Pure blue and white light electroluminescence in a multilayer organic light-emitting diode using a new blue emitter

We characterized the 6,12-bis{[N-（3,4-dimethylphenyl）-N-（2,4,5-trimethylphenyl）]amino} chrysene （BmPAC）, which has been proven to be a blue fluorescent emission with high EL efficiency. The blue fluorescent device exhibits good performance with an external quantum efficiency of 5.8% and current efficiency of 8.9 cd/A, respectively. Using BmPAC, we also demonstrate a hybrid phosphorescence/fluorescence white organic light-emitting device （WOLED） with high efficiency of 36.3 cd/A. In order to improve the relative intensity of blue light, we plus a blue light-emitting layer （BEML） in front of the orange light emitting layer （YEML） to take advantage of the excess singlet excitons. With the new emitting layer of BEML/YEML/BEML, we demonstrate the fluorescence/phosphorescence/fluorescence WOLED exhibits good performance with a current efficiency of 47 cd/A and an enhanced relative intensity of blue light.

High color rendering index white organic light-emitting diode using levofloxacin as blue emitter

Levofloxacin （LOFX）, which is well-known as an antibiotic medicament, was shown to be useful as a 452-nm blue emitter for white organic light-emitting diodes （OLEDs）. In this paper, the fabricated white OLED contains a 452-nm blue emitting layer （thickness of 30 nm） with 1 wt% LOFX doped in CBP （4,4＇-bis（carbazol-9-yl）biphenyl） host and a 584-nm orange emitting layer （thickness of 10 nm） with 0.8 wt% DCJTB （4-（dicyanomethylene）-2-tert-butyl-6-（1,1,7,7- tetramethyljulolidin-4-yl-vinyl）-4H-pyran） doped in CBE which are separated by a 20-nm-thick buffer layer of TPBi （2,2＇,2＂-（benzene-1,3,5-triyl）-tri（1-phenyl-lH-benzimidazole）. A high color rendering index （CRI） of 84.5 and CIE chromaticity coordinates of （0.33, 0.32）, which is close to ideal white emission CIE （0.333, 0.333）, are obtained at a bias voltage of 14 V. Taking into account that LOFX is less expensive and the synthesis and purification technologies of LOFX are mature, these results indicate that blue fluorescence emitting LOFX is useful for applications to white OLEDs although the maximum current efficiency and luminance are not high. The present paper is expected to become a milestone to using medical drug materials for OLEDs.

Highly Efficient and Stable Hybrid White Organic Light Emitting Diodes with Controllable Exciton Behavior by a Mixed Bipolar Interlayer

Highly efficient and stable hybrid white organic light-emitting diodes （HWOLEDs） with a mixed bipolar interlayer between fluorescent blue and phosphorescent yellow emitting layers are demonstrated. The bipolar interlayer is a mixture of p-type diphenyl （l0-phenyl-lOH-spiro [acridine-9,9＇-fluoren]-3Lyl） phosphine oxide and n-type 2＇,2- （1,3,5-benzinetriyl）-tris（1-phenyl-l-H-benzimidazole）. The electroluminance and Commission Internationale de l＇Eclairage （CIE1931） coordinates＇ characteristics can be modulated easily by adjusting the ratio of the hole- predominated material to the electron-predominated material in the interlayer. The hybrid WOLED with a p-type：n-type ratio of 1：3 shows a maximum current efficiency and power efficiency of 61.1 ed/A and 55.8 lm/W, respectively, with warm white CIE coordinates of （0.34, 0.43）. The excellent efficiency and adaptive CIE coordi- nates are attributed to the mixed interlayer with improved charge carrier balance, optimized exciton distribution, and enhanced harvesting of singlet and triplet excitons.

High-brightness organic light-emitting diodes

The research of high-brightness organic light-emitting diodes, as an important branch of organic light-emitting diodes （OLEDs）, makes it possible for achieving high-brightness lighting source and lasing. Heat dissipation and efficiency roll off, as two main factors, affect the brightness of the OLEDs heavily. In this paper, high-brightness OLEDs are obtained by utilizing pulse voltage, small areas and micro-cavity structure to minimize the effect of the two factors. The major advances, ongoing challenges and future perspectives of this research frontier are also critically discussed.

