January 18, 2013

Light-emitting diodes: Warm-white lighting

Scientists have developed a yellow phosphor that can be used to provide a pleasing white light with a warm color temperature when combined with a blue light-emitting diode (LED) chip. Although YAG: Ce-based white LEDs show great promise as a highly efficient and long-lasting form of domestic lighting, their cool bluish-white light makes them undesirable for use in the home. Scientists from the USA and China have now shown that a new phosphor, Ba0.93Eu0.07Al2O4, when combined with a blue InGaN LED, provides a pleasing white light with a warm colour temperature of less than 4000K and a high colour-rendering index of more than 80. The phosphor has an orthorhombic structure and was manufactured by carbothermal reduction and vapour phase deposition in a tube furnace system. This work suggests that high-quality, warm-white lighting can be achieved using a combination of a single phosphor with single-emitting-center and a blue LED chip.