中性色温下两基色、三基色荧光粉转换白光LED的光谱优化

针对中性色温4 870 K,考虑斯托克斯损失,研究了两基色、三基色的白光LED的光谱优化。结果表明:InGaN/GaN基蓝光LED激发YAG荧光粉合成的白光光视效能可高达483.5 lm/W,但显色性较差,计算的斯托克斯效率为83.9%。加入窄带红色荧光粉或红光LED,优化后的光视效能降低为343 lm/W,但显色指数升至94.7,同时计算得到该LED的斯托克斯效率为84.4%。对该优化的三基色LED光谱进行可调色温白光的特性分析,发现较高色温 (＞4 000 K)对应的显色指数普遍高于低色温(＜4 000 K)的显色指数。     

LED lighting,ultra-low-power lighting schemes for new lighting applications

In 2018, Solid-State Lighting (SSL) can totally outperform, if properly designed, most of other lighting products used for general lighting applications. This concerns various attributes such as luminous efficacy, life, spectral qualities, dimming potential, and more and more total cost of ownership. SSL can also mimic a large variety of reference light sources from candlelight to sunlight. The absence of international standards concerning LED modules remains the major difficulty for luminaire manufacturers and their clients, since perfectly matching replacement of ever-changing LED modules is not guaranteed over time. But extraordinarily innovative lighting schemes can be developed, bridging the gap between the world of entertainment and the world of general lighting, and leading to new lighting schemes with more powerful emotional content. LED sources, mostly DC driven, also can benefit from progress in photovoltaics and batteries, as well as wireless control to offer integrated solutions. This could radically change the operation of lighting in the next 10 years.     

结温与热阻制约大功率LED发展

LED结温高低直接影响到LED出光效率、器件寿命、可靠性、发射波长等。保持LED结温往允许的范围内,是大功率LED芯片制备、器件封装和器件应用等每个环节都必须重点研究的关键因素,尤其是LED器件封装和器件应用设计必须着重解决的核心问题。首先介绍pn结结温对LED器什性能的影响,接着分析大功率LED结温与器件热阻的关系．基于对器件热阻的分析,得出了结温与热阻已经制约大功率LED进一步向更大功率发展的结论,并提出了如下两个观点：1．要在保持低成本和自然散热方式下提高LED器件的功率,根本的出路是提高光转换效率;2．在日前没有提高光转换效率的情况下,发展超过5W的大功率器件对工程应肘没有实质意义。     

LED柔性照明及显示用超弹性柔性荧光膜

柔性LED是近年来照明及显示领域研究的热点之一.本文提出了一种新的基于有机硅胶(PDMS)制备的兼具超弹性和柔性的荧光薄膜,它不仅在-50~230℃这一较宽的温度范围内展现了良好的热稳定性,还保持了原料荧光粉的光学性能.所制备的透明PDMS基质膜和相应的荧光膜具有完全的柔性和超弹性,其最大伸长率分别高达400%与275%.此外,采用所制掺YAG荧光膜和普通商用1 W蓝光芯片简单封装的白光LED灯珠满足日常白光照明的应用要求,呈现出约6925 K的平均色温,约71的平均显色指数,115.7 lm/W左右的平均发光效率.最后,基于所提出荧光膜成膜工艺而制备的三色3×3柔性阵列显示,可以轻易被拉伸、卷曲和折叠,显示了它在柔性照明及显示器件方面具有应用价值和潜力.     

Warm-white light-emitting diode with yellowish orange SiALON ceramic phosphor

A warm-white light-emitting diode (LED) without blending of different kinds of phosphors is demonstrated. An approach that consists of a blue LED chip and a wavelength-conversion phosphor is carried out. The phosphor is a newly developed yellowish orange CaEuSiAlON ceramic phosphor with high efficiency. The CIE1931 chromaticity coordinates (x, y) are (0.458, 0.414), the color temperature is 2750 K, and the luminous efficacy of this LED is 25.9 lm/W at room temperature and with a forward-bias current of 20 mA. The chromaticity of the assembled LED is more thermally stable than that of a LED with a conventional oxide phosphor (YAG:Ce) because of the better thermal stability of the oxynitride phosphor.     

