Introduction / History

The first commercial white LED was produced by Nichia in 1996. It was similar to existing LEDs being round with a 5mm diameter. These first LEDs produced less than a lumen of light from 60mW, hence, many were needed to produce a light suitable for caving. This type of LED is still used for pilot lights.

Typical 5mm White LED

In 1999 Philips-lumileds launched the first power LED the ‘luxeon’. In the luxeon LED the PN junction is mounted on a metal slug that can be bonded to a heatsink, thus, allowing the efficient removal of heat. The first generation luxeon emitters required a drive current of 350mA, used approximately 1W of power, and produced 18 lumens of light. Lumileds now produce a range of LED’s from 1W to 5W, the most efficient producing 42 lm/W.

Lumileds Luxeon Emitter

Seoul Semiconductors have entered the market more recently. Their latest product the Z-Power P4, produces 100 lm/W and is currently the most efficient LED on the market. It has a power rating of 4W. Seoul aim to improve the luminous efficacy to 145 lm/W by the first quarter 2008.

Seoul Z-Power P4

Nichia have in development an LED claimed to produce 150 lm/W. This is 10 times the efficiency of the first generation of LEDs. It will first be produced in a 5mm form factor, with power LEDs following later.