蓝光LEDs的转换荧光粉发光效率的测量

本文研究了YAG:Ce荧光粉的色点红移的现象.当YAG晶格点阵中的Y被 Gd 激发或添加了Pr作为 Ce 的共同催化剂时就会发生这种现象.测量了在(Y,Gd)AG:Ce和YAG:Ce,Pr荧光粉样品内部的效率,其激发光线的波长为 470 nm.其结果表明这两种荧光粉的发光效率分别随着Gd和Pr聚集而降低.SrGa2S4:Eu.是另外一种常用的转换蓝光 LED 的颜色的荧光粉.室温下,这种荧光粉效率很高,理论上其发光效率比 YAG:Ce 的发光效率高出 33%.对这种荧光粉效率的测量结果表明其制作过程是影响性能的主要因素.将这种荧光粉印刷在放在-个或多个蓝光 LED 前面的屏幕的表面,测得其发光效率高达 364 lm/W.     

光转换白光LEDs的研究

采用固相法制备YAG：Ce、Gd光转换荧光粉，测量其激发光谱和荧光光谱，发现激发光谱存在2条激发带，其中428—501nm的激发带与GaN LEDs的发射光谱匹配，荧光光谱呈黄色宽带。将荧光粉与GaN管芯用环氧树脂封装在一起，制成白光LEDs，其CIE色度坐标为(0．27，0．33)，显色指数为78.2，发光强度8cd，流明转换效率为6．37，优于市场同类产品。     

Sb~(3+)掺杂的YAG:Ce荧光粉的合成与发光性能研究

通过高温固相法制备了白光LED用Sb3+掺杂的Y1.94-yGdSbyAl5O12:0.06Ce荧光粉,使用荧光分光光度计研究了样品的发光性能,并采用紫外-可见-近红外光谱分析系统分析了所制荧光粉的封装性能。结果表明,Y1.94-yGdSbyAl5O12:0.06Ce荧光粉为立方晶系,其发射中心波长为550 nm,Sb3+掺杂有助于提高YAG:Ce的发光强度。将合成的Y1.92GdSb0.02Al5O12:0.06Ce(CL-Y-550)荧光粉封装成白光LED,其平均色温为5 376 K,属于冷白;平均显色指数为81.2,达到了基本的应用水平。     

GaAs量子阱太阳能电池转换效率的计算

采用细致平衡模型计算了GaAs量子阱太阳能电池的转换效率,同时对量子阱结构带来的几种效应,如准费米能级分离、热载流子效应等进行了分析,并将碰撞离化效应引入此细致平衡模型中,通过计算研究了其对量子阱太阳能电池转换效率的影响.结果表明碰撞离化效应可以提高电池的转换效率,但提高幅度有限.     

GaAs量子阱太阳能电池转换效率的计算

采用细致平衡模型计算了GaAs量子阱太阳能电池的转换效率,同时对量子阱结构带来的几种效应,如准费米能级分离、热载流子效应等进行了分析,并将碰撞离化效应引入此细致平衡模型中,通过计算研究了其对量子阱太阳能电池转换效率的影响.结果表明碰撞离化效应可以提高电池的转换效率,但提高幅度有限.     

YAG:Ce3 荧光粉对白光LED衰减的影响

对封装的蓝光和白光LED进行了光衰对比试验,结果表明,白光LED初期衰减明显比蓝光LED快.因此,又对自制的YAG:Ce3 荧光粉进行了光照、温度测试,结果发现,荧光粉在光照作用下,荧光强度出现先降后升然后稳定的现象,跟白光LED的衰减相吻合,结合色坐标的偏移,蓝光LED本身的衰减仍是白光LED衰减的主要原因.     

一种红光增强型白光LED特性研究

为了使白光LED光谱中红光成分增强,以更适应人眼视觉,通过对YAG:Ce荧光粉掺杂的改进,引入Gd3+、Pr3+使白光LED光谱在610 nm处出现明显发射峰,并且荧光主峰发生红移。通过对LED的色坐标计算表明,用这种新型荧光粉封装的白光LED色坐标可以达到标准白点(0.33,0.33),理论上有可能符合"能源之星"的要求,用YAG:Ce封装的LED却不可能。     

