有机电致发光显示及其发展

本文介绍有机电致发光的发展历史、器件结构、发光材料以及发光机理，并阐述其目前的主要应用和未来的走向。     

基于有机电致发光显示的透明导电膜ITO

介绍了ITO作为OLED器件阳电极时，ITO各参数对OLED整体性能，如发光亮度、效率、寿命和稳定性的影响，并以溅射ITO工艺为例，分析了制备与处理环境对ITO的方阻、透过率、表面平整度及功函数的影响。针对其成因．提出了一些改进措施。对高性能平板显示OLED器件用透明导电阳极的研制具有一定的参考价值。     

有机电致发光显示技术

有机电致发光显示技术被看好是下一代最有竞争力的平板显示技术。经过短短十余年，该技术的研究得到了飞速的发展，已经达到了实用化的水平。本文将介绍OLED的发展背景、工作原理、驱动技术和封装材料。     

有机电致发光的效率

描述了评价有机电致发光性能的重要指标－－发光效率问题,从发光机制考虑,一般常用外量子效率和内量子效率来评价。外量子效率是有机电致发光器件输出光子数与注入电子数之比;内量子效率是产生在器件内部的光子数与液入电子数之比,对于光子能否输出到器件外部无关紧要。评价器件性能还有一些其他效率评价方法,如能量效率,功率效率等,特别是外功率效率（1m/W),电流效率（cd/A)也常常用于表征有机电致发光性能,但它们与发光光谱的视觉灵敏度有关,对紫外外辐射器件不适用,另外,利用三重态激子发射可以提高EL器件效率,理论上可达100％,器件结构及材料对器件外量子效率影响至关重要。     

彩色有机薄膜电致发光器件及显示技术

对性能稳定的彩色薄膜有机EL器件进行了研究.其中绿色有机器件的半亮度寿命为14000小时(初始亮度100cd/m2),已达到实用化的要求.红色、蓝色和白色器件的半亮度寿命(初始亮度100cd/m2)分别达到了3750、1016和2850小时.在得到稳定的绿色有机薄膜电致发光器件基础上,对矩阵显示屏及动态显示技术进行了研究.得到了面积为48mm×30mm、分辨率为2线/mm的96×60象素矩阵显示器,其中单位象素的有效发光面积为0.4mm×0.4mm,单元间隙为0.1mm.并设计了有效的驱动和控制电路,实现了无"交叉效应"的、高清晰度的动态图形显示.显示器在1/64的驱动占空比下的显示亮度大于100 cd/m2,屏的功耗为0.6W.     

有机电致发光显示板

本文介绍高性能多层有机电致发光显示器件。该器件可分为三类。多层器件的发光亮度超过１００ｃｄ／ｍ’，驱动电压低于２０Ｖ。文章也介绍了高亮度器件的发光机理和器件的稳定性。     

有机电致发光技术及其发展方向

介绍了有机ＥＬ的工作原理,有机ＥＬ器件的结构,材料和制造方法,以及今后的发展趋势。     

有机电致发光

详细介绍了有机电致发光的原理、结构和制备方法，分析了用于有机电致发光的各种材料的性能以及蓝色有机ＥＬ，最后提出了存在的问题及展望。     

有机电致发光显示器件的研究

基于有机电致发光器件的能级结构,阐述电极薄膜优化对提高载流子注入效率的作用。系统评述了红绿蓝三原色有机发光材料在荧光量子效率、稳定性、寿命等方面的进展。在对比分析有机显示器件被动矩阵和主动矩阵两种驱动方式技术特点的基础上,介绍了主动矩阵的薄膜晶体管TFT驱动电路的研究进展及相关技术难点。最后简要回顾有机面板在显示尺寸、色彩及寿命方面的研发成果,并探讨了大尺寸面板在产业化进程中面临的问题及可能的技术解决方案。     

基于DSA-ph的高效蓝色有机电致发光器件

以NPBX掺杂3%的DSA-ph作为发光层,BCP或TAZ作为空穴阻挡层,Alq3或Bphen作为电子传输层制作了一组蓝色有机电致发光器件。通过调整不同的空穴阻挡层与电子传输层之间的组合,得到了一组高效的蓝光OLED。测试结果表明,当空穴阻挡层为TAZ,电子传输层为Bphen时,器件的性能最优。当驱动电压为5V时,器件最大电流效率为4.59cd/A。在12V时亮度最大,为6 087cd/m2。     

有机小分子掺杂的聚合物共混发光二极管

报道了用可溶性发光材料聚（２,５－二丁氧基苯）做发光材料,分别与母体聚合物聚乙烯基咔唑（ＰＶＫ）和聚甲基丙烯酸甲脂（ＰＭＭＡ）共混,并掺杂电子传输材料叔丁基联苯基苯基口恶二唑和空穴传输材料二胺衍生物作发光层,用铟锡氧化物和铝分别作正负电极,制作了两种蓝紫光有机／聚合物单层发光器件。通过比较两种器件的器件特性,发现以ＰＭＭＡ做母体的器件比用ＰＶＫ做母体的器件有更好的稳定性,器件开启电压为１０Ｖ左右,发光峰值波长均位于４２４ｎｍ,电致发光效率可达２．９％,比用ＰＶＫ做母体的器件效率高一倍多。     

