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How Do White Light LEDs Work? | Photonics in Everyday Life

The blue light-emitting diode received the Nobel prize in physics in 2014 for its global impact and enabling bright white sources with phosphor converted LEDS. Phosphor converted LEDs contain a blue light-emitting diode, covered by a fluorescent or phosphorescent material called a phosphor. The phosphor absorbs some of the blue light and remits it at longer wavelengths spanning the green, yellow, orange, and red spectrum. When combined with the unabsorbed blue light, white light is observed. While white light can be generated through the combination of separate red, green, and blue emitters, it’s often not as efficient and does not have as high a color rendering index compared to the phosphor converted LED. The choice and amount of phosphor controls how much blue light transmits and tunes the color temperature, where warm white light contains less blue light than cold white light. These phosphor converted LEDs are identified by their yellow phosphor coatings and can be illuminated by external blue light source. This same technique is used for remote phosphor lighting and is the same technology used for some laser projectors as well as laser driven car headlights.