Power LED technology will likely become the technology of choice for solid state lighting (SSL) applications. The technology is progressing rapidly, but there are still areas that must be improved before SSL substantially replaces conventional lighting technology. These include cost, efficiency, and uniformity of the emission spectrum. Associated technologies especially electronic drivers also need to be improved. It is now clear that SSL will dominate virtually all lighting applications, and the transition is in progress, but the timing for substantial market penetration is less certain.

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Many studies have documented the success of light therapy in treating disorders of the human internal clock (circadian rhythm). Recent biological research has shown the importance of developing light sources that are tunable in the blue region of the spectrum for treatment to be safe and effective. A novel tunable broadband solid-state light source is presented here that mimics the diurnal variation in sunlight by modulating the intensity of blue light emission.

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This paper reviews physical pictures of phosphor materials, which can meet requirements of diversified white-LED applications in the next stage. Suppression of thermal quenching and suitable band width of luminescence are the main concern. Basically tight space around an emitting ion and rigid chemical bonding can improve thermal quenching and narrow the band width. There are, however, other factors such as delocalization of an excited state leading to nanradiative processes. Preferable properties are discussed with reference to examples, e.g. La₂O₂S:Eu³⁺, Y₃Al₅O₁₂:Ce³⁺ and CaAlSiN₃:Eu²⁺, which show a difference in quenching temperature and β-SiAlON:Eu²⁺, which has a narrow band width.

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Organic Light Emitting Diode (OLED) is one of the strongest candidates for the next generation solid state lighting alternative to conventional incandescent bulbs and fluorescent lamps. There are still a lot of issues to overcome in order to commercialize OLED lighting, but a number of elemental technologies indispensable for OLED lighting such as high efficiency, long lifetime at high luminance and large area uniform emission have been developed.

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We demonstrated AlGaN multi-quantum well (MQW) deep ultraviolet (UV) light-emitting diodes (LEDs) with wavelength in the range of 227-261 nm fabricated on high-quality AlN buffers on sapphire substrates. We achieved crack-free, thick AlN buffer on sapphire with low threading dislocation density (TDD) and atomically flat surface by introducing an ammonia (NH₃) pulse-flow multi-layer (ML) growth method through metal-organic chemical vapor deposition (MOCVD). The edge- and screw-type dislocation densities of AlGaN layer on AlN buffer were reduced to 7.5×10⁸ and 3.8×10⁷ cm^-2, respectively, by using a ML-AlN buffer. We achieved single-peaked high-brightness operations of AlGaN deep-UV LEDs by fabricating them on the ML-AlN buffers on sapphire substrates. The maximum output power and external quantum efficiency (EQE) of the 261 nm and 227.5 nm LEDs were 1.65 mW and 0.23% under room-temperature (RT) CW operation, and 0.15 mW and 0.2%, under RT pulsed operation, respectively.

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High output power 340 nm-band InAlGaN-based multi-quantum-well (MQW) ultraviolet (UV) light-emitting diodes (LEDs) were achieved by using p-type InAlGaN layers. The output power of a UV-LED with p-type InAlGaN layers was approximately 4.7 times larger than that achieved with p-type AlGaN layers. We obtained an output power of 8.4mW from a 346 nm InAlGaN-QW LED by optimizing the band line-up to suppress electron overflow and by reducing the threading dislocation density (TDD) of the AlN/AlGaN template.

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We attempted the development of highly efficient fishing lights using LEDs for saury fishing. Considering the spectral luminous efficacy characteristic of a Pacific saury, LED fishing lights were fabricated. Transmission properties in sea water in LED fishing lights were investigated, and it was found that the fabricated LED fishing lights sufficiently can be utilized even in sea water. Furthermore, we attempted the saury-fishing experiments by using the LED fishing lights, and comparable catch of Pacific saury was achieved by approximately 55% electric power by using both LED poles and incandescent lamp poles.

