17 Jun 2002
Commercially viable white LEDs and high power colour LEDs are announced.
Announcements of LED breakthroughs seem to be the flavour of the month. Following Cree's demonstration of a 32% quantum efficiency violet InGaN LED (see Optics.Org 16 February), it is now the turn of Toshiba and LumiLeds.
Toshiba is to launch a white LED that, the company claims, has the luminosity (100 mcd) required to replace incandescent lamps. The InGaN device was jointly developed with Toyoda Gosei and the two companies will commercialize and market it independently. Samples will be available from April and mass-production will start in November with unit prices of between USD 1.70 and 2.60.
This latest LED integrates Toshiba's phosphors and packaging with Toyoda's LED, which has a peak wavelength in the near ultraviolet at 380 nm. This light excites red, green and blue phosphors in the transparent resin of the device to output white light. The emission from the LED does not directly contribute to the white color. This is a departure from conventional LEDs where temperature changes in the LED produce a change in the output color.
LumiLeds Lighting, the joint venture between Agilent Technologies and Philips Lighting, has demonstrated laboratory devices based on InGaN technology that exhibit wallplug efficiencies of 25% at 425 nm. The previous record was 22%. The new device emits more than 200 mW of optical power, which beats the previous record of 17 mW.
Frank Steranka, materials R&D and product development manager at LumiLeds, said: "These are the most efficient, highest flux, large-junction devices in the world. Where the rest of the world is talking about 1 lumen devices, we are exhibiting 55 lumen devices in certain colours."
These devices could be used in backlighting for LCD computer monitors, LCD televisions and in the general signalling and lighting markets.
The company says that, until now, it was only possible to obtain a few lumens of light in an area of 1 cm2, whereas with this latest LumiLed it will be possible to get 25 to 50 lumens in the same area within the next year.