光源的色特性与现代照明

本文简要地介绍了光源色特性所包含的个参数及测量方法，给出了对应于ＣＩＥ和我国国家标准ＧＢ５７０２－８５中１５个色样品在昼光照明下的色貌及近似的Ｍｕｎｓｅｌｌ标号。     

单芯片白光发光二极管研制成功

发光二极管在固态照明工程中占有重要的地位,在未来5～10年将逐步取代传统的照明灯具,成为节能、环保的新型光源。与传统的光源（白炽灯,日光灯,卤素灯等）相比,发光二极管光源具有许多优点,如长寿命,体积小,低功耗,低环境污染,高电光转换效率,适用性好和使用安全等。随着GaN基Ⅲ-Ⅴ族化合物技术的发展和蓝光LED的实现,人们已经可以获得实现白光的三基色发光二极管。     

白光有机发光二极管照明材料及其产业化前景

<正>一、有机电致发光二极管简介自从C.W.Tang在电致发光领域取得开创性的进展后[1],有机发光二极管(OLED)因其具有超薄、高对比度、超轻、反应迅速、视角广、低功率的特点引起了科技界和工业界的研究热情。OLED被认为是非常理想的平面显示器,它几乎可以满足显示应用的所有苛刻要求。除了在显示方面的应用,白光有机发光二极管(WOLEDs)还被认为是下一代固体照明光源,这一应用也必将会引起广泛     

白光发光二极管用荧光粉的研究进展

针对目前获取发光二极管(LED)白光的3种主要方法,即三基色荧光粉配合、蓝光LED芯片激发YAG:Ce3+荧光粉和单一离子(Dy3+)的发射进行综述,着重介绍各种方法中所需荧光粉的制备方法和结构体系及其优、缺点,简单总结白光发光二极管研究领域存在的问题及发展趋势。     

有机半导体照明(有机照明)研究进展

采用有机发光二极管(OLEDs)的有机半导体照明(有机照明)是绿色环保、健康安全的新型面光源,有望在固态照明领域得到广泛的应用。有机照明的发展是随着有机发光材料的不断进步而进步的。有机发光材料从最初的荧光材料发展到磷光材料以及最近提出的热活化延迟荧光材料,其性能在不断地提升。基于这些材料的白光OLEDs的性能也在不断提升。最早的白光器件基于荧光小分子材料,但是由于只能利用单线态激子发光,效率很低。随后磷光材料的引入使得白光器件的效率大幅度提升,但是由于蓝色磷光材料本身的稳定性问题,全磷光白光器件的寿命较短。为了结合荧光和磷光的优点,人们提出了荧光/磷光杂化的白光器件,这是目前最有前景的一类白光器件结构。目前针对有机照明的研究,已从早期只关注效率突破阶段,进入到综合提高效率和寿命阶段。从荧光白光、磷光白光以及荧光/磷光混合白光3个方面对有机照明的研究状况、发展趋势进行了介绍。     

新型发光二极管向稳定纯白光目标又迈进一步

印度科学家开发出一种能够稳定地发出纯白色光的新型发光二极管（LED）。这一成果有望对照明业产生重大影响，并最终让纯白光LED走进千家万户。 白光二极管要真正应用到日常生活当中，更加明亮、持久耐用和能效更高是科学家必须面对和解决的问题。只有这样，发光二极管才有望最终取代白炽灯和荧光灯。[第一段]     

大功率白光发光二极管光源的制作

采用GaN基蓝色发光芯片为激发源,结合黄色硅酸盐系列荧光粉封装成大功率白光发光二极管(W-LEDs).利用24颗大功率5W白光发光二极管制作了两种不同连接方式的W-LEDs路灯:2并12串,和4并6串.设计了相应的驱动电路,对这两种不同连接方式的大功率W-LEDs路灯的光电特性及其在照明光源中的应用条件作了深入地研究和对比,测试了它们的伏安特性,发光效率以及功效,结果表明2并12串连接方式的W-LEDs路灯具有更加稳定的伏安特性,更高的照度以及更高的功效.与高压钠灯和荧光灯的特性相比较,W-LEDs路灯作为绿色环保光源灯,具有更高的显色指数,更加环保,节能.     