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Eu²⁺-doped BaSi₂O₅ glasses were prepared by melting method and the glass-ceramics (GCs) were obtained by heat-treatment at various temperatures between 800 °C and 1000 °C. The single phase of BaSi₂O₅ micro-crystal precipitated in the GCs by heat-treatment above 950 °C, and the quantum yield (QY) of Eu²⁺ fluorescence became higher than that of other GCs, in which other crystal phases precipitated. When the BaSi₂O₅ precipitated, the QY increased drastically.

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In this paper we evaluated the effects of 1/f fluctuation of Green LED light emitted from the specific object by using psychological and physiological experimental tests of spectral electroencephalogram (EEG) topography. In addition, we also verified that the combination of appropriate aroma, blue LED light irradiation and music such as “Mozart: Serenade in Eine Kleine Nacht Musik” has improved mental healing conditions. We confirmed the possibility that the effect of “Healing” would be improved by the above mentioned environments.

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The phosphor of ScPO₄:Zr⁴⁺,Mn²⁺ has been synthesized in order to increase the photoluminescence (PL) intensity of the blue-green (BG) band at 2.52 eV in YPO₄:Zr⁴⁺,Mn²⁺ phosphor. PL properties of this material have been investigated. A PL band is predominantly observed at 2.34 eV in ScPO₄:Zr⁴⁺,Mn²⁺. This green (G) band is most likely caused by the intra-3d transition of the Mn²⁺ ion occupying a Sc³⁺ site, in analogy with PL properties of the BG band. The G band surpasses the BG band in PL intensity. Discussions are conducted on the change of PL properties in ScPO₄:Zr⁴⁺,Mn²⁺ phosphor.

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We demonstrate high power blue and green InGaN/GaN multiple-quantum-well (MQW) light emitting diodes (LEDs) grown on low extended defect density semipolar (10 1 1) and (11 2 2) bulk GaN substrates by metal organic chemical vapor deposition. The output power and external quantum efficiency (EQE) at 20 mA under pulsed operation (10 % duty cycle) were 19.7 mW and 34.4 % for the blue LED and 9.0 mW and 18.9 % for the green LED, respectively. The blue LED showed <1 nm red-shift with change in drive current from 1 - 200 mA, indicating a significant reduction of polarization related internal electric fields.

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We have demonstrated the ability to increase the luminous flux and luminous efficacy of white light-emitting diodes (LEDs) by randomly patterning the surface of the yellow phosphor matrix. The phosphor was moved away from the LED die by placing it on top of a silicone optic and then roughening the surface of the phosphor/resin mixture. It was found that the roughening increases the luminous flux and efficacy by 10% over the smooth, non-patterned phosphor mixture. The roughened sample’s operating voltage, luminous flux, luminous efficacy, CCT, color coordinates, and CRI were 3.2 V, 7.4 lm, 115.6 lm/W, 4244 K, (0.388, 0.448), and 61 at 20 mA, CW, and room temperature operation. A brief presentation on phosphor scattering is introduced to help explain the effect of the roughening.

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The accuracy of results from Monte Carlo ray-tracing analysis significantly depends on the input values of the optical properties of the various package components. One important piece of input information is the phosphor particle MFP (mean-free-path), which is not easily determined. This study introduced a method to determine the MFP by matching the experimental results with optical ray-tracing analysis at a wavelength beyond the phosphor excitation range. Using these experiment values for MFP in an optical ray-tracing analysis of a white LED package showed an excellent match with measured results for light output and chromaticity.

