Coarse Red Nitride Phosphors for LED Stability
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Solution Overview
Problem
Nitride phosphors used in wavelength converters for LEDs degrade significantly over time due to high temperature and high current intensity, leading to instability in red light emission.
Innovation Solution
The use of coarse particles of (Ca, Sr, Ba)2Si5N8:Eu phosphors with a median particle size greater than or equal to 5 microns, either encapsulated in an organic matrix or as part of an inorganic wavelength converter, enhances stability by improving crystallinity and resistance to degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If nitride phosphors are used in wavelength converters for LEDs, then red light emission is achieved, but stability degrades significantly over time due to high temperature and high current intensity
Solution Approach 1:
The patent changes the particle size parameter of the nitride phosphor to coarse particles with D50 greater than or equal to 5 microns. This parameter change improves the phosphor's resistance to degradation under high temperature and high current intensity conditions, thereby maintaining stability and extending service life without compromising red light emission performance
Solution Approach 2:
The patent uses composite material structure by combining coarse particles of (Ca, Sr, Ba)2Si5N8:Eu phosphor with an inorganic matrix material. This composite structure enhances the overall stability and durability of the wavelength converter, allowing it to withstand high temperature and high current intensity conditions for extended periods while maintaining reliable red light emission
2Reliability
If coarse particles of (Ca, Sr, Ba)2Si5N8:Eu phosphors with D50 ≥ 5 microns are used, then stability increases, but manufacturing precision requirements increase
Solution Approach 1:
The patent specifies a minimum particle size threshold (D50 ≥ 5 microns) rather than targeting a precise nominal value. This approach prioritizes achieving sufficient particle coarseness for stability while allowing manufacturing variability, thereby reducing the stringency of particle size control requirements compared to specifying an exact target size
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The coarse particle size of (Ca, Sr, Ba)2Si5N8:Eu phosphors significantly increases the stability of wavelength converters, maintaining high conversion ratios and fluorescence properties even after prolonged exposure to testing conditions, such as LED maintenance and high-power laser testing.
Implementation Method 1
Absorption of the primary light can excite the wavelength conversion material to a higher energy state. When the wavelength conversion material returns to a lower energy state, it emits secondary light, generally of a different wavelength/wavelength range than the primary light.
Implementation Method 2
The use of coarse particles of (Ca, Sr, Ba)2Si5N8:Eu phosphors with a median particle size greater than or equal to 5 microns, either encapsulated in an organic matrix or as part of an inorganic wavelength converter, enhances stability by improving crystallinity and resistance to degradation.
Data Source
AI summary
Wavelength converters including coarse particles/grains of a red nitride phosphor are disclosed. In some embodiments the red nitride phosphor is a (Ca,Sr,Ba)2Si5N8:Eu phosphor with a D50 grain size or a D50 particle size that is ≥5 microns. The red nitride phosphor may be encapsulated within an organic matrix or present in an inorganic matrix. In the latter case, the inorganic matrix may include fine grains with a D50 grain size <5 microns. Methods of making such wavelength converters and devices including such wavelength converters are also described.