Core-Shell Red Phosphor With Mn4+ Gradient for Moisture Resistance
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Solution Overview
Problem
Existing red phosphors, such as K2SiF6:Mn4+, exhibit poor moisture resistance due to surface hydrolysis of MnF62−, leading to performance deterioration in LED packaging devices, while methods to enhance moisture resistance negatively impact luminous efficiency.
Innovation Solution
A core-shell structured red phosphor with varying Mn4+ concentrations, where the innermost layer has the lowest Mn4+ content and the outermost layer has the highest, combined with an outer shell containing minimal Mn4+, to improve moisture resistance and maintain high luminous efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If K2SiF6:Mn4+ phosphor material is used to achieve high luminous efficiency, then the luminous efficiency is improved, but the moisture resistance deteriorates due to surface hydrolysis of MnF62− group
Solution Approach 1:
The phosphor particle is divided into an inner core and an outer shell with different Mn4+ concentrations. The inner core contains the activator Mn4+ for luminous efficiency, while the outer shell has reduced Mn4+ content to prevent surface hydrolysis and improve moisture resistance. This segmentation allows each region to fulfill its specific function independently.
Solution Approach 2:
Different regions of the phosphor particle are given different properties: the inner core has high Mn4+ concentration for strong absorption and high luminous efficiency, while the outer shell has low Mn4+ concentration to minimize surface hydrolysis and maximize moisture resistance. This local differentiation resolves the contradiction between luminous efficiency and moisture resistance.
2Reliability
If reductive agent treatment is applied to enhance moisture resistance, then the moisture resistance is improved, but the luminous efficiency deteriorates
Solution Approach 1:
Instead of uniformly treating the entire phosphor surface with reductive agents, the invention segments the particle into an inner core (with activator) and an outer shell (with reduced activator content). This allows the outer shell to provide moisture resistance while the inner core maintains high luminous efficiency.
Solution Approach 2:
The outer shell is specifically designed with low Mn4+ content to provide moisture resistance without compromising the luminous efficiency generated by the inner core. This local quality differentiation avoids the need for harsh reductive agent treatment that would damage the activator.
3Quantity of substance
If high Mn4+ concentration is used throughout the phosphor particle, then the absorption capability is improved, but the scattering effect increases and luminous efficiency decreases
Solution Approach 1:
The Mn4+ concentration is locally optimized: high concentration in the inner core for strong absorption, and low concentration in the outer shell to minimize scattering and improve light transmission. This spatial distribution resolves the contradiction between absorption capability and luminous efficiency.
Solution Approach 2:
The invention transitions from a uniform three-dimensional distribution of Mn4+ to a radially varying distribution, with concentration increasing from the outer shell toward the inner core. This dimensional variation in concentration allows simultaneous optimization of absorption and light transmission properties.
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 enhances moisture resistance and luminous efficiency by minimizing surface contact with the environment and optimizing activator distribution, ensuring high absorption and reduced scattering of excitation light.
Implementation Method 1
the excitation light is emitted from the blue chip, and after being absorbed by the phosphor in the LED package
Implementation Method 2
after being absorbed by the phosphor in the LED package, the emitted light of the phosphor is transmitted out
Data Source
AI summary
The present application discloses an anti-deterioration red phosphor, and a preparation method and an application thereof, and relates to the field of phosphor materials technology. The anti-deterioration red phosphor of the present application comprises a core-shell structure, the core-shell structure comprises an inner core and an outer shell, the inner core and the outer shell are independently selected from substances shown in a chemical formula I, and the chemical formula I is A2M(1-x)F6:xMn4+. The present application enhances the moisture resistance and anti-deterioration resistance of the phosphor by controlling the atom percentage of Mn4+ to be the lowest in the innermost layer of the inner core and the highest in the outermost layer of the inner core. Additionally, by incorporating an outer shell with minimal or even no Mn4+ content to encapsulate the inner core of the phosphor, it helps maintain a higher luminescent efficiency in coordination with the inner core.