有机电致发光材料的研究

有机LED平板显示器具有效率高、亮度强、能耗低、色彩丰富以及响应速度快等优点，是近年来发光显示领域的研究热点。作为有机LED平板显示器的物质基础，电致发光(EL)材料是直接影响其器件性能的关键因素。本文在阐述器件结构和发光机理的基础上，重点介绍有机LED器件的电致发光材料，并对其应用前景进行展望。     

有机电致发光彩色平板显示器

由于有机电致发光器件具有驱动电压低，亮度高，全彩色化及成本低等优点，因此，近年来用它制作平板显示器的工作备受关注。下文论述了彩色有机发光器件平板显示器的发展现状。     

稀土配合物有机电致发光

稀土元素具有独特的电子层结构，是一类丰富的发光材料宝库。将稀土配合物应用于有机电致发光显示器件（OLED）对于实现全彩色显示具有重要意义。与通常的有机电致发光显示器件相比。稀土配合物有机电致发光器件具有高色纯度发射和高内量子效率的优点。本文概述了稀土配合物分类、稀土配合物有机电致发光器件研究进展和优点，着重研究了稀土离子及其OLED器件的发光机理。     

有机白光LED

有机白光LED主要有电致发光与光致发光两类。电致发光的主要机理有:量子阱发光、激基复合物发光和能量转移。人们对有机电致发光白光LED研究较多,不久将有产品问世;而对光致发光研究较少。与电致发光相比,光致发光造价更小,其荧光量子效率或许比电致发光更高。有机白光LED制备工艺简单、成本低功耗小,具有巨大的应用价值及潜在的市场。对发光显示技术,有机白光LED代表了一条“便宜”经济的路径。综述了有机白光LED的机理及发展现状。     

有机电致发光器件中载流子的动态分析

通过对有机电致发光器件中电子和空穴进行动态分析,对其发光机理进行详细研究与探讨,得出以下结论:有机电致发光材料的载流子传输性能影响着载流子在发光层禁带中的分配和载流子复合区域位置;有机电致发光器件的工作过程分为载流子陷阱填充和载流子复合发光两个主要过程.     

有机电致发光器件中载流子的动态分析

通过对有机电致发光器件中电子和空穴进行动态分析,对其发光机理进行详细研究与探讨,得出以下结论:有机电致发光材料的载流子传输性能影响着载流子在发光层禁带中的分配和载流子复合区域位置;有机电致发光器件的工作过程分为载流子陷阱填充和载流子复合发光两个主要过程.     

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。     

利用PtOEP掺杂改善Spiro发光器件的发光效率

为了利用有机三线态发光提高有机发光器件的发光效率,用磷光材料掺杂到聚合物主体中作为发光层,制备有机电致发光器件.在测量器件的电流-电压特性、发光亮度-电压特性和电致发光谱的基础上,计算了器件的外量子效率,研究了磷光材料的掺杂浓度对器件发光效率的影响.结果表明,对特定的材料体系,适当控制掺杂浓度,可以同时观察到荧光和磷光光谱,使掺杂器件的外量子效率在纯聚合物发光器件的基础上得到明显提高.     

有机电致发光材料的研究进展

有机电致发光(OEL)是近年来国际上的一个研究热点。有机电致发光器件具有低压驱动、高亮度、高效率以及能实现大面积彩色显示等优点。介绍了有机电致发光材料特别是金属配合物和聚合物材料的国内外研究进展，并在此基础上探讨了分子结构与发光性能的关系．     

利用PtOEP掺杂改善Spiro发光器件的发光效率

为了利用有机三线态发光提高有机发光器件的发光效率,用磷光材料掺杂到聚合物主体中作为发光层,制备有机电致发光器件.在测量器件的电流-电压特性、发光亮度-电压特性和电致发光谱的基础上,计算了器件的外量子效率,研究了磷光材料的掺杂浓度对器件发光效率的影响.结果表明,对特定的材料体系,适当控制掺杂浓度,可以同时观察到荧光和磷光光谱,使掺杂器件的外量子效率在纯聚合物发光器件的基础上得到明显提高.     

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.     

白光LED的实现及荧光粉材料的选取

主要介绍了目前主流白光LED的封装方法,简述了各种方法的原理及优缺点。重点介绍了蓝光芯片与黄光荧光粉混合实现白光LED的机制。通过测试芯片发射谱、不同荧光粉材料的激发和发射谱,重点研究了蓝色芯片与黄色荧光粉材料的光谱匹配性,讨论了荧光粉材料的选取对器件的电学、光学性能的影响。     

The effect of gamma irradiation and forward bias on the 76 K electroluminescence spectrum of GaP:Zn,O

Both the effects of gamma irradiation and high-current forward bias on the low temperature electroluminescence (EL) spectra of GaP:Zn,O light emitting diodes (LEDs) have been studied by measuring constant current (1 mA) 76 K EL spectra below 1000 nm. The LEDs were divided into two sets: a control set which was subjected only to forward bias, and a set exposed to gamma irradiation and forward bias. The EL spectra reveal the growth of sharp, bound exciton emission bands (Z lines) in the range 580 nm to 620 nm following extended high current bias at 300 K of irradiated LEDs and, more weakly, in control LEDs which show pre-bias evidence of these lines. The emergence of these lines is tenatively associated with the recombination-enhanced motion of a defect, possibly the Zn interstitial, which can be introduced by irradiation and is sometimes present in unirradiated LEDs. This article sponsored by the U. S. Department of Energy (DOE) under Contract No. DE-AC04-76-DP00789. A United States Department of Energy Facility.     