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First, we investigated the transient characteristics of poly(9,9-dioctylfluorene)(PFO)-based polymer OLEDs (PLEDs) doped with green emissive phosphor fac-tris(2-phenylpyridine)iridium(III) [Ir(ppy)₃] and red emissive phosphor tris(1-phenylisoquinoline)iridium(III) [Ir(piq)₃] by applying the voltage pulse on the devices, and achieved the maximum luminance of 4800 cd/m² and the ideal white emission with the Commission Internationale de L’Eclairage (CIE) coordinates of (0.33, 0.35) at the pulse width and frequency of 100 ns and 1 kHz, respectively. Especially, the CIE coordinates can be tuned from (0.25, 0.29) to (0.51, 0.40) by varying pulse width and frequency. Second, we investigated white OLEDs with blue emissive phosphor bis[(4,6-difluorophenyl)-pyridinato-N,C²] (picolinate)iridium(III) (FIrpic) and some red emissive materials. Using FIrpic and red emissive rare earth complex of tris(divenzoylmethane)-mono(4,7-dimethylphenanthroline) europium(III) [Eu(dbm)₃phen] doped in poly(N-vinyl-carbazole) (PVK), the white emission of (0.31, 0.38) in the CIE coordinates was obtained at a current density of 0.5 mA/cm². Utilizing the different transient characteristics between the host and dopant, emission color has been successfully tuned by varying the applied pulse width and frequency.

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The fabrication of InGaN/GaN light emitting diodes with reverse-tapered microholes (RH-LEDs) and their optical —electrical properties were demonstrated. A high light extraction efficiency was realized with the RH-LEDs owing to the diffraction of light and effective extraction of photons caused by the microholes. The estimated light extraction efficiency of the RH-LEDs was as high as 85%; this is 1.5 times higher than that of conventional LEDs having no microholes. The theoretical results were highly consistent with the experimental results.

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In this overview paper, novel rare-earth doped silicon nitride based phosphors for white LEDs applications have been demonstrated. The luminescence properties of orange-red-emitting phosphors (M₂Si₅N₈:Eu²⁺) and green-to-yellow emitting phosphors (MSi₂N₂O₂:Eu²⁺, M = Ca, Sr, Ba) are discussed in detail with a focus on the relationship between the properties and structures. With high conversion efficiency in the near UV/blue region, along with high chemical/physical stability, Eu²⁺ - and Ce³⁺ - activated alkaline-earth silicon nitride and oxynitride materials are excellent wavelength-conversion phosphors for white LEDs.

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A novel red phosphor of CuAlS₂:Mn for white LEDs has been successfully prepared by solid-state-reaction method using an opened-tubular-furnace. It has been found that both photoluminescence (PL) intensity and thermal stability are improved by Si-codoping. The currently obtained PL stimulus value Y under 380-nm-excitation is about 67 % compared to La₂O₂S:Eu. The PL intensity at 100°C maintains 95 % of that at a room temperature.

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Ba₂SiS₄:Ce has been proposed as a novel blue phosphor for white LED application. It has been found that photoluminescent characteristics are improved by Al-codoping, which realizes a high doping of Ce³⁺ luminescent centers. The relative PL luminance of 145% has been achieved compared to the commercial BAM under 405-nm-excitation. The internal quantum efficiency is about 36 %. The PL intensity at 150°C maintains about 80% of that at room temperature. It has been also confirmed that Ba₂SiS₄:Ce is chemically stable enough for applying to white LEDs.

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MOCVD growth of InGaN on ZnO substrates has achieved indium concentration as high as 43% as observed by high-resolution X-ray diffraction (HRXRD). The uniqueness of this finding is the absence of phase separation and the higher indium incorporation compared to growth on thick GaN/sapphire. Transmission electron microscopy (TEM) shows perfectly matched GaN and ZnO lattices. In addition, atomic layer deposition (ALD) transition layers have been grown in order to provide a transition layer on ZnO substrates to block Zn diffusion and allow for future substrate removal for thin nitride fabrication.

