白光LED用Ce，Sm共掺杂YAG单晶荧光材料的光谱性能

对白光发光二极管（light-emitting diode,LED）用Y3Al5O12（YAG）单晶荧光材料的制备和光谱性能进行了研究。采用提拉法生长了白光LED用Ce：YAG及Sm,Ce：YAG晶体,并通过吸收光谱、激发光谱和发射光谱等对晶体的光谱特性进行表征。结果表明：Ce：YAG单晶作为荧光材料被发射波长460 ...     

白光LED用定向凝固Al2O3/YAG:Ce^(3+)共晶荧光复合陶瓷研究进展EI北大核心CSCD

白色发光二极管(WLED)具有长寿命、高光效、节能环保等独特优势,是目前公认的第四代绿色照明光源,在照明等高技术领域具有重要的应用前景.目前,WLED的主要实现形式为蓝光芯片搭配YAG:Ce^(3+)荧光粉,封装荧光粉的树脂导热性较差,导致LED的发光性能随温度的升高逐渐下降,难以应用于大功率照明.因此,如何获得高质量、高稳定性、无需树脂的块体荧光材料成为提升WLED发光效率和应用可靠性的关键.近年来,利用定向凝固方法制备的高性能Al2O3/YAG:Ce^(3+)块体共晶荧光复合陶瓷以其优良的发光性能、高温强度、热稳定性以及低的背散射损失和高量子效率,被认为是一种有望替代荧光粉、用于大功率WLED照明的新型块体荧光材料.总结了近年来发展的定向凝固Al2O3/YAG:Ce^(3+)共晶荧光复合陶瓷的主要制备方法,阐述了共晶荧光复合陶瓷的凝固组织、发光机理以及影响发光性能的主要因素,展望了白光LED用Al2O3/YAG:Ce^(3+)共晶荧光复合陶瓷的发展趋势.     

稀土荧光高分子的制备及其荧光性能研究

以黄色Y3Al5O12:Ce、红色Ca Al Si N3:Eu发光材料和有机硅树脂为原料,通过模压法制备了不同Y3Al5O12:Ce含量的稀土荧光高分子,并进一步封装出白光LED。采用X射线衍射、荧光光谱仪、高精度快速光谱辐射计对荧光高分子样品和白光LED的晶型结构、荧光特性、波长转换效率、发光效率、光通量等光色参数进行了测试和计算。结果表明:发光材料的混合并未破坏其本身的晶型结构,X射线衍射谱图与标准卡一致;样品具有宽带激发光谱,峰值位于467 nm,发射光谱峰值548 nm,半波宽90.3 nm,适于宽光谱白光LED的制备,其发射强度随着Y3Al5O12:Ce质量分数的增加而提高。样品的波长转换效率与质量分数表现出正相关关系,但由于吸收饱和效应,其增幅逐渐降低。根据所封装白光LED中色坐标点分布和色温的综合分析结果,确定Y3Al5O12:Ce的最优用量为5.66%,对应的白光LED的发光效率为126 lm/W,色温为6 196 K,显色指数为62。不同电流下的光谱变化测试结果表明样品具有电流稳定性。此外,通过加入Ca Al Si N3:Eu,可将白光LED的显色指数提高至81,色温则变化至暖白区的2 726 K。     

白光LED用定向凝固Al_2O_3/YAG:Ce~(3+)共晶荧光复合陶瓷研究进展

白色发光二极管(WLED)具有长寿命、高光效、节能环保等独特优势,是目前公认的第四代绿色照明光源,在照明等高技术领域具有重要的应用前景。目前,WLED的主要实现形式为蓝光芯片搭配YAG:Ce~(3+)荧光粉,封装荧光粉的树脂导热性较差,导致LED的发光性能随温度的升高逐渐下降,难以应用于大功率照明。因此,如何获得高质量、高稳定性、无需树脂的块体荧光材料成为提升WLED发光效率和应用可靠性的关键。近年来,利用定向凝固方法制备的高性能Al_2O_3/YAG:Ce~(3+)块体共晶荧光复合陶瓷以其优良的发光性能、高温强度、热稳定性以及低的背散射损失和高量子效率,被认为是一种有望替代荧光粉、用于大功率WLED照明的新型块体荧光材料。总结了近年来发展的定向凝固Al_2O_3/YAG:Ce~(3+)共晶荧光复合陶瓷的主要制备方法,阐述了共晶荧光复合陶瓷的凝固组织、发光机理以及影响发光性能的主要因素,展望了白光LED用Al_2O_3/YAG:Ce~(3+)共晶荧光复合陶瓷的发展趋势。     

