My physics/electronics teacher told me some thing really interesting and confusing a wile ago and I have been trying to get my head round it. The forward voltage in a LED (voltage needed to drive the current) is proportional to the band gap energy. However Blue LEDs have a higher forward voltage than the band gap energy suggests. I haven’t been able to figure out why. Does any one know? This is a link to a page with some band gap energies for different semi-conductors. http://en.wikipedia.org/wiki/Bandgap This is a link to a page on LED’s and what they are made out of http://en.wikipedia.org/wiki/LED I up loaded a .txt of forward voltages and band gap energies so you don't have to look through lots of internet pages. The blue LED forward voltage defiantly looks too high. If any one knows a reason for this your help would be appreciated.