Red Phosphor Crystal Phase Control for Narrow-Band LED Emission
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Solution Overview
Problem
Current phosphors used in white light-emitting LEDs have unclear emission intensity and conversion efficiency, with a need for improved red phosphors that offer better color rendering and conversion efficiency.
Innovation Solution
A light-emitting device comprising a phosphor with a specific crystal phase composition, where the intensity ratio of peaks in a powder X-ray diffraction spectrum is controlled, and the phosphor has a narrow full width at half maximum, optimizing emission characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional red phosphors (KSF, S/CASN) are used, then red light emission is achieved, but emission intensity is insufficient and conversion efficiency is poor
Solution Approach 1:
The patent changes the chemical composition parameters of the phosphor by incorporating specific ratios of Sr, Ca, and Ba in the formula RexMAaMBbMCcNdXe, where MA includes Sr, Ca, and Ba. This compositional parameter change optimizes both emission intensity and conversion efficiency by adjusting the crystal structure and electronic properties of the phosphor material.
2Illumination intensity
If phosphors with broad FWHM (80-90 nm) are used, then red light emission is achieved, but color purity is reduced and emission wavelength includes low luminous efficiency regions
Solution Approach 1:
The patent achieves narrow FWHM (50-70 nm) by precisely controlling the compositional parameters in the phosphor formula, particularly the ratios of alkali earth metals (Sr, Ca, Ba) and the doping concentration of rare earth elements (Eu, Ce, Pr, Tb, Dy). This parameter optimization narrows the emission spectrum while maintaining high luminous efficiency.
3Illumination intensity
If KSF phosphor is used, then red light emission is achieved, but harmful effects to humans and environment are caused
Solution Approach 1:
The patent replaces harmful KSF phosphor with an environmentally friendly alternative having the formula RexMAaMBbMCcNdXe containing Sr, Ca, and Ba. This substitution maintains red light emission performance while eliminating the harmful effects associated with KSF phosphor, achieving both functional and safety requirements.
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 provides a light-emitting device with enhanced color rendering, color reproducibility, and conversion efficiency, suitable for illumination, image display, and vehicle indicator lamps.
Implementation Method 1
a nitride phosphor that emits red light and a phosphor that emits green light, with blue light from the blue LED chip as excitation light
Implementation Method 2
in a powder X-ray diffraction spectrum, the intensity of a peak for a heterogeneous phase where 2θ is in a specific region and the intensity of a peak for the crystal phase represented by the specific composition
Data Source
AI summary
A phosphor having a favorable emission peak wavelength, narrow full width at half maximum, and/or high emission intensity is provided. Additionally, a light-emitting device, an illumination device, an image display device, and/or an indicator lamp for a vehicle having favorable color rendering, color reproducibility and/or favorable conversion efficiency are provided. The present invention relates to a phosphor including a crystal phase having a composition represented by a specific formula, and when, in a powder X-ray diffraction spectrum of the phosphor, the intensity of a peak that appears in a region where 2θ=38-39° is designated as Ix and the intensity of a peak that appears in a region where 2θ=37-38° is designated as Iy, the relative intensity Ix/Iy of Ix to Iy is 0.140 or less, and a light-emitting device comprising the phosphor.