LED Lights At Home

I have a deep curiosity about science, took my share of chem and physics in high school. But that’s about it. When you delve deep into LED’s you quickly get beyond my meager knowledge. So here’s my translation (with apologies to any scientists who shake their heads at my oversimplification!).

Incandescent lights work by using electricty to heat a filament until it glows. The fact that so much heat is given off explains why they are relatively inefficient sources of light.

LEDs work on principles of subatomic physics — but don’t get scared off, I’m not going to go too deep into it. Electrons orbit around the nucleus of an atom at various levels, some of which have higher energy states, others have lower. When an electron “drops” from a higher energy state to a lower energy state, it gives off some of its energy in the form of a photon, which is a unit of light.

The tricks to getting LEDs to work as efficient, bright lighting devices are:

1. Making sure the photons escape. As the photon is emitted, is may get absorbed by another electron which would use the energy to “jump” up to a higher energy state.
2. Getting the right kind of light. Depending on the materials involved and the “gap” between the energy states the electrons move between, the light will be of different wavelenghts. Different wavelenghts result in different colors of light.
3. Concentrating the light. The light can go in any direction as it leaves the “diode”, so additional components in the “bulb” need to direct and focus the light into a usable beam.
4. Getting enought light out of the materials. LEDs have been used for years a indicator lights, which don’t need to emit a lot. To get enough light to read by or to light a room becomes much trickier. You can pack a whole bunch of individual LEDs into a single “bulb” but this gets expensive. Fortunately, the basic materials are semiconductors and some of the processes to make LEDs are similar to the materials used in computer chips. So just as computer speed and memory have increase dramatically as the technology has improved (Moore’s Law), similar efficiency gains have been seen and are predicted for LEDs.

If you want to dig into more of the details, Wikipedia (as usual) has an excellent entry.

Another good article is at How Stuff Works.