Phosphor Compositions for High Color Rendering White LEDs
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Solution Overview
Problem
Current white light emitting diodes (LEDs) using complex fluoride phosphors have poor color rendering properties and high color temperature, failing to accurately imitate natural light, necessitating improved phosphor compositions that efficiently absorb blue radiation and enhance quantum efficiency.
Innovation Solution
Development of phosphor compositions comprising specific phases such as L3ZO4(Br2-nXn):Eu2+, L9Z3O12(Br6-nXn):Eu2+, and L5Z2O7(Br4-nXn):Eu2+, where L is Zn, Mg, Ca, Sr, or Ba, and Z is Si or Ge, combined with K2SiF6:Mn4+, to achieve improved color rendering and quantum efficiency in white light emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If YAG phosphor is used in white LED systems, then quantum efficiency is improved, but color rendering properties deteriorate
Solution Approach 1:
The patent combines multiple phosphors with different emission characteristics (yellow-green YAG phosphor, red phosphor, green phosphor) into a single phosphor blend that works together to produce white light with both high quantum efficiency and improved color rendering properties
Solution Approach 2:
The invention uses composite phosphor materials consisting of YAG:Ce3+ combined with red-emitting phosphors (such as CaAlSiN3:Eu2+) and green-emitting phosphors (such as β-SiAlON:Eu2+), creating a composite material that achieves both high efficiency and good color rendering
2Use of energy by moving object
If blue LED excitation is used, then quantum efficiency is maximized, but color temperature becomes too high
Solution Approach 1:
The patent adjusts the color temperature parameter by selecting phosphors with appropriate emission spectra and ratios, transforming the high color temperature blue LED light into warm white light with CCT around 2700K or 3000K while maintaining high quantum efficiency
Solution Approach 2:
The invention uses phosphors that convert blue light into yellow-green, red, and green wavelengths, changing the overall color perception from blue to warm white, thereby reducing the perceived color temperature while preserving energy efficiency
3Illumination intensity
If complex fluoride phosphors are used, then red emission is achieved, but color rendering properties deteriorate
Solution Approach 1:
The patent enhances the red emission component locally by incorporating specific red-emitting phosphors (such as CaAlSiN3:Eu2+ and complex fluoride phosphors) into the phosphor blend, while maintaining overall color rendering balance through complementary yellow-green and green phosphors
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 proposed phosphor compositions enhance red-green color contrast and quantum efficiency, producing white light with improved color rendering properties and reduced color temperature, suitable for general illumination and specific applications like traffic lights.
Implementation Method 1
phosphor compositions and blends that efficiently absorb blue radiation, provide high quantum efficiency, and result in improved color rendering in white light emitting lighting devices
Implementation Method 2
Red-emitting phosphors based on complex fluoride materials activated by Mn4+... absorb blue light strongly
Data Source
AI summary
A lighting apparatus that includes a light source and a phosphor composition radiationally coupled to the light source is presented. The phosphor composition includes a first phosphor that includes a phase of general formula (I):L3ZO4(Br2-nXn):Eu2+wherein 0≦n≦1; L is Zn, Mg, Ca, Sr, Ba, or combinations thereof; Z is Si, Ge, or a combination thereof; and X is F, Cl, I, or combinations thereof.