Is there a known light source that also produces no heat?

Dog collars according to
[From ivillage.com 2004 article, no longer online]

A USB Flex Light.

Electric eels, glowworms and fireflies. And they don't use fossil fuels...

http://www.sciencefocus.com/qa/it-possible-produce-light-without-heat

I have heard that glowworms and fireflies create light energy directly from conversion of ADP to ATP inside specialised cells and that this is the most efficient source of light production known on the planet (a standard light bulb produces about 5% light and 95% heat). However, light is formed by stimulating electrons into higher energy levels and this will always produce some heat. While the insects are efficient, they will produce some heat and the answer to the question is no.

if anyone's interested, here's how fireflies "light up"
http://science.howstuffworks.com/question554.htm
I think you got it backwards gm but I don't really understand so I don't know.