The LED is a semiconductor light source. It’s light-emitting diode . LEDs are semiconductor diodes, electronic devices that permit current to flow in only one direction. The diode is formed by bringing two slightly different materials together to form a PN junction.
In a PN junction, the P side contains excess positive charge (“holes,” indicating the absence of electrons) while the N side contains excess negative charge (electrons). When a forward voltage is applied to the semiconducting element forming the PN junction (heretofore referred to as the junction), electrons move from the N area toward the P area and holes move toward the N area. Near the junction, the electrons and holes combine. As this occurs, energy is released in the form of light that is emitted by the LED.