Wavelength Converting Material Narrowing Emission Bandwidth
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Solution Overview
Problem
Current wavelength converting materials for light-emitting devices, particularly red-emitting phosphors, face challenges in achieving narrow emission bands and high luminous efficacy due to issues like inhomogeneous broadening, spectral overlap, and excessive Stokes shift, which are not adequately addressed by existing host lattice materials.
Innovation Solution
Development of luminescent host lattice materials with specific compositions and structures, such as AE3−x1−y+zRE3−x2+y−z[Si9−wAlw(N1−yCy)[4](N16−z−wOz+w):EUx1,Cex2, featuring a cubic crystal structure, coordinated Eu2+ dopant sites, and optimized cation sizes to minimize secondary phase formation and enhance luminescence properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional host lattice materials are used for red-emitting phosphors, then the emission band becomes broad due to inhomogeneous broadening and spectral overlap, but the luminous efficacy and color rendition deteriorate
Solution Approach 1:
The patent applies local quality by creating distinct substitutional lattice sites with different local environments. The host lattice is designed with specific cation sites (e.g., Ca, Sr, Ba sites) that provide well-defined coordination geometries and chemical environments for the Eu2+ activator. This ensures that Eu2+ ions occupy specific sites with consistent local structures, reducing inhomogeneous broadening while maintaining strong activator-ligand interactions for high luminous efficacy.
Solution Approach 2:
The patent employs parameter changes by systematically varying the host lattice composition and structure to control the Eu2+ emission properties. By adjusting the host material parameters (such as using different alkaline earth metals, controlling stoichiometry, and modifying lattice constants), the patent optimizes the activator-ligand bond lengths and coordination numbers to achieve narrow emission bands with high luminous efficacy, avoiding both excessive broadening and spectral overlap.
2Adaptability or versatility
If multiple substitutional lattice sites are present in the host lattice, then the structure becomes more flexible for activator incorporation, but spectral overlap of emission bands occurs
Solution Approach 1:
The patent resolves this contradiction by designing the host lattice with differentiated local environments at each substitutional site. Each cation site (e.g., Ca-site, Sr-site, Ba-site) is engineered with distinct coordination geometries, bond lengths, and chemical compositions. This ensures that Eu2+ ions at different sites produce well-separated emission bands with minimal spectral overlap, while still allowing flexible activator incorporation through the availability of multiple suitable substitutional sites.
3Stability of the object's composition
If the activator site has low symmetry, then more structural relaxation modes are available in the excited state, but the Stokes shift increases excessively
Solution Approach 1:
The patent applies composite materials by combining the Eu2+ activator with specifically designed host lattice structures that provide optimal symmetry and coordination environments. The host lattice is engineered as a composite system with high-symmetry cation sites (such as cubic, tetrahedral, or octahedral coordination) that constrain structural relaxation modes. This composite structure maintains compositional stability while minimizing the Stokes shift by limiting excited state relaxation pathways, thereby reducing energy loss.
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 materials exhibit high stability, tunable luminescence, and efficient wavelength conversion, leading to improved luminous efficacy and color rendition in light-emitting devices by minimizing Stokes shift and spectral overlap, while maintaining a high degree of lattice condensation and band gap.
Implementation Method 1
luminescent host lattice materials with specific compositions and structures, such as AE3−x1−y+zRE3−x2+y−z[Si9−wAlw(N1−yCy)[4](N16−z−wOz+w):EUx1,Cex2, featuring a cubic crystal structure, coordinated Eu2+ dopant sites
Data Source
AI summary
Embodiments of the invention include a wavelength-converting material defined by AE3−x1−y+zRE3−x2+y−z[Si9−wAlw(N1−yCy)[4](N16−z−wOz+w)[2]]:Eux1,Cex2, where AE=Ca, Sr, Ba; RE=Y, Lu, La, Sc; 0≤x1≤0.18; 0≤x2≤0.2; x1+x2>0; 0≤y≤1; 0≤z≤3; 0≤w≤3.