Edge-emitting electroluminescence polarization investigation of InGaN/GaN light-emitting diodes grown by metal-organic chemical vapor deposition on sapphire (0001)

The edge-emitting electroluminescence (FL) state of polarization of blue and green InGaN/GaN light-emitting diodes (LEDs) grown in EMCORE’s commercial reactors was studied and compared to theoretical evaluations. Blue (∼475 nm) LEDs exhibit strong EL polarization, up to a 3:1 distinction ratio. Green (∼530 nm) LEDs exhibit smaller ratios of about 1.5:1. Theoretical evaluations for similar InGaN/GaN superlattices predicted a 3:1 ratio between light polarized perpendicular (E⊥c) and light polarized parallel (E‖c) to the c axis. For the blue LEDs, a quantum well-like behavior is suggested because the E⊥c mode dominates the E‖c mode 3:1. In contrast, for the green LEDs, a mixed quantum well (QW)-quantum dot (QD) behavior is proposed, as the ratio of E⊥c to E‖c modes drops to 1.5:1. The EL polarization fringes were also observed, and their occurrence may be attributed to a symmetric waveguide-like behavior of the InGaN/GaN LED structure. A large 40%/50% drop in the surface root mean square (RMS) from atomic force microscopy (AFM) scans on blue/green LEDs with and without EL fringes points out that better surfaces were achieved for the samples exhibiting fringing. At the same time, a 25%/10% increase in the blue/green LED photoluminescence (PL) intensity signal was found for samples displaying EL interference fringes, indicating superior material quality and improved LED structures.     

聚合物液体LED和有机激光

描述了两种液态聚合物LED器件特性及发光机制,一种是溶液LED（SLED）,活性层为溶液介质;另一种是凝胶介质,其中含有溶剂,二者发光机理都产生于电产生的化学发光（ECL）。前者载流子是带电的聚合物链,靠近阴极处被氧化的聚合物分子及靠近阳极的被还原的分子分别向对电极移动时复合产生辐射跃近;后者仅是在阴极处被氧化的溶剂分子,在凝胶中迁移时与在阳极附近被还原的高分子链相遇而产生辐射复合。它们与固体聚合物LED和EL发光机制有些不同。另外,描述了聚合物激光及Bell实验室研制的电注入激光现象。     

InGaN-AlInGaN multiquantum-well LEDs

InGaN-GaN and InGaN-AlInGaN multiquantum-well (MQW) light-emitting diodes (LEDs) were both fabricated and their optical properties were evaluated by photoluminescence (PL) as well as electroluminescence (EL). We found that the PL peak position of the InGaN-AlInGaN MQW occurs at a much lower wavelength than that of the InGaN-GaN MQW. The PL intensity of the InGaN-AlInGaN MQW was also found to be larger. The EL intensity of the InGaN-AlInGaN MQW LED was also found to be larger than that of the InGaN-GaN MQW LED under the same amount of injection current. Furthermore, it was found that EL spectrum of the InGaN-AlInGaN MQW LED is less sensitive to the injection current. These observations all suggest that we can improve the properties of nitride-based LEDs by using AlInGaN as the barrier layer     

染料掺杂型有机电致发光器件

叙述了采用共蒸发法进行有机小分子掺杂对有机ＥＬ器件效率、寿命和发光色的影响规律。结果表明,小分子掺杂法不但可以大幅度提高有机ＥＬ寿命,还可以获得希望的发光色,同时还提出了掺杂剂的选择标准。     

Temperature-dependent electroluminescence in InGaN/GaN multiple-quantum-well light-emitting diodes

We present a comparative study on temperature dependence of electroluminescence (EL) of InGaN/GaN multiple-quantum-well (MQW) light-emitting diodes (LEDs) with identical structure but different indium contents in the active region. For the ultraviolet (UV) and blue LEDs, the EL intensity decreases dramatically with decreasing temperature after reaching a maximum at 150 K. The peak energy exhibits a large redshift in the range of 20–50 meV with a decrease of temperature from 200 K to 70 K, accompanying the appearance of longitudinal-optical (LO) phonon replicas broadening the low energy side of the EL spectra. This redshift is explained by carrier relaxation into lower energy states, leading to dominant radiative recombination at localized states. In contrast, the peak energy of the green LED exhibits a minimal temperature-induced shift, and the emission intensity increases monotonically with decreasing temperature down to 5 K. We attribute the different temperature dependences of the EL to different degrees of the localization effects in the MQW regions of the LEDs.     

Near-Ultraviolet Light-Emitting Devices Using Vertical ZnO Nanorod Arrays

Reports on electroluminescence (EL) in solid-state, nanomaterial-based devices emitting in the lower wavelength range of the visible spectrum are limited, and the emission stability of these devices is rarely reported. We have fabricated light-emitting devices (LEDs) based on integration of n-ZnO nanorods and p-GaN films, which emit in the violet to near-ultraviolet (NUV) region. We also present data on the stability of EL in fabricated devices. Vertical arrays on ZnO nanorods, with estimated ZnO nanorod density ~10⁸ cm⁻², were grown on p-GaN films with typical length of ~4 μm and width of ~120 nm. The NUV LEDs show low turn-on voltage (~3.0 V), small reverse saturation current (~10 μA), and more than two orders of magnitude rectification ratio, all of which indicates a good-quality p–n junction at the p-GaN/n-ZnO nanorod interface. The EL spectra of LEDs present an emission band centered at ~403 nm. Gaussian fitting of the EL peak revealed three emission peaks at 378 nm, 405 nm, and 431 nm with dominant emission in the NUV region. Significantly, the fabricated NUV LEDs present stable and repeatable EL characteristics, as revealed by bias-stress stability tests. The good electrical properties and stable EL performance make these nanostructure-based NUV LEDs potential candidates for mass production of next-generation lighting devices.