高效有机发光二极管的光提取技术及其研究进展

高性能材料研究使有机发光二极管（Organiclight⁃emittingdiode,OLED）取得了突飞猛进的发展,但是器件内部生成的光子由于光学损耗无法全部发射到外部空间,从而极大地降低了OLED效率,并阻碍了其在节能照明市场的应用。通过调控光损失区域的波传导,光提取技术能够有效抑制衬底、波导、表面等离子激元等损耗模式,理论上可使效率扩大4倍。具有1.05~2倍扩大效果的光提取技术已被大量报道,但与理论极限仍存在很大差距。为此,本文简要分析了OLED光学损耗模式,综述了近年来高效的、特别是能实现2倍以上扩大效果的光提取技术。     

非周期微纳结构增强有机发光二极管光耦合输出的研究进展

有机发光二极管（OLED）具有功耗低、重量轻、色域宽、响应时间快及对比度高等优点,在全彩平板显示和固态照明等领域均显现出巨大的应用潜力,受到人们的广泛关注.然而,较低的光输出效率使得器件的外量子效率远低于内量子效率,这严重制约了OLED器件的发展和应用.因此如何提高OLED器件的光耦合输出效率已成为备受关注的研究课题.本文主要介绍了采用非周期微纳结构提高OLED器件光耦合输出效率的最新研究进展,对随机微纳透镜结构、光散射介质层、聚合物多孔散射薄膜、随机凹凸波纹结构及随机褶皱结构等多种对器件亮度分布和光谱稳定性无明显影响的光耦合输出技术进行了总结和讨论.最后,对提高OLED器件光耦合输出研究做了总结和展望.     

氧化锌纳米线耦合硅金字塔微纳复合结构的制备及其自清洁特性研究

光伏器件粉尘堆积伴随的遮光效应极其严重,可导致太阳能电池的光电转换效率降低一半以上,这是任何其他提高光伏器件性能的高新技术所不能弥补的.本文根据Cassie-Baxter理论构建出一种基于光伏器件应用的超疏水自清洁微纳复合结构,即氧化锌纳米线耦合硅金字塔.通过调控硅金字塔的尺寸和均匀性,使其尺寸效应不被遮盖以符合存在微米构型的疏水要求,同时尽量不破坏硅光伏器件绒面的减反性能.本文采用水热法在金字塔表面生长氧化锌纳米线的方案,通过系统的实验设计,首次成功地制备了符合光伏器件应用的接触角高达154?,且接触角滞后小于10?的超疏水自清洁微纳复合结构.此外,我们不仅发现硅金字塔的刻蚀存在\"高温促进硅金字塔刻蚀\"的温度效应和硅金字塔顶部有\"圆润-方正-圆润\"的时间效应,还从物理上对高温促进刻蚀、晶体的各向异性刻蚀导致的硅金字塔和我们所制备的氧化锌纳米线耦合硅金字塔复合结构的陷光效应等进行了比较充分的分析.     

微腔结构对铕配合物有机电致发光二极管(OLEDs)性能的提高

成功制备了铕配合物的微腔结构有机发光二极管(OLEDs),其发射层采用质量比为1:3的空穴传输材料(TPD)和电子传输材料(Eu(DBM)₃bath)的混合层.该器件实现了Eu³⁺高色纯度红光发射,其色坐标为(x=0.651,y=0.338);并克服了微腔器件的发光颜色随探测角度增大而变化的缺点.在微腔器件中,最大亮度在19V时达到1160cd/m²;在高电流密度时的EL效率得到明显提高.     

表面微纳结构对光的透射性能影响分析

针对传统光学元件增透的方法中存在物理、化学性质的限制而导致热失配、稳定性不足等问题,提出了对光学表面直接加工圆球和圆锥形两种微纳结构的增透方式;构建了两种微结构模型并以0.38～0.9μm的入射光在不同入射角的条件下对二者进行数值仿真;分析了两种模型随波长与入射角变化的反射率、透射率和电场的变化情况,并对两种实验元件进行实验测试;结合两种微纳结构的仿真和实验数据结果进行对比,获得了两种微纳结构对光透射性能的影响情况。结果表明:入射光波长由小增大时,光学元件透射率增大,并随着波长继续增大透射率逐渐趋于稳定。可为表面微纳结构对光透射性能的影响研究,以及对微纳光学器件的优化设计、制造提供参考。     

