可弯曲式有机电玫发光器件的出光率

基于几何光学模型及其原理,推导出在不同弯曲情况下可弯曲式有机电致发光器件的出光率表达式,分析了器件出光率受基板曲率、厚度及有机层折射率的影响,并与平整有机电致发光器件的出光情况作了比较.结果表明:当器件向外弯曲时,出光率随着基板曲率与基板厚度的增大而增大,随着有机层折射率的增大而减小;当器件向内弯曲时,出光率随着基板曲率与基板厚度的增大而减小,随着有机层折射率的增大而减小.对于平整器件,其出光率随有机层折射率的增大而减小.     

温度不敏感的错位熔接-粗锥型光子晶体光纤曲率传感器

提出了一种可以用于曲率矢量测量的温度不敏感的错位熔接-粗锥型光子晶体光纤(PCF)曲率传感器,它由两段普通单模光纤(SMF)之间熔接一段PCF组成,呈SMF-PCF-SMF结构。其中PCF的一端与SMF错位熔接导致传感器圆柱轴不对称,使得传输光谱在两个对称弯曲方向上出现明显的红移和蓝移现象;另一端与SMF通过过度熔接形成粗锥,最终形成马赫-曾德尔干涉仪。实验研究了传感器的曲率和温度特性,结果表明,在0.12~1.06m-1的曲率范围内,凹向弯曲时的光谱发生红移,其灵敏度为11.22nm/m-1,凸向弯曲时的光谱发生蓝移,其灵敏度为-13.62nm/m-1,且凹向弯曲时和凸向弯曲时均具有较好的线性度;在20~80℃的温度范围内,此传感器的温度灵敏度仅为1.63pm/℃,具有对温度不敏感的特性。该传感器与传统光纤传感器相比,能够避免温度与曲率同时测量时的交叉敏感问题,具有易于制备、结构简单、灵敏度高等优势,可用于工业生产、建筑监测、航天航空等领域。     

溶胶-凝胶法制备Zn1-xMgxO薄膜及其发光性质

采用溶胶-凝胶工艺在玻璃衬底上制备了Zn1-xMgxO(x=0.1,0.2,0.3,0.4,0.5,0.6,0.7)薄膜。X射线衍射(XRD)谱测试结果发现:在0.10.3时出现MgO立方相。薄膜光致发光谱研究表明紫外发光峰随Mg含量的增加向短波方向移动,且随着退火温度的升高发生明显蓝移,禁带宽度增大。但是退火温度为590℃的样品较560℃样品的发光峰出现红移。     

微腔有机电致发光器件角度依赖性的模拟与实验验证

为了分析微腔有机电致发光器件(MOLED)发光的角度依赖性,根据微腔计算公式,采用传输矩阵法进行了模拟计算,并进行了实验验证。所设计器件的结构为Glass/DBR/ITO(58 nm)/NPB(46 nm)/DPVBi(20 nm)/Alq₃(56 nm)/LiF(1 nm )/Al(150 nm)。由实验得到的电致发光(EL)谱可以观察到:随着探测角度的加大,发光峰蓝移、强度减小。与模拟得出的不同观测角度下的反射谱进行比较,发现透射峰值与EL峰值相对应。模拟分析发现,这是由于观测角不同,微腔两个反射镜的S和P偏振的反射率及反射相移不同,同时腔内光学厚度发生变化,即微腔长度变化共同作用所导致。     

NPB/Alq3有机量子阱光电特性研究

利用热蒸发的方法制备了有机量子阱发光器件和Alq3单层发光器件,其中NPB(N,N′-Di-[(lnaphthalenyl)-N,N′-diphenyl]-(1,1′-biphenyl)-4,4′-diamine)作垒层,Alq3(Tris-(8-quinolinolato) aluminum)作阱层,量子阱结构类似于无机半导体的Ⅱ型量子阱结构.实验发现有机量子阱发光器件结构中存在垒层向阱层的F(o)rster无辐射共振能量转移,具有良好的电流-电压特性,光谱的窄化及蓝移,并且光谱的蓝移程度随电压的增大而逐渐增强.     

