发光二极管的色度分析

主要对蓝光、绿光、白光LED的色度特性进行分析,首先通过单色仪,分别测得蓝光、绿光、白光LED的相对光谱功率分布并以色度学理论为基础,计算出光源主波长、色纯度、色温和显色指数.计算结果表明:蓝光LED和绿光LED主波长随标准光源的不同变化不大,色纯度比较高,分别在0.64和0.87左右,一般显色指数为-29和-14,显色性很差,不适合用来做照明光源.白光LED主波长随标准光源的不同变化较大,色纯度相当低,接近0,一般显色指数为82,显色性很好,完全符合照明光源的要求.     

用染料掺杂聚合物降低白光LED灯的蓝光危害

由于二基色白光LED的辐射光中蓝光具有相对较高的强度,因而会对人眼造成潜在的危害。本文报道通过采用香豆素540染料掺杂的PMMA聚合物有针对性地吸收白光LED灯中的大部分蓝光,并通过染料的荧光辐射将其转换为绿光和黄光,从而降低LED灯的蓝光危害。实验对经过二次光谱转换后所得到的LED灯的辐射光的光谱和色度坐标进行了测量,并通过对彩色图案中不同颜色的显示对比了其显色效果。研究结果表明:通过适当控制染料掺杂浓度和吸收片的厚度,可以获得具有较低蓝光成分且不影响一般的显色效果的LED灯光。该技术有助于获得对人眼更健康的LED照明光源,对将LED灯用于室内照明具有一定的参考价值。     

两基色、三基色和荧光粉转换白光LED配色研究

根据色度学基本原理,对荧光粉转换白光发光二极管(LED)和两基色、三基色白光LED进行了配色计算,得到了距离理想白光点色度坐标(1/3,1/3)小于0.5%范围内的众多基色组合,同时对光视效能、显色指数和荧光粉转换效率等参数进行了分析,提出了荧光粉转换白光LED和两基色、三基色白光LED的最佳基色组合,并在实验上对荧光粉转换白光LED进行了验证。     

峰值波长和浓度对转光膜与白光LED发光性能的影响

本文以高折射率有机硅胶和无机Y3Al5O12:Ce3+发光材料为原料,采用加热固化的方法制备出有机/无机转光膜,系统的研究了发光材料的峰值波长和浓度对于转光膜和制备的白光LED光色性能的研究,并进行了机理分析。研究结果表明：不同峰值波长变量中,545nm对应白光LED最大的光通量,是由于其光谱与人眼明视觉曲线具有最大的重叠面积有关;不同浓度变量中,由于存在发光材料的吸收饱和现象,在9%浓度时白光LED最大的光通量,色温则与浓度变化呈现单向递减趋势,色坐标和光色均匀度则随着浓度的提高而提高,综合多种指标获得本研究中最佳工艺参数为峰值波长为545nm,浓度为9%,对应白光LED器件光通量为131.5lm,色温4551K,色坐标（0.3479,0.3758）,光色位置处于黑体辐射曲线的白光区,说明了转光膜在白光LED领域应用的可行性。     

GaN基功率LED高低温特性研究

首次对自制的GaN基大功率白光和蓝光发光二极管在-30~100°C的温度下进行了在线的光电特性测试,对两种不同LED的正向电压、相对光强、波长、色温等参数随温度变化的关系进行了数据曲线拟合,对比分析了参数变化的原因,以及这些变化对实际应用的影响。结果表明,温度对大功率LED的光电特性有很大影响,通过对比发现白光LED的部分光参数随温度的变化不仅与GaN芯片有关,同时受到荧光粉的影响。低温环境下,要考虑LED的正向电压升高和峰值波长蓝移对应用的影响;而高温条件下要考虑光功率降低和峰值波长红移对应用的影响。     

影响白光数码管光学性能的研究

通过分析LED封装材料中固晶胶对白光的影响,给出了不同固晶胶对白光LED光衰的效果图;通过分析荧光粉对白光LED光性能的影响,给出了用同一成分荧光粉加不同波长蓝光芯片形成的CCT/Ra关系图、同一波长蓝光芯片加不同成分荧光粉CCT/Ra关系图和蓝光芯片激发下荧光粉的相对亮度随温度的变化;通过分析配粉胶对白光LED光性能的影响,给出了不同折射率硅胶封装的白光LED光衰情况和膜清洗后不同折射率硅胶封装的白光LED光衰情况影响。从而可以依据光性能的需要,选择相应封装材料,并进行白光LED的封装设计与制造。     

功率型白光LED的热特性研究

大功率LED照明单元在光通量提高的同时伴随着散热，且普通功率型白光LED多采用蓝光芯片激发荧光粉的方法，随着温度的提升，荧光粉对应的波长会发生漂移。本文从功率型白光LED的发热原理出发，试验了其在脉冲源作用下，用于照明的可能性。试验表明，在此激励源的作用下，LED输出与散热很好，并从理论上进行了解释。     

