Question

what atomic particle is responsible for powering the LED light?

Answer 1

Electron is responsible for powering the LED light. When a voltage is applied across the anode and cathode of a LED, the electrons in the valence band absorbs that energy due to the applied voltage and jumps to the conduction band (this happens only when the applied energy E is greater than the band gap energy E_h, if the applied energy E is less than the band gap energy E_h then the electron will not be able to jump to the conduction band). Band gap energy is the difference between the valence band and the conduction band.

Now when the electron has jumped from the valence ban to the conduction band, it can not stay in the conduction band forever. The electron then falls back to the valence band, during this fall the electron emits an energy (releases the energy) which is equal to where h is the Planck's constant, c is the speed of light and is the wavelength, if this lies in the visible spectrum then we can see the light of the energy released during the fall and this released energy is responsible for the glow of a LED.

In a LED this phenomenon keeps on occuring and we get to see a constant glow.