In a breakthrough that could lead to accelerated adoption of LEDs in demanding applications such as LCD display backlights and pico-projectors, scientists at 3M have developed technology that doubles the efficiency of green LEDs.
LEDs are robust light sources, but their efficiency varies by color. Producing green LEDs with the stability, power and efficiency of other colors has proved particularly vexing to researchers. Green is the most important component of white light, and white light is critical to the brightness of a display or luminaire.
The 3M technology approach is to bond 3M’s color converting material to high-efficiency blue LEDs. The 3M material absorbs the blue light and re-emits it as green light. Other colors, including white, also can be made by engineering the composition and structure of the emitting layer.
High performance green LEDs will reduce the total number of LEDs required in a device, while improving color performance, energy efficiency, heat dissipation and reliability.
Record green emission of 216 lumens was achieved, with 181 lumens per watt efficiency at a drive current of 350 mA/mm². Blue LEDs (ThinGaN high current UX:3) were supplied by OSRAM Opto Semiconductors GmbH, a leading producer of LEDs. An overview of 3M’s color converting technology will be presented at the SPIE Photonics West symposium, January 23-28, 2010, in San Francisco.
