A Thermally Robust La3Si6N11:Ce‐in‐Glass Film for High‐Brightness Blue‐Laser‐Driven Solid State Lighting

Abstract Color converter is a key luminescent material in the laser‐driven solid state lighting, which must bear high‐density excitation and serious thermal attack from the incident laser. Here, a thermally robust yellow‐emitting La 3 Si 6 N 11 :Ce‐in‐glass (LSN:Ce‐PiG) film for laser lighting is reported by co‐firing the LSN:Ce and glass powders on a thermally conductive sapphire substrate. No detectable interfacial reaction occurs between the LSN:Ce particle and glass matrix, enabling the film to fully inherit the original thermal robustness and high quantum efficiency. The optical performance of LSN:Ce‐PiG‐converted white laser light has been effectively optimized by changing the phosphor‐to‐glass (PtG) ratio and the film thickness. The highest light conversion efficiency is respectively achieved at PtG = 2:3 and the thickness of 70 µm, and the saturation threshold is found to decrease with either a higher PtG ratio or a thicker film. The optimized LSN:Ce‐PiG film (P2G3‐50) can withstand a maximum laser power density of 12.91 W mm −2 and produce a cool white light with a high luminous flux of 1076 lm (luminance of 773 Mcd m −2 ), a luminous efficiency of 166.05 lm W −1 , a color rendering index of 70. These results make the LSN:Ce‐PiG film a considerably promising color converter for laser lighting.