A phosphor-converted LED refers to an LED package that uses phosphor conversion (PC) to broaden the spectral power distribution (SPD) of its optical radiation. An LED chip by nature is a narrow-band emitter with a full width at half maximum (FWHM) value in the range of from about 15 nm to about 30 nm. In order to provide a broad spectrum light source, such as a white light source, the narrow emission spectrum of an InGaN LED chip must be shifted and/or spread in wavelength. In a phosphor-converted blue-pump LED, a phosphor or a mix of phosphors is applied to an LED chip. Part of the light emitted from a blue LED chip is absorbed by the phosphor and re-emitted at longer wavelength by Stokes shift. The re-emitted broad spectrum light and the blue light from the LED chip are mixed to produce composite white light. In a phosphor-converted violet-pump LED, the emission from a violet LED is fully converted by red, green and blue phosphors.
