白色LED与照明系统

1 前 言白色发光二极管(LED)作为下一代节能照明光源已崭露头角。利用Ⅲ-Ⅴ族化合物半导体(InGaN,AlGaInP)开发了电光转换效率非常高的LED,从而使具有极高发光强度的固体光源实用化,发光效率在10年中约提     

有机EL和LED与无机EL和LED发光机制的异同

比较了有机EL和LED与无机EL和LED的主要差异。有机EL属于电注入发光,无机EL属于高场激发下的碰撞离化机制,而且有机LED和无机LED的激发和发光机制也不同。无机半导体中往往存在着局域载流子,而有机LED必须从电极注入,在未注入载流子之前,它们是绝缘体。不能简单地用无机LED中的p-n结理论来解释有机LED的发光现象。     

绿色照明与发光

本文主要阐述绿色照明的重要性及其主要内容，回顾了20世纪照明电源发展概况和所取得的巨大成果，并分析了照明与发光之间互相依赖、互相促进的发展现状。     

德国研究机构利用白色有机EL实现发光效率124lm／W高于荧光灯

德国德累斯顿市（Dresden）的研究机构Institute for Applied Photophysics（IAPP）,利用白色发光有机EL元件实现了发光效率124lnl／W。相关论文已刊登在学术杂志《Nature》上。124lm／W的发光效率远远高于普通荧光灯。     

超亮LED领军“绿色照明市场”

超亮及白光发光二极管LED技术飞速发展，在产品产业化方面也有很大突破，其发光强度、发光效率、光输出、寿命等特性不断提高，拓展了LED应用领域及市场。其中，白光LED被认为是21世纪最有价值的新光源，很多国家先后推出LED半导体照明计划，其首要目的就是绿色环保、高效节能。     

用LED照明道路

日本岩崎电气与日本道路公团、高速公路保守公司合作共同开发出一种LED道路照明系统新系统是在道路一侧 1 1m高处配置光强相异的三种 1 4个LED(按 1m间隔 ) ,通过微调对路面进行均匀照射。其亮度达 7～ 1 0lx ,虽比现在使用的高压纳灯稍逊一筹 ,但可改善交通照明条件。发光元件的寿命达 4× 1 0 4 h～ 5× 1 0 4 h ,是高压钠灯的 3倍。因为设置在矮处 ,所以便于维修和检查 ,可按道路通行规则在最短时间内完成检修。与以往照明系统安装工程费用相比 ,其费用稍高一些 ,但其突出优点是运转成本和维护费用少。除了用在高速公路外 ,在公路事…     

有机EL与无机EL和LCD的比较及其未来前景

通过比较有机EL与无机EL、LCD在平板显示应用方面的差异，展示了OELD的美好应用前景。由于无机薄膜EL缺乏高亮度蓝基色成分以及驱动电压是100V左右的交流，难于制成低压彩色超薄显示器；无机分散型EL屏采用的是十几微米厚的粉末材料，也难于制成高分辩率超薄显示器，因此它们都无法与OELD相比。OELD显示器体积可以是LCD的1/2，功耗也大低于LCD，所以OELD将有望取代LCD。评述了当前OELD的最新发展趋势：采用荧光染料掺杂式的模糊界面结构的电致荧光器件和采用荧光染料掺杂式的电致磷光器件是当前OELD发展的主要潮流。文中还评述了采用低折射率材料提高外量子效率的情况。     

绿色LED照明技术及其应用研究

照明在人们日常生活和工业生产等领域发挥着重要的作用,也是能源消耗的重要领域.随着绿色发展理念影响的不断扩大,在照明领域如何节约能源引起人们的关注,各国在发展中纷纷加强了对绿色节能照明技术的研究工作.而绿色LED照明技术正是在这种大环境下诞生的,这一技术能耗少,能源的转化率高,充分实现了节能环保的目标,这使绿色LED在现代社会中得到了广泛应用.     

高效发光的绿色LED

太阳能电池制造技术能制造出能源消耗减少20％的LED。     

发光效率高达30lm／W的白色发光二极管

化成OPTONIX、STANLEY电气、三菱电线工业联合开发出了发光效率达30lm/W的白色发光二极管（LED）。该LED在发出波长382nm紫外光的GaN类LED（紫外LED）中配合使用了将紫外光分别转换为红色光、绿色光、蓝色光的荧光体材料。获得的白色光是 CIE色度上的（x=0.297,y=0.362）。     

用有机混合物实现对微腔电致发光光谱的调制

制做了一种新型的有机电致微腔器件，将两种有机材料混合作为发光材料，通过改变NPB和Alq的重量比(从1：28改变到17：1)，达到了调节腔长从而改变器件发光颜色的目的，且器件发光颜色不随所加电压变化；通过合理地调节两种材料的配比，可以实现微腔白光发射。5种配比的微腔器件均发出半宽度很窄的双模发射(8～12nm)；与传统的异质结微腔器件相比，开启电压从7V降到4V，亮度也得到了提高。     

白光有机电致发光器件的研究

白光有机电致发光器件在显示和照明领域有着极大的应用前景，受到人们广泛的关注。本文对白光有机电致发光器件的结构、工作原理、工艺流程、存在的问题等进行了简单的概述，力求总结出制备白光有机发光器件的新途径。     