Efficient top-emitting white organic light emitting device with an extremely stable chromaticity and viewing-angle

In this paper,we report on the fabrication of a top-emitting electrophosphorescent p-i-n white organic lightemitting diode on the basis of a low-reflectivity Sm/Ag semi-transparent cathode together with a thickness-optimized ZnS out-coupling layer.With a 24-nm out-coupling layer,the reflectivity of the cathode is reduced to 8% at 492 nm and the mean reflectivity is 24% in the visible area.By introducing an efficient electron blocking layer tris（1phenylpyrazolato,N,C2 ＇）iridium（III）（Ir（ppz） 3） to confine the exciton recombination area,the current efficiency and the colour stability of the device are effectively improved.A white emission with the Ir（ppz） 3 layer exhibits a maximum current efficiency of 9.8 cd/A at 8 V,and the Commission Internationale de L＇Eclairage（CIE） chromaticity coordinates are almost constant during a large voltage change of 6 V-11 V.There is almost no viewing angular dependence in the spectrum when the viewing angle is no more than 45,with a CIE x,y coordinate variation of only（±0.0025,±0.0008）.Even at a large viewing angle（75）,the CIE x,y coordinate change is as small as（±0.0087,±0.0013）.

The effect of spacer in hybrid white organic light emitting diodes

Two kinds of highly efficient,bright hybrid white organic light emitting diodes have been fabricated by utilizing ambipolar material 4,4-N,N-dicarbazolebiphenyl(CBP)and unipolar material N,N0-di(naphthalene-1-yl)-N,N0-diphenyl-benzidine(NPB)as the spacer,respectively.By adjusting the thickness of spacers together with effectively utilizing combinations of exciton-harnessed orangephosphorescence/blue-fluorescence,the current efficiency of optimal device with CBP spacer and device with NPB spacer are 31.0 and 38.9 cd/A,the maximum power efficiency are 23.9 and 29.1 lm/W,the maximum brightness are 87,249 and 75,501 cd/m2,and the Commission Internationale de l’Eclairage(CIE)coordinates are(0.42,0.43)and(0.47,0.44)at a voltage of 11 V,respectively.Furthermore,systematic investigations focused on the effects of spacers on device performance have been performed.By virtue of the multifunctional spacer,energy transfer between the phosphorescent and fluorescent emitters can be avoided while the carriers still can pass through this spacer bridge,which is important to realize such high device performance.In addition,a novel concept that both ambipolar materials and unipolar materials can be the promising candidates for spacers has been proposed if the thickness of spacers with high triplet energy is optimized.

Novel high-brightness tunneling-regenerated multi-activeregion AlGaInP light-emitting diode

In order to resolve the prevailing problems in conventional light-emitting diodes (LEDs), novel high-efficiency tunneling-regenerated multi-active-region (TRMAR) LEDs are proposed, which have such advantages as low heat generation, carrier overflow level and non-radiation re-combination rate and whose quantum efficiency and the output optical power can be scaled with the number of the active regions. Experiments show that the on-axis luminous intensity of TRMAR LEDs increases linearly with the number of active regions. The novel LEDs have high quantum efficiency under low current injection and their maximum on-axis luminous intensity exceeds 5 candelas at 20 mA current injection at the peak wavelength of 625 nm with a 15?angle cap.

高亮绿光氮化镓基Micro-LED微型显示器制备

Micro-LED作为一种新型的显示技术,具有对比度高、响应快及寿命长等优点,已成为当前研究的热点。然而,尽管潜力巨大,Micro-LED技术的商业化之路仍面临诸多技术上的挑战与瓶颈。本文旨在探讨高亮绿光氮化镓基Micro-LED微型显示器的制备过程及其相关技术。基于WVGA041全数字信号电路CMOS硅基驱动电路,制作了0.41 inch、分辨率为800×480的主动式单色绿光Micro-LED微型显示器。利用高精度倒装焊接技术实现了CMOS驱动电路与LED发光芯片的电气连接。结果表明,制备出LED显示芯片正常启亮电压为2.8V,EL光谱峰值波长524nm;在硅基CMOS电路驱动范围内,Micro-LED微型显示器在5V电压下,器件亮度为108000cd/m^(2)(最大亮度可达250000 cd/m^(2)),电流密度达到0.61A/cm^(2)时色坐标为(0.175,0.756)。当电流密度从0.3A/cm^(2)增加到1.3A/cm^(2)时,色坐标从(0.178,0.757)变化到(0.175,0.746),器件的色稳定性能够满足实际应用要求。

