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The development and demonstration of a highly efficient warm‐white all‐nitride phosphor‐converted light emitting diode (pc‐LED) is presented utilizing a GaN based quantum well blue LED and two novel nitrogen containing luminescent materials, both of which are doped with Eu2+. For color conversion of the primary blue the nitridosilicates M2Si5N8 (orange‐red) and MSi2O2N2 (yellow‐green), with M = alkaline earth, were employed, thus achieving a high luminous efficiency (25 lumen/W at 1 W input), excellent color quality (correlated color temperature CCT = 3200 K, general color rendering index Ra > 90) and the highest proven color stability of any pc‐LED obtained so far. Thus, these novel all‐nitride LEDs are superior to both incandescent and fluorescent lamps and may therefore become the next generation of general lighting sources. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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.

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High power light emitting diodes (LEDs) continue to increase in output flux with the best III‐nitride based devices today emitting over 150 lm of white, cyan, or green light. The key design features of such products will be covered with special emphasis on power packaging, flip‐chip device design, and phosphor coating technology. The high‐flux performance of these devices is enabling many new applications for LEDs. Two of the most interesting of these applications are LCD display backlighting and vehicle forward lighting. The advantages of LEDs over competing lighting technologies will be covered in detail.

Phosphor conversion of light‐emitting diode (LED) radiation has been used in many configurations and combinations to generate white light. The concept of down conversion of, e.g., blue LED emission, offers also the possibility to provide efficient generation of monochromatic, high‐color‐purity light, especially in wavelength ranges in which direct radiation from non‐converted LEDs is relatively inefficient, i.e., in the “yellow gap”. In the case described here, a blue‐emitting LED is ‘fully’ converted to amber emission with a peak wavelength of 595 nm and a color purity of >96%, while demonstrating an external quantum efficiency exceeding that of direct AlGaInP LEDs of the same wavelength by a factor of almost two at room temperature, and the lumen output under equal drive conditions at 85 °C by more than a factor of four. An essential component in this high performance is, besides the choice of the right – nitride – phosphor, the use of this phosphor in a densely sintered ceramic form which has considerable optical advantages over powders. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

In the Editor's Choice [1] the development and demonstration of a highly efficient warm‐white all‐nitride phosphor‐converted light emitting diode (pc‐LED) is presented utilizing a GaN based quantum well blue LED and two novel nitrogen containing luminescent materials doped with Eu2+. These novel LEDs are superior to both incandescent and fluorescent lamps and may therefore become the next generation of general lighting sources. The cover picture is an artist's view of the 2‐pc‐LED: On a copper slug and underneath a plastic lens a ‘flip‐chip’ is soldered to metal contacts; ‘flip‐chip’ meaning the substrate on which the stack of GaN and InGaN layers has been deposited is used as light exit, the (bottom) p‐contacts being highly reflective. The color converting phosphors are placed on top of the chip, embedded in silicone. Primary blue as well as color‐converted red and green photons are emitted. The first author, Regina Mueller‐Mach, manages the Charac‐terization Laboratory at Lumileds which runs R&D work on phosphor converted LEDs in close cooperation with Philips Research Laboratories and the Department of Chemistry and Biochemistry of the University of Munich.

White light for illumination can be produced from LEDs either by combining red, green and blue emitting chips in one lamp, or by using phosphors to down-convert the emission of short wavelength emitting InGaN LEDs. Both concepts will be critically reviewed, and simulations compared with experimental evaluations. As expected, each solution has advantages, but also drawbacks, which are weighted by the specifics ofthe applications. The overall picture strongly depends on the efficiencies of the single color chips, the temperature coefficients of all involved materials, and the wanted light output per lamp.