Fluoride Phosphor Mn4+ Ratio for LED Luminance
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Solution Overview
Problem
Fluoride phosphors excited by blue light to emit red light face challenges in providing sufficient luminance and durability for white LEDs, with existing solutions not adequately addressing light emitting properties and compatibility with color filters.
Innovation Solution
A fluoride phosphor with a composition of A2SiF6:Mn4+, where A is at least one alkali metal, specifically potassium, and a controlled peak area ratio determined by XPS measurement to optimize the amount of Mn4+ bonded to oxygen and fluorine, enhancing light emitting properties and luminance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a fluoride phosphor with Mn4+ as luminescent center is used to achieve sharp emission spectrum, then color rendering property and color reproducibility are improved, but durability decreases and luminescent color changes over time
Solution Approach 1:
The patent applies parameter changes by precisely controlling the Mn4+ concentration and the ratio of fluoride to oxygen in the phosphor composition. By adjusting these chemical parameters within specific ranges, the patent achieves a balance between emission spectrum sharpness and durability, preventing luminescent color changes while maintaining the desired spectral characteristics.
Solution Approach 2:
The patent uses composite materials by combining Mn4+ activated fluoride phosphor with other phosphors in a multi-phosphor system. This composite approach allows the fluoride phosphor to provide sharp emission for color reproduction while other phosphors compensate for durability issues and maintain stable luminescent color over time.
2Power
If red phosphor with broad emission spectrum is used to improve fluorescence conversion efficiency, then luminance increases, but color reproduction range decreases
Solution Approach 1:
The patent segments the red phosphor emission into multiple narrow bands using different phosphors with distinct emission wavelengths. Instead of using a single broad-emission phosphor, the patent employs multiple phosphors (including the fluoride phosphor with Mn4+) that collectively cover the red spectrum with sharp, well-defined emission lines, thereby achieving both high conversion efficiency and excellent color reproduction.
Solution Approach 2:
The patent uses composite materials by combining multiple red-emitting phosphors with different emission characteristics. This composite phosphor system maintains high fluorescence conversion efficiency while providing a broader and more accurate color reproduction range through the complementary emission spectra of the individual phosphors.
3Illumination intensity
If Mn4+ concentration in fluoride phosphor is increased to enhance red light emission, then color rendering improves, but luminescent color stability decreases
Solution Approach 1:
The patent applies parameter changes by optimizing the Mn4+ concentration within a specific range rather than simply increasing it. By controlling the Mn4+ content and the fluoride-to-oxygen ratio within precise boundaries, the patent achieves strong red light emission while maintaining luminescent color stability and preventing degradation over time.
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 optimized fluoride phosphor exhibits improved light emitting properties and luminance when used in white LEDs, maintaining durability and compatibility with color filters, thereby enhancing the performance of light emitting devices.
Implementation Method 1
fluoride phosphors excited by blue light to emit red light
Implementation Method 2
a ratio (A1/A2) of an area (A1) of a spectrum in a range of from 637 eV or more to less than 645 eV in XPS measurement
Data Source
AI summary
Provided is a fluoride phosphor having a composition represented by the general formula (1):A2SiF6:Mn4+ (1)in which A represents at least one alkali metal comprising at least K. The fluoride phosphor has a ratio (A1/A2) of an area (A1) of a spectrum in a range of from 637 eV or more to less than 645 eV in XPS measurement to an area (A2) of a spectrum in a range of from 682.8 eV or more to less than 690 eV in XPS measurement, of 0.0008 to 0.0025.