Light-emitting diode

A light-emitting diodes (LED) is a semiconductor component emitting light as current flows through. 

Its electrons recombine with electron holes, releasing energy in form of photons (light). A light's color (corresponding to photon's energy) is determined by energy needed for electrons to cross the band gap of the semiconductor.

White light is obtained with many semiconductors or a layer of light-emitting phosphor on the semiconductor device.

Unlike incandescent bulbs, LEDs don't have filaments that burn out, use less electricity, and aren't really hot. Illuminated only by electron movements in a semiconductor material, they last as long as a normal transistor. LED lifespans surpasses the incandescent bulb's lifespans by thousands hours, so LEDs are among the most used tech used to light LCD TVs.