Realization of blue,green and red emission from top-emitting white organic light-emitting diodes with exterior tunable optical films

We developed an approach to realize blue, green and red emission from top-emitting white organic light-emitting diodes (OLEDs) through depositing exterior tunable optical films on top of the OLEDs. Three primary colors for full color display including blue, green and red emission are achieved by controlling the wavelength-dependent transmittance of the multilayer optical films overlaid on the emissive layer. The advantage of such a device configuration is that the emissive color of the OLEDs can be tuned via the exterior optical films which do not affect the electrical characteristics of the device. This may provide a way to realize full color display by using white top-emitting OLEDs.     

Liquid-crystal color light valve

A multilayer color display device employs two kinds of liquid-crystal films, One is a field-effect nematic liquid crystal; the other comprises a mixture of cholesteric and nematic liquid crystals that have the same function as circular polarizers used in place of crossed polarizers. Three colors (red, green, and blue) can be modulated independently by changing three voltages.     

掺杂浓度对ZnS∶Er~(3+)EL器件发光特性的影响

研究了ZnS：Er3+薄膜电致发光（EL）器件中，不同Er3+掺杂浓度的发光特性。发现，随发光中心Er3+的浓度增加而红色发光峰相对两个绿色峰有所增强，而两个绿色峰的相对强度却不变，在器件结构相同的情况下，浓度低于5×10－3克分子浓度时发光随浓度的增加而增强，两个绿色峰的亮度没有红色峰的亮度增加幅度大。当浓度大于1×10－2克分子浓度时，绿色发光峰的强度开始下降，红色峰的强度明显增强。说明，发光器件中存在交叉弛豫现象。     

Three-Band White Light-Emitting Diodes Based on Hybridization of Polyfluorene and Colloidal CdSe–ZnS Quantum Dots

The authors have demonstrated the hybridization of polyfluorene (PFO) polymer light-emitting diodes with CdSe–ZnS core/shell quantum dots (QDs) in different device structures. To achieve white light emission, the green and red QDs have been incorporated into the PFO as the single emissive layer. Furthermore, the whole structures were also optimized to engineer the emission spectra. Accordingly, the incorporation of QDs increased the turn-on voltage from 10 to 23 V in device with the blend ratio of PFO : green QD : red QD being 6 : 1 : 1, while the maximum brightness was dramatically decreased.      

Thin film ZnS:Mn AC-electroluminescent device with a Ge layer

A new thin film electroluminescent device (indium tin oxide ITO-Y2O3- (ZnS:Mn)- Ge-Y2O3- Al) (type II) has been prepared, and is compared to the conventional structure (ITO- Y2O3- (ZnS:Mn) - Y2O3- Al) (type I). The optically active conduction charge is measured for both types in order to ascertain the effect of the Ge layer which is believed to act as a carrier injection source. We found that in this new structure, compared to type I, the amount of the conduction charge is larger, but the maximum luminance value is lowered by a factor of 2 to 3 and the breakdown voltage is slightly lowered. These results can be explained from the experimental observation that remarkable assymmetry of luminescence waveforms is present in the type II device, i.e., the Ge layer influences the electric field near the ZnS-Ge interface. The appearance of the type II display is improved compared to type I.     

Effect of CdSe/ZnS quantum dots on color purity and electrical properties of polyfluorene based hybrid light emitting diode

We report enhanced color purity of hybrid organic-inorganic light emitting diode based on polyfluorene-CdSe/ZnS quanum dot (QD) blend as emissive layer. Effect on structural, optical and electrical properties of different doping concentration (0–100 wt.%) of QD in polyfluorene (PFO) was studied. Photoluminescence and electroluminescence spectra confirm the β-formation of PFO by incorporation of CdSe/ZnS QD. Photoluminescence (PL) of blend film was also compared with another method based on one dimensional photonic band gap (1D-PBG) structure that has been used for color purity. In both the cases, that is, QD doped device and 1D-PBG based structures the narrowing of PL spectra was observed. But the fabrication of QD-doped device for color purity is easier than fabricating 1D-PBG structure using multilayer dielectric coating. The present study might find application for QD based color displays, where color purity is an important requirement.     

Full color organic electroluminescent display with shared blue light-emitting layer for reducing one fine metal shadow mask

To make a full color organic electroluminescent display, conventionally it requires three fine metal shadow masks (FMM) to pattern the red, green and blue light-emitting layer. In this work, by arranging the blue light-emitting layer as a shared layer for all sub-pixels, we demonstrate that a full color display can be achieved by two FMM processes, thus reducing one FMM process compared to conventional method. The red, green and blue sub-pixels can be optimized independently despite the reduction of one FMM process. Also, the performance of the red and green sub-pixels is not degraded by the shared blue light-emitting layer. Due to elimination of one FMM, the process TACT time, mask cost and alignment error can all be reduced, thus cutting down the manufacturing cost of full color organic electroluminescent display.     

