It was in 1907 that the phenomenon known as electro-luminescence was first discovered by Captain Henry Joseph Round of the Marconi Labs. Little did he know that his discovery would pave the way for what would be one of the most life-changing light sources of the 21st century.
More popularly known as LED, Light Emitting Diodes make use of the science of electro-luminescence. Although it was originally used for advertisement purposes, the use of LED as an alternative light source has grown over the past few years. Although smaller than their counterpart, the incandescent, they offer two advantages: (1) they do not make use of filament in order to produce light, which, in turn, leads to the second advantages; (2) it does not heat up. This efficiency makes LED light the more preferred choice in today's world. So, without the filament, how does exactly those LED work lights and LED light bar that we normally see in ad boards work?
In its most basic sense, LED driving lights as well as other products that make use of LED operate by taking advantage of the movement of electrons. Once the correct combination is made, photons are produced, which, in turn, causes the LED to light up.
To be more specific, in order to produce the luminescence that you see in LED work lights, a diode typically made of aluminum, gallium, and arsenide are used. You have to keep in mind that a diode is a semiconductor. Although they are mostly used in order to conduct electricity, not all kinds of diode are able to produce light effectively, with LED being the best one as it is especially structured for such. In some cases, these semiconductors contain atoms of other materials. In its pure form, the Aluminum-Gallium-Arsenide combination bonds perfectly that there is no electron left in order to conduct electricity. By doping, which is the process of adding other atoms, either free electrons are typically formed, or extra spaces are formed where electrons can fit in. This, in turn, makes the material more conductive.
Now, in a LED light bar, the electricity is made to flow to one direction only. For this to happen, electricity has to flow from the P-type layer, or the area where there are holes where the electrons can go to; to the N-type layer. In the absence of electricity, the electrons in the N-type layer flow to the P-type and cover up the holes causing the material to become an insulator. If the electricity is made to run the other way, the current will not flow as the depletion zone is increased.
One of the things that you would have to keep in mind is that the type of material used can have an effect on the light that would be produced. For example, silicone diode can only produce infrared light, which is typically used in TV remote controls. In the same manner, materials that have wider gaps between the lower orbitals and the conduction band might be able to provide a more visible light spectrum.
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