>>6174651Such shilling.
Leds emit light via an optical recombination in a direct gap semiconductor.
The gap energy is normally in the 0.5-3 eV range, in short, the "energy gap" happens if you have an odd number of charge carriers in the brillouin zone of the material lattice. The pauli principle inhibits electrical conductivity, because all occupieable spots are already taken.
Thus there is a filled valence band, and the next higher energies (in the n+1 brillouin zone) will form the conductance band, with a small energy gap inbetween.
Small simply because this only affect the "outermost" electrons, as the inner ones already form compete multiplets and are inert. So the biggest possible energy _at all_ would be about 20ev for helium.
But the other requirement is that it actually has to be solid and be able to be doted (as, like explained before, there is no conductance in the valence band, so the electricity has to find some way to actually get in the recombination zone).
There is simply not enough energy to generate the velocity for the electrons to form xrays.
