金属氧化物掺杂调控空穴迁移特性构建高效率低电压OLED

采用金属氧化物掺杂的双空穴传输层[NPB:5%MoOx]/[NPB:3%TiO2]构建了高效率低电压有机电致发光器件(OLED)。以Alq3为发光层,器件的最大发光效率和功率效率分别达到了5.1 cd/A和2.7 lm/W,比非掺杂型NPB空穴传输层构建的OLED分别提高了46%和93%,而驱动电压则降低了约1.5 V。这是由于掺杂型双空穴传输层能有效调控空穴迁移特性,改善电荷平衡因子,从而促进了发光效率和功率效率的提高。     

Emission mechanism in rubrene-doped molecular organiclight-emitting diodes: direct carrier recombination at luminescentcenters

The emission mechanism in molecularly doped organic light-emitting diodes, where the emitting layer is composed of N,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine (TPD) as the host and 5,6,11,12-tetraphenylnaphthacene (rubrene) as the dopant, is investigated in terms of energy transfer and direct carrier recombination. Hole trapping by rubrene is identified by current versus voltage and mobility measurements in single-layered devices. Shallow traps are formed and are found to be filled by injected holes at electric field above 2×10⁵ V/cm. Electroluminescence observed in single-layered devices indicate that electrons can be injected directly into the hole transporter, TPD. In double-layered devices composed of TPD and tris-(8-hydroxyquinolinato) aluminum(III) (Alq₃), the penetration depth of electrons into undoped TPD is determined to be ⩽5 nm from the Alq₃ interface. Upon doping with rubrene, the emission zone is extended to 20 nm due to the increase in the electron penetration depth. This is attributed to the transition of the electron hopping sites from TPD to rubrene molecules. At high-rubrene concentration, electron transport occurs via hopping on the rubrene molecules. The dominant emission mechanism in rubrene-doped TPD is attributed to the electron-hole recombination at the dopant molecule. This is maximized by hole trapping and electron transport of rubrene     

Energy-band schemes of highly stable organic electroluminescent devices

Host-guest systems in organic electroluminescent (EL) devices have been studied. Organic EL cells doped with blue to red guest emitters were prepared and their characteristics and the energy bands of the materials were measured. A green EL cell doped with 2,3-quinacridone showed a maximum efficiency of 18.1 lm/W. A yellow EL cell doped with 5,6,11,12-tetraphenylnaphthacene (rubrene) showed a maximum efficiency of 14.4 lm/W and a half-decay time of 25000 h from 130 cd/m/sup 2/. The energy-band schemes of those cells were analyzed and requirements for the scheme and a guest emitter are discussed.     

High-efficiency white phosphorescent polymer light-emitting devices

White phosphorescent light emission from polymer light-emitting devices (PLEDs) has been demonstrated. To fabricate the white-emitting PLED, blue phosphorescent polymer (BPP) and red phosphorescent polymer (RPP) were used for the emissive layer, and the emission color was tuned by controlling the concentration ratio of BPP to RPP. The external quantum efficiency of the white-emitting PLED, with CIE coordinates of (0.34, 0.36), was 6.0% at luminance of 100 cd/m/sup 2/. To investigate the emission mechanism in the PLED, its photoluminescence spectrum and transient decay were measured. These experimental measurements indicate that direct excitation of the iridium-complex (Ir-complex) units by carrier trapping is a major excitation process for white-emitting PLED. A 3.6-in full-color display based on the white phosphorescent PLED and color filters was demonstrated.     

Blue organic light-emitting diode based on 1,2,3,4,5-pentaphenyl-1-(8-phenyl-1,7-octadiynyl)silole

A new silole derivative, 1,2,3,4,5-pentaphenyl-1-(8-phenyl-1,7-octadiynyl)silole, is synthesized, characterized, and used as the electron-transport/emission layers in organic light-emitting diodes. Blue emission at 492 nm is observed, with a maximum luminance of 10 460 cd/m/sup 2/ at 18 V. The respective maximum current and power efficiencies are 8.47 cd/A and 3.8lm/W. A triple-layer composite cathode was used, consisting of tris(8-hydroxy-quinolne)aluminum (Alq/sub 3/) lithium fluoride and aluminum. The dependence of emission efficiency on the thickness of TPD and Alq/sub 3/ is investigated and explained.     