新有机材料的电致发光的研究

采用新合成的有机材料－硅烷衍生物作为发光物质制备了发蓝、绿光的薄膜电致发光器件。其结构为glass/ITO/PVK SiH/Alq/Mg:Ag。分别测量了SCS－SiH,聚乙烯咔唑（PVK）薄膜的光致发光光谱以及器件的电致发光光谱。其中SCS－SiH薄膜的光致发光谱峰位置在496nm,有机器件的电致发光光谱的峰值为500nm。随着驱动电压的增加发光谱峰蓝移,其变化范围为25nm。在电流密度为89mA/cm^2下器件的发光亮度可达810cd/m^2。     

影响GaN基蓝光LED能带结构与光谱特性关系的仿真研究

本文采用Silvaco TCAD软件对GaN基InGaN/GaN量子阱蓝光发光二极管(LED)的光谱特性进行了仿真研究。研究结果表明:光谱会随着注入电压的增加而产生蓝移现象,并出现0.365μm处的紫外光发光峰;发光效率在正向电流较小时增长很快,随着正向电流进一步增加而逐渐趋于饱和;随着量子阱中In组分和量子阱阱层厚度的增加,发光光谱出现红移现象,并且发光效率下降。仿真结果对GaN基InGaN/GaN量子阱结构蓝光LED的设计和优化提供一定的依据。     

4-inch蓝宝石图形衬底上GaN基白光LED制备及表征

在4-inch蓝宝石图形衬底上,基于InGaN/GaN多量子阱结构制备了蓝光LED芯片,并通过与钇铝石榴石黄色荧光粉(YAG∶Ce~(3+))结合,封装成白光LED器件。简要介绍了外延生长和芯片工艺及封装流程,并对材料特性及器件性能进行了表征。外延片表面形貌良好,蓝光外延片荧光光谱(PL)显示峰值波长为442 nm。对封装后白光芯片进行电学特性测试,得出其开启与限流电压分别为2.7 V与3.6 V。此外,电致发光光谱(EL)含有两个主要的发光峰,分别是440 nm的蓝光峰以及540 nm的黄绿光峰,而随着注入电流的增加,蓝光峰位先蓝移后红移,黄绿光峰位先红移后蓝移再红移。本文中相关的芯片制备及表征技术将对固态照明研究起到一定的促进作用。     

瓦级大功率InGaN蓝光LED的光色电特性

封装并测量了瓦级大功率InGaN蓝色发光二极管(LED)在不同正向电流I_F驱动下的光通量、电功率、发光效率、发射光谱和色品坐标等参数的变化。研究表明, 光通量与电功率随I_F的增大呈亚线性增加,而发光效率η则下降。当I_F从50 mA一直增大到450 mA左右时,发射光谱的峰值波长λ_p随I_F的增加发生蓝移,蓝移现象可能与InGaN蓝光LED芯片在较大电流时能带被拉平以及In成分的作用有关。当I_F大于500 mA或800 mA后,λ_p又发生红移,红移现象可能与大电流注入下InGaN蓝光LED芯片产生的热效应以及电子-空穴对辐射复合有关。此外,光谱的半峰全宽(FWHM)产生宽化现象,色坐标x和y值也发生变化。     

多周期激光相位对H2+谐波频移的影响

理论研究了多周期激光相位角对H2+谐波频移的影响。结果表明,在多周期激光驱动下H2+谐波光谱在零相位时呈现蓝移现象。随着激光相位增大,谐波光谱由蓝移转向红移。随着激光相位进一步增大,谐波红移减弱。理论分析表明谐波频移是由激光上升和下降区域谐波辐射强度变化引起的。并且谐波辐射强度变化对激光相位比较敏感。     

Improvement of the outcoupling efficiency of an organic light-emitting device by attaching microstructured films

