An efficient white-light LED
DOI: 10.1063/1.2062887
(Light-emitting diode) has been designed and built with very stable, environmentally friendly nitride compounds. Compared to incandescent or fluorescent lighting, solid-state devices for general illumination hold much promise for reducing costs and energy use, but many technical challenges remain. (See Physics Today, December 2001, page 42 ) One scheme being explored is the phosphor-conversion approach, in which light from a short-wavelength LED excites luminescent materials that then emit at longer wavelengths; the combined emissions produce white light. A team of scientists led by Wolfgang Schnick (University of Munich) used europium to dope two new phosphors—of a type called nitridosilicates—that are chemically and thermally stable and emit red and green light when excited by a blue-light LED. The resulting white light is of excellent quality and renders the colors of illuminated objects more faithfully than does a fluorescent lamp. In addition, at 25 lumens per watt, the new device’s efficiency greatly exceeds that of an incandescent lamp (15 lm/W), and the researchers think the efficiency can be increased by another factor of 2 to 4. The team also reports that the materials used pose no environ mental hazards during production, service, and disposal. (