半导体照明大功率LED进展

半导体照明是21世纪最具发展前景的高技术领域之一。20世纪90年代年以来，随着氮化镓基第三代半导体的兴起，蓝色和白色发光二极管的研究成功，半导体照明已经成为人类照明史上继白炽灯、荧光灯之后的又一次飞跃，其经济和社会意义巨大。     

基于新型红色材料的有机发光二极管

对一种名为N，N－双－[4-2-(4-二氰甲烯基－6－甲基）－4H－吡喃－2－基]乙烯基]苯基苯胺的新型有机红色材料（BDCM）进行了薄膜发光行为的研究，此材料的一个三苯胺（给电子基）和两个二氰甲烯吡喃（受电子基）所形成的较好空间位阻和强荧光发射能力，使得其固体薄膜具有很高的红色荧光量子产率。所构成ITO／CuPc/DPPP/BDCM/Mg:Ag的红色薄膜电致发光器件，在外加19V直流电压时达到582cd/m^2的发光亮度，同时，此器件的发光色度具有不随所加电流密度变化而改变的特点，表明此材料有很好的电子传输和红色发射性能。     

基于双蓝光有源区激发YAG:Ce荧光粉的高显色性白光LED

在(0001)蓝宝石衬底上利用金属有机化学气相沉积系统,分别生长含有p-AlGaN电子阻挡层和反对称n-AlGaN层的双蓝光波长发射的InGaN/GaN混合多量子阱发光二极管(LED)。结果发现,与传统的具有p-AlGaN电子阻挡层的双蓝光波长LED相比,这种n-AlGaN层能有效改善电子和空穴在混合多量子阱活性层中的分布均匀性和减少电子溢出,并减弱双蓝光发射光谱对电流的依赖性。此外,基于这种双蓝光波长发射的芯片与YAG:Ce荧光粉封装成白光LED能实现高显色性的白光发射,在20 mA电流驱动下,6500 K色温时显色指数达到91,而基于单蓝光芯片的白光LED显色指数只有75。     

White top-emitting organic light-emitting diodes using one-emissive layer of the DCJTB doped DPVBi layer

White top-emitting organic light-emitting diodes (TEOLEDs) composed of one doped emissive layer which emits two-wavelength light though the radiative recombination were fabricated. As the emissive layer, 4,4-bis(2,2-diphenylethen-1-yl)biphenyl (DPVBi) was used as the host material and 4-(dicyanomethylene)-2-tert-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) was added as the dopant material. By optimizing the DCJTB concentration (1.2%) and the thickness of the DPVBi layer (30 nm), the intensity ratio of the two wavelengths could be adjusted for balanced white light emission. By using the device composed of glass/Ag (100 nm)/ITO (90 nm)/2-TNATA (60 nm)/NPB (15 nm)/DPVBi:DCJTB (1.2%, 30 nm)/Alq₃ (20 nm)/Li (1.0 nm)/Al (2.0 nm)/Ag (20 nm)/ITO (63 nm)/SiO₂ (42 nm), the Commission Internationale d'Eclairage (CIE) chromaticity coordinate of (0.32, 0.34) close to the ideal white color CIE coordinate could be obtained at 100 cd/m².     

Efficient light harvesting from flexible perovskite solar cells under indoor white light-emitting diode illumination

This is the first report of an investigation on flexible perovskite solar cells for artificial light harvesting by using a white light-emitting diode (LED) lamp as a light source at 200 and 400 lx,values typically found in indoor environments.Flexible cells were developed using either low-temperature sol-gel or atomiclayer-deposited compact layers over conducting polyethylene terephthalate (PET)substrates,together with ultraviolet (UV)-irradiated nanoparticle TiO2 scaffolds,a CH3NH3PbI3-xClx perovskite semiconductor,and a spiro-MeOTAD hole transport layer.By guaranteeing high-quality carrier blocking (via the 10-40 nm-thick compact layer) and injection (via the nanocrystalline scaffold and perovskite layers) behavior,maximum power conversion efficiencies (PCE) and power densities of 10.8％ and 7.2 μW.cm-2,respectively,at 200 lx,and 12.1％ and 16.0 μW·cm-2,respectively,at 400 lx were achieved.These values are the state-of-the-art,comparable to and even exceeding those of flexible dye-sensitized solar cells under LED lighting,and significantly greater than those for flexible amorphous silicon,which are currently the main flexible photovoltaic technologies commercially considered for indoor applications.Furthermore,there are significant margins of improvement for reaching the best levels of efficiency for rigid glass-based counterparts,which we found was a high of PCE ～24％ at 400 lx.With respect to rigid devices,flexibility brings the advantages of being low cost,lightweight,very thin,and conformal,which is especially important for seamless integration in indoor environments.     

