Investigation of White LED Performance with Multi-layer Phosphors

The most common phosphor in white LEDs is YAG:Ce; however, low radiant energy produced by this phosphor in the long wavelength (red) portion of the spectrum results in low color rendering (CRI) values, making the white LEDs less acceptable for general illumination. Mixing a suitable red phosphor with YAG:Ce improves CRI. Past studies have shown that when more than one phosphor is used in a conventional white LED package, mixing two types of phosphors into a single mixture results in lower light output compared to stacking the individual phosphors in layers of specific order. In this manuscript, we present results where two types of phosphor were used in a remote phosphor configuration with scattered photon extraction (SPE). Results show that when using two types of phosphors in an SPE white LED package, several factors will influence its performance.