How LED Works • • • • •
The light-emitting section of an LED is made by joining n-type and p-type semiconductors together to form a pn junction. When the pn junction is forward-biased, electrons in the n side are excited across the pn junction and into the p side, where they combine with holes. As the electrons combine with the holes, photons are emitted. The pn-junction section of an LED is encased in an epoxy shell that is doped with light scattering particles to diffuse light and make the LED appear brighter. Often a reflector placed beneath the semiconductor is used to direct the light upward.