Abstract
Phosphor-in-glass (PiG) is promising for high-power LEDs. However, its practical application still suffers from thermal saturation and carbonization due to poor heat dissipation. This paper developed a robust PiG film which sintered onto a rough, thermal-expansion-matched, high-thermal-conductivity sapphire substrate via a two-step process without organic additives. The composite Ce:LuAG PiG retained 93.91% emission at 225°C. To enhance the light extraction, a refractive-index-matched silicone gel (
n
≈ 1.54) was adopted to eliminate the air gap between PiG and LED chips, obtaining a 13.33–22.95% increase compared to direct chip-on-board. Remarkably, a high luminous flux value of 16911 lm and an electro-optical efficiency value of ~120 lm/W were achieved at 138 W electrical power, higher than the commercial PiG sample tested (saturation at 9608 lm). These superior properties of the PiG-based LED device originated from the rapid heat spreading of sapphire, and the corresponding heat was transferred through the high-thermal-conductivity silicone gel to the LED chips and heat sink. Besides, the maximum operating temperature of PIG1 was 155.7°C at 138 W, with negligible decay and a high luminance exceeding 400 lm/mm
2
, demonstrating great potential for high-power LED lighting and displays.