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High-power LED should reject about 6 times of heat of the conventional lighting device and keep the LED junction temperature below 80°C to assure reliability and low light decay. In addition, no fan is allowed and the heat dissipation design should not interfere with the industrial design of lighting fixture and have a light weight. This thus creates an extreme thermal management problem. The present study has shown that, using a special heat dissipation technology (loop heat pipe), the high-power LED lighting luminaire with input power from 36 to 150W for outdoor and indoor applications can be achieved with light weight, among 0.96 to 1.57 kg per 1,000 lumen of net luminous flux output from the luminaire. The loop heat pipe uses a flexible connecting pipe as the condenser which can be wounded around the reflector of the luminaire to dissipate the heat to the ambient air by natural convection. For roadway or street lighting application, the present study shows that a better optical design of LED lamps can further result in power consumption reduction, based on the same illumination on road surface. The high-power LED luminaries developed in the present study have shown that the energy saving is > 50% in road lighting applications as compared to sodium light or > 70% compared to mercury light.

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The use of light emitting diodes (LEDs) is expanding rapidly, in areas ranging from lighting, signalling and escape route indication to medical diagnosis and treatment. For all these applications, knowledge of the spectral and spatial characteristics of the devices is essential. In addition, recent significant advances in the brightness of LEDs and the introduction of devices emitting at shorter wavelengths has led to increasing concern regarding the safety of LED products.

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By using Blue, Green and Red LEDs it is shown that the Broca-Sulzer effect holds for a continuous pulse operated LED lighting system. The effective enhancement at 5% duty ratio and frequency of 60 Hz is between 1.01 to 2.22 times that of DC operation although this is not as high as it is in the single pulse discharge lamp case. However, this result shows that there is a possibility of improving the efficiency of an LED and a PWM circuit for pulsed operation for developing a highly efficient lighting system.

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By using Blue, Green and Red LEDs it is shown that the Broca-Sulzer effect holds for a repetitive pulse operated LED lighting system. In other words Talbot-Plateau Law does not hold. The effective enhancement at 60 Hz with a 5% duty ratio is about 1.5 to 2.7 times that of DC operation for blue and green light. This result suggests that pulsed operation can be a way to solving the energy saving problem of lighting.

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In this paper, the high quality AlGaN with high-Al content was grown on in-situ monitoring controlled selective area growth (SAG) GaN and the dislocation density of AlGaN is 1-3×10⁸ cm^-2. Furthermore, we use SAG to fabricate InGaN/GaN pyramid structures. CL (Cathodoluminescence) measurements reveal that the thickness, CL peak wavelength and CL intensity gradually increased from the bottom to the top of the facet. Furthermore, Vacuum fluorescent display (VFD) based on InGaN/GaN pyramid structures was demonstrated.

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In this work, an empirical model for the emission spectra of LEDs is proposed to describe some crucial optical properties of LEDs. As well known, the junction temperature and the electric driving current are two most important factors of all. According to the phenomenal observation, the empirical model for the emission spectra of LEDs is established to simultaneously include the effects from both the junction temperature and the electric driving current. As a result, the empirical model can be applied for the prediction of the chromatic shifts due to the drift of the operating junction temperature. In addition, the stabilization of the chromatic characteristics is obvious.

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This paper presents the results using an alternative defects and strain minimizing technique with nanostructures as the compliant layer to grow III-V nitrides onto foreign substrates. Defects reduction and stress relaxation had been observed through HRTEM on GaN grown on sapphire and silicon. Results of LED devices on silicon with performance compatible with those on sapphire are presented.

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The internal quantum efficiency (IQE) of InGaN-based light-emitting diodes has been studied by means of excitation-power-density- and temperature-dependent photoluminescence spectroscopy. The IQE was evaluated at various excitation photon energies using a wavelength-tunable dye laser system. The IQE obtained under selective excitation of InGaN active layers was higher than that obtained under band-to-band excitation of GaN and AlGaN cladding layers. The enhanced value of IQE under selective excitation reflected the intrinsic optical quality of the InGaN active layer itself.

