10/11/2018
History of White LEDs
The first white LEDs weren't explicitly white LEDs. Instead, red, green, and blue LEDs were packed into a single LED enclosure. However, if you mix red, green, and blue light, you will get white light, it's really just a matter of getting the correct proportions of different colored photons.
This remains the standard for RGB LEDs, and some have even experimented with improving the range of color these LEDs can produce. The human eye is extremely sensitive to green frequencies of light, and by adding a fourth LED to a package — it's best called 'emerald', or a slightly bluer shade of green than what we're used to in green LEDs — you can make an LED with a wider color range, or if you prefer, a whiter white.
This was the first method of developing a white LED, and while the LED light bulbs you pick up at the hardware store don't have individual red, green, and blue LEDs inside, it is still a fantastically popular way of creating more colors with LEDs. Those neopixels, WS2812s, or APA101s, all have red, green, and blue LEDs tucked inside one enclosure. Some of the more advanced individually addressable RGB LEDs even add a fourth LED, for white. But how are those individual white LEDs made?
The first white LEDs, made without three individual LEDs, were made with the magic of phosphors. Phosphors are a well-understood science, most commonly found in lighting applications in fluorescent bulbs. Fluorescent bulbs don't produce white light on their own, they produce ultraviolet light by exciting mercury v***r. However, by coating the inside of a fluorescent bulb with a powder, this ultraviolet light can be converted into red, green, and blue light. The result is a fluorescent bulb that lights your garage or workshop.
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