HBC/PMMA复合膜的制备及发光性能

分别采用溶液成膜法和原位本体聚合法制备了六苯并蔻/聚甲基丙烯酸甲酯(HBC/PMMA)复合膜,并采用紫外光谱、荧光光谱和荧光绝对量子产率研究了HBC/PMMA复合膜的发光性能。结果表明,溶液成膜法制备的复合膜的荧光强度和绝对量子产率分别是原位本体聚合法的10倍和6倍,但由于PMMA对激发光的吸收,两者的荧光绝对量子产率都较低。随着HBC质量分数逐渐减小,复合膜的荧光强度和绝对量子产率都先增大再降低,绝对量子产率极大值时的HBC质量分数要比荧光强度极大值时的低一个数量级。随着复合膜厚度的降低,荧光强度和绝对量子产率都出现先增大后减小的现象,荧光强度极大值时的厚度为0.44mm,而绝对量子产率极大值时的厚度为0.56 mm。     

SPS烧结制备新型荧光玻璃材料

以实验室自制SiO2粉体和商用Ce∶YAG荧光粉为玻璃原料,采用放电等离子体烧结（SPS）技术,在1 200℃保温2 min烧结得到有望用于白光LED封装的Ce∶YAG荧光玻璃。用X射线衍射仪（XRD）、荧光光谱（PL）等方法对制备获得的荧光玻璃样品进行表征。结果显示,烧结并没有破坏Ce∶YAG荧光粉的晶体结构,且荧光玻璃主体相仍为玻璃体,该荧光玻璃在460nm具有强吸收峰,在此波长激发下发射出530 nm左右的黄光。研究结果表明,本实验制备的Ce∶YAG荧光玻璃是一种具有重要应用前景的LED封装用新型荧光材料。     

聚碳酸酯基荧光复合塑料的制备及发光性能的研究

采用高温熔融混合和高温模压的方法,以聚碳酸酯和稀土荧光材料为原料,制备出不同厚度(0.5、1.0、和1.5 mm)的荧光复合塑料。通过扫描电子显微镜、荧光分光光度计和荧光光谱分析系统等测试手段,对其进行了测试表征。研究结果表明:稀土荧光材料在聚碳酸酯中均匀分散;荧光复合塑料的激发与发射光谱强度与其厚度成正比关系,在1.5 mm厚度时最大,光谱的形状没有随着厚度的改变而改变;荧光复合塑料在激发光不同功率(600、850、1 100、1 350和1 600 mW)的激发下,其发光强度与激发光功率成正比关系,荧光转换效率与激发光功率成反比关系,对于给定厚度和浓度的荧光复合塑料,其所制备的白光LED的光通量与激发光功率满足线性关系,φ光通量=0.226·P激发光+23.08,表明荧光复合塑料是一种适合于白光发光二极管(LED)应用的材料。     

微波辅助沉淀法荧光粉体的制备及其用于白光LED的研究

本项目拟采用微波辅助共沉淀法制备Ce:YAG荧光粉体,接着通过高温真空烧结得到了Ce:YAG透明陶瓷。利用透明荧光陶瓷进行LED封装,使其在蓝光LED芯片照射下产生白光,实现"蓝光芯片+Ce:YAG透明荧光陶瓷"发光和外壳一体化。通过XRD、SEM等手段对粉体和陶瓷进行了表征和研究,优化纳米粉体制备条件和陶瓷烧结工艺,制备性能优良的透明荧光陶瓷。     