用单片机实现数码管多种颜色显示

传统的LED数码管都是单色(如红色或绿色)的,随着蓝光LED芯片的普及,单颗彩色LED成品已经得到了广泛的应用,但成品数码管还没有彩色的;在一些特殊场合,需要数码管显示多种颜色.基于实际需求,本文设计了一种单片机方案,实现了LED数码管的任意颜色显示.     

Design of white tandem organic light-emitting diodes for full-color microdisplay with high current efficiency and high color gamut

Microdisplays based on organic light-emitting diodes (OLEDs) have a small form factor, and this can be a great advantage when applied to augmented reality and virtual reality devices. In addition, a high-resolution microdisplay of 3000 ppi or more can be achieved when applying a white OLED structure and a color filter. However, low luminance is the weakness of an OLED-based microdisplay as compared with other microdisplay technologies. By applying a tandem structure consisting of two separate emission layers, the efficiency of the OLED device is increased, and higher luminance can be achieved. The efficiency and white spectrum of the OLED device are affected by the position of the emitting layer in the tandem structure and calculated via optical simulation. Each white OLED device with optimized efficiency is fabricated according to the position of the emitting layer, and red, green, and blue spectrum and efficiency are confirmed after passing through color filters. The optimized white OLED device with color filters reaches 97.8% of the National Television Standards Committee standard.     

Multilayer Dielectric Color Filters for Optically Written Display Using Up-Conversion of Near Infrared Light

An optically written display based on up-conversion of near-infrared light is a newly emerging display technology. For filtering out unwanted colors from this light generator, multilayer dielectric color filters are designed for red, green, and blue screens, respectively. Layer-symmetric films are used in the designed filters and the conjugate gradient method is used to optimize the design. It is observed that the characteristics of the filters are good in the whole visible wavelength range when the incident angle is less than 40deg. The encompassed color triangle of the display with the color filters is larger than that without the color filters, and images with more saturated colors are obtained.     

Improving color saturation of blue light-emitting electrochemical cells by plasmonic filters

In consideration of the advantages of light-emitting electrochemical cells (LECs), it is desired to develop the saturated blue LECs for LEC display, which is hindered by the features of broad emission spectrum and emission peak not short enough. In this study, we demonstrated a novel method to improve blue saturation of the sky-blue LECs by engineering its emission spectrum through the plasmonic filters. These plasmonic filters composed of randomly distributed silver nanoparticles (Ag-NPs) can absorb the green and red emission tail of the sky-blue LECs due to localized surface plasmon resonance (LSPR). The LSPR wavelengths of Ag-NPs are tuned by manipulating the effective refractive index of materials around Ag-NPs through the accurate control of the TiO₂ thickness using atomic layer deposition technique. By integrating with the plasmonic filters, the CIE1931 coordinate of the blue LECs can approach to (0.14, 0.22), which is comparable to or even better than the reported bluest values of blue LECs. Combination with the green and red LECs, the color gamut increases from 34% (without filters) to 54% of National Television System Committee (NTSC) color gamut, corresponding to 1.6 times enhancement. In addition, the blue LECs integrated with plasmonic filters still have better efficiency than those of the reported bluest LECs.     

Highly Efficient Green ZnAgInS/ZnInS/ZnS QDs by a Strong Exothermic Reaction for Down‐Converted Green and Tripackage White LEDs

Highly efficient bright green‐emitting Zn?Ag?In?S (ZAIS)/Zn?In?S (ZIS)/ZnS alloy core/inner‐shell/shell quantum dots (QDs) are synthesized using a multistep hot injection method with a highly concentrated zinc acetate dihydrate precursor. ZAIS/ZIS/ZnS QD growth is realized via five sequential steps: a core growth process, a two‐step alloying–shelling process, and a two‐step shelling process. To enhance the photoluminescence quantum yield (PLQY), a ZIS inner‐shell is synthesized and added with a band gap located between the ZAIS alloy‐core and ZnS shell using a strong exothermic reaction. The synthesized ZAIS/ZIS/ZnS QDs shows a high PLQY of 87% with peak wavelength of 501 nm. Tripackage white down‐converted light‐emitting diodes (DC‐LEDs) are realized using an InGaN blue (B) LED, a green (G) ZAIS/ZIS/ZS QD‐based DC‐LED, and a red (R) Zn?Cu?In?S/ZnS QD‐based DC‐LED with correlated color temperature from 2700 to 10 000 K. The red, green, and blue tripackage white DC‐LEDs exhibit high luminous efficacy of 72 lm W^?1 and excellent color qualities (color rendering index (CRI, R_a) = 95 and the special CRI for red (R₉) = 93) at 2700 K.     

