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.     

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.     

LED lighting efficacy: Status and directions

A monumental shift from conventional lighting technologies (incandescent, fluorescent, high intensity discharge) to LED lighting is currently transpiring. The primary driver for this shift has been energy efficiency and associated cost savings. LED lighting is now more efficacious than any of the conventional lighting technologies with room to still improve. Near term, phosphor-converted LED packages have the potential for efficacy improvement between 160 lm/W (now) to 255 lm/W. Longer term, color-mixed LED packages have the potential for efficacy levels conceivably as high as 330 lm/W, though reaching these performance levels requires breakthroughs in green and amber LED efficiency. LED package efficacy sets the upper limit to luminaire efficacy, with the luminaire containing its own efficacy loss channels. In this paper, based on analyses performed through the U.S. Department of Energy Solid State Lighting Program, various LED and luminaire loss channels are elucidated, and critical areas for improvement identified. Beyond massive energy savings, LED technology enables a host of new applications and added value not possible or economical with previous lighting technologies. These include connected lighting, lighting tailored for human physiological responses, horticultural lighting, and ecologically conscious lighting. None of these new applications would be viable if not for the high efficacies that have been achieved, and are themselves just the beginning of what LED lighting can do.     

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.     

Research challenges to ultra‐efficient inorganic solid‐state lighting

Solid‐state lighting is a rapidly evolving, emerging technology whose efficiency of conversion of electricity to visible white light is likely to approach 50% within the next several years. This efficiency is significantly higher than that of traditional lighting technologies, giving solid‐state lighting the potential to enable significant reduction in the rate of world energy consumption. Further, there is no fundamental physical reason why efficiencies well beyond 50% could not be achieved, which could enable even more significant reduction in world energy usage. In this article, we discuss in some detail: (a) the several approaches to inorganic solid‐state lighting that could conceivably achieve “ultra‐high,” 70% or greater, efficiency, and (b) the significant research questions and challenges that would need to be addressed if one or more of these approaches were to be realized.     

一种高效稳定的光伏LED照明系统设计

为提高光伏照明系统中太阳能电池的光能利用率,对太阳能电池输出进行最大功率跟踪。设计以最大功率跟踪芯片SM72442为核心的太阳能充电控制电路,采用光伏全桥驱动芯片SM72295驱动MOS管,构成同步Buck电路,实现太阳能输出最大功率跟踪;利用LED驱动芯片XL6005设计LED驱动电路。测试数据表明,太阳能光伏电池的充电效率平均达到87.92%,LED驱动电路效率最高为91.6%。系统工作稳定,能满足特定场合下的照明需求。     

LED智能光源混光呈色模型构建方法研究

LED智能光源具有色光可调的特点,其内置微处理系统可以通过无线数据传输等技术调整发光方式,控制光色及发光强度,进而实现照明光源的动态调节,因此特别适合于博物馆展陈、家居照明等智能化照明设计环节。现阶段,鉴于LED光源智能混光技术尚未普及,目前绝大多数商用LED智能光源在混光控制方面仅局限于设备制造商所设定的几类固定模式,无法充分发挥智能LED光源色光可调的技术优势。针对此问题,提出了一种基于BP神经网络以及有效集算法的LED智能光源混光呈色模型构建方法,实现了LED智能光源控制信号与对应发光光谱辐亮度分布之间的双向高精度映射。研究中首先提出了一种基于BP神经网络的LED混光呈色预测方法,实现了由LED智能光源驱动控制值向光源实际发光光谱辐亮度分布的准确预测;在此基础上运用有效集算法实现了由光源实际发光光谱辐亮度分布向LED智能光源驱动控制值的反向高精度预测。实验结果显示,所提出的方法整体建模误差显著小于人眼视觉可分辨阈值(CIEUCS Duv值可低至0.002 7),达到了较为理想的建模效果。该方法的提出,将为当前LED智能光源制造以及现有商用LED智能光源的二次开发与优化提供有效的理论与方法支撑。     

彩色变焦照明系统设计

针对基于RGB混色技术在小角度、近距离空间内较难实现彩色LED,且有关彩色变焦照明相关文献也较少的问题,设计了一款彩色变焦照明系统。系统主要由LED光源、TIR透镜、微结构透镜组成,可在650mm处实现良好混色照明,变焦范围为4.2°~9.1°(半光强角),且变焦照明过程中,在光强下降为20%的角度内能量利用率达85%以上,半光强角内的能量利用率始终在75%以上,满足设计要求。     

Design, Synthesis and pH Sensing Properties of Novel PAMAM Light-Harvesting Dendrons Based on Rhodamine 6G and 1,8-naphthalimide

Herein we report on the design, divergent synthesis and photophysical behavior of novel PAMAM light-harvesting dendrons from first and second generation. The surface of novel compounds is labeled with 4-alkylamino-1,8-naphthalimide yellow-green emitting “donor” fluorophores capable of absorbing light and efficiently transferring the energy to a single rhodamine “acceptor” dye. Due to the pH dependent rhodamine absorption the novel systems show “off-on” switching energy transfer mechanism from alkaline to acid media. The results obtained illustrate the high potential of the synthesized wavelength-shifting fluorophores as efficient pH chemosensing materials.     