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The encapsulation optical component shaped in an elliptical dome over the LED chip and the mixing of multiple types of fluorescent materials in an appropriate ratio improves colour rendering properties and distribution controllability while suppressing colour variation. The developed technologies can be applied to produce an LED luminaire that resembles a compact ceiling-light but can be used as a downlight with the light intensity equivalent to a 60W incandescent lamp and light quality comparable to a fluorescent lamp.

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High-luminous green phosphors and a red phosphor have been newly developed for white LEDs. The developed green phosphors are Ca₃(Sc,Mg)₂Si₃O₁₂:Ce made by replacing with Mg a part of Sc of green phosphor Ca₃Sc₂Si₃O₁₂:Ce, a new green phosphor CaSc₂O₄:Ce, and a new host material doped with a rare-earth element, Ba₃Si₆O₁₂N₁₂:Eu. The new red phosphor is (Sr,Ca)AlSiN₃:Eu made by replacing a part of Ca of CaAlSiN₃:Eu with Sr.

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The advantages of LED lighting are discussed. We report experiments where observers graded the quality of several light-emitting diode (LED) illuminations. One experiment is based on color discrimination and two experiments are based on the judgement of appearance. We conclude that clusters with red, green, blue, and/or amber LEDs impair color discrimination, although they seem to locally enhance the color gamut. We also conclude that LED clusters that include white LEDs and a few correcting color LED may render colors faithfully.

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I, who is a musician, was stimulated by own childbirth experience, and developed the ultimate “delivery room” which enabled relaxation support using sound and light. This paper explains regarding its development and the improvement of childbirth environment in Department of Obstetrics and Gynecology in Japan.

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A new LED lighting system that uses Ise Paper Stencils as a lampshade is demonstrated, and its optical properties are investigated. It is found that clear patterns in the Ise Paper Stencils can be observed using blue and green lights as exciting sources. The transmission of the Ise Paper Stencils for red, green, and blue lights is 10%, 0.40%, and 0.15%, respectively. Therefore, the green and blue lights are suitable as the sources for LED lighting with an Ise Paper Stencils lampshade.

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We have studied LED irradiation effects on plants and animals in the visible to UV region of light from GaN LEDs. The results are as follows. Blue light considers to be effective for pearl cultivation or for attraction of small fishes living in near the surface of sea such as Pompano or Sardine, white light radiation is effective for cultivation of botanical plankton for shells. Other experiments of UV light irradiation attracting effect on baby sea turtle and the germination UV effect of mushroom, green light weight enhance effect on baby pigs, light vernalization effect of vegitable and Ge far infrared therapic effect on human body are also given.

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We are developing the emergency vehicle alarm system for deaf drivers by using LEDs and vibration devices. In order to design the alarm for deaf drivers, we have conducted basic experiment in order to evaluate perceptual characteristic on visibility of LED.

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Based on a standard chromatic calculation the luminous efficiency and color rendering properties of white phosphor-converted light emitting diodes (pc-LEDs) is analyzed and discussed. In the present work the broadband emission spectrum of the phosphor is best fitted by an asymmetric Gaussian function. It is found that the maximum luminous efficiency of the pc-LED is about 260lm/W.

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We have recently fabricated high-power near-ultraviolet (n-UV) light-emitting diodes (LED) on ceramic packages without sub-mount by direct flip-chip bonding (DFCB) technique. In ceramic packages, for example, pad electrodes of near-ultraviolet (n-UV: λ_peak∼405nm) LED chips the size of a 0.35mm square were bonded on the metallized packages using metal stud bumps. The cross-sectional microstructures of the chip/bump/ceramic of non-degraded and degraded DFCB packages have been investigated by electron microscopic observation with an Energy Dispersive X-ray fluorescence (EDX) spectrometer, an X-ray CT, and Ultrasonic Scanning Inspection. For the first time, we have confirmed the firm flip-chip interfaces of DFCB packages while the crack between the GaN layer and the 1^st metal for p-type electrode reflector which caused failure has been observed in the degraded chip. Ultrasonic testing is quite effective to detect small defects in the package and can be expected to support process optimization.