基于ZnS/SiO2量子点的EL器件及宽谱发射

将ZnS/SiO2量子点与PVP在甲醇溶液中充分混合作为活性层材料,通过匀胶方法制备了ITO//ZnS/SiO2∶PVP//Al结构的电致发光(EL)薄膜器件。器件的EL光谱由510～560nm波段的绿光发射和相对较弱的蓝紫光(400nm左右)发射组成,通过对发光光谱的分析发现,上述两个区域的发射均来自ZnS的缺陷能级。其中,绿色发光峰来源于较低能态的缺陷能级;而高能区域的蓝色发光则是由于高能态的缺陷能级俘获电子的几率增大,在这过程中,PVP形成的能级阶梯有效增加了高能态缺陷能级俘获电子的几率,提升了高能波段的发光效率,相应地,器件的色坐标也随之从(0.37,0.42)变化到(0.30,0.34),趋于白光发射。     

Color in projection displays

This paper presents how full-color is created and optimized in rear projection television systems. It discusses briefly how color is quantified and considers a general method for choosing primary red, green,, and blue for maximum corrected brightness in common three-panel projection systems. It uses the commercially successful CQ90 architecture as an example. An external passive approach to white correction using tunable double notch polarization filters is also introduced before considering color optimization in single and two-panel projectors.     

Room-temperature color center lasers

A survey of results is presented on the development of room-temperature tunable lasers using color centers in ionic crystals and on using color center crystals as nonlinear filters and passive Q switches for neodymium lasers     

A full-color matrix liquid-crystal display with color layers on the electrodes

A full-color matrix liquid-crystal display panel with color stripe layers of red, green, and blue on theY-electrodes is proposed. The color stripe layers of 300-µm pitch are made by photolithography. The color purities of greenish, bluish, and purplish colors obtained by the liquid-crystal display panel are as good as those of typical printed inks, while those of yellowish and reddish colors are poor at present. In addition, effects of the color layers on the display properties are discussed.     

长寿命电致发光暗室显示器的光谱研究

长寿命电致发光暗室显示器的光谱研究朱宁，孟宪棫，石磐（天津理工学院光电显示研究室，天津３００１９１）利用感光胶片对特种波长感光灵敏度低和电致发光单色性的特点，作出了系列暗室照明光源和显示器件［１．２．３．４］．根据天津感光胶片公司提出航空胶片生产车间...     

核/壳结构ZnS:Mn/ZnS量子点光发射增强研究

利用水溶性前驱体材料在水性介质中制备了ZnS:Mn和ZnS:Mn/ZnS核/壳结构量子点(QDs,quantum dots),并用X射线衍射(XRD)、光致发光(PL)对ZnS:Mn和ZnS:Mn/ZnS核/壳结构QDs的结构和发光性能进行研究.ZnS:Mn和ZnS:Mn/ZnS QDs XRD谱与标准谱吻合,根据De...     

Mechanoluminescence Color Conversion by Spontaneous Fluorescent‐Dye‐Diffusion in Elastomeric Zinc Sulfide Composite

Color conversion, long‐wavelength light emission by absorbing short‐wavelength light, is an attractive approach for developing a broad‐color expression technology and is widely used in solid‐state lighting, dye‐lasers, and colorful displays. Up to now, many papers have been published reporting various mechanoluminescent materials emitting color of ultraviolet, blue, green, orange, and red. However, the strategies of previous reports have focused on color‐tuning of mechanoluminescent material itself through newly developing inorganic mechanoluminescent compounds. Here, a new strategy for the color manipulation of mechanoluminescence (ML) is introduced by physically combining fluorescent dyes with existing mechanoluminescent materials. An elastomeric zinc sulfide (ZnS) composite is prepared in a polydimethylsiloxane framework with spontaneously diffused 4‐(dicyanomethylene)‐2‐t‐butyl‐6‐(1,1,7,7‐tetramethyljulolidyl‐9‐enyl)‐4H‐pyran (DCJTB), and red luminescence by complete color conversion via DCJTB is demonstrated, which fully absorbed green ML from ZnS. Based on this approach, color‐tuning of ML from red to green is successfully achieved and color expression range is expanded by employing electroluminescence (EL). Various‐color‐emitting EL/ML electromechanical display is demonstrated using color discrepancy between DCJTB employed EL and ML. As the implementation is fairly straightforward, it is believed that present color conversion is a viable and common method to manipulate broader color expression for future ML applications.     

White light photoluminescence from ZnS films on porous Si substrates

ZnS films were deposited on porous Si (PS) substrates using a pulsed laser deposition (PLD) technique.White light emission is observed in photoluminescence (PL) spectra, and the white light is the combination of blue and green emission from ZnS and red emission from PS. The white PL spectra are broad, intense in a visible band ranging from 450 to 700 nm. The effects of the excitation wavelength, growth temperature of ZnS films, PS porosity and annealing temperature on the PL spectra of ZnS/PS were also investigated.