Vertical‐type organic device using thin‐film ZnO transparent electrode

We propose a double heterojunction organic light‐emitting diode (OLED) using a zinc oxide (ZnO) film, which works as a transparent and electron injection layer. The crystal structure of the ZnO films as a function of Ar/O₂ flow ratio and the basic characteristics of the OLED depending on the ZnO sputtering conditions are investigated. Excellent characteristics of the novel OLED were obtained, as high as 470 cd/m² at 22 V and 7.6 mA/cm². The results obtained here demonstrate that the vertical organic light‐emitting transistor (OLET) using a ZnO layer as an electron injection layer is promising as a key element for flexible sheet displays. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 158(2): 49–55, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20151     

Reliability and degradation of small molecule-based organiclight-emitting devices (OLEDs)

Studies of degradation mechanisms in small molecule-based organic light-emitting devices (OLEDs) are reviewed. A special emphasis is given to OLEDs based on tris (8-hydroxyquinoline) aluminum (AlQ₃), an emitter and electron transport material used in the majority of OLEDs emitting from the green to the red part of the spectrum. Different strategies used for increasing device stability are addressed and the models proposed to explain experimental observations related to OLED operational stability are discussed. Although none of the presently proposed models can explain all experimental observations, the largest body of experimental evidence appears to be consistent with a model based on the instability of cationic AlQ₃ species, produced by the injection of holes into the AlQ₃ electron transport and emitter layer. Other models may be of importance in explaining degradation behavior on different time scales. Models based on redistribution of space charge appear to be responsible for reversible short-term degradation, while a model based on indium migration may be important for degradation on very long time scales     

Polymer thermosetting organic light-emitting devices

We report a systematic study of novel single- and double-layer thermosetting light-emitting devices (LED's) based on triarytamines for hole transport layer and fluorenes for the emitting and electron transport layer. These devices possess high-thermal stability, high-quantum efficiency, and high-bandgap emission (blue and green). We have fabricated dot matrix displays based on analogs of these materials     

Rare-earth-doped GaN: growth, properties, and fabrication of electroluminescent devices

A review is presented of the fabrication, operation, and applications of rare-earth-doped GaN electroluminescent devices (ELDs). GaN:RE ELDs emit light due to impact excitation of the rare earth (RE) ions by hot carriers followed by radiative RE relaxation. By appropriately choosing the RE dopant, narrow linewidth emission can be obtained at selected wavelengths from the ultraviolet to the infrared. The deposition of GaN:RE layers is carried out by solid-source molecular beam epitaxy, and a plasma N/sub 2/ source. Growth mechanisms and optimization of the GaN layers for RE emission are discussed based on RE concentration, growth temperature, and V/III ratio. The fabrication processes and electrical models for both dc- and ac-biased devices are discussed, along with techniques for multicolor integration. Visible emission at red, green, and blue wavelengths from GaN doped with Eu, Er, and Tm has led to the development of flat-panel display (FPD) devices. The brightness characteristics of thick dielectric EL (TDEL) display devices are reviewed as a function of bias, frequency, and time. High contrast TDEL devices using a black dielectric are presented. The fabrication and operation of FPD prototypes are described. Infrared emission at 1.5 /spl mu/m from GaN:Er ELDs has been applied to optical telecommunications devices. The fabrication of GaN channel waveguides by inductively coupled plasma etching is also reviewed, along with waveguide optical characterization.     

100 dpi 4-a-Si:H TFTs active-matrix organic polymer light-emitting display

In this paper, we report on 100 dpi four hydrogenated amorphous silicon thin-film transistors (4-a-Si:H TFTs) active-matrix organic polymer light-emitting display (AM-PLED). For this display, we have established the operational limitation of our 4-a-Si:H TFTs pixel electrode circuit by performing a load line analysis. Combining this result with the extracted pixel organic polymer light-emitting device (PLED) characteristics, we have found that the change of the AM-PLED pixel operating point, especially of a driving TFT, limits the operational range of AM-PLED pixel. The predicted results are compared with the measured data of 100 dpi monochromatic red light-emitting 4-a-Si:H TFTs AM-PLED. For our AM-PLED, we obtained luminance up to /spl sim/20 cd/m/sup 2/ and Commission Internationale de l'Eclairage color coordinates of (0.67, 0.33), which are calculated from the measured AM-PLED electroluminescence spectrum.     

