CaAlSiN3 Phosphor Co-Doped with Europium and Cerium for Warm White LEDs
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Solution Overview
Problem
Current phosphor materials used in light emitting diodes (LEDs) for producing warm white light often suffer from suboptimal color rendering index (CRI) and reduced conversion efficiency, particularly when combining yellow and red phosphors, which can lead to unnatural color representation and increased re-absorption issues.
Innovation Solution
The use of CaAlSiN3 phosphors co-doped with Europium (Eu2+) and Cerium (Ce3+) to produce a phosphor with an emission band ranging from 500 to 700 nm, offering improved CRI and conversion efficiency when used with blue emitting LEDs, thereby generating warm white light with a correlated color temperature (CCT) between 2500 and 4500K.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple phosphors are combined to produce warm white light, then color rendering index is improved, but conversion efficiency decreases due to re-absorption issues
Solution Approach 1:
The patent combines yellow-emitting and red-emitting phosphors in a single composition to achieve warm white light with improved color rendering. The phosphors are integrated at the material level rather than being separate layers, which reduces re-absorption losses while maintaining broad spectral coverage for accurate color representation.
Solution Approach 2:
The invention uses a composite phosphor material containing multiple dopants (Europium and Cerium) in a host matrix (such as Sr2Si5N8). This composite structure allows simultaneous optimization of color rendering properties and conversion efficiency by coordinating the emission spectra of different phosphor components within a single integrated material system.
2Measurement precision
If yellow and red phosphors are combined for warm white light, then color accuracy improves, but manufacturing complexity increases
Solution Approach 1:
The patent merges multiple phosphor functions into a single compositional system that can be processed as one homogeneous material. This unified approach simplifies manufacturing by eliminating the need for separate deposition or assembly steps for different phosphor layers, while still achieving accurate color rendering through the coordinated emission of yellow and red components.
3Device complexity
If conventional phosphors are used in LEDs, then device simplicity is maintained, but color rendering index remains suboptimal
Solution Approach 1:
The patent modifies the compositional parameters of the phosphor material by incorporating specific dopant concentrations (Europium and Cerium) in optimized ratios. This parameter optimization enables the phosphor to emit a broader spectrum that improves color rendering index while maintaining compatibility with standard LED fabrication processes, thus preserving device simplicity.
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
This approach provides warm white light with a CRI of at least 80, improved conversion efficiency of 60% to 100%, and reduced re-absorption, while simplifying manufacturing by using a single type of phosphor, thus enhancing the color accuracy and efficiency of LED lighting.
Implementation Method 1
phosphor particles, which may responsively emit light at a second wavelength
Implementation Method 2
The light from a single-color LED may be converted to white light by surrounding the LED with a wavelength conversion material, such as phosphor particles
Data Source
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AI summary
New compounds are disclosed which may be used as phosphors in solid state light emitting devices. The compounds have the general Formula I: AaBbCcDdEe (I) wherein A comprises one or more elements selected from Ca, Sr, Ba, Mg, Y, Hf, the lanthanide elements and the alkali metals; B comprises Eu and Ce; C comprises one or more tetrahedrally-coordinated trivalent elements; D comprises one or more tetrahedrally-coordinated tetravalent elements; E comprises one or more elements selected from N, O, F, C, S, Cl, Br and I, wherein a+b=1 and c+d=2; and the compound has a CaAlSiN3-type crystal structure. Compounds of Formula I which include both cerium and europium, may be useful as phosphors in solid state light emitting devices. Light emitting devices including such phosphors may emit warm white light.