Stabilized Fluoride Phosphor for LED Applications
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Solution Overview
Problem
Manganese-activated potassium fluorosilicate (KSF:Mn) phosphors used in LEDs are sensitive to moisture and high temperature, leading to reliability issues and corrosive byproduct formation, limiting their widespread commercial adoption in solid-state lighting.
Innovation Solution
A stabilized fluoride phosphor is developed by coating manganese-activated potassium fluorosilicate particles with an inorganic silicate layer, which acts as a protective barrier against moisture and oxygen, and also shields LED components from corrosive fluoride species, using a sol-gel process involving a reactive silicate precursor, catalyst, and controlled water content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If manganese-activated potassium fluorosilicate phosphors are used in LED applications, then luminous efficacy and color rendering are improved, but reliability deteriorates due to sensitivity to moisture and high temperature
Solution Approach 1:
An aluminum oxide coating layer is applied as an intermediary barrier between the KSF:Mn phosphor particles and the external environment (moisture and oxygen). This coating acts as a protective mediator that prevents direct contact between water/moisture and the phosphor, thereby maintaining reliability while preserving the phosphor's high luminous efficacy and color rendering properties
Solution Approach 2:
The invention creates a composite material structure consisting of KSF:Mn phosphor particles coated with aluminum oxide. This composite structure combines the optical advantages of the fluorosilicate host with the protective properties of the aluminum oxide coating, achieving both high performance and improved stability under moisture and high temperature conditions
2Illumination intensity
If manganese-activated potassium fluorosilicate phosphors are used in LED applications, then color rendering index is improved, but harmful factors increase due to generation of corrosive fluoride species
Solution Approach 1:
The aluminum oxide coating serves as a protective intermediary that prevents corrosive fluoride species generated by the phosphor from reaching and damaging LED components. This barrier layer maintains the phosphor's ability to provide excellent color rendering while isolating the harmful fluoride byproducts from the LED structure
Solution Approach 2:
The invention acknowledges that corrosive fluoride species are generated during phosphor operation, but converts this harmful effect into a manageable issue by containing the fluoride within the coating layer. The coating transforms the potentially damaging fluoride release into a controlled, contained phenomenon that does not compromise LED component integrity
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 silicate coating significantly enhances the stability of KSF:Mn phosphors, maintaining over 90% luminous intensity and reducing color shift during high-temperature storage and operating life tests, while minimizing mass loss and chemical interaction with silicone encapsulants, thus improving the reliability and longevity of LED components.
Implementation Method 1
An inorganic coating on each of the particles. The inorganic coating comprises a silicate
Implementation Method 2
As the reactive silicate precursor undergoes hydrolysis and condensation in the reaction mixture, an inorganic coating comprising a silicate is formed on each of the particles
Implementation Method 3
As the reactive silicate precursor undergoes hydrolysis and condensation in the reaction mixture, an inorganic coating comprising a silicate is formed on each of the particles
Implementation Method 4
using a sol-gel process involving a reactive silicate precursor, catalyst, and controlled water content
Data Source
Figure 1A~2B
Figure 2C~3A
Figure 3B~4
AI summary
A stabilized fluoride phosphor for light emitting diode (LED) applications includes a particle comprising manganese-activated potassium fluorosilicate and an inorganic coating on each of the particles. The inorganic coating comprises a silicate. A method of making a stabilized fluoride phosphor comprises forming a reaction mixture that includes particles comprising a manganese-activated potassium fluorosilicate; a reactive silicate precursor; a catalyst; a solvent; and water in an amount no greater than about 10 vol.%. The reaction mixture is agitated to suspend the particles therein. As the reactive silicate precursor undergoes hydrolysis and condensation in the reaction mixture, an inorganic coating comprising a silicate is formed on the particles. Thus, a stabilized fluoride phosphor is formed.