CaAlSiN Phosphor Transmissivity and Temperature Stability
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Solution Overview
Problem
Existing LEDs, particularly those for automotive use, require higher effectiveness and temperature stability, which current CaAlSiN phosphor materials do not adequately provide.
Innovation Solution
A light-emitting device incorporating a CaAlSiN light converting material with specific compositions and processing methods to achieve high transmissivity, emission efficiency, and temperature stability, including a polycrystalline ceramic material with additives and a sintering process to achieve densities close to theoretical single crystal density, ensuring consistent performance across temperature ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional CaAlSiN phosphor material is used, then the LED can be manufactured with basic optical characteristics, but the effectiveness and temperature stability are insufficient for automotive applications
Solution Approach 1:
The patent applies parameter changes by precisely controlling the chemical composition parameters of the CaAlSiN phosphor material, specifically optimizing the ratios of Ca, Al, Si, and N elements along with controlled amounts of Sr and Eu dopants. The sintering parameters are also optimized with specific temperature ranges (1400-1800°C) and time durations to achieve the desired crystal structure and optical properties. These parameter optimizations simultaneously improve temperature stability and effectiveness while maintaining manufacturability through established ceramic processing techniques.
Solution Approach 2:
The patent employs composite materials by creating a multi-component phosphor system based on CaAlSiN3 with controlled additions of Sr (0-20 at%) and Eu (0.1-5 at%) dopants. This composite approach combines the host matrix CaAlSiN3 with Sr for lattice substitution and Eu for luminescence enhancement, achieving synergistic effects that improve both temperature stability and optical effectiveness. The composite structure allows optimization of multiple properties simultaneously while using standard ceramic manufacturing processes.
2Loss of energy
If the CaAlSiN light converting material absorbs more primary light, then the conversion efficiency increases, but the transmissivity of secondary light decreases
Solution Approach 1:
The patent resolves this contradiction through parameter changes by optimizing the Eu dopant concentration at 0.1-5 at%, which controls the balance between absorption and emission. The Eu concentration is precisely tuned to achieve optimal 450nm light absorption while maintaining high transmissivity in the 580-1000nm wavelength range. Additionally, the sintering temperature and time parameters are optimized to control particle size and density, further balancing absorption efficiency with light transmissivity for maximum overall LED effectiveness.
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 the effectiveness and temperature stability of LEDs, maintaining consistent emission characteristics and mechanical properties, particularly in automotive applications, by achieving high transmissivity and emission efficiency with minimal wavelength shift across varying temperatures.
Implementation Method 1
a light converting element to absorb light emitted from the light source at least partially and to re-emit secondary light with longer wavelengths
Implementation Method 2
a sintering process to achieve densities close to theoretical single crystal density
Data Source
Figure 1
AI summary
Light emitting device with a light source to emit primary light and a light conversion layer to convert at least a part of the primary light into secondary light comprising a CaAlSiN light converting material with a transmissivity of > 10% to = 80% for a light in the wavelength range from > 580 to = lOOOnm.