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A '''light-emitting diode''' ('''LED''') is a semiconductor device that emits light when current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy in the form of photons. The color of the light (corresponding to the energy of the photons) is determined by the energy required for electrons to cross the band gap of the semiconductor. White light is obtained by using multiple semiconductors or a layer of light-emitting phosphor on the semiconductor device.

Appearing as practical electronic components in 1962, the earliest LEDs emitted low-intensity infrared (IR) light. Infrared LEDs are used in remote-control circuits, such as those used with a wide variety of consumer electronics. The first visible-light LEDs were of low intensity and limited to red.

Early LEDs were often used as indicator lamps, replacing small incandescent bulbs, and in seven-segment displays. Later developments produced LEDs available in visible, ultraviolet (UV), and infrared wavelengths with high, low, or intermediate light output, for instance, white LEDs suitable for room and outdoor lighting. LEDs have also given rise to new types of displays and sensors, while their high switching rates are useful in advanced communications technology. LEDs have been used in diverse applications such as aviation lighting, fairy lights, strip lights, automotive headlamps, advertising, stage lighting, general lighting, traffic signals, camera flashes, lighted wallpaper, horticultural grow lights, and medical devices.

LEDs have many advantages over incandescent light sources, including lower power consumption, a longer lifetime, improved physical robustness, smaller sizes, and faster switching. In exchange for these generally favorable attributes, disadvantages of LEDs include electrical limitations to low voltage and generally to DC (not AC) power, the inability to provide steady illumination from a pulsing DC or an AC electrical supply source, and a lesser maximum operating temperature and storage temperature.

LEDs are transducers of electricity into light. They operate in reverse of photodiodes, which convert light into electricity.

== Materials needed ==

* P-doped semiconductor
* N-doped semiconductor
* Wire
* A way to put these together and keep them together

== Crafting instructions ==
First, add some P-doped semiconductor and the N-doped semiconductor next to each other. For red LEDs, use aluminum gallium arsenide (AlGaAs), gallium arsenide phosphide (GaAsP), aluminium gallium indium phosphide (AlGaInP), or gallium(III) phosphide (GaP). For green LEDs, use indium gallium nitride (InGaN) or gallium(III) nitride (GaN). For blue LEDs, use zinc selenide (ZnSe) or indium gallium nitride (InGaN). For other colors, mixing red, green, and blue LEDs works, although other compounds exist that generate those colors. Attach two wires to the P-doped semiconductor and the N-doped semiconductor, and now passing electrons from N to P causes it to emit light.
[[Category:Lighting]]