新型半导体激光照明用荧光材料的制备及其应用

通过改性采用自稳定沉淀聚合法制备的共聚物,得到了一组具有聚集诱导发光特性的荧光聚合物。结果表明:荧光聚合物的荧光发射波长为450～750 nm,量子产率最大可达21.72%;可以通过控制制备过程中的pH值来调控聚合物分子链中的空间共轭结构,从而控制材料的荧光发射峰位;在波长为450 nm的蓝光半导体激光器照射下,材料可以发射出CIE 1931坐标为(0.365,0.335),色温4 177 K的中性白光。该新型荧光聚合物具有成本低、制备方法简单的特点,可以作为半导体激光照明用荧光材料。     

1,8-萘酰亚胺类化合物的荧光光谱性能研究

研究了11种新型1，8-萘二甲酰亚胺类荧光化合物的荧光光谱性能。利用紫外光谱仪和荧光光谱仪测定了这两类化合物的紫外光谱和荧光光谱，分别得到最大吸收波长、最大激发波长、最大荧光发射波长，并以硫酸奎宁的0.5mol／l硫酸水溶液为参比标准，测定了各化合物的荧光量子产率在此基础上，研究了浓度、溶荆对荧光性能的影响、以及化合物结构与荧光性能的关系。结果表明，1，8-萘酰亚胺粪化合物随着浓度的增大，荧光光谱发生红移，且斯托克斯位移增大。随着溶剂极性的增大，最大荧光发射波长发生红移，斯托克斯位移增大，荧光量子产率增大在1，8-萘酰亚胺类化合物的4-位引入笨并呋喃取代基后，最大荧光发射波长红移70nm～100nm，斯托克斯位移增大20nm～50nm，荧光量子产率明显增大。     

Influence of lighting conditions on the appearance of typical interior materials

Two studies investigated how lighting influences perception of various materials. Experiment 1 focused on preferences of cold or warm light. Participants' task was to indicate preference for either coolish or warmish light for 20 different materials. The selection included materials typically used for wall or floor of interior spaces. Different hues and surface characteristics were present. Specifically two materials of blue color (cold hue) were preferred in a cold light while red carpet (warm hue) and synthetic turf materials were preferred in warm light. This latter choice was explained by automatic reference of synthetic turf to the appearance of natural grass. There were no clear light source preferences for other materials. Experiment 2 explored how the same 20 materials are evaluated under LED lighting in comparison to three other lighting situations (halogen lamp, high‐intensity discharge lamp, and compact fluorescent lamp). The results of this explorative study were not conclusive. The materials chosen for this experiment differed greatly in their structure and optical properties. In conclusion, light influence on the evaluation of materials needs systematic investigation in future research. © 2013 Wiley Periodicals, Inc. Col Res Appl, 40, 50–61, 2015     

Combustion synthesis of multicomponent ceramic phosphors for solid state lighting

About 50% of the world’s need for lighting is provided by artificial lighting. For over the last decade, the world has witnessed rapid shift from conventional Hg-based lighting to LED-based solid state lighting (SSL). SSL technology extensively uses YAG:Ce³⁺ phosphor for production of white light emitting devices (LEDs). Part of the blue light from the (In,Ga)N LED chip is absorbed by a thin layer of Ce³⁺-doped YAG and is converted into yellow light. The combination of blue and yellow gives a bright white light source with an overall energy efficiency exceeding that of a compact fluorescent lamp. Several soft chemical routes have been explored for synthesis of YAG but were discarded due to their complex nature, high cost for the industrialization, phase impure materials, etc. In this paper we describe rapid one-step modified combustion synthesis of YAG:Ce³⁺ and related phosphors carried out at 500°C using a mixed fuel. Photoluminescence spectra of YAG:Ce³⁺ and LED prepared thereof are comparable with those of commercial phosphors.     

