Philips Lumileds researchers have developed a monochromatic nitride diode that closes the yellow light LED gap.
The phosphor-converted (PC) amber LED demonstrated by Regina Mueller-Mach and her colleagues uses the down-conversion of blue light from an indium-gallium-nitride (InGaN) LED to longer-wavelength light by a phosphor, in a variation of a well-established process for producing cold or warm white light from blue LED light.
Monochromatic LEDs cover a large part of the visible spectrum with high efficiency. For blue light, nitride diodes achieve external quantum efficiencies in excess of 65%.
For red light, phosphor diodes achieve efficiencies of approximately 50%. However, so far no highly efficient monochromatic LEDs have been available for the “yellow gap” at around 560 nm.
Leveraging previous research on warm white light, the researchers succeeded in down-converting blue LED light into monochromatic amber light with a 595 nm wavelength and a color purity of 98.7%. The external quantum efficiency of the PC amber LED is at 30-40%, depending on temperature.
Compared to direct amber LEDs, the new PC amber LED is two to five times as bright. It achieves a light output of 70 lumens at a 350 mA current.
The LUXEON Rebel PC Amber LED can be used in yellow traffic lights or signals as well as in cars’ turn signals or warning lights for construction sites, or in consumer electronics because their high efficiency makes them relatively inexpensive.
–Posted by Gail Overton from Laser Focus World
