Engineering the Glass Network to Eliminate Interfacial Reactions in CaAlSiN 3 :Eu 2+ Phosphor‐in‐Glass for High‐Power White Lighting and Amber Laser Lighting

ABSTRACT Thermally induced interfacial reactions between nitride phosphors and glass matrices remain a critical bottleneck in the development of high‐performance phosphor‐in‐glass (PiG) for high‐power LED and laser‐driven lighting applications. Herein, we address this challenge by the rational glass design to reconcile its glass transition temperature (T g ), structural stabilization and chemical compatibility. By establishing a correlation between structural evolution and interfacial diffusion, we develop a six‐component glass matrix (CaF 2 ‐Al 2 O 3 ‐SiO 2 ‐B 2 O 3 ‐Na 2 O‐P 2 O 5 ) featuring a low T g (∼453°C) and high chemical inertness. This glass matrix effectively alleviates the thermal degradation of embedded CaAlSiN 3 :Eu 2+ (CASN:Eu 2+ ) phosphors and suppresses interfacial reactions. The resulting CASN:Eu 2+ ‐PiG achieves a high internal quantum efficiency of ∼96%, and its fluorescence lifetime is relatively reduced by only 0.02 µs. A wLED incorporating Y 3 Al 5 O 12 :Ce 3+ and CASN:Eu 2+ in the PiG exhibits a high color rendering index of 90.4 while maintaining a luminous efficiency of 93.1 lm/W. Furthermore, by tuning the (Y,Gd) 3 Al 5 O 12 :Ce 3+ /CASN:Eu 2+ ratio in the PiG film, laser‐driven amber light is achieved for specialized lighting, with a maximum luminous flux of 536.0 lm and a peak luminous efficiency of 101.6 lm/W. This work presents a universal strategy for designing chemically robust, low‐melting glass to advance PiG applications in high‐power solid‐state lighting and specialty light sources.