White organic light-emitting diodes from three emitter layers

Three-wavelength white organic light-emitting diodes (WOLEDs) were fabricated using two doped layers, which were obtained by separating the recombination zones into three emitter layers. A sky blue emission originated from the 4,4′-bis(2,2′-diphenylethen-1-yl)biphenyl (DPVBi) layer. A green emission originated from a tris(8-quinolinolato)aluminum (III) (Alq₃) host doped with a green fluorescent 10-(2-benzothiazolyl)-1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H,11H-[1]benzopyrano [6,7,8-ij]-quinolizin-11-one (C545T) dye. An orange emission was obtained from the N,N′-bis(1-naphthyl)-N,N′-diphenyl-1,1′-biphenyl-4,4′-diamine (NPB) host doped with a red fluorescent dye, 4-(dicyanomethylene)-2-tert-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB). A white light resulted from the partial excitations of these three emitter layers by controlling the layer thickness and concentration of the fluorescent dyes in each emissive layer simultaneously. The electroluminescent spectrum of the device was not sensitive to the driving voltage of the device. The white light device showed a maximum luminance of approximately 53,000 cd/m². The external quantum and power efficiency at a luminance of approximately 100 cd/m² were 2.62% and 3.04 lm/W, respectively.     

Pure white organic light-emitting diode with lifetime approaching the longevity of yellow emitter

A high-efficiency pure white organic light-emitting diode was fabricated with lifetime approaching that of the low-excitation-energy (yellow) emitter containing counterpart, or six times that of the deep-blue counterpart. The white device was composed of two emission layers with mixed hosts of different compositions. They were respectively doped with yellow rubrene and deep-blue 4,4'-bis-[4-{N,N,N',N'- tetrakis-(4-fluoro-diphenylamino)-phenyl}-vinyl]-biphenyl. The resulting efficiency was 6.0 lm/W (12.4 cd/A) at 20 mA/cm(2). The long device lifetime may be attributed to the double mixed-host architecture employed that effectively dispersed the injected carriers into three different recombination zones and consequently diluted the damaging effect arising from the accumulated charge from un-recombined carriers, hence leading to a markedly improved lifespan.     

Highly efficient white organic light-emitting devices based on a multiple-emissive-layer structure

Characteristics of white organic light-emitting devices based on phosphor sensitized fluorescence are improved by using a multiple-emissive-layer structure, in which a phosphorescent blue emissive layer is sandwiched between red and green&yellow ones. In this device, bis[(4,6–difluorophenyl)–pyridinato–N,C²] (picolinato), bis(2,4–diphenyl–quinoline) iridium (III) acetylanetonate, fac tris (2-phenylpyridine) iridium, and 5,6,11,12–tetraphenylnaphthacene are used as blue, red, green, and yellow emitters, respectively. The device has a maximum luminance of more than 30,000 cd/m², a maximum luminous efficiency of 27 cd/A, a maximum external quantum efficiency of 12.4%, and a color rendering index of 81 at 100 cd/m².     

A study on single-layered white organic light-emitting diodes based on Co-host system using solution process

Two color white organic light-emitting diode (WOLED) that used a co-host system in a solution process method was prepared. A device configuration is ITO/PEDOT:PSS (40 nm)/emitting layer (50 nm)/TPBi (20 nm)/LiF (1 nm)/Al. The emitting layer consists of TATa+ alpha-NPB or beta-NPB + DPAVBi (blue dopant) + Rubrene (yellow dopant). The device using alpha-NPB or beta-NPB showed white color of CIE (0.30, 0.40) and (0.29, 0.39), respectively. Device efficiency of alpha-NPB was 3.85 cd/A at 100 mA/cm2, which is about 15% higher than beta-NPB's.     

Non-reflective black cathode in organic light-emitting diode

A black conductive electrode with a resistivity of 6.75×10⁻⁴ Ω cm was fabricated by doping silicon monoxide into aluminum by simple thermal evaporation. The relative optical reflectance of such electrode layers within the visible spectral range was between 0.12 and 0.05. The black electrode was incorporated in an organic light-emitting diode (OLED) by sequential deposition of α-napthylphenylbiphenyl diamine, tris-(8-hydroxyquinoline) aluminum and the black layer on indium-tin-oxide-coated glass substrates. The black layer reduced the reflection of ambient light entering the device and resulted in a significant increase of the OLED display contrast ratio. The electroluminescence properties of the device incorporating the black layer were investigated.     

Device based on the coupling of an organic light-emitting diode with a photoconductive material

We have realized a device based on the coupling of an organic light-emitting diode (with tri(8-hydroxyquinoline)aluminium for light emission) as an input unit with a photoconductive material as an output unit. Various photoconductive materials like pentacene, Cu-phtalocyanine and fullerene were investigated under green light illumination with an emission peak at 550 nm. Photocurrent measurements versus light intensity and bias voltage (applied between two 50 μm distant indium-tin oxide bottom electrodes for the current to flow through the materials) were realized at room temperature a photocurrent gain around 4 is obtained when the materials are subjected to a luminance of about 5000 cd/m² and for bias voltage of − 50 V. Besides, it was shown that to obtain a device with a fast photocurrent response by switching the light off and on, it is necessary to apply a bias voltage higher than − 200 V in these conditions, the gain is multiplied by a factor of 3.