Alkaline Earth Aluminate Phosphors for pc-LED Color Quality
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Solution Overview
Problem
Current phosphor converted light emitting diodes (pc-LEDs) using blue-emitting LEDs face challenges such as sensitivity to variations in blue LED chip emission wavelength, lack of red component in white light emission, and low thermal stability, which affect color quality and efficiency.
Innovation Solution
Development of alkaline earth aluminate phosphors excited in the near-UV or violet region, specifically Ba0.75Al11O17.25 doped with Eu2+, which exhibit strong absorption in the near-UV or violet region and efficient emission in the green spectral region, reducing sequential absorption and emission processes and enhancing luminescence efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If blue-emitting LED chips are used as primary light sources, then white light can be generated through phosphor conversion, but the system becomes sensitive to variations in blue LED emission wavelength affecting color quality
Solution Approach 1:
The patent introduces a near-UV or violet LED as an intermediary primary light source that excites multiple phosphors (including the alkaline earth aluminate phosphor) to generate white light. This intermediary approach eliminates direct dependence on blue LED wavelength variations, as the near-UV/violet excitation source operates at a different spectral region, thereby improving reliability and reducing sensitivity to blue LED chip variations.
2Illumination intensity
If blue LED + yellow phosphor systems are used, then white light is produced, but the red component is missing resulting in poor color rendering
Solution Approach 1:
The patent employs a composite phosphor system consisting of multiple phosphor materials including the alkaline earth aluminate phosphor with specific emission characteristics. This composite approach combines phosphors with different emission spectra to generate a complete white light output with adequate red, green, and blue components, thereby improving color rendering index while maintaining manufacturing feasibility through a unified phosphor conversion layer.
3Use of energy by moving object
If conventional phosphors are used in pc-LEDs, then light conversion is achieved, but thermal stability is insufficient at operating temperatures above 150°C
Solution Approach 1:
The patent modifies the chemical composition parameters of the phosphor material by incorporating specific alkaline earth metals and controlling the stoichiometry of the aluminate structure. This parameter optimization enhances the thermal stability of the phosphor, allowing it to maintain its luminescence properties and structural integrity at elevated operating temperatures above 150°C, thereby resolving the thermal stability issue while preserving light conversion 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 alkaline earth aluminate phosphors provide improved color rendering index, thermal stability, and quantum efficiency, enabling the production of high-quality white light with reduced sensitivity to blue LED chip variations and enhanced emission efficiency.
Implementation Method 1
alkaline earth aluminate phosphors excited in the near-UV or violet region, specifically Ba0.75Al11O17.25 doped with Eu2+, which exhibit strong absorption in the near-UV or violet region and efficient emission in the green spectral region
Data Source
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AI summary
The present invention relates to alkaline earth aluminate phosphors, to a process for the preparation thereof and to the use thereof as conversion phosphors. The present invention also relates to an emission-converting material comprising at least the conversion phosphor according to the invention, and to the use thereof in light sources, in particular pc-LEDs (phosphor converted light emitting devices). The present invention further more relates to light sources, in particular pc-LEDs, and to lighting units which comprise a primary light source and the emission-converting material according to the invention.