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Philips Lumileds solves LED efficacy 'droop'

15 Feb 2007

Philips Lumileds develops an undisclosed technology that enables LEDs to maintain their efficacy at higher drive currents.

Philips Lumileds claims that it has solved the problem of efficacy "droop" – the reduction in an LED's lumens per watt output as its drive current is increased.

While typical high-performance devices suffer from a decrease in lumens per watt of at least 50% when the LED's drive current is increased from 100 to 1000 mA, Lumiled's latest emitters deliver a constant efficacy over this current range (see graph).

The company provided no details about how the efficacy problem was solved. However, it did say that new epitaxial technology will enable the first high-power LEDs that deliver 70 lm/W at drive currents of 1000 mA and higher.

Lumileds plans to introduce the technology into its Luxeon LEDs this year. Product sampling will begin in the next three months, with full production slated for the third quarter of 2007.

The company believes that the increased light output and efficacy of LEDs incorporating the new technology will help to drive the opening of new lighting markets and expand the reach of LED lighting into residential lighting segments.

LEDs that do not suffer from the efficacy "droop" have already been built by the Ioffe Institute in Russia (see related story). However, their initial LEDs, which feature an n-p-n structure and maintain their efficacy at higher drive currents, produce an external quantum efficiency of only 1%.

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