超高分辨LED显示

分辨率是评估一个显示器性能的重要指标之一。不仅限于消费电子产品领域中厂商的竞争需求,科研、工业和医学等领域的发展也迫切需要更高分辨率的显示设备以显示精度更高的图像。除此之外,虚拟和增强现实技术使超高分辨率显示器能提供更丰富的人机交互体验。超高分辨率显示技术也逐渐成为一个热门的研究方向。本文介绍了基于发光二极管的各类新型显示技术中实现高分辨率显示的技术手段和实现方案,总结了每种方案的适用条件和优缺点,并指出了各项技术现阶段面临的主要挑战。一直以来,我们团队长期致力于量子点发光二极管显示的电致发光图案化和高分辨率显示研究,本文也介绍了本团队近期取得的突破性的研究成果。

有机高亮度黄光发光二极管

用有机小分子制备的高亮度黄光电致发光器件，在１９Ｖ 下器件亮度可达４００００ｃｄ／ｍ ２，外量子效率达３．４％ ．

多色有机薄膜电致发光器件及其稳定性

研究了绿色、红色、蓝色和白色四种有机薄膜电致发光器件。通过掺杂得到了高稳定性的绿色及红色器件 ,绿色器件的半寿命达 140 0 0h(初始亮度 10 0cd/m2 ) ,红色器件的半寿命为 75 0 0h(初始亮度 5 0cd/m2 )。还研究了具有空穴锁定层及非锁定层的两种不同结构的蓝色及白色器件。研究表明无论蓝色还是白色器件 ,具有空穴锁定层的器件稳定性较差 ,老化过程中界面势垒的变化很大。非锁定层的蓝色及白色器件的半寿命分别为 45 0h(初始亮度 5 0cd/m2 )和 30 0h(初始亮度 5 0cd/m2 )。在稳定性改善的基础上研制成功 96× 6 0线 ,分辨率为 2线 /mm的绿色矩阵显示屏 ,设计和研制了驱动及控制电路 。

稳定的蓝色及白色有机薄膜电致发光器件

报道了一种稳定的蓝色和白色有机薄膜电致发光器件 ,蓝色器件最大亮度为 75 2 6cd/m2 ,最大效率1 45lm/W ,半亮度寿命 10 35h(初始亮度 10 0cd/m2 )。白色器件的最大亮度为 1485 0cd/m2 ,最大效率2 88lm/W ,色度x =0 31,y =0 38,且色度不随电流增大而变化 ,半亮度寿命为 2 86 0h(初始亮度 10 0cd/m2 )。

OLED微显示器的原子扫描策略

为了实现2K及以上超高清微型显示器的高效率高性能扫描,建立了微型显示器的原子扫描模型。对该模型采用的数学矩阵、基于分形延伸的植入运算进行研究,提出了原子扫描策略并推导了原子扫描序列。首先,对现有的PWM(脉冲宽度调制)扫描策略进行扫描性能分析。然后,在分析比较几种扫描策略性能的基础上,说明原子扫描是实现较优性能的最佳选择。实验结果表明:对于256级灰度,采用32位子空间,8位权值比为128∶64∶32∶16∶9∶4∶2∶1的原子扫描策略具有较好的线性度和较高的传输效率。在分辨率为1 600×1 600的原子扫描方案中,时钟频率为50MHz,帧频可达90Hz,线性度接近99.8%,传输效率高达100%,基本满足超高分辨率扫描系统中高帧频、较低时钟、高线性度的要求。

