Abstract: High-power laser lighting has set stringent requirements on phosphor conversion materials in terms of luminous efficacy, color rendering performance, and thermal stability, whereas a single phosphor usually cannot simultaneously satisfy these requirements. In this work, GdYAG:Ce/LuAG:Ce composite phosphor films were fabricated on alumina substrates by screen printing, and the effects of the ratio of glass-to-phosphor (GtP) and the ratio of the two phosphors on their microstructure and optical properties were systematically investigated. The results show that, with increasing GtP, the connection mode between phosphor particles gradually changed from necking to bonding by the glass matrix, and no obvious corrosion of phosphor grains caused by the glass matrix was observed. As the LuAG:Ce content increased, the emission peak of the samples blue-shifted from 568 nm to 520 nm, accompanied by a continuous increase in luminous flux. The optimized sample achieved a luminous flux of 462 lm under 3.2 W blue-laser excitation without significant luminescence saturation. It had a luminous efficacy of 198 lm/W, and a color rendering index of 67. The correlated color temperature remained in the range of 7300-12500 K, and the luminous exitance was higher than 1100 lm/mm². Infrared thermal imaging results under different laser powers demonstrate that the sample maintains excellent luminescence stability even at high power excitation, exhibiting strong resistance to thermal saturation. These results demonstrate that synergistic optimization of luminous efficacy, color quality, and operational stability can be achieved by regulating the GtP and the composition of the phosphors, providing a useful reference for the performance optimization and application of composite phosphor films in high-power laser lighting.

Key words: laser lighting, composite phosphor films, GdYAG:Ce, LuAG:Ce, synergistic optimization