中国半导体照明发展综述

半导体照明是21世纪初兴起的产业,也是我国第三代半导体材料成功产业化的第一个突破口,技术发展日新月异,是国际高科技领域竞争的焦点之一。目前,我国半导体照明产业已经形成了完整的产业链,功率白光LED、硅基LED和全光谱LED等核心技术同步国际,紫外LED、可见光通讯、农业光照和光医疗等创新应用走在世界前列。介绍了我国在半导体照明方面的研究进展,回顾了相关产业的发展情况,并对未来进行了展望。     

Excitonics of semiconductor quantum dots and wires for lighting and displays

In the past two decades, semiconductor quantum dots and wires have developed into new, promising classes of materials for next‐generation lighting and display systems due to their superior optical properties. In particular, exciton–exciton interactions through nonradiative energy transfer in hybrid systems of these quantum‐confined structures have enabled exciting possibilities in light generation. This review focuses on the excitonics of such quantum dot and wire emitters, particularly transfer of the excitons in the complex media of the quantum dots and wires. Mastering excitonic interactions in low‐dimensional systems is essential for the development of better light sources, e.g., high‐efficiency, high‐quality white‐light generation; wide‐range color tuning; and high‐purity color generation. In addition, introducing plasmon coupling provides the ability to amplify emission in specially designed exciton–plasmon nanostructures and also to exceed the Förster limit in excitonic interactions. In this respect, new routes to control excitonic pathways are reviewed in this paper. The review further discusses research opportunities and challenges in the quantum dot and wire excitonics with a future outlook.     

Efficient nanocoax‐based solar cells

The power conversion efficiency of most thin film solar cells is compromised by competing optical and electronic constraints, wherein a cell must be thick enough to collect light yet thin enough to efficiently extract current. Here, we introduce a nanoscale solar architecture inspired by a well‐known radio technology concept, the coaxial cable, that naturally resolves this “thick–thin” conundrum. Optically thick and elec‐ tronically thin amorphous silicon “nanocoax” cells are in the range of 8% efficiency, higher than any nanostructured thin film solar cell to date. Moreover, the thin nature of the cells reduces the Staebler–Wronski light‐induced degradation effect, a major problem with conventional solar cells of this type. This nanocoax represents a new platform for low cost, high efficiency solar power. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Towards hybrid circuit quantum electrodynamics with quantum dots

Cavity quantum electrodynamics allows one to study the interaction between light and matter at the most elementary level. The methods developed in this field have taught us how to probe and manipulate individual quantum systems like atoms and superconducting quantum bits with an exquisite accuracy. There is now a strong effort to extend further these methods to other quantum systems, and in particular hybrid quantum dot circuits. This could turn out to be instrumental for a noninvasive study of quantum dot circuits and a realization of scalable spin quantum bit architectures. It could also provide an interesting platform for quantum simulation of simple fermion–boson condensed matter systems. In this short review, we discuss the experimental state of the art for hybrid circuit quantum electrodynamics with quantum dots, and we present a simple theoretical modeling of experiments.     

Effectiveness of full spectrum light soaking on solar cell degradation analysis

This study examined the effect of UV-spectrum light soaking on solar cell degradation tests. An indoor light soaking test was evaluated over three different spectral ranges: “UV only”, “UV blocked” and “Full spectrum”. a-Si:H and poly-crystalline silicon solar cell technologies were studied by light soaking tests with the same optical filter configurations.The I–V measurement results demonstrated that “UV only” irradiated solar cells exhibited the smallest output power degradation, which was only half of a percent variation compared with the full spectrum light soaking case. Using a filter that excluded the effect of the UV spectral range on light soaking, the “UV blocked” case also exhibited a significant output power degradation of the solar cells. A comparative analysis of the solar cell response, based on the I–V characteristics and the diode ideality factor under these different light soaking spectra, demonstrated the importance of the full spectrum light soaking test in the evaluation of the long-term performance of solar cells.     