基于复合纳米结构的局域表面等离子体光学传感器

局域表面等离子体光学传感器由于其体积小、灵敏度高、免标记等特点成为目前传感器研究热点之一。然而由于银纳米结构的生物兼容性以及氧化问题,成为该传感器发展的瓶颈。提出了利用金／银混合的金属纳米结构克服上述困难,并从有限时域差分数值计算方法入手,设计了银层50nm,金层5nm的六边形分布三角形复合传感结构,并利用纳米球自组装技术实现了该类型传感器。同时,与生物分子蛋白A的结合实验结果表明,该传感器在生物分子溶液浓度213．85nM的条件下仍然具有较高的灵敏度。     

正方形孔径纳米半球阵列提高LED光提取效率研究

为提高氮化镓（GaN）基发光二极管（LED）的光提取效率,基于等效介质理论设计了底面100%占空比、半径为320nm的正方形孔径纳米半球阵列。利用时域有限差分法（FDTD）对正方形孔径纳米半球阵列结构底面占空比、半径对光提取效率的影响进行了仿真计算研究。仿真结果表明：LEDp-GaN表面刻蚀半径为320nm、底面占空比为100%的正方形孔径纳米半球阵列的光提取效率最优。采用电子束曝光配合热回流技术和ICP刻蚀完成正方形孔径纳米半球阵列的GaN基LED制作及测试实验。结果表明：在20mA和150mA工作电流下,有微纳结构的LED较无微纳结构的参考样品的发光效率分别提高4.67倍和4.59倍,计算结果与实验结果比较一致,说明加入方形孔径纳米半球阵列可以有效提高LED光提取效率。

     

基于微纳结构与金属纳米层的颜色调控技术研究

本文提出一种基于微纳结构及金属纳米层的颜色调控方法. 通过理论分析研究, 建立了基于多孔氧化铝(PA) 微纳结构与金属纳米层的颜色调控物理模型. 以此为基础, 在孔深分别为250 nm和410 nm的PA模板表面磁控溅射铝(Al)金属纳米层, 对其反射干涉光谱分析可知, 通过控制PA模板的孔深可实现可见光谱范围内的颜色调控. 此外, 基于掩膜在孔深为410 nm的PA模板表面局域溅射铬(Cr)金属纳米层, 通过对其反射干涉光谱分析并与相同孔深的镀Al金属纳米层的PA颜色进行对比, 可以发现改变金属纳米层的材料和厚度同样可以实现颜色调控, 并通过局域颜色调控制备出彩色图案. 研究结果表明, 基于微纳结构及金属纳米层的颜色调控是一种切实可行和有效的方法.     

表面微纳结构对光的透射性能影响分析北大核心CSCD

针对传统光学元件增透的方法中存在物理、化学性质的限制而导致热失配、稳定性不足等问题,提出了对光学表面直接加工圆球和圆锥形两种微纳结构的增透方式;构建了两种微结构模型并以0.38~0.9μm的入射光在不同入射角的条件下对二者进行数值仿真;分析了两种模型随波长与入射角变化的反射率、透射率和电场的变化情况,并对两种实验元件进行实验测试;结合两种微纳结构的仿真和实验数据结果进行对比,获得了两种微纳结构对光透射性能的影响情况。结果表明:入射光波长由小增大时,光学元件透射率增大,并随着波长继续增大透射率逐渐趋于稳定。可为表面微纳结构对光透射性能的影响研究,以及对微纳光学器件的优化设计、制造提供参考。     

Fabrication and design of various dimensions of multi-step ashperical microlens arrays for OLED package

An optical film with aspherical microlens array (A-MLA) by using multi-step lithography process for an OLED (Organic Light-Emitting Diode) package is fabricated, by which method the luminance of OLEDs can be enhanced. The method of design and fabrication of an A-MLA is explored in this study. In the design process, various parameters of an A-MLA such as curved profiles, layout template and dimensions of microlens are analyzed and characterized. Curved profiles include hyperbola, parabola, ellipse and sphere; and layout templates include square, hexagon, triangle and tangential circle. The profile of the A-MLA was determined by using a commercial optical simulation software, FRED. Based on the simulated result, a film with an A-MLA was fabricated using the LIGA-like (Lithographie Galvanoformung Abformung, LIGA) process, including lithography, sputtering, micro-molding with PDMS (Polydimethylsiloxane) and UV (Ultraviolet)-cured technology. The major challenge to this process is to use JSR-126N negative thick photoresist to manufacture an approximate A-MLA optical film with multi-step lithography method. Finally, the films with A-MLAs are attached to an OLED to measure their optical-electric properties. The effectsof A-MLA optical films on OLED luminance are analyzed. In addition, the measured results are compared with simulated ones. They show good agreement with each other.     