In this paper, we present and analyse the optical characteristics, such as spectral shift, CIE coordinates, viewing angle dependence, luminous current efficiency and luminous power efficiency, of an organic light-emitting device (OLED) with a commercial diffuser film or a brightness-enhancement film (BEF) attached. Compared to a planar green OLED, the luminous current efficiencies of the OLED with an attached diffuser film or BEF increase by 29% and 23%, respectively. The overall luminous power efficiencies are enhanced by 28% and 7%. Compared to the planar green device, we observe blue shifts at different viewing angles when microstructured films are attached, which is the evidence that the waveguiding modes are being extracted. In our planar OLED, the peak wavelength blue shifts and the full width at the half maximum (FWHM) decrease with increasing viewing angles due to the microcavity effect. When the diffuser is attached, the spectral peak has a constant blue shift (6 nm) compared to that of the planar OLED. On the other hand, in the BEF case, the spectral shift depends on the viewing angle (2-12 nm blue shifts from 0 to 80°). This is due to the different operating principles (scattering and redirected light) of the diffuser and BEF. Since the transmittance spectra of both the diffuser film and the BEF are flat over the visible range, it is suitable for lighting applications by using white OLED. When attaching the films on a commercial white OLED, the luminous current efficiencies of the OLED with an attached diffuser film or BEF increase by 34% and 31%, respectively. The overall luminous power efficiencies are enhanced by 42% and 8%.     

Efficiency improvement and spectral shift of an organic light-emitting device with a square-based microlens array

In this paper, we present and analyze the influences of the fill factor and the height ratio of square-based microlens arrays on the optical characteristics of an organic light-emitting device (OLED). These properties include spectral shift, CIE coordinates, viewing-angle dependence, luminous current efficiency and luminous power efficiency. Both the luminous current efficiency and luminous power efficiency of the OLED were found to increase linearly with increasing the fill factor of microlenses. It is also found that the full width at half maximum (FWHM) of the OLED spectra and CIE coordinate decreased linearly with increasing the fill factor of the microlenses. Besides, the efficiency improvement of the OLED increased with the height ratio of attached microlenses. Compared to the OLED, the luminous current efficiency and luminous power efficiency of the device can be enhanced by 42% and 47%, respectively, by attaching the microlens array having a fill factor of 90% and a height ratio of 0.57. We also observed blue shifts at different viewing angles when microlens arrays were attached to the OLED, which is the evidence that the waveguiding modes are being extracted. In our planar OLED, the peak wavelength blue shifted and the FWHM decreased with increasing the viewing angles due to the microcavity effect.     

微腔有机电致发光器件的角度依赖性

设计并制作了两个器件,一个是微腔有机电致发光器件(MOLED):G/DBR/ITO/NPB(46 nm)/DPVBi(20 nm)/Alq₃(56 nm)/LiF(1 nm)/Al(150 nm);一个是无腔器件(OLED):G/ITO/NPB(46 nm)/DPVBi(20 nm)/Alq₃(56 nm)/LiF(1 nm)/Al(150 nm)。测试并分析了器件性能。OLED在电流密度30 mA/cm²时的电致发光(EL)光谱随观测角度由0°~70°都是一宽谱带,是发光层DPVBi的特征发光谱,峰值都在452 nm处,半峰全宽均为70 nm,色坐标均为(x=0.18,y=0.19),无腔器件没有角度依赖性。相同电流密度下,微腔器件的EL谱随观测角度由0°~70°,发光峰值蓝移,由472 nm逐渐移至428 nm;峰值相对强度渐弱,由0.32变至0.02;半峰全宽由14 nm增加至120 nm;色坐标由(x=0.14,y=0.10)变至(x=0.19,y=0.25),颜色由紫蓝变成蓝白到接近白色。微腔器件具有明显的角度依赖性。     

