New Process Boosts YAG Ce Glass for Highpower Lighting

When high-power LED chips operate at peak performance, they generate significant heat, often causing traditional phosphor encapsulation materials to yellow and lose efficiency due to insufficient thermal stability. Achieving the delicate balance between high luminous efficiency and long lifespan in high-power lighting applications—such as laser lighting and automotive headlights—presents both a materials science challenge and a packaging technology dilemma.

Traditional phosphor encapsulation materials face severe performance degradation in high-power lighting scenarios. While conventional high-temperature sintering can produce phosphor-in-glass (PiG) materials, the extreme heat often damages the phosphor's crystal structure. Additionally, interfacial reactions between the matrix and phosphor create harmful layers, drastically reducing luminous efficiency.

In contrast, emerging low-temperature stirring processes optimize glass matrix formulations to lower processing temperatures while preserving the phosphor's crystal integrity. This innovation marks a significant step forward in addressing thermal stability issues.

The study employed a SiO2-P2O5-Al2O3-Na2O-K2O-BaO system as the glass matrix, with precise control over component ratios (40:6:25:15:10:4) to create an optimized glass network:

• Performance Enhancement: Na+ and K+ effectively reduced the glass melting point, while Ba2+ significantly improved mechanical strength. P5+ and Al3+ formed a denser, more stable glass network structure.
• Process Innovation: Researchers replaced traditional high-temperature co-sintering with low-temperature stirring technology to uniformly disperse YAG:Ce phosphors in the glass matrix. Processing at 750°C minimized damage to the phosphor crystal lattice.

A comprehensive comparison between PiG (stirring method) and S-PiG (traditional sintering) samples revealed:

• Quantum Efficiency (IQE): PiG samples achieved 88.03% internal quantum efficiency—close to the original phosphor's 93.72%—and significantly outperformed traditional S-PiG (84.97%).
• Thermal Stability: At 423K, PiG maintained 92.6% of initial luminescence intensity versus S-PiG's 90.3%.
• Photoelectric Conversion: Under 4.26 W/mm² blue laser excitation, PiG demonstrated 222.41 lm/W luminous efficiency. Even at high current (1000 mA), it retained 73.2% initial efficiency, showcasing exceptional thermal resistance.
• Microstructure: HRTEM imaging confirmed clear phosphor-glass interfaces in PiG samples, with intact crystal lattices (0.31 nm spacing), proving the stirring method's superiority in preventing interface corrosion.

This research successfully resolves the longstanding conflict between thermal stability and luminous efficiency in high-power LED packaging through optimized glass matrix composition and low-temperature processing. The innovative stirring method not only reduces production costs but also enhances material reliability under extreme conditions, paving the way for commercial adoption in next-generation high-power white lighting devices.