基于混合光源的星模拟器光谱研究

提出了一种基于氙灯和卤钨灯混合光源的星模拟器光谱模拟方案.采用氙灯和卤钨灯组成宽光谱光源灯阵,并通过色温模拟与控制模块后射入积分球,为星模拟器提供理想光源,模拟出与特定色温3 900K,4 800K,6 500K相近的光谱曲线.通过对标准黑体光谱曲线的仿真,计算出滤光片各个微小波段最优透过率,并对微小波段区间的透过率进行区间合并处理,得到满足设计指标要求的滤光片透过率,实现对特定色温光谱曲线的模拟.仿真结果表明,采用本文方案能够满足微小波段匹配模拟误差在10%以内,用相对面积法验证匹配误差在4%以内,从而为星模拟器模拟特定色温的光谱曲线提供有效的方法.     

光速处理的高精度光电混合相关探测图像运动位移

为测量航天遥感相机因姿态不稳定以及各种扰动引起的图像运动,提出了基于光速处理的高精度光电混合相关探测测量方法.利用高速CCD和主CCD对同一目标进行成像,在曝光时间内高速CCD获取序列图像,利用联合变换相关器对所采集的图像序列进行光学运算,测量出相邻序列图像的运动位移.阐述了光学相关方法测量图像运动的原理,并模拟分析了噪声和不同运动条件下的测量精度.建立了相应的测量像移的实验系统,实验数字模拟及实验结果都证实了该方法的有效性,测量精度优于0.1像元,满足卫星遥感相机的使用要求.     

Fabrication of the Fully Hybrid Microcavities Based on Zn(S)Se Epilayers and Amorphous Dielectrics

A technique of fabrication of fully-hybrid microcavities using II-VI semiconductor compound epilayers and distributed Bragg reflectors based on amorphous dielectric coating is described. The fully hybrid microcavities with Zn(S)Se epilayers are created. High structural and optical quality of the embedded Zn(S)Se thin films was established by atomic-force microscopy and optic studies. The analysis of excitonic spectra for Zn(S)Se epilayers embedded in the fully hybrid microcavities indicates that such structure can be perspective for creation of a new type of light-emitting devices – polariton lasers.     

Measurement of Reflected and Scattered Light for Monitoring Fluctuation of Structures

A laser spectroscopic technique for studying fluctuations of structural objects is presented, together with some results of our investigations including an observation of forced vibration of a refrigerator, intrinsic vibrations of buildings, and appearance of a fluctuation in rotational speed due to fatigue. An alternative detection technique which uses the scattered light for monitoring in place of the mirror-reflected beam is also presented. A leak of water out of a pipeline was detected with this method.

The results obtained with this laser spectroscopic technique should form a useful collection of data regarding fluctuation analysis of various objects.     

Effect of Interface Nanotexture on Light Extraction of InGaN-Based Green Light Emitting Diodes

We report the enhancement of the light extraction of InGaN-based green light emitting diodes （LEDs） via the interface nanotexturing. The texture consists of high-density nanocraters on the surface of a sapphire substrate with an in situ etching. The width of nanocraters is about 0.5 μm and the depth is around 0.1 μm. It is demonstrated that the LEDs with interface texture exhibit about a 27% improvement in luminance intensity, compared with standard LEDs. High power InGaN-based green LEDs are obtained by using the interface nanotexture. An optical ray-tracing simulation is performed to investigate the effect of interface nanotexture on light extraction.     

Mechanism of Bragg Diffraction-Assisted Light Extraction in GaN-based Light-Emitting Diodes Based on a Self-Consistent Model

By introducing the distribution of the light energy density in GaN-based light-emitting diode （LED）, the LED model based on the incoherent regime and the light extraction efficiency are investigated. The energy density as a function of the angle of incidence is calculated to demonstrate the mechanism of the light extraction. The deviation between the tendencies of the transmissivity of the output layer and the extraction efficiency is also demonstrated.     

Mechanism of Bragg Diffraction-Assisted Light Extraction in GaN-based Light-Emitting Diodes Based on a Self-Consistent Model

By introducing the distribution of the light energy density in GaN-based light-emitting diode (LED), the LED model based on the incoherent regime and the light extraction efficiency are investigated. The energy density as a function of the angle of incidence is calculated to demonstrate the mechanism of the lightextraction. The deviation between the tendencies of the transmissivity of the output layer and the extraction efficiency is also demonstrated.     

提高LED光提取效率的研究

通过模拟计算的方法分析了倒装结构LED中衬底材料折射率及厚度对光提取效率的影响,并在此基础上提出一种新的菱形结构.结果表明:该菱形结构可大幅度提高LED光提取效率,在使用Si、蓝宝石、SiC作为芯片衬底材料时,菱形结构的光提取效率分别提高到传统方形结构的1.51、2.03、3.65倍.