Cr-Doped Monoclinic Phosphor for Broad-Band NIR LED Emission
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Solution Overview
Problem
Current light sources for broad band near-infrared (NIR) radiation, such as incandescent lamps and NIR light emitting diodes, face limitations in efficiency, size, lifetime, and thermal stability, while NIR phosphor converted LEDs struggle with low quantum efficiency and narrow emission spectra.
Innovation Solution
A light emitting device comprising a fluorescent material with a monoclinic lattice structure doped with trivalent chromium, specifically Li1-xMIxSc1-a-bCr a MIIb(Si1-yGe y)2O6, which converts blue to near UV light into broad band NIR light, offering improved efficiency, temperature stability, and tunable emission characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If incandescent sources are used for broad band NIR radiation, then broad band emission is achieved, but efficiency is low and size is large
Solution Approach 1:
The patent changes the emission parameters by using LED excitation sources with specific wavelength ranges (380-480 nm or 480-550 nm) combined with phosphor materials having specific absorption and emission characteristics, achieving broad band NIR emission (700-2500 nm) with higher energy efficiency compared to incandescent sources
Solution Approach 2:
The patent employs composite phosphor systems combining multiple phosphor materials (e.g., Y3Al5O12:Cr3+, Gd3Sc2Ga3O12:Cr3+, NaYF4:Yb3+,Er3+) with different emission characteristics to achieve broad band NIR coverage while maintaining high quantum efficiency and reducing the need for large device size
2Use of energy by moving object
If NIR light emitting diodes are used, then efficiency and compact size are improved, but emission spectrum is narrow
Solution Approach 1:
The patent introduces phosphor materials as intermediary substances that absorb LED emission in the blue to near UV range (380-480 nm or 480-550 nm) and convert it to broad band NIR light (700-2500 nm), thereby extending the emission spectrum while maintaining LED energy efficiency and compact size
Solution Approach 2:
The patent achieves spectrum broadening by selecting phosphor materials with specific absorption coefficients and emission characteristics, including materials with broad emission bands (FWHM > 200 nm) and tunable emission peaks across the NIR range through compositional adjustments
3Illumination intensity
If quantum dot based fluorescent materials are used, then broad band emission and high internal quantum yield are achieved, but long term stability is limited
Solution Approach 1:
The patent replaces quantum dot materials with inorganic phosphor materials that, while potentially having lower internal quantum yield in some cases, provide superior long term stability, chemical inertness, and resistance to degradation, ensuring reliable operation for extended periods
Solution Approach 2:
The patent uses composite inorganic phosphor systems with stable crystal structures (e.g., Y3Al5O12, Gd3Sc2Ga3O12, NaYF4) that resist thermal degradation, photo-oxidation, and chemical decomposition, maintaining stable broad band NIR emission over long operational periods
4Illumination intensity
If quantum dot based fluorescent materials are used, then broad band emission is achieved, but external quantum efficiency is low
Solution Approach 1:
The patent optimizes the intermediary phosphor materials to minimize non-radiative recombination losses and energy transfer inefficiencies by selecting materials with matched energy levels, proper surface treatments, and optimized host-guest configurations, achieving external quantum efficiency improvements
5Use of energy by moving object
If NIR phosphor converted LEDs are used, then efficiency is improved, but emission spectrum is narrow
Solution Approach 1:
The patent systematically adjusts phosphor composition parameters (e.g., Cr3+ doping concentration, rare earth element ratios, host matrix composition) to broaden emission spectra while maintaining high quantum efficiency, achieving FWHM > 200 nm in some implementations
Solution Approach 2:
The patent combines multiple phosphor materials with complementary emission spectra in single devices, using materials such as Y3Al5O12:Cr3+ (broad band), Gd3Sc2Ga3O12:Cr3+ (tunable), and NaYF4:Yb3+,Er3+ (NIR specific) to achieve comprehensive broad band NIR coverage while maintaining LED energy 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 device achieves enhanced NIR emission efficiency, broadness, and stability, suitable for applications like spectroscopy and bioimaging, with improved control over emission peak position and reduced temperature-induced quenching.
Implementation Method 1
The fluorescent material is configured to convert, e.g. down convert, at least part of the light emitted by the light source into NIR light
Data Source
Figure 1A~1B
Figure 2
Figure 3A~3B
AI summary
The present disclosure relates to a near infrared (NIR) light emitting fluorescent material that is configured to convert light having a wavelength predominantly within the blue part of the electromagnetic spectrum into the NIR light. The present disclosure further relates to a light emitting device. The device comprising a light source configured to emit blue to near UV light and the fluorescent material. The fluorescent material is doped with trivalent chromium and comprises a mono clinic lattice structure. At least part of one or more of the metal ions in the lattice are substituted for a chemically similar ion. As such the fluorescent material may be understood to form solid solution. The fluorescent material has an overall composition: Li1-xMIxSc1-a-bCraMIIb(Si1-yGey)2O6, wherein "MI" represents Na and/or K, and wherein "MII" represents at least one element selected from the group consisting of Ti, V, In, Ga, Y, Lu, Ce, Eu, La and Gd.