Development of high efficiency GaN-based multiquantum-welllight-emitting diodes and their applications

Highly efficient GaInN-GaN multiple quantum-well (MQW) light-emitting diodes (LEDs) were successfully developed by the low-temperature AlN buffer layer method for metal-organic vapor phase epitaxy (MOVPE). The light-emitting layer of the GaInN-GaN MQW drastically enhances the performance of GaN-based LEDs in terms of the efficiency and spectrums. Flip-chip (FC) type MQW LEDs have been newly developed to increase efficiency in extracting light from the GaN-based crystal to the outside. The luminous intensities of FC type blue and green LEDs are typically 6 and 14 cd, respectively, at 20 mA. The output power of the FC-type LEDs was 14 mW at 20 mA, which was approximately two times higher than that of the conventional face-up type blue LEDs. The external quantum efficiency of blue FC-type LEDs was as high as 20% at 20 mA. New multicolor package was developed using these high performance nitride-based LEDs and commercial AlGaInP-based red LEDs, the color range of which is the largest among other flat panel display devices     

Novel iridium complex and its copolymer with N-vinyl carbazole for electroluminescent devices

A novel iridium complex having the polymerizable functional group as one of the ligands, bis(2-phenylene pyridine) acrylate iridium lr(ppy)2Ac was synthesized as a phosphorescent dopant for electroluminescent (EL) devices. It has a photoluminescence spectrum peak at about 530 nm. EL devices were fabricated by doping lr(ppy)2Ac into host materials, such as BCP (2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline) and poly(N-vinyl carbazole) (PVCz). Bright blue-green luminescence of about 12 000 cd/m2 was observed for an EL device having a structure of indium-tin oxide JTO)/1r(ppy)2Ac-doped TPD:PVCz/BCP/Alq3 [tris(8-hdroxyquinoline) aluniinuml/Mg:Ag. Furthermore, the iridium complex was copolymerized with N-vinyl carbazole (VCz) to form a random copolymer with a number average molecular weight of about 1000. An EL device using this hole-transport layer gave bright blue-green emission of more than 6000 cd/m2. These results indicate that lr(ppy)2Ae, especially its copolymer with VCz, can be a promising phosphorescent material for organic EL devices.     

Realization of polymeric optical integrated devices utilizing organic light-emitting diodes and photodetectors fabricated on a polymeric waveguide

Direct fabrication of organic light-emitting diodes (OLEDs) and organic photodetectors (OPDs) on polymeric substrates, i.e., polymeric waveguide substrates to form flexile optical integrated devices is demonstrated. The OELD and OPD were fabricated by organic molecular beam deposition (OMBD) technique on a polymeric or a glass substrate, for comparison. The device fabricated on a polymeric substrate shows similar device characteristics to that on a glass substrate. Optical signals of faster than 100 MHz have been created by applying pulsed voltage directly to the OLED utilizing diamine derivative, or rubrene or porphine doped in 8-hydoxyquinolinum aluminum derivatives, as an emissive layer. Electrical signals are successively converted to optical signals for optical transmission of moving picture signals with OLED fabricated on a polymeric waveguide. OPDs utilizing phthalocyanines derivatives with superlattice structure provide increased pulse response with input optical signals, and the OPD with the cutoff frequency of more than 5 MHz has been realized.     

High-speed resonant cavity light-emitting diodes at 650 nm

State-of-the-art resonant cavity light-emitting diodes (RC-LEDs) optimized for short-haul communication systems on polymethyl methacrylate (PMMA) plastic optical fiber (POF) are presented. The devices, emitting in the 650-nm wavelength range, are achieving, under different structure and working regime variants, high output power (15 mW), high external quantum efficiency (9.5%), record small-signal modulation bandwidth (f_{-3 dB} UP to 350 MHz), error free back-to-back transmission rates beyond 622 Mb/s, adjustable far-field pattern and good coupling efficiency into step index plastic optical fibers with reasonably large tolerances and without using auxiliary optics. The paper discusses the design concepts, modeling approaches, fabrication issues and performance characteristics of monolithic RC-LEDs emitting at 650 nm     

Optical properties of Zn(II) complex using1,2-bis(8-hydroxyquinolin-2-yl)ethane

Optical properties of Zn(II) complex using 1,2-bis(8-hydoxyquinolin-2-yl)ethane (Zn(BQOEH)), such as optical absorption, photoluminescence, and electroluminescence, are studied. Zn complex film emits a yellow photoluminescence band centered at 564 nm and an electroluminescence band at 567 nm. Transient characteristic of the organic light-emitting devices (OLEDs) with Zn(BQOEH) as the emitting material are demonstrated. An optical pulse of more than 5 MHz is obtained from the OLED with Zn(BQOEH)     

