Chromium-Doped Pyroxene Phosphors for Broadband NIR Emission
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Solution Overview
Problem
Existing luminescent materials for phosphor-converted LEDs often lack broad band emission, thermal stability, and chemical stability, particularly against moisture and air, which limits their efficiency and reliability in infrared applications.
Innovation Solution
Development of a luminescent material composition E1-wSc1-x-y-u-wMyZuA2wSi2-z-uGezAluO6:Crx, where Cr3+ substitutes for octahedrally coordinated Sc and/or M atoms, offering broad band emission in the 700-1100 nm range with high quantum efficiency and stability, and adjustable emission characteristics through Sc and M atom ratios, along with the incorporation of elements like Mg and Ni for enhanced properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional phosphor materials are used, then narrow spectral emission is achieved, but broadband emission is not obtained
Solution Approach 1:
The patent employs a composite phosphor system combining multiple chromium-doped phosphor materials with different emission characteristics. Specifically, it uses a combination of LiSc1-x-y Lu_y Si2O6:Cr_x and LiSc1-x-y (Lu,Al)_y Si2O6:Cr_x phosphors, where each component contributes to different portions of the infrared spectrum, achieving broadband emission through material composition rather than structural modification.
2Use of energy by moving object
If phosphor concentration in optical path is increased, then light absorption by phosphor is improved, but thermal stability deteriorates
Solution Approach 1:
The patent optimizes the phosphor concentration parameter within specific ranges (0.5-5 wt% for first phosphor, 2-10 wt% for second phosphor) to achieve the optimal balance between light absorption efficiency and thermal stability. This quantitative parameter control prevents excessive phosphor loading that would cause thermal degradation while ensuring sufficient absorption of LED emission.
3Quantity of substance
If phosphor layer thickness is increased, then light absorption is enhanced, but chemical stability against moisture and air deteriorates
Solution Approach 1:
The patent uses a composite phosphor system where chromium-doped pyroxene phosphors are combined with other infrared phosphor materials. This composite approach distributes the functional requirements across multiple stable materials rather than relying on a single thick layer of one phosphor type, thereby maintaining chemical stability while achieving sufficient light absorption through the synergistic effects of the composite system.
4Use of energy by moving object
If chromium concentration is increased, then quantum efficiency is improved, but emission bandwidth is reduced
Solution Approach 1:
The patent segments the infrared emission spectrum by using multiple phosphor materials, each doped with chromium at optimized concentrations. The first phosphor (LiSc1-x-y Lu_y Si2O6:Cr_x) and second phosphor (LiSc1-x-y (Lu,Al)_y Si2O6:Cr_x) are each formulated with specific chromium content ranges (0.01≤x≤0.1 and 0.01≤x≤0.05 respectively) to achieve high quantum efficiency in their respective emission bands, while the combination of multiple segmented phosphors produces the overall broadband emission spectrum.
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 luminescent material composition provides high quantum efficiency, broad spectral emission, and improved thermal and chemical stability, enabling efficient broadband NIR emission with high reliability for infrared applications, such as in phosphor-converted LEDs.
Implementation Method 1
Cr 3+ substitutes for octahedrally coordinated Sc and/or M atoms and provides broadband emission in the 700-1100 nm range
Data Source
Figure 1~2
Figure 3~7(III)
Figure 8A~8B
AI summary
The invention provides luminescent material (1) comprising E1-wSc1-x-y-u-wMyZuA2wSi2-z-uGezAluO6:Crx, wherein: - E comprises one or more of Li, Na, and K; - M comprises one or more of Al, Ga, In, Tm, Yb, and Lu; - Z comprises one or more of Ti, Zr, and Hf; - A comprises one or more of Mg, Zn, and Ni; - 0<x≤0.25; - 0≤y≤0.75; - 0≤z≤2; - 0≤u≤1; - 0≤w≤1; - x+y+u+w≤1; and - z+u≤2.