基于Spectr0320e光谱仪的白光LED荧光粉性能测试

我国LED产业发展非常迅速,稀土钇铝石榴石（YAG）系列荧光粉广泛应用于白光LED。德国InstrumentSystems公司的Spectr0320e光谱仪适合光谱的精确测量,文章结合Spectr0320e和远方公司的PE-5荧光粉激发装置,实现蓝光激发下黄色YAG荧光粉的色品坐标、相对亮度、量子效率等参数精确的测试,研究了仪器在不同的测试条件如暗电流、光电倍增管、密度滤光片等设置的不同,对测试结果的影响,并给出利用本装置测试荧光粉时应该注意的事项。     

Fraunhofer研究所的“n型”单晶硅太阳能电池效率达到23．4％

德国弗劳恩霍夫太阳能系统研究所（FraunhoferISE）宣布,该机构研制的以n型半导体为底板,然后在其上面形成较薄的P型半导体层的单晶硅太阳能电池,其能量转换效率达到了23.4％。太阳能电池单元面积为2cm见方。FraunhoferISE有可能量产该款电池,并参与三洋电机等公司推进的提高结晶硅类太阳能电池效率的竞争。     

基于蓝光LED的白光器件:用于固体发光的小颗粒YAG:Ce型荧光粉的合成

文章介绍了小颗粒 YAG:Ce 荧光粉的三种合成方法.这种荧光粉受到蓝光 LED 发出的光线的激发会发出黄光.在合成的 pcLEDs 里,蓝光和黄光混合形成了白光.本文解释了这种涂有 YAG:Ce 荧光粉的 pcLED 的色点的依赖性以及通过添加修复晶格点阵的催化剂以改变这种依赖型的方法.另外,文章还讨论了 Ce3 聚集中心的YAG:Ce 荧光粉的效率的测量、烧成温度、激发波长.     

YAG:Ce,Yb近红外下转换荧光粉中的离子簇集

通过457 nm和915 nm连续激光器对固相反应法和溶胶-凝胶法制备的YAG:Ce,Yb荧光粉中的Yb3+近红外发光和可见上转换发光能量转移机制进行了研究。两种激发下,溶胶-凝胶法样品的近红外发光猝灭浓度均在5%左右,发光强度变化曲线趋势相近;固相反应法产物,915 nm直接激发猝灭浓度为5%左右,457 nm间接激发猝灭浓度为10%左右,说明固相反应法掺杂离子分布更不均匀。样品中存在来自Yb3+到杂质离子间能量传递和Yb3+-Yb3+离子对的两种上转换发光;固相反应法产物Yb3+-Yb3+离子对协同发光强于溶胶-凝胶法产物,说明Yb3+离子簇集现象较为明显,可能降低此类材料的实际近红外转换效率。     

多孔硅的不稳定性对太阳电池的影响

研究了多孔硅（PS）的特性及其在太阳电池上的应用,并对PS太阳电池性能以及由于PS的不稳定性对电池产生的影响进行了研究。实验表明,将PS的光致发光（PL）以及减反射特性应用于太阳电池能有效提高电池的效率,同比提高了T83．89％,效率为14．73％,但其不稳定性对电池效率的影响较为明显。     

Realizing improved performance of down-conversion white organic light-emitting diodes by localized surface plasmon resonance effect of Ag nanoparticles

Down-conversion structure white organic light-emitting diodes (WOLEDs), in which white light is generated by a blue emission organic light-emitting diodes (OLEDs) in combination with a color conversion layer (CCL) outside the substrate, has attracted extensive interest due to its significant advantages in low cost and stabilized white-light emissions. However, low color-conversion efficiency of CCL is still a bottleneck for the performance improvement of down-conversion WOLEDs. Here, we demonstrate an approach to enhance the color-conversion efficiency of CCL-WOLEDs by localized surface plasmon resonance (LSPR) effect. In this approach, a blend of Ag nanoparticles and polyvinyl alcohol (PVA) is solution-deposited between the blue organic light emitting diodes and color-conversion layer. Based on the LSPR effect of this modified structure, the color conversion efficiency has improved 32%, from 45.4% to 60%, resulting a 14.4% enhancement of the current efficiency, from 9.73 cd/A to 11.14 cd/A. Our work provides a simple and low-cost way to enhance the performance of down-conversion WOLEDs, which highlights its potential in illumination applications.     