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We have demonstrated large-scale integrated light-emitting diodes (LSILEDs) by using direct flip-chip bonding (DFCB) technique on a size of 30 × 40 mm² ceramic package. Radiant flux measured at DC current of 9.1 A and forward voltage of 4.0 V was 3.3 W. Luminous flux, luminous efficacy and color-rendering index of white LED fabricated with the LSILED as the excitation source measured at DC current of 9.1 A and forward voltage of 4.0 V was 766 lm, 21.0 lm/W, and 82, respectively. The LSILED is very promising as a compact, high dense and high luminous flux white light source.

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This thesis focuses on the development of fashion design, especially a dress coordinated with White LED Lighting (=LED). As for the design concept a fusion of the advanced science and local culture was aimed for. For such a reason this development is a very experimental one. Here in particular I handled an Imperial Court dinner dress for the last Japanese First Lady, Mrs. Akie Abe who wore it at the Imperial Court dinner for the Indonesian First Couple held on November 2006 to. This dress made by Prof. T. Taguchi and I open up a new field in the dress design.

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In this paper, I will describe three cases; a roadway lighting (universal design), sign built-in lighting (PV system), and an enactment lighting for facade on buildings (interactive). These cases are some of the projects utilizing white LED lighting completed by lighting designer Miki Matsushita in 2007.

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The present report discusses wearable objects with LEDs and various sensors. The objects detect physiological reactions and transform them into light so that they make the reactions visible in a new way and express our internal energy of life in the form of art.

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The scope and significance of light on the culture and development of human societies throughout history is nothing short of astounding. From ancient times, light has provided essential substance for life and spirituality, spawning cultural diversity and artistic inspiration around the globe. Indeed, from the rudiments of civilization to the Enlightenment, throughout the Industrial Revolution to contemporary societies, the lighting technology that humankind has brought into this world has enhanced civilizations, driving advances in productivity and ever higher standards of living. And yet, we presently stand at an important crossroads, where evolutionary factors are taking us in new directions, and a choice must be made about the course and meaning of lighting in our lives. Paramount to this issue is the growing significance of LED as a source of light and the behavioral change it is causing within our industry. The technological innovation driven by LED has drastically changed the systems of manufacturing and distribution and, thus, is transforming the economy. Perhaps, equally significant, this influence has begun to alter the philosophy and culture of our industry. The direction of this evolutionary process is not automatic, however. We lighting designers, lighting equipment manufacturers, and astute judges of life quality through lighting, have a choice to lead or be led by recognizing the constraints of industry standards and reactionary views of technology, and what can be done to remain flexible and artistically expressive. In this effort, my belief is that we must remain sensitive to the delicate connection between light and people, as a means to an important new priority that I call Communicative Lighting.

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In this paper we discuss the real cost of fuel based lighting in the developing world and in comparison the incredible wealth creating prospects associated with safe, healthy and affordable solid state lighting (SSL), based on renewable energy (RE) and Micro Credit (MC). SSL technology and a number of SSL projects promoted by the Light Up The World Foundation (LUTW) are presented. A multi stake holder approach for the accelerated adoption of SSL in the developing world is proposed in order that those at the Base of the Pyramid (BOP) can get onto the first rung of the ladder of economic progress. The potential contributions of SSL to the Millennium Development Goals (MDGs) and the fundamental importance of MC are discussed in detail. The wholesale adoption of SSL by the BOP would be an added ‘incentive’ for the Top and Middle of the Pyramid to also adopt SSL wholesale. A Bottom Up plus a Top Down adoption of SSL can help combat climate change. LUTW promotes SSL systems for the benefit of the world’s poor, and its strategy is in line with the Jeffrey Sachs plan for the developed world to help the developing world pull itself up by its own bootstraps.

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