一种计算有机发光二极管体电势的方法

建立了计算有机发光二极管（OLED）体电势的理论模型,把在光照下所产生电流与暗电流相等时所加的电压称为补偿电压,得出了补偿电压与体电势函数关系式,该函数只与材料参数及温度有关,在温度较低时,补偿电压即为体电势,在室温情况下,因受扩散运动影响,体电势低于补偿电压,该理论模型计算得出结果与实验结果符合得很好。     

A Review on Encapsulation Technology from Organic Light Emitting Diodes to Organic and Perovskite Solar Cells

Organic light emitting diodes (OLEDs) employing organic thin-film based emitters have attracted tremendous attention due to their widespread applications in lighting and as displays in mobile devices and televisions. The novel thin-film photovoltaic techniques using organic or organic–inorganic hybrid materials such as organic photovoltaics (OPVs) and perovskite solar cells (PSCs) have become emerging competitive candidates with regard to the traditional photovoltaic techniques on account of high-efficiency, low-cost, and simple manufacturing processing properties. However, OLEDs, OPVs, and PSCs are vulnerable to the undesired degradation induced by moisture and oxygen. To afford long-term stability, a robust encapsulation technique by employing materials and structures that possess high barrier performance against oxygen and moisture must be explored and employed to protect these devices. Herein, the recent progress on specific encapsulation materials and techniques for three types of devices on the basis of fundamental understanding of device stability is reviewed. First, their degradation mechanisms, as well as, influencing factors are discussed. Then, the encapsulation technologies and materials are classified and discussed. Moreover, the advantages and disadvantages of various encapsulation technologies and materials coupled with their encapsulation applications in different devices are compared. Finally, the ongoing challenges and future perspectives of encapsulation frontier are provided.     

Dependence of Light‐Emitting Characteristics of Blue Phosphorescent Organic Light‐Emitting Diodes on Electron Injection and Transport Materials

We investigate the light‐emitting performances of blue phosphorescent organic light‐emitting diodes (PHOLEDs) with three different electron injection and transport materials, that is, bathocuproine(2,9‐dimethyl‐4,7‐diphenyl‐1,10‐phenanthroline) (Bphen), 1,3,5‐tri(m‐pyrid‐3‐yl‐phenyl)benzene (Tm3PyPB), and 2,6‐bis(3‐(carbazol‐9‐yl)phenyl)pyridine (26DCzPPy), which are partially doped with cesium metal. We find that the device characteristics are very dependent on the nature of the introduced electron injection layer (EIL) and electron transporting layer (ETL). When the appropriate EIL and ETL are combined, the peak external quantum efficiency and peak power efficiency improve up to 20.7% and 45.6 lm/W, respectively. Moreover, this blue PHOLED even maintains high external quantum efficiency of 19.6% and 16.9% at a luminance of 1,000 cd/m² and 10,000 cd/m², respectively.     

Candle Light‐Style Organic Light‐Emitting Diodes

In response to the call for a physiologically‐friendly light at night that shows low color temperature, a candle light‐style organic light emitting diode (OLED) is developed with a color temperature as low as 1900 K, a color rendering index (CRI) as high as 93, and an efficacy at least two times that of incandescent bulbs. In addition, the device has a 80% resemblance in luminance spectrum to that of a candle. Most importantly, the sensationally warm candle light‐style emission is driven by electricity in lieu of the energy‐wasting and greenhouse gas emitting hydrocarbon‐burning candles invented 5000 years ago. This candle light‐style OLED may serve as a safe measure for illumination at night. Moreover, it has a high color rendering index with a decent efficiency.     

GaN基发光二极管外量子效率研究进展

近年来,GaN基发光二极管发展迅猛,但其发光效率一直是制约LED在照明领域广泛应用的主要瓶颈。本文简要介绍了提高发光二极管外量子效率的几种途径：生长分布布喇格反射层（DBR）结构,表面粗化技术,异性芯片技术,采用光子晶体结构,倒装芯片技术,激光剥离技术,透明衬底技术等。     

Simplified Bilayer White Phosphorescent Organic Light‐Emitting Diodes

We report on highly efficient blue, orange, and white phosphorescent organic light‐emitting diodes consisting only two organic layers. Hole transporting 4, 4,’ 4”‐tris (N‐carbazolyl)triphenylamine (TcTa) and electron transporting 2‐(diphenylphosphoryl) spirofluorene (SPPO1) are used as an emitting host for orange light‐emitting bis(3‐benzothiazol‐2‐yl‐9‐ethyl‐9H‐carbazolato) (acetoacetonate) iridium ((btc)2(acac)Ir) and blue light‐emitting iridium(III)bis(4,6‐difluorophenyl‐pyridinato‐N,C2’) picolinate (FIrpic) dopant, respectively. Combining these two orange and blue light‐emitting layers, we successfully demonstrate highly efficient white PHOLEDs while maintaining Commission internationale de l'éclairage coordinates of (, ). Accordingly, we achieve a maximum external quantum, current, and power efficiencies of 12.9%, 30.3 cd/A, and 30.0 lm/W without out‐coupling enhancement.     

