Manufacturers generally opt instead for a simpler and less expensive route, using a blue-emitting LED, indium gallium nitride (InGaN), coupled with a yellow phosphor powder, most commonly an yttrium aluminum garnet (YAG), such as Y3Al5O12, doped with Ce3+. In this design, referred to as a phosphor-converted LED, the blue light excites the phosphor powder, which is usually encapsulated in the outer casing. The light emitted by the yellow phosphor combines with the blue light emitted by the LED to produce white light. This single-phosphor design is energy efficient, and the luminescent materials are chemically and thermally stable, according to Christian Maak, who works in Wolfgang Schnick’s phosphor research group at Ludwig Maximilian University Munich.
by Mitch Jacoby |
November 19, 2018