YAG:Ce films for laser-driven white lighting: Annealing temperature and atmosphere-controlled luminescence performances

Abstract

The availability and performance of color converters are crucial for the development of laser-driven white lighting. A challenging and important research topic is the discovery of new and efficient color converters. In this work, a color converter, YAG:Ce films as thin as 12.64 µm on thermally conductive single crystal sapphire, was reported. Spray pyrolysis technique was used to deposit YAG:Ce films. The as-deposited films were smooth, semitransparent, and free of macroscopic defects. The quality of YAG:Ce films, which influenced their luminescence performance under high-power-density laser excitation, was controlled by annealing temperature and atmosphere. The best luminescence performance under high-power laser excitation was exhibited by the films annealed at 1500 °C in CO atmosphere. The YAG:Ce film annealed at 1500 °C in the CO atmosphere remained bright yellow, smooth, semitransparent, and free of macroscopic defects, despite being subjected to 1500 °C for 5 h in the CO atmosphere and being as thin as 12.64 µm. The luminous flux and conversion efficiency of YAG:Ce film annealed at 1500 °C in the CO atmosphere were around 2.6 times higher than those of the film annealed at 1500 °C in the air atmosphere under 10 W·mm−2 laser excitation. The saturation threshold of YAG:Ce film annealed at 1500 °C in the CO atmosphere was 9 W·mm−2. This color converter has great potential for advancing laser-driven white lighting technology.