LED Light Source with Fluoride Phosphor Gradient Distribution
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Solution Overview
Problem
Luminescent materials used in semiconductor lighting devices, such as K2SiF6:Mn4+, degrade when exposed to moisture and elevated temperatures, leading to a decrease in quantum efficiency and color point shift, potentially causing LED failure due to local heating.
Innovation Solution
A lighting device with a polymeric host matrix that hosts particulate luminescent materials of the type M2AX6 doped with tetravalent manganese, where the luminescent material is positioned at a distance from the silicone-air interface, reducing exposure and degradation, with a polymeric host matrix having a reduced luminescent material content in its outer layer to prevent water penetration and maintain stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If luminescent material particles are placed close to the silicone-air interface to maximize light conversion efficiency, then the light conversion efficiency is improved, but the luminescent material degrades faster due to direct exposure to moisture and water penetration
Solution Approach 1:
The patent applies local quality by creating a gradient distribution of luminescent material particles within the polymeric host matrix. The outer layer (within 5μm of the surface) has reduced particle concentration (y/x ≤ 0.1) compared to the bulk material, while inner regions maintain higher concentrations for optimal light conversion. This spatial variation in composition allows the surface to resist moisture degradation while preserving efficient light conversion in the protected interior regions.
2Reliability
If the polymeric host matrix is made thicker to protect luminescent material from water penetration, then the protection from moisture is improved, but the light extraction efficiency decreases due to increased absorption and total internal reflection
Solution Approach 1:
The patent employs a thin polymeric host matrix layer (5μm or less) at the silicone-air interface to provide moisture protection. This thin film approach is sufficient to prevent water penetration to luminescent material particles located in deeper regions, while minimizing light absorption and total internal reflection losses that would occur with thicker layers. The thin film configuration maintains high light extraction efficiency while providing adequate environmental protection.
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 solution results in a more stable color point and efficiency, even when exposed to moisture, with a significant reduction in degradation and LED failure, as the luminescent material is protected from direct water exposure, maintaining performance and extending the lifespan of the lighting device.
Implementation Method 1
a converter element, configured to convert at least part of the light source light into converter element light
Implementation Method 2
the converter element comprises a polymeric host matrix element hosting a particulate first luminescent material
Data Source
AI summary
The invention provides alighting device (1) comprising a solid state light source (10) configured to generate light source light (11) and a converter element (100) configured to convert at least part of the light source light (11) into converter element light (101), wherein the converter element (100) comprises a polymeric host matrix element (120) hosting a particulate first luminescent material (110) of the type M2AX6 doped with tetravalent manganese, wherein M comprises an alkaline cation, wherein A comprises a tetravalent cation, and wherein X comprises a monovalent anion, at least comprising fluorine (F), wherein the particulate first luminescent material (110) is available in the polymeric host matrix element (120) with an average weight percentage x averaged over the polymeric host matrix element (120), wherein the polymeric host matrix element (120) has a first outer face (121), wherein an outer layer volume defined by at least part of the first outer face (121) and a first distance (d1) from said first outer face (121) hosts the particulate first luminescent material (110) with a first local weight percentage y averaged over the outer layer volume with a ratio of the first local weight percentage y over the averaged weight percentage x of y/x≤0.1, and wherein the first distance (d1) is at least 10 μm.