How Does a LED Work?

We've heard all the talk about LED's. How they're the newest and best lighting technology. Well, all of that is true, but how do LED's work? In this post, I thought that we would tackle that question.

Have you ever wondered how an LED flashlight
like the FOURSEVENS Maelstrom MMS worked?
Let's start by quickly looking at some basic lighting technology. We've all seen incandescent bulbs. They're your average light bulb. They work by heating up a tiny metal filament that glows. These bulbs generate a lot of heat vs. the amount of light produced. This wastes a lot of energy. To the flashlight user, this means that runtimes are shortened drastically and the lights are usually not very bright.

The inefficiency of incandescent bulbs was a problem. When there's a problem, people try and find a solution. Moving forward a few decades, we come to the LED, which stands for Light Emitting Diode. LED's are the brightest, most compact light emitters that are commonly available in flashlights. They are very energy efficient, small, durable and are quickly becoming less and less expensive. I wouldn't call them the future of lighting technology, since they're here already, it's just that some people haven't caught up with the times yet.

This leads me to my original question: How does a LED work?

A LED emitter is called a diode, not a bulb. A diode is a device that conducts and electrical current in only one direction. A bulb is not a diode since it will work with an electrical current flowing through it in either way. An LED will only work with current flowing through it in one direction.

Illustration of simple light emitting diode (LED)
Source: http://www1.eere.energy.gov/buildings/ssl/how.html
An LED is made up of semiconductors, which are materials that have a varying ability to conduct electricity. Inside of an LED, there are two types of semiconductors: one that has an abundance of electrons (N-Type) and one that has room for more electrons (P-Type). The P-Type semiconductor can be thought of as having many holes for electrons to fall into. As a quick chemistry reminder, electrons are negatively charged particles that orbit atoms. The flow of electrons is what we normally call electricity.

Anyways, when an electrical current is applied to the diode, electrons travel from the N-type side to the P-Type side. When the electrons fall into one of the holes in the P-Type side, they release energy. Think of what happens when you drop a ball into a hole; the energy from the ball is transferred to whatever the hole is in. What can happen when an electron releases energy is really amazing, though. The energy from the electron falling into the hole is released in the form of a photon, which is a particle of light.

This continuous movement of electrons falling into the holes releases light, causing the LED to glow. This phenomena doesn't create much heat, so it's a lot more efficient than an incandescent bulb.

The yellow phosphor on the Quark Tactical QT2A
changes blue light to white light.
LED's can also be specialized to emit specific wavelengths of light based on the semiconductor used. A red LED uses aluminum gallium arsenide (ALGaAs), a green LED uses aluminum gallium phosphide (AlGaP) and a blue LED uses indium gallium nitride (InGaN). While LED's, which are unique since white light consists of all colors of the rainbow, can be made by either combining red, green and blue LED's or by coating a blue LED with a yellow phosphor. In case you were wondering why your LED flashlight has a thin coating of yellow on the emitter, this is why.

Now, I hope that you guys understood all that and that it didn't all go over your head. I figured that with a Flashlight Blog, and with so many LED flashlight reviews, you would be wondering how the technology worked. It's amazing and you can be assured that in the future, the technology will get better and better.

The future does seem pretty bright, doesn't it? (pun intended)

Sources Used:
-Wikipedia. Diode. http://en.wikipedia.org/wiki/Diode
-How Stuff Works. How Light Emitting Diodes Work.
 http://electronics.howstuffworks.com/led.htm
-U.S. Department of Energy. Using Light-Emitting Diodes.
 http://www1.eere.energy.gov/buildings/ssl/how.html