Phosphorescence
How does your computer display work, or you television or smartphone screen? Information is transmitted via energy and somehow projected on the screen's surface, right? Sorta right, but right enough. The LED chip uses highly energized short wavelengths to create the image you see, but the wavelengths are far too short to be within the visible spectrum. As a matter of fact, the wavelengths emitted by an LED chip would probably burn the eyes out of your head. This is where phosphors come into the picture. Phosphors absorb the super short UV wavelengths and convert them into a lower energized longer wavelength that your eye is capable of seeing. Each type of phosphor absorbs a certain wavelength and displays a correspondingly lower wavelength.
The Rare Earth Phosphors
All that is missing is a rare earth element that phosphors yellow and you would have the three primary colors. Luckily, magnesium and copper doped zinc sulfide does the trick.
- Yttrium - red
- Europium - blue
- Terbium - green