Warm-white light-emitting diodes integrated with colloidal quantum dots for high luminous efficacy and color rendering

Warm-white LEDs (WLEDs) with high spectral quality and efficiency are required for lighting applications, but current experimental performances are limited. We report on nanocrystal quantum dot (NQD) hybridized WLEDs with high performance that exhibit a high luminous efficacy of optical radiation exceeding 350lm/W(opt) and a high color rendering index close to 90 at a low correlated color temperature <3000K. These spectrally engineered WLEDs are obtained using a combination of CdSe/ZnS core/shell NQD nanophosphors integrated on blue InGaN/GaN LEDs.     

Invention,development, and status of the blue light-emitting diode,the enabler of solid-state lighting

The realization of the first high-brightness blue-light-emitting diodes (LEDs) in 1993 sparked a more than twenty-year period of intensive research to improve their efficiency. Solutions to critical challenges related to material quality, light extraction, and internal quantum efficiency have now enabled highly efficient blue LEDs that are used to generate white light in solid-state lighting systems that surpass the efficiency of conventional incandescent lighting by 15–20×. Here we discuss the initial invention of blue LEDs, historical developments that led to their current state-of-the-art performance, and potential future directions for blue LEDs and solid-state lighting.     

光无线技术及其应用

通信领域对带宽越来越大的需求正推动着传统无线通信技术的发展。虽然光通信系统和光网络能为人们提供极大的带宽,但这也意味着必须能开发出来新的设备和系统。半导体发光二极管(LED)被认为是未来在建筑、汽车和飞行器上的主要光源。相比于白光光源和荧光光源,LED能提供更高的能量效率,且由于其出色的节能性能,LED在目前全球性的二氧化碳减排行动中也扮演着重要的角色。另外,激光器目前也处在于LED类似的情形中。这些核心器件的出现很可能会大大改变我们对光的使用,不仅是在照明方面,还包括通信、传感、导航、定位、监控和成像等各个方面。     

Historical perspective on the physics of artificial lighting

We describe the evolution of lighting technologies used throughout the ages, and how the need for improvements was such that any new technology giving better and cheaper lighting was immediately implemented. Thus, every revolution in energy sources – gas, petrol electricity – was first put to large-scale use in lighting. We describe in some detail several “ancient” techniques of scientific interest, along with their physical limitations. Electroluminescence – the phenomenon by which LEDs directly convert electricity into light – was long thought to only be of use for indicators or flat panel displays supposed to replace the bulky cathode-ray tubes. The more recent uses of LEDs were mainly for street traffic lights, car indicators, small phone displays, followed by backlighting of TV screens. LED lamps for general lighting only emerged recently as the dominant application of LEDs thanks to dramatic decrease in cost, and continuous improvements of color quality and energy conversion efficiency.     

白光LED面阵及其主要参数指标

本文主要利用白光LED单管制备了白光LED面阵,将制备的白光LED面阵与日亚公司的同类产品进行了对比。研究了不同电流条件下,亮度、流明效率、色坐标和显色指数的变化。     

LED advances accelerate universal access to electric lighting

A rapid increase in the performance and quality of white LED light sources has changed the dynamics of electricity access in the last 10 years, reaching tens of millions of people with electric light who previously had no viable alternatives to fuel-based lighting, which is dangerous and expensive. Eliminating fuel-based lighting is a key public health, safety, social equality, and environmental opportunity that is now achievable. Technology advances in LEDs, other super-efficient appliances, solar photovoltaic generation, advanced batteries, and coordinating information technology systems have combined to significantly expand the reach of off-grid energy systems. With support and effort, it is plausible that small “pico-solar” and “solar home” systems could serve over a billion people within a generation, providing basic but highly valued services. Continued progress can be achieved with attention to continued improvements in technology, supporting a growing range of new businesses and enterprises in energy access markets, and synergy with broader human development effort around access to clean water, financial inclusion, and fair access to resources.     

