This
achievement is based on improved output of the
primary blue emitting
chip, which was combined
with acommercially available yellow phosphor.
The results are on par with some compact fluorescent
lighting systems and up to 10 times as efficient
as incandescent sources.
Cree's achievement
is part of a three-year project focused on demonstrating
that existing white LED technology could be successfully
scaled up (in terms of electrical input/optical
output power) to levels suitable for general
illumination applications, with superior energy
efficiency. This goal requires significant improvements
in such diverse areas as chip efficiency, optical
design, and thermal management.
Critical Milestone
Builds on Blue LED Breakthrough
The primary light source in the white lamps
is an InGaN-based blue LED that is covered with a
phosphor to produce white light. Efficiency and output
power of the blue chip are therefore critical parameters.
Recent technical breakthroughs enabled new record
performances for 1-watt class blue LEDs operating
at a current of 350 mA. A key modification to Cree's
experimental LED chip design resulted in a 17-20%
increase in brightness and, in addition, the demonstration
of packaged blue LEDs with external quantum efficiency
of 40%.
Using these latest generation blue LEDs with
a commercially available yellow phosphor, white
LEDs were fabricated based on Cree's XLamp 7090
power LED platform, with proven long-term reliability.
In spite of the blue chip's slightly higher than
optimal operating voltage, the output from the
XLamp devices averaged over 65 lumens per watt,
with individual devices as high as 70 lumens
per watt for a 0.9 x 0.9 mm2 chip operating
at 350 mA. The color-coordinated temperature
of the lamps was ~6000 K.
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