View source for Light emitting diode

[[Category:Done 2018-12-10]] 
[[File:LED_traffic_light_on_red.jpg|360px|thumb|right|Figure 1. An LED traffic light on red.<ref>Wikimedia Commons. (July 27, 2015). ''LED Traffic Light on Red'' [Online]. Available: https://upload.wikimedia.org/wikipedia/commons/3/3a/LED_traffic_light_on_red.jpg</ref> Note that each individual little circle is a separate LED.]]

<onlyinclude>'''Light emitting diodes''' or '''LEDs''' are electronic components that exploit the movement of [[electron]]s in [[diode]]s to produce [[light]]. These LEDs have numerous advantages over other forms of illumination, including high [[efficiency]] and a long lifespan.</onlyinclude> LEDs are now widely used in products like traffic lights, some [[cell phone|smartphone screens]] and digital clocks.<ref>How Stuff Works. (July 27, 2015). ''How Light Emitting Diodes Work'' [Online]. Available: http://electronics.howstuffworks.com/led.htm</ref>

==Operation==
:: [[Diode operation|''main article'']]
When current flows through a diode, [[electron]]s combine with positive "holes" within the diode (see [[diode operation]] for more information). In this process, the electrons continuously move from a high [[energy]] conduction band to a lower energy orbital surrounding each of the holes. Electrons are said to have more energy the farther they are from positively charged nuclei, so this jump from a conduction band to an orbital surrounding a nucleus is energetically favorable. This means that [[energy]] is released in the process in the form of a [[photon]]. Although all diodes undergo this phenomenon, electrons in the standard [[silicon]] diode undergo a much smaller drop in energy than for visible LEDs, which results in the production of photons of a lower energy, namely in the [[infrared]] spectrum. <ref>How Stuff Works. (July 27, 2015). ''How Can a Diode Produce Light?'' [Online]. Available: http://electronics.howstuffworks.com/led2.htm</ref> These infrared LEDs are useful in applications like remote controls.

[[File:LEDs.jpg|thumbnail|Figure 2. Red, green, and blue LEDs.<ref>Wikimedia Commons. (July 27, 2015). ''RBG LED'' [Online]. Available: https://upload.wikimedia.org/wikipedia/commons/c/cb/RBG-LED.jpg</ref>]]

Visible LEDs are specifically constructed so that the energy released by electrons filling the holes in the diode corresponds to photons of visible [[wavelength]]s of light. Furthermore, the plastic housing around most LEDs focuses the light in one direction. Although standard diodes end up absorbing a significant fraction of the photons released in them, LEDs are designed to project photons outward from the diode (see Figure 2).<ref>How Stuff Works. (July 27, 2015).''LED Advantages'' [Online]. Available: http://electronics.howstuffworks.com/led3.htm</ref>

==Developments==
A principle challenge during the emergence of LEDs was the difficulty in finding the right combination of [[doping]] materials and coatings to produce coloured light. For example, as recently as the 1990s Shuji Nakamura's invention of blue LEDs were commercialized.<ref>Edison Tech Center. (July 27, 2015). ''LEDs and OLEDs'' [Online]. Available: http://www.edisontechcenter.org/LED.html</ref> He won a Nobel Prize in Physics for his invention in 2014, as this discovery allowed for the invaluable pioneering of high-efficiency white LEDs as well. For more information on Shuji Nakamura and his Nobel Prize, see [http://www.nobelprize.org/nobel_prizes/physics/laureates/2014/nakamura-facts.html here].

==For Further Reading==
*[[Diode]]
*[[Light]]
*[[Infrared]]
*[[Electron]]
*[[Photon]]
*Or explore a [[Special:Random|random page]]

==References==
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