The external quantum efficiency of the PC amber LED

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 light-emitting diodes 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.

HA7305 is ideal for netbook and notebook panels with LED-backlight. Recently, continuous cost drop of white LED has triggered the growing demand of LED backlights for mid- to large-sized panels. According to Topology Research Institute, it is estimated that around 60% of netbooks and notebooks shipped worldwide in 2009 are adopting white LEDs as backlights. Furthermore, white LEDs are expected to replace CCFLs (Cold Cathode Fluorescent Lamps) completely in netbook and notebook applications in the next two years.