An optimum design and fabrication of lens on luminous uniformity and light extraction of high-power light-emitting diode

The effect of lens inner structure on radiation pattern and light extraction efficiency of light-emitting diode (LED) and the application to artificial light in compact greenhouse is demonstrated. A commercial software package of Trace Pro and one-factor at-a-time (OFAT) method are used to simulate the lens with different inner structure. The optimum parameters of lens inner structure design for the maximum light extraction efficiency and the best uniform luminous are described by the corner radius of curvature, lens width, and lens height, respectively. For a real single LED module, base on the optimum parameters of lens inner structure, the corresponding best luminous uniformity is 62% and corresponding output extraction is 14.11 lm. The maximum uniformity of illumination for LED matrix assembled by LED modules with optimum lens is 88% and corresponding light extraction 1141 lm. In comparison with a commercial artificial light of LED matrix used in agriculture, the high-power LED module with proposed lens inner structure exhibit good improvement in uniformity of illumination and light extraction. This study may provide a practical guideline for design and fabrication of a high-performance lens used in various compact agricultural applications.     

白光LED极限流明效率的计算

对蓝光芯片加黄色荧光粉制备白光LED方法的流明效率进行了理论计算。根据光度学原理,我们考虑到视觉函数V(λ)的修正,以色坐标为x=0.325,y=0.332,显色指数为81.5,色温为5 914 K的白光LED发光光谱为依据,计算了白光LED流明效率的理论极限:得出每瓦白光LED辐射光功率产生的光通量为298.7 lm,白光LED发射的总光子数为2.7×10¹⁸。在理想情况下,注入一个电子-孔穴对产生一个蓝光光子,设荧光粉的量子效率为1,因此,注入的电子-孔穴对数亦等于白光光子数,进而计算出白光LED每辐射1 W的光功率所需的电功率为1.51 W,上述白光LED发光光谱对应的白光LED的电-光转换的理论极限流明效率为197.8 lm/W。     

双层荧光粉涂覆对COB封装LED出光的影响

为了提高LED出光量，基于传统的荧光粉涂覆设计了一种双层荧光粉涂覆结构。通过对上下涂覆层浓度及上层涂覆量的研究，探究双层涂覆结构对COB封装LED出光的影响。结果表明在通电电流为440 mA时，可在实验中实现15 W的COB封装结构的白光LED:涂覆单一黄色荧光粉，上下层胶粉比为14.2～28且上层涂覆体积为下层的0.8倍时，COB封装LED的光通量为2 179 lm，光效可达145.3 lm/W，显指为63，出光量最大提升为7.82%；荧光粉调整为黄绿粉和红粉的配合使用后，最终实现色温、光效及显指分别为4 854 K、129.7 lm/W和81.2。因此，双层荧光粉涂覆结构可以提高COB封装LED的光学性能，对实际生产有一定的应用价值。     

A new‐generation color converter for high‐power white LED: transparent Ce3+:YAG phosphor‐in‐glass

Currently, the major commercial white light‐emitting diode (WLED) is the phosphor‐converted LED made of the InGaN blue‐emitting chip and the Ce³⁺:Y₃Al₅O₁₂ (Ce:YAG) yellow phosphor dispersed in organic epoxy resin or silicone. However, the organic binder in high‐power WLED may age easily and turn yellow due to the accumulated heat emitted from the chip, which adversely affects the WLED properties such as luminous efficacy and color coordination, and therefore reduces its long‐term reliability as well as lifetime. Herein, an innovative luminescent material: transparent Ce:YAG phosphor‐in‐glass (PiG) inorganic color converter, is developed to replace the conventional resin/silicone‐based phosphor converter for the construction of high‐power WLED. The PiG‐based WLED exhibits not only excellent heat‐resistance and humidity‐resistance characteristics, but also superior optical performances with a luminous efficacy of 124 lm/W, a correlated color temperature of 6674 K and a color rendering index of 70. This easy fabrication, low‐cost and long‐lifetime WLED is expected to be a new‐generation indoor/outdoor high‐power lighting source.     