铋碲酸盐玻璃中三价铕离子多通道跃迁发射的三维荧光光谱分析

在初步观察到三价铕离子多通道跃迁发射的基础上,测定了Eu3 掺杂铋碲酸盐玻璃的三维荧光光谱。三维光谱显示,罕见的铕离子5D3、5D2、5D1向下能级跃迁的蓝光和绿光多通道发射在较宽的激发范围内均可被有效地观察和记录到。通过对铕离子能级结构和玻璃基质声子能量的综合分析,认定最大声子能量较低是铋碲酸盐玻璃中获得铕离子多通道跃迁发射主要原因。激发光谱表明,紫色光源可有效激发样品,获得由蓝到红的多峰发射;对于始于5D0态的Eu3 常规发射,氩离子激光器,紫色、蓝色和绿色激光二极管及发光二极管均为有效泵浦光源。     

Optimization of LED‐based light blendings for object presentation

This study looks at the perceived quality of light‐emitting diode (LED)‐based lighting of various colors. The objective was to find out whether LEDs could provide better (i.e., more relevant and acceptable) lighting than that which is obtained with standard halogen or fluorescent sources. The perception of objects was assessed under different lighting schemes. Subjects were invited to add red, cyan and/or amber to white LED‐based light to match the halogen and fluorescence rendering on specific targets: a color chart and a painting. They were also asked to rate the difference between the two, and to express their preference. The results obtained for the perception of LED‐based lighting were quite positive. Color blendings of LED light were found to provide illuminated situations similar to halogens or fluorescent sources. These blendings were well accepted, and indeed often preferred, although the color rendering index (CRI) was always low. This indicates that the CRI as it stands is inadequate to characterize the color rendering of solid‐state light sources, and needs to be updated. LED‐based lighting systems seem to have considerable potential for use in shops and display units, where they may well outperform existing lighting systems. © 2009 Wiley Periodicals, Inc. Col Res Appl, 34, 310–320, 2009     

白光LED用Ca_6Sr_4(Si_2O_7)_3Cl_2:Ce~(3+),Eu~(2+),Sm~(3+)荧光粉的合成及其发光性质

采用传统的高温固相法合成了Ce3+,Eu2+,Sm3+离子分别单激活和三种稀土离子共激活的Ca6Sr4(Si2O7)3Cl2荧光粉,并通过X射线粉末衍射、荧光光谱和CIE色坐标对其结构和发光性质进行了研究。荧光粉Ca5.91Sr3.96(Si2O7)3Cl2:0.02Ce3+,0.04Eu2+,0.04Sm3+在365 nm激发下能发射高强度白光,其色坐标为x=0.2183,y=0.2187,有望成为一种新型白光LED灯用荧光粉。     

Dependence of the color appearance of some flowers on illumination

Seven flower colors perceived by five color experts using visual color measurement under 2800 K warm white fluorescent lamps, 3500 K plant growth lamps, and 6500 K light‐emitting diodes (LEDs) were compared with those under 6500 K fluorescent lamps, which represented illuminants in florist shops. Fluorescent lamps (6500 K, 1000 lx) were found to be effective for displaying flower colors and were used as the standard condition. The colors of flowers generally shifted in the same direction as those of the illuminants in CIELAB space. The color differences were highest under the 3500 K fluorescent lamp at both 500 and 2000 lx. At 500 lx, the ΔE values under the 6500 K LED were higher than those under the 2800 K lamp. The C* and ΔE values revealed that the 2800 K lamp was unsatisfactory for purple‐blue and purple flowers and was more suitable for floral displays at lower illuminance. Under the 3500 K lamp, the highest color distortion occurred in cool‐colored flowers, but C* increased for purple‐blue and purple flowers. The 6500 K LED tended to decrease C* for warm‐colored flowers under both illuminances, but it was effective for displaying purple‐blue and purple flowers with increased C*. © 2012 Wiley Periodicals, Inc. Col Res Appl, 39, 28–36, 2014     

Glass-Ceramics and Solid-State Lighting

Yttrium aluminum garnet (YAG) doped with Ce³⁺ ion is known as an excellent phosphor for light-emitting diode (LED), usually used as a powder form dispersed in organic resins. We have developed translucent glass-ceramics (GC) of YAG: Ce³⁺ microcrystals in 2004. The GC sheet with half millimeter thick can work efficiently to make identical emission spectra with conventional white LED when combined with a blue LED. This report reviews the development history of the GC materials and impact for all inorganic solution for solid-state lighting.     