用于投影机的发光二极管照明单元

目前的投影机光源——高压汞灯存在寿命短、色温高、存在有害光线、发热集中等缺点,严重制约了投影机进入家庭应用领域。发光二极管的最近发展为其作为高压汞灯的替代光源提供了可能性。提出了一种由一个发光二极管、一个准直镜、一个前蝇眼透镜和一个后蝇眼透镜组成的用于投影机的发光二极管照明单元,由数个照明单元加上会聚透镜则构成一个基本的照明系统。发光二极管的发光经准直镜压缩光束发散角后被前蝇眼透镜分割为多个细光束,会聚透镜将每个细光束都叠加会聚到显示芯片上,实现光能量的会聚和光场再分布．以满足投影机对光通量和光场均匀性等方面的要求,后蝇眼透镜用于与后续光路的匹配。作为照明单元的一个应用实例,文中分析了一种单片式硅上液晶投影机。     

基于ZigBee与WiFi的无线智能照明系统设计

为了提高照明系统的使用效率,减少电能的浪费。设计了一种以TI公司的CC2530芯片与Ralink公司RT5350芯片为核心的,结合了ZigBee与WiFi技术的无线智能照明系统。该系统在控制终端与各照明节点之间构建混合型无线通信网络,并实现了将ZigBee网络与UPnP标准相结合。控制终端可实时监测各照明节点的状态,同时可发送控制命令到各终端节点。分析了系统的工作原理、硬件架构、软件设计。实验结果表明,该系统能够可靠的完成信息的采集与发送,误包率在50m 范围内可控制在4.0%以内,系统具有误包率低,稳定可靠,成本低等优点,实现了照明系统的网络化管理。     

基于LED照明与弱光收集的节能车灯双向二次配光设计

为进一步利用太阳能,提出了“双向”利用光线的LED车灯设计新理念。运用光路可逆原理与边缘光线原理,构造矩形复合抛物面,对LED车灯进行“双向”二次配光设计。计算了远光灯矩形复合抛物面反光杯所需的最大出光半角、理论长度,借助tracepro软件,模拟研究了该矩形复合抛物面结构的最高光通量、平均光通量、光通量利用率随长度的变化关系,进一步截取较理论长度综合光学性能更好的反光器应用长度L=130 mm,并在此长度下,模拟了该LED远光灯照度分布情况与弱光收集情况。该类型车灯的LED照明与弱光收集互为补充,双向提高了LED车灯空间重复利用率。在照明方面,该灯能够满足现行标准GB25991-2010的要求,相同照度下,照明范围更大;相同照明范围内,照度更高;在弱光收集方面,是对当前太阳能汽车非聚光模式收集太阳能的补充。     

基于天空模型的公共场所照明智能控制

公共场所照明具有全天候、多应用、能耗大的特点。掌握任意时间的天空亮度分布情况是充分利用自然光、实现智能照明的基础。基于国际照明委员会（CIE）给出的天空亮度计算公式,建立自然光对公共照明区域产生的天空照度模型。引入数学和光学相关原理建立公共场所人造光和自然光的混合模型。利用改进蚁群算法求解模型,得出最佳的灯具亮度组合,实现舒适和及节能的综合最优。最后,选择典型的大跨度带天窗建筑物为采光对象,用实验仿真验证策略的有效性。     

Maxwell: A new vision of the world

The paper outlines the crucial contributions of James Clerk Maxwell to Physics and more generally to our vision of the world. He achieved 150 years ago a synthesis of the pioneering works in magnetostatics, electrostatics, induction and, by introducing the notion of displacement current, gave birth to Electromagnetics. Then, he deduced the existence of electromagnetic waves and identified light as one of them.Maxwell equations deeply changed a Newtonian conception of the world based on particle interactions by pointing out the vital role of waves in physics. This new conception had a strong influence on the development of quantum physics. Finally, the invariance of light velocity in Galilean frames led to Lorentz transformations, a key step toward the theory of relativity.     

飞机夜视兼容照明技术

飞机夜视兼容照明技术作为保证飞机上微光夜视仪正常使用的军用光电子高新技术,其在现代高新技术局部战争和夜间战争中具有重要的作用和地位。在对国内外微光像增强器技术的发展现状、关键技术和主要发展趋势简要介绍的基础上,详细分析了普通光源对微光夜视仪的干扰,说明飞机夜视兼容照明技术存在的重要性,介绍了飞机夜视兼容照明技术的主要实现手段、测试方法及国内外发展现状。结合我国目前技术水平的现状,指出国内飞机夜视兼容照明技术的发展方向和重要的关键技术。