Stand-Alone Ceramic Phosphor Composites for Laser-Excited Solid-State White Lighting

Background

Solid state lighting using higher power sources, such as high-power blue light emitting diodes (LEDs) and blue laser diodes (LDs), depend on an inorganic phosphor to absorb the solid-state radiation and emit longer wavelengths. The simplest arrangement is a blue emitting solid state device with a cerium doped yttrium aluminum garnet (Ce:YAG). Current phosphor encapsulation processes utilize a resin or glass component that caps the maximum operating temperature of the device to avoid thermal instability, making these processes unsuitable for the higher flux imposed by high power LEDs or LDs. There is a need for improved methods for achieving high power solid-state lighting systems, and the realization of encapsulation-free phosphor ceramics is required for the next generation of laser-based white lighting due to the temperature limitations of resins.

Description

Researchers at the University of California, Santa Barbara have devised a durable, encapsulation-free ceramic phosphor composite that helps high-power LEDs and laser diodes deliver brighter white light while operating at substantially lower temperatures. This innovative approach reduces the operating temperature of the phosphor material by 50%, reduces the cost of materials, decreases preparation time, and increases lumen output. The composite consists of a phosphor material and a filler oxide. The phosphor material is a UV and blue absorbing inorganic phosphor, such as Ce:YAG, that efficiently converts blue light to yellow. The method uses spark plasma sintering (SPS) material preparation that promotes densification in less than 30 minutes, resulting in very dense and robust samples.

Patent: https://patents.google.com/patent/US11286419B2/en 

Advantages

• Reduces phosphor operating temperature by 50% or more under laser excitation
• Increases light output and supports favorable color quality
• Eliminates the need for resin or glass encapsulation
• Enables rapid preparation, with densification in less than 30 minutes
• Produces dense, mechanically robust composites suited to vibration and mechanical stress
• Can lower material costs through flexible phosphor-to-filler ratios

Applications

• High-power LED white-lighting systems
• Blue laser diode-excited solid-state lighting
• Automotive headlights and other lighting exposed to vibration or mechanical stress
• Phosphor converters and ceramic components for advanced lighting products

Patent Status