白光合成模拟软件及其应用

为了更高效的计算照明工程和显示技术中常用的色度学参量,且对白光合成进行模拟和优化、探究色域随基色光荧光光谱参数值变化时的改变情况,设计了一种基于Matlab/GUI环境的白光合成模拟软件。从而可给出,当白光光效最大、显色指数最大时,参与配色的基色光配比值。对于色域变化趋势的模拟结果表明,当荧光光谱半高宽小于15nm以后,色域随半高宽减小的增大效果并不明显。此外,绿光量子点发光峰的移动对色域的影响较为显著。     

大功率LED的光衰机制研究

为了研究大功率LED的光衰机制,选用了一系列的大功率白光、蓝光发光二极管分别进行恒流点亮,在点亮不同时间阶段测量其光通量、发光谱及伏安特性.发现在光衰过程中,光通量有时会上升;通过LED光谱测定,发现光谱分布有明显变化;同时,pn结内阻也逐渐变大.研究表明大功率LED光衰有较为复杂的过程:其中荧光粉老化及pn结性能退化是最主要的.文章对此进行了初步的分析,为白光LED的应用及进一步研究白光LED衰减提供了参考.     

InGaN/GaN MQW双波长LED的MOCVD生长

利用金属有机物化学气相淀积(MOCVD)系统生长了InGaN/GaN多量子阱双波长发光二极管(LED).发现在20 mA正向注入电流下空穴很难输运过蓝光和绿光量子阱间的垒层,这是混合量子阱有源区获得双波长发光的主要障碍.通过掺入一定量的In来降低蓝光和绿光量子阱之间的垒层的势垒高度,增加注入到离p-GaN层较远的绿光有源区的空穴浓度,从而改变蓝光和绿光发光峰的强度比.研究了蓝光和绿光量子阱间垒层In组分对双波长LED的发光性质的影响.此外,研究了双波长LED发光特性随注入电流的变化.     

Color rendering and luminous efficacy of trichromatic and tetrachromatic LED-based white LEDs

White light-emitting diode (LED) spectra for general lighting should be designed for high luminous efficacy as well as good color rendering, which are generally in a trade-off relationship. White LEDs have uncountable metameres, they have different luminous efficacy and color rendering. Appropriate designed trichromatic and tetrachromatic LED-based white LEDs are presented that have acceptable color rendering as well as good luminous efficacy. Triachromatic white LEDs, with a wavelength combination of 460, 540, and 615 nm, offer high general color rendering index exceeding 89, and luminous efficacy 336 lm/W. The general color rendering index of tetrachromatic LED-based white LEDs combined from 460, 525, 590, and 640 nm is 95, the luminous efficacy is 306 lm/W. Further analysis shows the changing trends of the luminous efficacy, color rendering and the chromaticity coordinate of the optimized trichromatic and tetrachromatic white LEDs depending on the wavelength shift of the primary LEDs. For the optimized trichromatic white LEDs, both the luminous efficacy and color rendering change more with the wavelength shifts of the primary red LEDs than with the wavelength shifts of the blue and green LEDs. For the optimized tetrachromatic white LEDs, the changes of the luminous efficacy caused by the wavelength shifts of one red LED are smaller than the changes of trichromatic white LEDs. And the wavelength shifts of the red primary LED that have shorter wavelength affect the color rendering more than the other primary LEDs. The wavelength shifts of the blue primary LED change the chromaticity coordinate of the white LEDs more. The small changes of the chromaticity coordinate of the white LED do not mean small changes of the k and R_a.     

Highly Efficient Green Zn?Ag?In?S/Zn?In?S/ZnS QDs by a Strong Exothermic Reaction for Down‐Converted Green and Tripackage White LEDs

Highly efficient bright green‐emitting Zn? Ag? In? S (ZAIS)/Zn? In? S (ZIS)/ZnS alloy core/inner‐shell/shell quantum dots (QDs) are synthesized using a multistep hot injection method with a highly concentrated zinc acetate dihydrate precursor. ZAIS/ZIS/ZnS QD growth is realized via five sequential steps: a core growth process, a two‐step alloying–shelling process, and a two‐step shelling process. To enhance the photoluminescence quantum yield (PLQY), a ZIS inner‐shell is synthesized and added with a band gap located between the ZAIS alloy‐core and ZnS shell using a strong exothermic reaction. The synthesized ZAIS/ZIS/ZnS QDs shows a high PLQY of 87% with peak wavelength of 501 nm. Tripackage white down‐converted light‐emitting diodes (DC‐LEDs) are realized using an InGaN blue (B) LED, a green (G) ZAIS/ZIS/ZS QD‐based DC‐LED, and a red (R) Zn? Cu? In? S/ZnS QD‐based DC‐LED with correlated color temperature from 2700 to 10 000 K. The red, green, and blue tripackage white DC‐LEDs exhibit high luminous efficacy of 72 lm W^?1 and excellent color qualities (color rendering index (CRI, R _a) = 95 and the special CRI for red (R ₉) = 93) at 2700 K.     

