SWIR Garnet Phosphor Compositions for Broad LED Spectroscopy
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Solution Overview
Problem
Existing LED light sources struggle to efficiently emit light in the short-wave infrared (SWIR) spectrum of 1300 - 2200 nm, particularly for applications requiring miniaturized, temperature-stable, and high-sensitivity spectroscopy in devices like smartphones and wearable devices, and lack the mechanical robustness and fast modulating capabilities needed for IR absorption spectroscopy.
Innovation Solution
Development of SWIR phosphors with structurally disordered garnet host lattices doped with sensitizer and rare earth emitter ions, which convert blue or red light into broad-band SWIR wavelengths, providing continuous emission spectra with high efficiency and temperature stability, and can be combined with additional phosphors to extend the emission range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional LED light sources are used, then device structure is simple and ease of manufacture is good, but emission efficiency in SWIR spectrum (1300-2200 nm) is poor and spectral coverage is limited
Solution Approach 1:
The patent employs phosphor-converted LEDs (pcLEDs) that combine a blue LED chip with SWIR-emitting phosphor materials (including garnet-type phosphors like CaAlSiN3:Eu2+ and Li2SiO3:Eu2+). This composite structure allows the blue LED to excite the phosphors, which then emit in the SWIR range, achieving efficient SWIR emission while maintaining the simplicity of LED technology.
Solution Approach 2:
The patent optimizes phosphor composition parameters (rare earth dopant concentrations, host matrix ratios) and physical parameters (particle size distribution, layer thickness) to maximize SWIR emission efficiency. By adjusting these parameters, the system achieves high conversion efficiency from blue light to SWIR wavelengths without requiring fundamentally new device architectures.
2Volume of moving object
If LED size is reduced for miniaturization, then device size decreases suitable for smartphones and wearables, but maintaining high emission intensity and spectral power becomes difficult
Solution Approach 1:
The patent uses phosphor particles with optimized local properties (size distribution, composition homogeneity) to ensure efficient light conversion even in miniaturized devices. The phosphor layer is engineered with specific local characteristics that maximize SWIR emission intensity per unit volume, allowing small devices to maintain high spectral power.
Solution Approach 2:
By combining multiple phosphor materials with complementary SWIR emission characteristics, the patent creates a composite phosphor system that maintains high intensity across the 1300-2200 nm range. This composite approach allows miniaturization while preserving spectral power through synergistic material interactions.
3Reliability
If temperature stability is improved for spectroscopy applications, then measurement reliability increases, but device complexity and thermal management requirements increase
Solution Approach 1:
The patent selects phosphor materials with inherently high thermal stability parameters, including garnet-type phosphors known for their temperature-insensitive emission characteristics. By choosing materials with favorable thermal properties and optimizing their composition, the system achieves temperature stability without complex thermal management systems.
Solution Approach 2:
The phosphor materials themselves provide thermal stabilization through their intrinsic properties, eliminating the need for external temperature control mechanisms. The materials' physical and chemical characteristics naturally resist temperature-induced spectral shifts, making the device self-regulating in terms of thermal performance.
4Adaptability or versatility
If continuous spectral power distribution over wide wavelength range is achieved, then spectroscopy application capability improves, but phosphor material complexity and manufacturing difficulty increase
Solution Approach 1:
The patent achieves continuous SWIR spectrum coverage by segmenting the spectral range and assigning different phosphor materials to different wavelength sub-ranges. For example, certain garnet phosphors cover 1300-1700 nm while others extend to 2200 nm. This segmentation allows each phosphor to be optimized for its specific range while collectively providing continuous coverage, simplifying the manufacturing approach compared to attempting to create a single broadband material.
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 SWIR phosphors enable efficient, miniaturized light sources that provide continuous spectral power distribution over a wide wavelength range, maintaining high conversion efficiency and temperature stability, suitable for spectroscopy, imaging, and point-of-care diagnostics, reducing power consumption and device size.
Implementation Method 1
LEDs may be combined with one or more wavelength converting materials (generally referred to herein as 'phosphors') that absorb light emitted by the LED and in response emit light of a longer wavelength
Data Source
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AI summary
A first luminescent material having peak emission wavelengths in the range of 1600 - 1900 nm comprises a Cr3+ and Tm3+ co-doped garnet phosphor having the general formula (Gd3- u-yTmyREu)[Ga2-a-b-d-eLuaCrbScd Ale]{Ga3-cAlc}O12 with RE = La, Y, Yb, Nd, Ho, Er, Ce, Lu, Sc and 0 ≤ u ≤ 2, 0 < y ≤ 1.5, 0 ≤ a ≤ 1, 0 < b ≤ 0.3, 0 ≤ c ≤ 3, 0 ≤ d ≤ 0.5, 0 ≤ e ≤ 1.8. A second luminescent material having peak emission wavelengths in the range of 1400 - 1600 nm comprises a Cr3+ and Ni2+ co-doped garnet phosphor having the general formula (Gd3-uREu)[Ga2- a-b-d-eNiaCrbLd Ale]{Ga3-cAlc}O12 with RE = La, Y, Yb, Nd, Ho, Er, Ce, Lu, Tm, Sc and L = Ti, Zr, Hf, Sn, Ge, Si and 0 ≤ u ≤ 2, 0 < a ≤ 0.1, 0 < b ≤ 0.3, 0 ≤ c ≤ 3, 0 < d ≤ 0.15, 0 ≤ e ≤ 2. A light source comprises the first and second luminescent materials and one or more semiconductor light emitting diodes arranged to excite luminescence from the luminescent materials to provide short wavelength infrared emission over the range 1300 -2000 nm.