135 cd/m2 could be achieved at a drive voltage of 15 V by selecting proper solvent using spin-coating technique, and its maximum lumi nance efficiency was 2.56 lm/W at a drive voltage of 5.5 V.     

Tris（8—Hydroxyquinoline）Aluminum／2—（4—Biphenylyl）—5—（4—Tertbutylphenyl）—1,3,3—O—xadiazole Organic Multiple Quantum Wells for Electroluminescent Devices

Organic multiple quantum wells(OMQWs) consisting of alternating layers of organic materials have been fabricated from tris(8-hdroxyquinoline) aluminum(Alq)and 2-(4-biphenylyl)-5-(4-tertbutylphenyl)-1,3,3-oxadiazole(PBD)by a multisource-type high-vacuum organic molecular deposition.From the small-angle X-ray diffraction patterns of Alq/PBD OMQWs,a periodically layered structure is confirmed through the entire stack.The Alq layer thickness in the OMQWs was varied from 1 nm to 4 nm.From the optical aborption, photoluminescence and electroluminescence measurements,it is found that the exciton energy shifts to higher energy with decreasing Alq layer thickness,The changes of the exciton energy could be interpreted as the confinement effects of exciton in the Alq thin layers.Narrowing of the emission spectrum has also been observed for the electroluminescent devices(ELDs)with the OMQWs structure at room temperature.     

Investigation of the s-shape caused by the hole selective layer in bulk heterojunction solar cells

A common failure mechanism of organic solar cells is the development of an s-shaped current voltage curve. Herein, we investigated the origin of this degradation mechanism by replacing the commonly used hole selective layer poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) with a co-evaporated layer of N,N′-bis(3-methylphenyl)-N,N′-bis(phenyl)benzidine (TPD) and Dipyrazino[2,3-f:2′,3′-h]quinoxaline-2,3,6,7,10,11-hexacarbonitrile (HATCN). By varying the ratio of TPD to HATCN we are able to tune both the mobility and work function of the hole selective layer. Using a combination of field effect mobility measurements, Kelvin-Probe work function measurements, and numerical modeling we demonstrate that a degraded mobility of the hole selective layer leads to a buildup of charge within the device and reduction of fill factor.     

Fabication of Organic／Polymeric Superlattice Structure and Its Use for Electroluminescent Device^①②

Superlattices consisting of alternating layers of organic/polymeric materials have been fabricated from tris(8-hydroxyquinoline) aluminum(Alq3) and poly(N-vinylcarbazole)(PVK) by a multisource-type high-vacuum organic molecular deposition.The characteristics of superlattice structures are determined by the smallangle X-ray diffraction,optical adsorption and photoluminescence.The electroluminescent devices with the superlattice structure have also been fabricated and the emission characteristics are discussed.     

Cyanocarbazole Derivatives for High‐Performance Electroluminescent Devices

3‐Cyano‐9‐diarylamino carbazoles have been synthesized. These new compounds emit in the blue to green region. Double‐layer electroluminescent devices using these compounds as the hole‐transport/emitting materials are highly efficient. Two of the compounds can be fabricated into single‐layer devices with good performance. Green‐ and blue‐emitting devices with good performance were also fabricated using one of the compounds as the hole‐injection layer.     

Characterization of organic thin films for OLEDs using spectroscopic ellipsometry

We report the optical characterization of thin, evaporated organic films used in fabrication of organic light emitting diodes (OLEDs): N,N'-diphenyl-N,N'-bis(3-methyl-phenyl)-l,l'biphenyl-4,4'diamine,or TPD,andtris(8-hydroxy)quinolato aluminum, or Alq3. In particular, we have obtained and analyzed spectroscopic eliipsometry (SE) data using a multi-sample approach, to determine the optical constants for Alq₃ and TPD films over the wavelength range 250-850 nm. We show that bi-layer Alq₃/TPD films on Si can be analyzed for individual layer thicknesses, even though the refractive index is nearly identical for these films in the visible region. Simulations of in situ monitoring are also presented, which show sub-nm thickness resolution for organic layer growth on a Si monitor wafer. SE has great utility for process control, either by ex situ or in situ thickness measurement.     