Highly Efficient Green ZnAgInS/ZnInS/ZnS QDs by a Strong Exothermic Reaction for Down‐Converted Green and Tripackage White LEDs

Highly efficient bright green‐emitting Zn?Ag?In?S (ZAIS)/Zn?In?S (ZIS)/ZnS alloy core/inner‐shell/shell quantum dots (QDs) are synthesized using a multistep hot injection method with a highly concentrated zinc acetate dihydrate precursor. ZAIS/ZIS/ZnS QD growth is realized via five sequential steps: a core growth process, a two‐step alloying–shelling process, and a two‐step shelling process. To enhance the photoluminescence quantum yield (PLQY), a ZIS inner‐shell is synthesized and added with a band gap located between the ZAIS alloy‐core and ZnS shell using a strong exothermic reaction. The synthesized ZAIS/ZIS/ZnS QDs shows a high PLQY of 87% with peak wavelength of 501 nm. Tripackage white down‐converted light‐emitting diodes (DC‐LEDs) are realized using an InGaN blue (B) LED, a green (G) ZAIS/ZIS/ZS QD‐based DC‐LED, and a red (R) Zn?Cu?In?S/ZnS QD‐based DC‐LED with correlated color temperature from 2700 to 10 000 K. The red, green, and blue tripackage white DC‐LEDs exhibit high luminous efficacy of 72 lm W^?1 and excellent color qualities (color rendering index (CRI, R_a) = 95 and the special CRI for red (R₉) = 93) at 2700 K.     

GaN基白光LED温度特性实验研究

实验研究了恒流驱动条件下,GaN基白光LED的正向电压、发光光谱和发光效率随环境温度的变化情况.结果表明,在输入电流恒定的情况下,随着温度的升高,结电压和发光强度与温度具有良好的线性关系,并且GaN基白光LED的发光颜色总是向蓝光漂移,而小电流驱动时比大电流驱动时蓝光漂移更明显.根据实验结果,分析了器件的最佳额定工作电流.

Abstract：

Under a constant driving current, the changes of the forward voltage, emission spectrum and luminous efficiency of GaN-based White LEDs with the ambient temperature are studied experimentally. It is found that the forward voltage and the luminous intensity depend on the temperature linearly with constant injection current, and luminous colors of GaN-based White LEDs always shift towards blue. And the blue shift with low driving current is more obvious than that with high driving current. According to the results, the best rated operating current of GaN-based white LEDs is discussed.     

High performance Ga N-based hybrid white micro-LEDs integrated with quantum-dots

Hybrid white micro-pillar structure light emitting diodes(LEDs)have been manufacture utilizing blue micro-LEDs arrays integrated with 580 nm CIS((CuInS2-ZnS)/ZnS)core/shell quantum dots.The fabricated hybrid white micro-LEDs have good electrical properties,which are manifested in relatively low turn-on voltage and reverse leakage current.High-quality hybrid white light emission has been demonstrated by the hybrid white micro-LEDs after a systemic optimization,in which the corresponding color coordinates are calculated to be(0.3303,0.3501)and the calculated color temperature is 5596 K.This result indicates an effective way to achieve high-performance white LEDs and shows great promise in a large range of applications in the future including micro-displays,bioinstrumentation and visible light communication.     

White-light emission from near UV InGaN-GaN LED chip precoated with blue/green/red phosphors

Phosphor-converted light-emitting diodes (LEDs) were fabricated by precoating blue/green/red phosphors onto near ultraviolate (n-UV) LED chips prior to package into LED lamps. With a 20-mA injection current, it was found that the color temperature T/sub c/ was around 5900 K and the color-rendering index R/sub a/ was around 75 for the "n-UV+blue/green/red" white LED lamps. It was also found that no changes in color temperature T/sub c/ and color-rendering index R/sub a/ could be observed when we increased the injection from 20 to 60 mA. These results indicate that such "n-UV+blue/green/red" white LEDs are much more optically stable than the conventional "blue+yellow" LEDs.     

多基色白光LED的配色研究

利用基色光混色的方法对三基色和四基色白光LED进行了配色研究。固定相关色温为(5 500±20)K的条件下,在可见光范围内将不同峰值波长、半宽的基色光进行混色,得到显色指数和光视效能与峰值波长和半宽的关系。其中,三、四基色白光LED的显色指数最高分别达到89和96.7,对应的光视效能分别为353lm/W和340lm/W。同时,计算结果表明,增加基色光的数目后,提高了白光LED的显色性及显色稳定性。