High-power continuous-wave intracavity frequency-doubled Nd:GdVO/sub 4/-LBO laser under diode pumping into the emitting level

The continuous-wave high power laser emission of Nd:GdVO/sub 4/ at the fundamental wavelength of 1.06 /spl mu/m and its 531-nm second harmonic obtained by intracavity frequency doubling with an LBO nonlinear crystal is investigated under pumping by diode laser at 808 nm (on the /sup 4/I/sub 9/2//spl rarr//sup 4/F/sub 5/2/ transition) and 879 nm (on the /sup 4/I/sub 9/2//spl rarr//sup 4/F/sub 3/2/ transition). It is shown that, in spite of a lower absorption at 879 nm, the infrared emission is comparable under these two wavelengths of pump. The green emission performances were, however, improved by the 879 nm pump: 5.1 W at 531 nm with M/sup 2/=1.46 and 0.31 overall optical-to-optical efficiency was obtained from a 3-mm-thick 1-at.% Nd:GdVO/sub 4/ laser medium and a 10-mm-long LBO nonlinear crystal in a Z-type cavity for 16.5 W pump power. In similar conditions, the maximum green power for the 808 nm pump was 4.4 W, with 0.26 overall optical-to-optical efficiency and M/sup 2/=3.40 beam quality; at this pump wavelength the green emission shows evident saturation for pump power in excess of 9.9 W. This behavior is connected with the enhanced heat generation under 809-nm pumping, as evidenced by the increased thermal lensing of the fundamental emission. A careful alignment of the laser enables emission almost free of chaotic intensity fluctuations.     

Leading light [portable device display illumination]

The need for a white light emitting diode driver to illuminate the displays and keyboards in portable devices has increased rapidly over the last few years. Demand has been fuelled by the market surge in colour displays, especially the active matrix liquid crystal displays found in handheld devices. Although almost every power management business can offer a white light emitting diode (LED) drive, the design engineer has to make the choice between a driver based on a charge pump or boost converter. While obvious reasons may exist for choosing a boost converter, efficiency being one, making the right decision is far from easy.     

发光涂料铺设范围对公路隧道照明影响研究

以公路隧道发光涂料为研究对象,对数值仿真模型进行研究,建立起以路面平均亮度作为关键评价指标的公路隧道发光涂料仿真计算模型。采用三维数值仿真方法,对隧道内墙壁发光涂料铺设范围以两侧3米高为基准向上铺设时的效果进行研究,分别模拟计算了不铺设和铺设至两侧2m、3m、4．54m、5．71m、6．5m、7m高度及全截面这8种情况。通过汇总分析隧道路面平均亮度及能效值等关键参数,得到隧道内平均亮度变化范围在8．7～12．1ed／m。,能效值随铺设范围增大而减小,在墙壁两侧3m高度范围内铺设时的经济技术性最优。     

利用数码相机测量亮度分布的实验研究

本文介绍了一种利用数码相机结合计算机图像数据处理技术对亮度分布进行快速测量的方法。实验分析了两台不同的数码相机拍摄的四十多张图像，以及彩色亮度计测得的近两百个亮度数据，得到了数码相片的颜色值与实际亮度值之间关系的经验公式。文章给出了近似测量场景的亮度分布的方法，讨论了经验公式适用性和局限性，测量得到残差平均值为0．124cd／m^2，标准估计误差为3．24cd／m^2。上述测量技术将会有较好的实际意义和应用前景。     

组合掺杂对低温烧结NiZn功率铁氧体功耗特性的影响

采用陶瓷工艺制备低温烧结Ni Zn软磁铁氧体材料,研究了掺杂Co_2O_3、Cu O、Bi_2O_3、V_2O_5、Si O_2等对材料烧结温度及主要磁性能如磁导率、功耗等的影响。结果表明,Bi2O3对降低材料烧结温度有益但对功耗改善无益,Si O2对功耗改善有益但效果不明显,而组合添加0.15mol%Co2O3、9.0mol%Cu O、0.40~0.50wt%V2O5不仅可达到大幅度降低材料功率损耗,改善功耗特性,而且可保证材料低温烧结和其它优良磁性能,并获得具有低温烧结(烧结温度900℃左右)、低功耗(功率损耗Pcv≤300k W/m3(20℃,1MHz,30m T))、适于LTCF工艺和片式功率器件应用的Ni Zn功率铁氧体材料。