ITO-free down-conversion white organic light-emitting diodes with structured color conversion layers for enhanced optical efficiency and color rendering

We report our study on white organic light-emitting diodes (WOLEDs) implemented in a down-conversion scheme based on an ITO-free, cavity-enhanced blue phosphorescent OLED and a micro-structured color conversion layer (CCL) containing red and green phosphors. Cavity resonance induced by a ZnS/Ag/MoO₃ anode structure enables both efficiency enhancement/spectral refinement of blue phosphorescent OLED. In accordance with the resonance-induced effect, outcoupling assistance provided by micro-structuring of CCLs works to yield WOLEDs with both high efficiency and illumination-quality color rendering. Highly flexible WOLEDs are also demonstrated in the proposed scheme and tested at a radius of curvature of 10.8 mm to illustrate its advantages in realizing versatile next-generation light sources.     

基于高效太阳电池的光诱导镀技术

介绍了光诱导镀(light-induced plating,LIP)应用于太阳电池的背景、发展历史及其工作原理。论述了光诱导镀技术对太阳电池性能的影响,并重点探讨了光诱导镀技术对太阳电池前表面电极接触性能的改善效果。同时,还讨论了光诱导镀技术应用于铝背表面场(Al-BSF)和激光烧制接触(laser fired contact,LFC)两种高效太阳电池上所取得的成果。当接触电阻成为串联电阻中的主要成分时,光诱导镀能够降低接触电阻、提高填充因子,从而提高电池的效率。光诱导镀特别适合于改善串联电阻较大的电池,利用光诱导镀也可以重新优化电池的烧结条件,得到更高的电池效率。     

Enhanced organic light emitting diode and solar cell performances using silver nano-clusters

Silver nano-clusters (NCs) were incorporated into organic light emitting diodes (OLED) and solar cells by means of thermal evaporation. Silver NCs enhance the efficiency of both OLEDs and polymer solar cells under tailored device architecture. In tris-(8-hydroxyquinoline) aluminum (Alq₃) based small molecule OLEDs, silver NCs were deposited under the Al cathode. The electron injection from the cathode to organic layer is promoted significantly owing to silver NCs induced lightning rod effect, the Alq₃ OLEDs luminous efficiency is increased up to a factor of 6. In poly(3-hexylthiophene) (P3HT) polymer solar cells, the active layer absorption is enhanced in the presence of silver NCs, which can be ascribed to NCs induced light scattering effect as well as to plasmon enhanced local electric field effect. As a result, photocurrent of the solar cells is increased and the power conversion efficiency (PCE) is improved up to 20%. The comparative study of surface plasmon effects in different organic optoelectronic devices reveals interesting features of the surface plasmon and allows optimization of optoelectronic devices from a novel point of view.     

稀土元素上转换材料在钙钛矿太阳能电池中应用的研究进展

无机有机杂化钙钛矿太阳能电池被认为是最有发展前景的第三代光伏技术之一,经过短短几年时间的研究,钙钛矿太阳能电池现今的最高效率已经突破22%.随着钙钛矿太阳能电池的效率越来越接近理论效率,为了进一步提升电池效率,研究人员将目光投向了钙钛矿材料不能有效吸收的近红外波段.在本文中,我们回顾了近两年来将上转换材料与钙钛矿太阳能电池相结合的研究,将它们分成较为传统的方法和新型方法.传统的方法即是使用较为单一的NYF纳米颗粒对钙钛矿太阳能电池进行掺杂,利用稀土离子的上转换效应,吸收近红外光,扩宽钙钛矿的吸收范围,从而提升太阳能电池的性能;而新型的方法即是在传统的单一使用稀土离子的基础上,添加其他离子或者引入重掺杂半导体材料来进一步提升太阳能电池性能的方法,从实验结果看,这两种方法都取得了较好的结果.     

Light Extraction From Solution-Based Processable Electrophosphorescent Organic Light-Emitting Diodes

Molecular dye dispersed solution processable blue emitting organic light-emitting devices have been fabricated and the resulting devices exhibit efficiency as high as 25 cd/A. With down-conversion phosphors, white emitting devices have been demonstrated with peak efficiency of 38 cd/A and luminous efficiency of 25 lm/W. The high efficiencies have been a product of proper tuning of carrier transport, optimization of the location of the carrier recombination zone and, hence, microcavity effect, efficient down-conversion from blue to white light, and scattering/isotropic remission due to phosphor particles. An optical model has been developed to investigate all these effects. In contrast to the common misunderstanding that light out-coupling efficiency is about 22% and independent of device architecture, our device data and optical modeling results clearly demonstrated that the light out-coupling efficiency is strongly dependent on the exact location of the recombination zone. Estimating the device internal quantum efficiencies based on external quantum efficiencies without considering the device architecture could lead to erroneous conclusions