微通道反应器合成高质量的无机钙钛矿量子点及其LED应用

提出一种快速、高效合成高质量无机钙钛矿量子点（CsPbBr₃）的微通道反应器,通过调节前驱体的浓度和流速,可实现荧光光谱绿色至蓝色的转变,波长范围为515~464 nm。利用合成的绿色CsPbBr₃量子点和红色荧光粉制备薄膜,覆盖在蓝色LED芯片表面上,在20 mA的驱动电流下获得流明效率最高可达62.93 lm/W的白光。这种高效的白光LED展示出钙钛矿量子点在低成本显示、照明和光通信等应用领域中巨大的潜力。     

Design of optocoupler for synthesizing four color spectra

LEDs with the advantage of high luminous efficacy and long life time show the potential of replacing traditional luminaire. Most commercial white LED light sources use blue or ultraviolet chip coated with emitting phosphor, but the sensitivity and instability of such phosphors has become a big issue. The typical RGB-LED by using individual chips has the problem of spatial separation and insufficient spectral overlap which leads to low CRI. This study suggests a novel and high-efficiency design of fiber optical optocoupler to synthesize four colors emitted by separate LEDs to provide the ideal light sources by adjusting the individual LEDs separately. By choosing different colored light to be synthesized, this optocoupler can be used as light sources which can be highly controlled to offer the best lighting conditions. Compared with other widely used commercial LED sources, this new design of light sources can be used in special experiments which require multi-spectral light.     

Silica encapsulated ZnO quantum dot-phosphor nanocomposites:Sol-gel preparation and white light-emitting device application

ZnO quantum dots(QDs) as an eco-friendly and low-cost material has bright fluorescence, which makes it promising material for healthy lighting and displaying. However, the low fluorescence efficiency and poor stability of ZnO QDs impede their applications in lighting application. In this work, silica encapsulated ZnO QD-phosphors nanocomposites(ZSPN) have been prepared through a sol-gel synthesis process, where yellow-emitting ZnO QDs and blue-emitting BaMgAl_(10) O_(17):Eu~(2+) are employed as the luminescence cores and silica as link between two luminescence materials. Tunable photoluminescence of ZSPN and the white light emission have been achieved through changing mass ratio of both of ZnO QDs and commercial phosphors. The PLQY of the ZSPN can reach 63.7% and they can maintain high luminous intensity even the ambient temperature up to 110?C and after 35 h of UV irradiation. In addition, they can keep stable for 40 days. By coating the ZSPN phosphors onto a ultraviolet chip, WLEDs with luminous efficiency of 73.6 lm/W and the color coordinate, correlated color temperature, and color rendering index can reach(0.32, 0.34), 5580 K, and 87, respectively,indicating the bright prospect of the ZSPN phosphors used in healthy lighting.     

MOCVD生长InGaN/GaN MQW紫光LED

利用LP－MOCVD系统生长了InGaN/GaN MQW紫光LED外延片，双晶X射线衍射测试获得了2级卫星峰，室温光致发光谱的峰值波长为399.5nm，FWHM为15.5nm，波长均匀性良好。制成的LED管芯，正向电流20mA时，工作电压在4V以下。     

用于CF-LCoS投影偏置LED照明光棒的角度分割原理及其偏振复用系统

研究了LED相对光棒中心位置存在偏置时光棒对LED的角度分割与虚像形成原理,籍此计算了不同偏置以及不同尺寸LED的光棒尺寸,再将计算所得的光棒与前端成像透镜、中间像面偏振复用系统、后端积分透镜及偏振分束器等进行综合优化设计,然后根据所得中间像确定不同情况下的偏振复用系统具体结构,确保LED发散角范围内光能的偏振复用,并实现对滤色片式硅基液晶芯片的均匀照明.最后设计了一款以白光LED为光源的滤色片式硅基液晶芯片微型投影光引擎,在1W LED功耗下实现12.8lm投射亮度(114lm/W),均匀性达93%.对比没有应用偏振光复用的微型投影光引擎,在保证均匀性的前提下,提升了微型投影系统的光效率,丰富了光棒偏振复用的内容.