Why does the intensity of a LED change as the temperature increases I am working with an array of LEDs and I am looking into how there properties change as they heat up. One of the things I found out is that the intensity of these the light decreases as the LEDs heat up. I knew that this would happen from the many reports I read on the internet about this, but I cant find a clear explaination on the internet for the theoretical background, one site talked about a reducion in the forward voltage, the other about an increase in the resistance of the P-N junction.
So I was wondering of anybody here could give me a clear explaination as to why the intensity of my LEDs decreases.
Thanks for taking the time to read my problem and I hope to see your awnser soon.
G.Wesseling
P.S.
I am sorry for my english, its not my first language
 A: LEDs are usually made from a semiconductor material, which have a greater resistivity value than conductors. As temperature increases, so does the number density of free electrons in the wire which causes an increase in electric current. Since made from a semiconductor material, its resistance doesn't increase much.
As current increases in the LED, so does the velocity of the electrons passing through the semiconductor, thus increasing intensity.
A: Depending on the material, thermal droop might also play a role. This is a three body process aka Auger, where instead of giving energy up as light, the electron hole pair recombination excites a third electron or hole to higher energy.  This requires higher carrier concentrations. There are two forms, direct and indirect; indirect requires a phonon for momentum conservation. At higher temperatures, there are more phonons available for the indirect Auger process. Howecer, you need to know if this is an issue in your semiconductor LED to start.
A: I think that when working in a warmer environment, the led needs less forward bias voltage. As voltage decreases, the forward current decrease; in this way the intensity of emitting light also decreases.
