How do LEDs convert electrical energy into light?

Light-emitting diodes (LEDs) convert electrical energy into light through a process called electroluminescence.

This process occurs at the junction of two semiconductor materials with different electronic properties: an n-type material, which has an excess of electrons, and a p-type material, which contains "holes" (the absence of electrons). When the LED is forward-biased by an electric current, electrons are injected from the n-type material into the conduction band of the p-type material.12

As these electrons drop into holes in the valence band, they release energy equal to the energy gap ($E_g$) of the material. In specific semiconductor compounds—such as gallium arsenide or gallium phosphide—a significant portion of this released energy is emitted as photons, or light. The frequency of the emitted light is determined by the relation $h\nu =E_g$, meaning the specific composition of the semiconductor can be tuned to produce different colors of light.21