Testing LED lighting for colour discrimination and colour rendering

Light‐emitting diode (LED) technology offers the possibility of obtaining white light, despite narrow‐band spectra. In order to characterize the colour discrimination efficiency of various LED clusters, we designed a classification test, composed of 32 caps equally distributed along the hue circle at about 3 ΔE* _ab‐unit intervals. Forty normal colour observers were screened under four different LED test light sources adjusted for best colour rendering, and under one control incandescent light of the same colour temperature. We used commercially available red, green, blue, and/or amber LED clusters. These yielded a poor colour rendering index (CRI). They also induced a significantly higher number of erroneous arrangements than did the control light. Errors are located around greenish‐blue and purplish‐red shades, parallel to the yellow‐axis direction, whereas when the distribution of light covers the full spectrum, the LED clusters achieve satisfactory colour discrimination efficiency. With respect to the lights we tested, the colour discrimination is correlated with the CIE CRIs as well as with a CRI based on our sample colours. We stress the fact that increasing the chroma of samples by lighting does not necessarily imply an improvement of colour discrimination. © 2008 Wiley Periodicals, Inc. Col Res Appl, 34, 8–17, 2009.     

Alternatives to Outdoor Daylight Illumination for Photodynamic Therapy—Use of Greenhouses and Artificial Light Sources

Daylight-mediated photodynamic therapy (daylight PDT) is a simple and pain free treatment of actinic keratoses. Weather conditions may not always allow daylight PDT outdoors. We compared the spectrum of five different lamp candidates for indoor “daylight PDT” and investigated their ability to photobleach protoporphyrin IX (PpIX). Furthermore, we measured the amount of PpIX activating daylight available in a glass greenhouse, which can be an alternative when it is uncomfortable for patients to be outdoors. The lamps investigated were: halogen lamps (overhead and slide projector), white light-emitting diode (LED) lamp, red LED panel and lamps used for conventional PDT. Four of the five light sources were able to photobleach PpIX completely. For halogen light and the red LED lamp, 5000 lux could photobleach PpIX whereas 12,000 lux were needed for the white LED lamp. Furthermore, the greenhouse was suitable for daylight PDT since the effect of solar light is lowered only by 25%. In conclusion, we found four of the five light sources and the greenhouse usable for indoor daylight PDT. The greenhouse is beneficial when the weather outside is rainy or windy. Only insignificant ultraviolet B radiation (UVB) radiation passes through the greenhouse glass, so sun protection is not needed.     

Ce:YScAG phosphor-converted transparent ceramics with high thermal saturation and weak concentration quenching for LED and LD white lighting

In the high-power white light LEDs/LDs area, obtaining phosphor-converted materials with high thermal stability and high luminous emittance with proper blue/yellow light ratio has been the main challenge in recent years. In this study, a group of (Ce_xY_1-x)₃(Sc_yAl_1-y)₅O₁₂ transparent ceramics with high optical quality were proposed to rise to that challenge. Their spectra were regulated by incorporating Sc³⁺, showing blue shifted emission bands (peak position from 554 nm–538 nm), blue shifted excitation bands (462–445 nm) and narrowed full width at half maxima (120–112 nm). Significantly, the prepared Ce:YScAG transparent ceramics (TC) exhibited decent thermal quenching performance with the photoluminescence intensity at 150 °C maintaining 88.7% of its original value at room temperature. The Sc incorporation impacted the atoms’ occupation and distance, crystal field splitting and energy band structure. Under remote LD excitation mode, the luminous efficiency of the prepared Ce:YScAG TC can achieve 164.8 lm/W. And even if the Ce³⁺ doping reaches 2.0 at%, the LE can still maintain 117.8 lm/W, exhibiting decent concentration quenching characteristic. Consequently, Ce:YScAG TCs have great potential as promising phosphor-converted materials in future high-power LED and LD white lighting.