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Temperature stability of the optical power output of colored (blue-red) light
emitting diode (LED) elements is considered. It is shown that LEDs based on blue 455 nm
semiconductor chips have the best thermal stability, which is expressed in just 4 % of optical
power losses with LED board temperature increasing from 25 œC up to 50 œC. The value of
optical power losses for red chips emitting at 660 nm and 730 nm were 7 % and 11 %,
respectively, while devices based on 455 nm blue chips and red nitride phosphors with 2 %
and 8 % phosphor concentration showed losses of 4 % and 8 %, respectively. Wall plug
efficiency of the studied samples demonstrated a similar trend with the temperature increasing
as the optical power did.
Keywords: LEDs; temperature stability; greenhouse emitters; phosphors |
full paper (pdf, 1344 Kb)