Download LED diodes

Franck TOUBOUL
390180199
Project no. 42
‫פרנק טובול‬
Thanks to the LED, the famous museum "The Louvre" expects to reduce its energy consumption by 73%.
A light-emitting diode (LED) is a semiconductor light source.
The LED consists of a chip of semiconducting material doped with impurities to create a p-n
junction. As in other diodes, current flows easily from the p-side, or anode, to the n-side, or
cathode, but not in the reverse direction.
The free electrons in the N-type material are repelled by the negative electrode and drawn
to the positive electrode. The holes in the P-type material move the other way. When the
voltage difference between the electrodes is high enough, the electrons in the depletion
zone are boosted out of their holes and begin moving freely again. The depletion zone
disappears, and charge moves across the diode. When current flows across a diode,
negative electrons move on way and positive holes move the other way.
The holes exist at a lower energy level than the free electrons, so when a free electron
falls it loses energy.
This energy is emitted in the form of a light photon. The size of the electron’s “fall”
determines the energy level of the photon, which determines its color (the Bohr model,
studied in class explains this). A bigger fall produces a photon with a higher energy level
and therefor a higher light frequency.
LED applications ( a few of them…. ):
LEDs have several advantages over conventional incandescent lamps. For one thing, they
don't have a filament that will burn out, so they last much longer. Additionally, their
small plastic bulb makes them a lot more durable. They also fit more easily into
modern electronic circuits.
Among other things, they form numbers on digital clocks, transmit information from
remote controls, light up watches and tell you when your appliances are turned on.
Collected together, they can form images on a jumbo television screen or illuminate a
traffic light.
Links:
http://www.20minutes.fr/article/838166/louvre-illumine-diodes-electroluminescentes
http://www.tetes-chercheuses.fr/magazines/numero-2/dossier/des-materiaux-comme-dessculptures-moleculaires-215/
mms://Ntstream2.ddns.ehv.campus.philips.com/efi/86090/ Lumalive.wmv
http://phycomp.technion.ac.il/~webteach/phys3/ph114053/adler/bohr.html
http://fr.wikipedia.org/wiki/Mod%C3%A8le_de_Bohr
http://www.led-fr.net/fonctionnement.htm
http://en.wikipedia.org/wiki/Energy_level
http://en.wikipedia.org/wiki/Light-emitting_diode > other applications
http://www.techno-science.net/?onglet=news&news=3194