how do LED’s work and why are they so much more energy efficient than light bulbs?
(Chemistry)
In: Technology
Normal lightbulbs work by running electricity through a small wire (filament) and heating it up until it glows. Well when you heat something to be white hot its going to give off some energy as visible light but most of it (96-98%) is going to be given off as heat (IR radiation). Normal incandescent and halogen bulbs only turn 2-3% of their energy into light.
LEDs work by exploiting some quirkier physics. If you take an electron that’s hanging out in a material with a high energy level and then you shove it across a boundary into a material at a much lower energy level then it has to get rid of the energy difference, and to do that it gives off a photon with that energy level. If you tune the difference between the energy levels you can make red, green, blue, even IR and UV LEDs, but each LED is only a single color. The LED bulbs in your home have a layer of phosphor over the LED and this phosphor absorbs the violet-UV light that the LED is setup to emit and turns it into a much broader spectrum of white light which is what you want.
LEDs have some losses because they need a power supply with some inefficiencies to provide the right voltages and currents for them to work, but a screw in LED bulb can turn 15% of the electricity it receives into light you can see while bigger commercial and industrial fixtures can be upwards of 20-28%. The upper limit for white mixing with a phosphor is about 44% so upper 20s is pretty close to ideal.
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