Green LEDs would be expected to age in the same way if it is the wafer itse=
lf that is aging since they are essentially made from the same thing (InGaN=
). =A0It could be that the shorter wavelength is causing solarization of th=
e plastic or whatever else is used to cover the LED chip itself. =A0This is=
 especially seen in UV emitters that have plastic encapsulation.

----------------------------------------
From: bobblick@ftml.net
To: piclist@mit.edu
Subject: [EE] Aging of blue LEDs
Date: Fri, 4 Jul 2014 14:18:47 -0700


My refrigerator has been set to 4F (freezer) and 38F (refrigerator)
since it was new, about 5 years ago. Last night I changed the
refrigerator to 40 and immediately noticed that one segment of the
display was considerably brighter than the others. That segment was one
that hadn't been lit for 5 years.

Attached is a picture I took. In real life the difference is even more
striking.

Five years is over 40000 hours, so it's perfectly reasonable that the
LEDs have aged, but I've had red and green displays running continuously
longer than that with no degradation.

I've also seen blue and white(phosphor) LEDs age very quickly running at
200% of their current rating, in just a thousand hours. But the display
in this refrigerator is probably running within its design spec.

I can't help thinking that blue LEDs age faster than other colors. If
anyone has real information on this I'd love to hear.

Thanks, Bob

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