How LEDs Work Page 2
This is a crude close-up of the semiconducting material, as you can see it consists of two materials separated by a thin gap in the middle –
The material on the left hand side with the + sign has been “doped”, or manufactured in such a way that it would like to gain an electron. A semiconducting material like this is said to have holes in it that it would like to fill up with electrons. It is also positively charged. For this reason it is called a P-Type semiconductor.
On the right hand side the semiconducting material has also been doped, but this time it has been manufactured in such a way that it would like to lose an electron. This material is negatively charged, for this reason it is called an N-Type semiconductor.
When a P-Type and N-Type semiconductor are brought together in such a way a P-N junction is created.
When a current is supplied to such a junction it begins to get interesting –
Both the negatively charged electrons and positively charged holes are forced by the current to move towards the P-N junction, with the electrons wanting to move around and the holes wanting to be filled by an electron.
When the two meet each other they combine, however, as the electron is in a higher state of energy than the hole, it must lose some energy in order to combine with the hole, it does this by releasing a photon of light each time an electron and hole combine –
This process continues and light is emitted out of the P-N junction and is magnified by the lens that surrounds the LED. Hopefully you now have a reasonable grasp of how an LED works, if not this video should clear up any remaining confusion –