Fluoride Phosphor Gradient Mn4+ Distribution for Moisture Resistance
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Solution Overview
Problem
Existing semiconductor light emitting devices face challenges in achieving reliable color reproduction and moisture resistance due to the uniform distribution of Mn4+ in fluoride phosphors, which affects their performance and longevity.
Innovation Solution
A fluoride phosphor with a composition of AxMFy:Mnz4+, where A is lithium, sodium, potassium, rubidium, or cesium, and M is silicon, titanium, zirconium, hafnium, germanium, or tin, with a gradually reduced Mn4+ concentration from the center to the surface, and an organic material like oleic acid physically adsorbed to enhance hydrophobicity, is used in a light emitting device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Mn4+ is uniformly distributed in fluoride phosphor, then manufacturing process is simple, but moisture resistance and reliability deteriorate
Solution Approach 1:
The patent applies local quality by creating a non-uniform Mn4+ concentration distribution within the fluoride phosphor particles. The concentration is higher at the core and lower at the surface, forming distinct zones with different functional properties. This gradient structure improves moisture resistance by reducing Mn4+ exposure at the surface while maintaining发光 performance through sufficient Mn4+ concentration in the core region.
Solution Approach 2:
The patent segments the fluoride phosphor particle into distinct concentration zones: a core region with high Mn4+ concentration (3-8 at.%) and a surface region with low Mn4+ concentration (0.1-2 at.%). This segmentation allows different regions to fulfill different functions - the core provides luminous efficiency while the surface provides moisture protection.
2Illumination intensity
If Mn4+ concentration is high throughout fluoride phosphor, then color emission intensity is improved, but vulnerability to moisture increases
Solution Approach 1:
The patent uses local quality to concentrate Mn4+ in the core region where it is needed for color emission, while reducing it at the surface where it would be vulnerable to moisture. The core region maintains high Mn4+ concentration (3-8 at.%) for strong color emission, while the surface region has low concentration (0.1-2 at.%) for moisture resistance.
3Reliability
If organic material is physically adsorbed onto fluoride particle surface, then hydrophobicity is improved, but manufacturing process complexity increases
Solution Approach 1:
The patent applies preliminary action by performing physical adsorption of organic material onto the fluoride particle surface as a post-synthesis treatment step. The organic material is adsorbed onto the already-formed fluoride particles with gradient Mn4+ distribution, providing hydrophobicity protection without requiring complex in-situ synthesis methods.
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 fluoride phosphor exhibits improved reliability and moisture resistance, leading to enhanced performance and longevity of light emitting devices by reducing the vulnerability to moisture and maintaining high internal quantum efficiency.
Implementation Method 1
an organic material physically adsorbed onto surfaces of the fluoride particles to allow the fluoride particles to have hydrophobicity
Implementation Method 2
a wavelength conversion unit absorbing excitation light emitted by the light emitting element to emit visible light
Data Source
AI summary
A fluoride phosphor includes fluoride particles represented by AxMFy:Mnz4+ where A is at least one selected from lithium (Li), sodium (Na), potassium (K), rubidium (Rb), and cesium (Cs), M is at least one selected from silicon (Si), titanium (Ti), zirconium (Zr), hafnium (Hf), germanium (Ge) and tin (Sn), a compositional ratio x of A satisfies 2≤x≤3, and a compositional ratio y of F satisfies 4≤y≤7; and an organic material physically adsorbed onto surfaces of the fluoride particles to allow the fluoride particles to have hydrophobicity. The fluoride particles have a concentration of Mn4+ gradually reduced from respective centers to respective surfaces of the fluoride particles.