Core-Shell Fluoride Red Phosphor Coating for Wet Resistance
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Solution Overview
Problem
Mn4+ activated fluoride red phosphors used in white light LEDs for liquid crystal displays and high-end lighting suffer from poor wet resistance, leading to reduced luminescence efficiency when exposed to water and oxygen, despite existing surface modification methods that only partially improve waterproof performance.
Innovation Solution
A core-shell structure is formed using a cubic perovskite-type CMgF3 coating layer on Mn4+ doped fluoride red phosphors, such as K2TiF6:0.08Mn4+@KMgF3, to enhance wet resistance, where the CMgF3 shell is generated through a simple co-precipitation method in a CHF2 aqueous solution, reducing hydrofluoric acid usage and synthesizing a water-resistant layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If Mn4+ activated fluoride red phosphor is used to achieve narrowband red emission and high quantum efficiency, then the color gamut and color contrast are improved, but the wet resistance deteriorates causing luminescence efficiency to decrease when exposed to water and oxygen
Solution Approach 1:
The patent applies composite materials by creating a core-shell structure where the core is Mn4+ activated fluoride red phosphor (K2TiF6:0.08Mn4+) and the shell is a protective coating layer (SiO2 or Al2O3). This composite structure combines the luminescent properties of the fluoride phosphor with the protective properties of the oxide shell, achieving both high luminescence efficiency and improved wet resistance.
Solution Approach 2:
The patent uses thin film coating technology to deposit a protective shell (SiO2 or Al2O3) on the surface of the fluoride phosphor particles. This thin film acts as a barrier layer that prevents water and oxygen from reaching the phosphor surface, thereby maintaining luminescence efficiency in humid environments while preserving the optical properties of the core material.
2Reliability
If surface coating methods are applied to improve waterproof performance, then the wet resistance is enhanced, but the luminescence intensity is reduced due to coating layers blocking light
Solution Approach 1:
The patent employs ultra-thin shell layers (SiO2 or Al2O3) that are sufficiently thin to allow light transmission while providing adequate protection against water and oxygen. The thin film structure minimizes light scattering and absorption, thereby reducing the impact on luminescence intensity while still achieving effective waterproofing.
Solution Approach 2:
The patent optimizes the thickness and composition parameters of the protective shell to balance protection and light transmission. By controlling the shell thickness within a specific range and selecting appropriate materials (SiO2 or Al2O3), the patent achieves maximum waterproof performance with minimal impact on luminescence intensity.
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 CMgF3 coated phosphors maintain high luminescent performance even after soaking in water, with absorbance, internal, and external quantum efficiencies remaining at 98.15%, 96.55%, and 94.8% of initial values, effectively overcoming the wet resistance issue and ensuring stable luminescence.
Implementation Method 1
a simple co-precipitation method in a CHF2 aqueous solution
Implementation Method 2
The Mn4+ activated fluoride red phosphor may be effectively excited by the blue light emitted by the LED chips
Implementation Method 3
The d-d orbital electron forbidden transition of Mn4+ may emit a narrow band spectra
Implementation Method 4
The fluoride compounds have low phonon energy and thus have high efficiency in energy conversion
Implementation Method 5
a layer of an inorganic substance or an organic substance so as to achieve a purpose of isolating water molecules in the environment
Data Source
AI summary
The present disclosure relates to the field of inorganic non-metallic optoelectronic functional materials, and discloses wet-resistant fluoride red phosphor and preparation and application thereof, and a white light LED device. The fluoride red phosphor is a core-shell structure: the core is Mn4+ doped fluoride red phosphor, and the chemical structural formula is A2B1-xF6:xMn4+, herein A is at least one of Li, Na, K, Rb, and Cs, B is at least one of Ti, Si, Ge, Zr, and Sn, and 0≤x≤0.4; and the shell is a cubic perovskite-type compound, and the chemical structural formula is CMgF3, herein C is at least one of Li, Na, K, Rb, and Cs. The present disclosure uses CMgF3 generated as a coating waterproof layer, to form the A2B1-xF6:xMn4+ core-shell structure of which the surface is coated by CMgF3, and a wet-resistant problem of the fluoride red phosphor is overcome.