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。     

Extremely Efficient White Organic Light‐Emitting Diodes for General Lighting

Highly power‐efficient white organic light‐emitting diodes (OLEDs) are still challenging to make for applications in high‐quality displays and general lighting due to optical confinement and energy loss during electron‐photon conversion. Here, an efficient white OLED structure is shown that combines deterministic aperiodic nanostructures for broadband quasi‐omnidirectional light extraction and a multilayer energy cascade structure for energy‐efficient photon generation. The external quantum efficiency and power efficiency are raised to 54.6% and 123.4 lm W^?1 at 1000 cd m^?2. An extremely small roll‐off in efficiency at high luminance is also obtained, yielding a striking value of 106.5 lm W^?1 at 5000 cd m^?2. In addition to a substantial increase in efficiency, this device structure simultaneously offers the superiority of angular color stability over the visible wavelength range compared to conventional OLEDs. It is anticipated that these findings could open up new opportunities to promote white OLEDs for commercial applications.     

Triplet Harvesting in Hybrid White Organic Light‐Emitting Diodes

White organic light‐emitting diodes (OLEDs) are highly efficient large‐area light sources that may play an important role in solving the global energy crisis, while also opening novel design possibilities in general lighting applications. Usually, highly efficient white OLEDs are designed by combining three phosphorescent emitters for the colors blue, green, and red. However, this procedure is not ideal as it is difficult to find sufficiently stable blue phosphorescent emitters. Here, a novel approach to meet the demanding power efficiency and device stability requirements is discussed: a triplet harvesting concept for hybrid white OLED, which combines a blue fluorophor with red and green phosphors and is capable of reaching an internal quantum efficiency of 100% if a suitable blue emitter with high‐lying triplet transition is used is introduced. Additionally, this concept paves the way towards an extremely simple white OLED design, using only a single emitter layer.     

Emission Color Trajectory and White Electroluminescence Through Supramolecular Control of Energy Transfer and Exciplex Formation in Binary Blends of Conjugated Polyrotaxanes

White electroluminescence and fine‐tuning of the emission color from binary blends of a blue‐emitting polymer and a green/yellow‐emitting threaded molecular wire consisting of a conjugated polymer supramolecularly encapsulated by functionalized cyclodextrins are demonstrated. Encapsulation controls the minimum intermolecular distance on the nanoscale, resulting in suppressed energy‐transfer between the blend constituents and reduced formation of interchain charge‐transfer complexes. The use of a green‐emitting polyrotaxane significantly improves the electrical properties with respect to blends of a blue electroluminescent polyrotaxane and leads to a significant reduction in the turn‐on voltage required for achieving white electroluminescence (V_ON = 3 V), with only 20% by weight of the encapsulated material.     

Controlling the Recombination Zone of White Organic Light‐Emitting Diodes with Extremely Long Lifetimes

The lifetime of the organic devices remains a major challenge that must be overcome before the wide application of white organic light‐emitting diodes (WOLEDs) technology. In this work, we present a new strategy to achieve WOLEDs with an extremely long lifetime by wisely control of the recombination zone. A blue emitting layer of 6,6′‐(1,2‐ethenediyl)bis(N‐2‐naphthalenyl‐N‐phenyl‐2‐naphthalenamine doped 9‐(1‐naphthyl)‐10‐(2‐naphthyl)‐anthracene was deposited on top of the mixed host blue emitting layer to prevent hole penetration into the electron transporting layer and to attain better confinement of carrier recombination. In this way, we obtained a WOLED with a record high lifetime of over 150 000 hours at an initial brightness of 1000 cd m^?2, 40 times longer than the conventional bilayer WOLED. The electroluminescent spectra of the long‐lived WOLED showed almost no color‐shifting after accelerated aging. It is anticipated that these results might be a starting point for further research towards ultrastable OLED displays and lightings.     

Hybrid White Light Emitting Diode Based on Silicon Nanocrystals

A novel design of white light emitting diodes (WLEDs) emerges to meet the growing global demand for resource sustainability while preserving health and environment. To achieve this goal, a facile method is developed for the chemical synthesis of a luminescent silicon nanocrystal (ncSi) with a large Stokes shift between absorption and emission. The WLED is prepared by a simple spin‐coating method, and contains a hybrid‐bilayer of the ncSi and luminescent polymer in its device active region. Interestingly, a well‐controlled ultrathin ncSi layer on the polymer makes possible to recombine electrons and holes in both layers, respectively. Combining red and blue‐green lights, emitted from the ncSi and the polymer layers, respectively, produces the emission of white electroluminescence. Herein, a hybrid‐WLED with a sufficiently low turn‐on voltage (3.5 V), produced by taking advantages of the large Stokes shift inherent in ncSi, is demonstrated.     

基于磷光材料的有机电致白光器件的研究进展

有机电致白光器件是近年来国际上的一个研究热点,它不仅可以作为液晶显示的背光源,也是未来照明技术的有效光源。有机磷光电致发光可以同时利用单重态和三重态的激子,理论上可使器件的内量子效率达到100%,而在近几年倍受关注。文章介绍了磷光材料的有机电致白光器件的研究进展,按多发射层、多重掺杂单发射层、单重掺杂单发射层以及基于激发二聚体和激基复合物发射4种结构进行了分析和阐述。