对称跨接电容型LED均流电路

高亮度发光二极管(LED)自身导通压降的离散性及负温度系数特性使得多个LED串并联时出现各串电流不均衡的现象。提出了一种简洁的对称跨接电容型LED均流电路,各LED支路串联的开关管轮流交错导通。利用各LED支路间的跨接电容在一个周期内的电荷守恒,实现了多路LED串的均流。对电路的均流原理、参数设计进行了详细的理论分析,并将其与非对称跨接电容型LED均流电路进行了对比。在此基础上,进行了三支路均流的实验验证,实验结果表明所提出的电路具有良好的均流效果,控制方式简单,电容、开关管两端电压应力低,无磁性元件,便于集成。

电容钳位型LED均流电路

高亮度发光二极管(LED)自身导通压降的离散性及负温度系数特性使得多个LED串并联时出现各串电流不均衡的现象。提出了一种简洁的电容钳位型LED均流电路,各LED支路串联的开关管轮流交错导通。利用各LED支路间跨接的钳位电容在一个周期内的电荷守恒,实现了多路LED串的均流。对电路的均流原理、参数设计进行了详细的理论分析,在此基础上,进行了三支路均流的实验验证,实验结果表明所提出的电路具有良好的均流效果,控制方式简单,电容、开关管两端电压应力低,无磁性元件,便于集成。

TPB3 TSi黄光OLED材料的制备及其性能优化

制备以TPB3TSi为发光材料的黄色发光器件。实验表明,当TPB3TSi薄膜厚度为20nm时,器件的发光谱峰位于580nm,其双层和3层器件的最大亮度分别达到7507.6和1385cd/m2(17V电压下),但是器件的电流较大,造成了器件的发光效率偏低,其原因是TPB3TSi材料本身的电荷陷阱(所谓陷阱指的是拥有比母体更容易接受电子或者空穴的能级的位置)较多,荧光效率低,从而降低了器件的效率。

基于混合主体结构的溶液法制备的高效蓝色磷光OLED

为了提高蓝色有机发光二极管的效率,本文借助溶液法采用TcTa和CzSi混合主体,制备了蓝色磷光有机发光二极管(PHOLEDs)。此外,针对三种电子传输材料Tm3PyP26PyB、TmPyPB和TPBi进行了优选,以进一步优化器件的效率。本文通过优化混合主体材料的掺杂比例和电子传输材料的选择,不断提高器件的效率。最终,当TcTa∶CzSi的掺杂比为6∶1、电子传输层TPBi为70 nm时器件性能最优,其最大亮度(B_(max))、电流效率(CE_(max))、功率效率(PE_(max))和外量子效率(EQE_(max))分别为6662 cd·m^(-2)、39.40 cd·A^(-1)、23.33 lm·W^(-1)和19.7%。此外,即使在1000 cd·m^(-2)的实际亮度下,电流效率和外量子效率仍高达33.43 cd·A^(-1)和16.7%。

固体光源和灯具的技术进展(二)

近十年来成功地开发出的固体光源和器具已进入照明市场 ,目前固体光源的品种主要为发光二极管(LED)和有机电致发光 (OEL) ,这些固体光源可在低电压下驱动 ,能耐各种恶劣环境 ,具有小型、轻量、电极损耗小、响应速度快、寿命长等特性。本文主要介绍固体光源LED和EL的结构、特性和技术发展动向。固体光源将发展成为 2

固体光源和灯具的技术进展(一)

近十年来成功地开发出的固休光源和器具已进入照明市场。目前固体光源的品种主要为发光二级管(LED)和有机电致发光 (OEL) ,这些固体光源可在低电压下驱动 ,能耐各种恶环境 ,具有小型、轻量、电极损耗小、响应速度快、寿命长等特性。本文主要介绍固体光源LED和EL的结构、特性和技术发展动向。固体光源将发展成为 2 1世纪新的节能新光源。

高亮度发光二极管(HB—LED)及应用概况

概述了HB—LED的发展,分析其优点并对HB—LED的国际进展作了简要的评述,同时对HB—LED在半导体照明领域的应用作了叙述。