Efficient solution-processed blue phosphorescent organic light-emitting diodes with halogen-free solvent to optimize the emissive layer morphology

Efficient solution-processed blue phosphorescent organic light-emitting diodes (OLEDs) featuring with halogen-free solvent processing are fabricated in this study. The organic molecule 3,6-bis(diphenylphosphoryl)-9-(4′-(diphenylphosphoryl) phenyl)-carbazole (TPCz) that possesses good solubility in halogen-free polar solvents is selected to serve as the host of blue phosphorescent iridium(III) [bis(4,6-difluorophenyl)-pyridinato-N,C²]-picolinate (FIrpic) dopant. The morphology of the TPCz:FIrpic emissive layer prepared with different polar solvents including chlorobenzene (CB), n-butanol (ButA) and isopropanol (IPA) and the effect on their electroluminescent performance have been investigated in detail. It is found that the more polar halogen-free solvent IPA restrains the FIrpic aggregation and renders a more densely packed emissive layer as compared to the CB-processed counterpart, which results in the enhanced electroluminescent performance. The luminous efficiency and power efficiency of the blue phosphorescent OLEDs prepared with CB are merely 5.7 cd/A and 3.3 lm/W, respectively. When using more polar halogen-free solvent IPA, the efficiencies are enhanced to 22.3 cd/A and 15.6 lm/W, about 2.9 and 3.7-time increment, respectively. This work provides an approach to fabricate efficient solution-processed phosphorescent OLEDs with environmental-friendly solvents, which is highly required in large-scale solution-processed manufacturing.     

Improved property in organic light-emitting diode utilizing two Al/Alq3 layers

We reported on the fabrication of organic light-emitting devices (OLEDs) utilizing the two Al/Alq₃ layers and two electrodes. This novel green device with structure of Al(110 nm)/tris(8-hydroxyquinoline) aluminum (Alq₃)(65 nm)/Al(110 nm)/Alq₃(50 nm)/N,N′-dipheny1-N, N′-bis-(3-methy1phyeny1)-1, 1′-bipheny1-4, 4′-diamine (TPD)(60 nm)/ITO(60 nm)/Glass. TPD were used as holes transporting layer (HTL), and Alq₃ was used as electron transporting layer (ETL), at the same time, Alq₃ was also used as emitting layer (EL), Al and ITO were used as cathode and anode, respectively. The results showed that the device containing the two Al/Alq₃ layers and two electrodes had a higher brightness and electroluminescent efficiency than the device without this layer. At current density of 14 mA/cm², the brightness of the device with the two Al/Alq₃ layers reach 3693 cd/m², which is higher than the 2537 cd/m² of the Al/Alq₃/TPD:Alq₃/ITO/Glass device and the 1504.0 cd/m² of the Al/Alq₃/TPD/ITO/Glass. Turn-on voltage of the device with two Al/Alq₃ layers was 7 V, which is lower than the others.     

电致发光材料三芳胺聚合物的能带结构表征

采用循环伏安(CV)法结合紫外-可见(UV-Vis)吸收光谱表征了4种新型电致发光材料三芳胺聚合物TPD(PTPD)的能带结构,并对引入的基团及分子结构对其能带结构的影响进行了探讨。结果表明,从聚合物TPD和小分子TPD的UV-VIS吸收光谱的最大吸收来看,聚合后TPD的能带结构没有太大的改变。从循环伏安图看出,材料的具有较好电化学稳定性。并制成了ITO(氧化铟锡)/PTPD/Alq3(8-羟基喹啉铝)/Mg:Ag异质结电致发光器件,与典型的ITO/TPD/Alq3/Mg:Ag器件进行了比较,研究发现其器件的稳定性有的明显提高。     

Tetrasubstituted-pyrene derivatives for electroluminescent application

Tetrasubstituted-pyrenes containing peripheral diarylamines (1–4) or fluorenes (5–6) have been synthesized. These compounds are highly fluorescent and possess high morphological stability and thermal stability. Compounds containing peripheral arylamines (1–3) can be used as the hole-transport and green-emitting materials for two-layered electroluminescent devices. Compounds with peripheral fluorenes (5–6) are efficient blue emitters and exhibit ambipolar carrier-transport characteristics with high electron mobilities (10⁻³–10⁻² cm²/V s) and high hole mobilities (>10⁻³ cm²/V s). Non-doped blue-emitting devices with promising electroluminescent performance (i.e., high efficiency and narrow/saturated emission) can be achieved using fluorene–substituted pyrenes as either the hole-transport/emitting layer or the electron-transport/emitting layer in the two-layered devices.