利用色彩转换法制备高色稳定性的柔性白色有机电致发光器件

本文利用色转换方法,将高效的蓝色柔性有机电致发光器件(flexible organic light emitting devices, FOLEDs)与色转换材料(color conversion material, CCM)相结合,制备了柔性白色有机电致发光器件(white organic light emitting devices, WOLEDs).首先利用2, 3, 5, 6-Tetrafluoro-7, 7, 8, 8-tetracyano-quinodimethane (F4-TCNQ)和4, 4', 4"-tris-(N-3-methylphenyl-N-phenylamino) tripheny-lamine (m-MTDATA)组成的多量子阱(multiple quantum well, MQW)结构作为空穴注入层(hole injection layer, HIL)结合新型蓝光材料N⁶, N⁶, N¹², N¹²-tetrap-tolylchrysene-6, 12-diamine (NCA)制备出高效的蓝光FOLEDs,然后将其与色转换材料4-(dicyanomethylene)-2-tert-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) 结合,通过沉积不同厚度的CCM来优化白光器件的发光光谱,获得了色稳定性较高的白光. 实验结果表明:在驱动电压为7 V, DCJTB的厚度为120 nm时得到较接近白光等能点的色坐标 (0.33, 0.27),且当驱动电压由6 V升至11 V 时,器件的色坐标变化仅为(±0.02, ±0.02), 表现出高色稳定性.     

不同电流下发光二极管温度和光谱特性的实验研究

利用WGD-6型光学多道分析仪和温度传感器设计了测量不同电流下发光二极管(LED)温度和光谱特性的实验,并测定了紫、蓝、绿、黄和红光二极管管温随电流变化和光谱的变化。各种二极管随电流的增加温度升高,紫、蓝和黄光LED升温速率要快。随电流增加,紫、黄和红光LED有明显的红移,绿光LED有明显的蓝移,而蓝光LED先蓝移后红移。随电流的增加LED有光输出饱和现象。电流的增加引起LED半峰宽宽化,红光LED宽化幅度最大,可达15nm。     

Self-talk of Reflection Hologram During its construction

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Effects of substrate treatment on the electroluminescence performance of flexible OLEDs

Electroluminescence (EL) performance of flexible organic light-emitting device (FOLED) has been found to be highly dependent upon the morphology of the surface of the indium thin oxide (ITO)/plastic substrate as well as the patterning and processing conditions of the substrate. We will present evidence showing that luminance efficiency of FOLED can be greatly improved by pretreatment. Surface analysis of the ITO/PET by means of atomic force microscope (AFM) and optical microscope will be compared with that of the ITO/glass and the influence of flexible OLEDs substrate treatment by various methods on EL performance will also be discussed.     

不同发光染料的顶发射有机电致发光器件的研制

通过设计合理的微腔结构,制备了基于绿光染料C545t、黄光染料Rubrene、红光染料DCJTB的3种顶发射有机电致发光器件。研究了不同发光染料对顶发射器件的光谱的影响。研究表明,微腔结构对光谱具有窄化作用。绿光、黄光器件的发光峰波长并未随视角增大而明显变化,体现出良好的光谱角度性,而红光器件却出现了明显的光谱蓝移现象。绿光器件的最大功率效率为8.7 lm/W,当电流密度为45 m A/cm2时,亮度能达到7 205 cd/m2;黄光器件的电流效率最大值为11.5 cd/A,当电流密度为48 m A/cm2时,亮度可达到3 770 cd/m2;红光器件的电流效率最大能达到3.54 cd/A,当电流密度为50 m A/cm2时,可获得1 358 cd/m2的亮度。采用合适的发光材料以及合适的器件结构,不仅可以提高顶发射器件的色纯度及发光效率,还可以改善器件发光光谱的角度依赖性。     

Electroluminescence spectra of an STM-tip-induced quantum dot

We analyze the electroluminescence spectrum of an STM-tip-induced quantum dot in a GaAs surface layer. A flexible model has been developed, that combines analytical and numerical methods and describes the key features of many-particle states in the STM-tip-induced quantum dot. The dot is characterized by its depth and lateral width, which are experimentally controlled by the bias and the tunneling current. We find, in agreement with experiment, that increasing voltage on the STM-tip results in a red shift of the electroluminescence peaks, while the peak positions as a function of the electron tunneling current through the STM-tip reveal a blue shift.