Toward Laser-Driven Lighting with High Overall Optical Performance: Thermally Robust Composite Phosphor-in-Glass Film

For laser-driven white light sources, phosphor-in-glass films (PiGFs), typically sintered onto substrates with high-thermal conductivity, are developed and emerged as the leading materials. However, compared to other all-inorganic color converters, such as single crystals, transparent ceramics, PiGF suffers from a low saturation threshold, poor thermal stability and limited irradiation durability, which restricts its practical applications. To overcome these limitations, in this study, a series of h-BN-YAG:Ce 3+ PiGF is developed on opaque Al 2 O 3 /transparent Al 2 O 3 (B-Y PiGF@o/t-Al 2 O 3 ) by directly incorporating high-thermal-conductivity fillers into the PiGF. The selective incorporation of h-BN establishes a local heat conduction network, significantly increasing the saturation threshold and luminous flux. Through optimization, a maximum luminous flux of 6015.46 ± 14.46 lm with a saturation threshold of 16.15 ± 0.48 W mm −2 is achieved in reflective excitation mode, outperforming previous high-performance PiGFs. The addition of h-BN both enhanced heat dissipation and improved the uniformity of white light output in transmissive excitation mode, addressing the “yellow ring” effect commonly seen in laser-driven lighting. The application potential of the developed composite has been proven ranging from automotive headlights to medical lighting, offering a path toward enhanced brightness, more efficient, and operational-stable next-generation lighting technologies.