Color temperature constancy of phosphor converted LED modules: a combined thermal and optical simulation study on the materials requirements

Abstract

Color temperature constancy and color maintenance are key issues in the context of the utilization of light-emitting diodes (LEDs) for general lighting applications. For a systematic approach to improve the white light quality of phosphor converted LEDs and to fulfill the demands for color temperature constancy, it is imperative to understand how compositional, optical and thermal properties of the color conversion elements (CCE), which typically consist of phosphor particles embedded in a transparent matrix material, affect the correlated color temperature of a white LED source. In this contribution we discuss, based on combined optical and thermal simulations, the dependencies of the quantum efficiency of the phosphor and the thermal conductivity of the matrix material on the temperature increase within the CCE. We show that even small improvements of these parameters may have a notable beneficial impact on the thermal load of the CCEs and therefore also temperature related insufficiencies of the device performance.