Rational Design of Chelating Phosphine Functionalized Os(II) Emitters and Fabrication of Orange Polymer Light‐Emitting Diodes Using Solution Process

A new series of charge neutral Os^(II) pyridyl azolate complexes with either bis(diphenylphosphino)methane (dppm) or cis‐1,2‐bis(diphenylphosphino)ethene (dppee) chelates were synthesized, and their structural, electrochemical, photophysical properties and thermodynamic relationship were established. For the dppm derivatives 3a and 4a , the pyridyl azolate chromophores adopt an eclipse orientation with both azolate segments aligned trans to each other, and with the pyridyl groups resided the sites that are opposite to the phosphorus atoms. In sharp contrast, the reactions with dppee ligand gave rise to the formation of two structural isomers for all three kind of azole chromophores, with both azolate or neutral heterocycles (i.e., pyridyl or isoquinolinyl fragments) located at the mutual trans‐disposition around the Os metal (denoted as series of a and b complexes). These chelating phosphines Os^(II) complexes show remarkably high thermal stability, among which and several exhibit nearly unitary phosphorescence yield in deaerated solution at RT. A polymer light‐emitting device (PLED) prepared using 0.4 mol % of 5a as dopant in a blend of poly(vinylcarbazole) (PVK) and 30 wt % of 2‐tert‐butylphenyl‐5‐biphenyl‐1,3,4‐oxadiazole (PBD) exhibits yellow emission with brightness of 7208 cd m^–2, an external quantum efficiency of 10.4 % and luminous efficiency of 36.1 cd A^–1 at current density of 20 mA cm^–2. Upon changing to 1.6 mol % of 6a , the result showed even better brightness of 9212 cd m^–2, external quantum efficiency of 12.5 % and luminous efficiency of 46.1 cd A^–1 at 20 mA cm^–2, while the max. external quantum efficiency of both devices reaches as high as 11.7 % and 13.3 %, respectively. The high PL quantum efficiency, non‐ionic nature, and short radiative lifetime are believed to be the determining factors for this unprecedented achievement.     

Langevin and Trap‐Assisted Recombination in Phosphorescent Organic Light Emitting Diodes

Bimolecular and trap‐assisted recombination mechanisms are investigated in small molecule‐based phosphorescent organic light emitting diodes (PhOLEDs) using the current?voltage?luminance characteristics in the diffusion current region, along with transient electroluminescence and capacitance measurements. Two different PhOLEDs, one with a single host, 4,4′‐Bis(carbazol‐9‐yl)biphenyl, and the other with an exciplex‐forming co‐host, are studied. Trap‐assisted recombination with a large number of trapped charges is dominant in the PhOLED with the single host because of the large energy gap between the host and the dopant state. In contrast, bimolecular Langevin recombination is dominant in the PhOLED with the exciplex forming co‐host, where a phosphorescent dye is doped in the co‐host. As a result, the accumulated charge density is lower in the co‐host system than in the single host emission layer, leading to high efficiency that approaches the theoretical limit, with an extremely low efficiency roll‐off.     

Novel Heterolayer Organic Light‐Emitting Diodes Based on a Conjugated Dendrimer

We demonstrate a novel organic light‐emitting diode (LED) heterolayer structure that contains a conjugated dendrimer as the light‐emitting molecule. The LED was prepared by spin‐coating two dendrimer layers from the same solvent. The device consists of a graded bilayer structure formed from a neat dendrimer film covered with a film consisting of the same dendrimer but doped with the electron‐transporting material 2‐(4‐biphenylyl)‐5‐phenyl‐1,3,4‐oxadiazole (PBD). In this device, the heterojunction interface present in conventional bilayer organic light‐emitting diodes is eliminated, and is replaced by a graded interlayer. By optimizing the concentration of PBD in the dendrimer, a peak electroluminescence (EL) external quantum efficiency of 0.16 % at 600 cd m^–2 was obtained. The EL quantum efficiency is significantly enhanced in comparison with devices based on a single layer, a conventional bilayer, and a single‐layer doped with PBD. The EL quantum efficiency is a factor of eight larger than that of a conventional bilayer LED made with the conjugated dendrimer as the emissive layer and poly(methylmethacrylate) (PMMA) doped with PBD as the electron‐transporting layer. The best blended device exhibited only one third of the efficiency of the graded device. The improvement in the operating characteristics of the graded device is attributed to the efficient device structure, in which exciton formation is improved by a graded doping profile of electron‐ and hole‐transporting components.