Layered Ceramic Wavelength Converter for LED Thermal Quenching
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Solution Overview
Problem
Ceramic wavelength converter assemblies used in LED applications face thermal quenching issues at elevated temperatures, particularly with YAG:Ce phosphors doped with Gd, which affect brightness, and attempts to improve thermal conductivity through composite materials like YAG:Ce in Al2O3 matrix result in light scattering and reduced internal quantum efficiency.
Innovation Solution
A layered structure ceramic wavelength converter assembly is introduced, comprising undoped and doped YAG layers with Al2O3 barrier layers to prevent dopant diffusion and enhance thermal conductivity, allowing for reduced Gd doping and improved thermal quenching without significant light scattering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If YAG:Ce phosphor is doped with Gd to achieve color steering and high internal quantum efficiency, then brightness and color rendering are improved, but thermal quenching occurs at elevated temperatures reducing brightness
Solution Approach 1:
The phosphor is segmented into multiple layers with different Gd doping concentrations. The first layer has higher Gd doping (1-20 at.%) for color steering and high IQE, while the second layer has lower or zero Gd doping to provide thermal quenching resistance. This segmentation allows each layer to optimize for its specific function without compromising the other.
Solution Approach 2:
Different regions of the phosphor structure are assigned different Gd doping concentrations tailored to local requirements. The first layer near the LED chip receives higher Gd doping for optimal color rendering and efficiency, while the second layer has reduced Gd doping specifically to resist thermal quenching at elevated temperatures.
2Temperature
If Gd doping is reduced or eliminated to improve thermal quenching performance, then brightness at elevated temperatures is improved, but color steering capability and internal quantum efficiency are compromised
Solution Approach 1:
The phosphor is divided into functional segments where the first layer maintains high Gd doping for color steering and high IQE, while the second layer has reduced Gd doping for thermal stability. This ensures that thermal quenching resistance is improved without sacrificing the color rendering and brightness properties provided by Gd-doped regions.
3Temperature
If composite ceramic converter materials like YAG:Ce in Al2O3 matrix are used to improve thermal conductivity, then thermal performance is enhanced, but light scattering increases due to non-cubic crystal structure and refractive index differences reducing in-line transmission
Solution Approach 1:
The crystal structure parameter is changed from non-cubic (Al2O3) to cubic (YAG) by using YAG as the host material for both layers. This eliminates the bi-infringe effect and refractive index mismatch problems associated with Al2O3 matrices, thereby reducing light scattering and improving in-line transmission while maintaining high thermal conductivity through the cubic YAG structure.
4Illumination intensity
If sintering temperature is increased or liquid phase is introduced to improve translucency of composite materials, then light transmission is enhanced, but internal quantum efficiency decreases due to chemical incompatibility and defects
Solution Approach 1:
The chemical composition parameter is optimized by using YAG as the host material for both layers, which provides chemical compatibility and prevents defect formation during sintering. This allows achieving high translucency through standard sintering processes without the chemical incompatibility issues that would reduce internal quantum efficiency.
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 enhances brightness at both room and elevated temperatures, maintaining color steering and internal quantum efficiency while enabling high thermal performance, suitable for high-power LED applications.
Implementation Method 1
two second layers comprising a barrier material and being disposed between the two first layers
Implementation Method 2
LED (light emitting diode) based on phosphors often combines a blue light emitting InGaN chip with a yellow oxide converter such as YAG:Ce(Gd) phosphor/ceramics
Implementation Method 3
a ceramic wavelength converter assembly having a layered structure, comprising two first layers comprising an undoped host material, or a doped host material, two second layers comprising a barrier material and being disposed between the two first layers, and a third layer comprising a doped host material, or an undoped host material and being disposed between the two second layers
Data Source
AI summary
A ceramic wavelength converter assembly has a layered structure. The ceramic wavelength converter assembly includes two first layers having an undoped host material, or a doped host material, two second layers having a barrier material and being disposed between the two first layers and a third layer having an undoped host material, or a doped host material and being disposed between the two second layers. The two first layers include the undoped host material and the third layer includes the doped host material, or the two first layers include the doped host material and the third layer includes the undoped host material.