Phosphor quenching in LED packages: measurements, mechanisms, and paths forward

Abstract

Phosphors in LED packages can experience much higher temperatures (&gt;100&deg;C) and light fluxes (&gt;10 W/cm²) versus traditional phosphors in fluorescent lighting. These conditions place stringent restrictions on LED phosphor selections and requires, to some extent, an understanding of the potential quenching mechanisms that occur within LED packages. In this report, we discuss flux-based and temperature-based quenching of LED phosphors, the measurements used to analyze these quenching processes, and some of the basic mechanisms behind this. It is shown that flux-based quenching in LEDs can be reasonably anticipated through simple design parameters. However, while it is more difficult to <i>a priori</i> predict the thermal quenching of new phosphors and their modifications, it is possible to make initial conclusions about phosphor design through a combination of spectroscopic measurements and chemical inference. This is specifically demonstrated within the Ce³⁺-doped garnet family of phosphors, where there is significant flexibility to modify compositions, leading to initial relationships between composition, emission color, and high temperature quenching.