MAS:Eu-YAG:Ce composite phosphor converters with excellent thermal performance and enhanced color rendering index for high-power white LDs

Abstract

Phosphor converters with excellent thermal performance and high color rendering index (CRI) demonstrate vast application prospects in the field of laser diodes (LDs) lighting. Nevertheless, the significant heat accumulation within the converters and the absence of red spectral components pose challenges in achieving both a high saturation threshold and a high CRI for Y3Al5O12:Ce phosphor converters destined for white LDs. In this work, Mg2Al4Si5O18:Eu/Y3Al5O12:Ce (MAS:Eu/YAG:Ce) composite phosphor converters with excellent thermal performance and enhanced CRI were designed and fabricated for reflective laser lighting. Impressively, MAS:Eu/YAG:Ce phosphor-glass-ceramic composites (PGCC) retained a remarkable 97.8 % of the room temperature emission intensity at 150 °C. The reasons for this could be attributed to the strong thermal quenching resistance exhibited by MAS:Eu phosphors, as well as the ultra-thin glass bonding layer of about 150–200 μm. Meanwhile, by integrating the MAS:Eu/YAG:Ce PGCC with a 450 nm laser source, white LD devices operating in a remote excitation mode were fabricated. These white LDs demonstrated an improved CRI of 76 and maintained a low surface temperature of 131.7 °C under an ultra-high laser power density of 47.8 W/mm2 (laser power ∼ 4.70 W). Moreover, the maximum luminous flux and luminous efficiency of the white LDs were 484 lm and 103 lm/W, respectively. Therefore, the design of MAS:Eu/YAG:Ce composite phosphor converters offers a new approach for the development of high-power white LDs.