LiF-Doped CaAlSiN3:Eu Phosphor Narrowband Emission
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Solution Overview
Problem
Existing red-emitting phosphors for LEDs suffer from broadband emission and poor thermal stability, limiting their efficiency and applicability in specific applications requiring shorter-wave emission and high visual effectiveness.
Innovation Solution
A red-emitting phosphor composed of an M-Al—Si—N system activated with Eu and incorporating LiF, which improves phase formation, homogeneity, and thermal stability, shifting emission towards shorter wavelengths and enhancing efficiency without adverse effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional red-emitting phosphors (calsins or nitrides) are used, then high efficiency and thermal stability are achieved, but broadband emission occurs which reduces visual effectiveness
Solution Approach 1:
The patent applies parameter changes by modifying the phosphor composition through LiF doping. Specifically, adding 0.1-5 mol% LiF to the CaAlSiN3:Eu phosphor changes the emission characteristics from broadband to narrowband while maintaining thermal stability. The LiF incorporation shifts the emission peak to shorter wavelengths (around 630-650 nm) and narrows the full width at half maximum (FWHM) to 80-120 nm, thereby improving visual effectiveness without sacrificing thermal stability.
2Use of energy by moving object
If conventional red-emitting phosphors are used, then high efficiency is achieved, but emission wavelength is too long which reduces visual useful effect
Solution Approach 1:
The patent changes the emission wavelength parameter by incorporating LiF into the phosphor lattice. The LiF doping shifts the emission peak from longer wavelengths (>650 nm) to shorter wavelengths (630-650 nm), which are more effective for human visual perception. This parameter change maintains the high quantum efficiency of the original phosphor while improving the visual useful effect by aligning the emission spectrum better with the human eye's sensitivity curve.
3Reliability
If LiF is incorporated into the phosphor, then thermal stability and emission wavelength are improved, but phase formation and homogeneity must be maintained
Solution Approach 1:
The patent carefully controls the LiF concentration parameter within the range of 0.1-5 mol% to achieve optimal phase formation and homogeneity. At these controlled concentrations, LiF incorporates uniformly into the phosphor lattice without forming separate phases or causing compositional inhomogeneity. This precise parameter control ensures that the thermal stability improvements are achieved while maintaining the structural integrity and homogeneity required for manufacturing consistency.
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 phosphor exhibits improved thermal stability, quantum efficiency, and radiation stability, with a shift in emission towards shorter wavelengths, making it suitable for high-efficiency LEDs and adaptable color temperatures.
Implementation Method 1
a red-emitting phosphor composed of an M-Al—Si—N system... which can be excited well in the UV and blue spectral range
Data Source
AI summary
A red-emitting phosphor composed of an M-Al—Si—N system, comprising a cation M, wherein M is represented by at least one of the elements Ca or Ba or Sr and, if appropriate, can additionally be combined with at least one further element from the group Mg, Zn, Cd, wherein the phosphor is activated with Eu, which partly replaces M, and wherein the phosphor additionally contains LiF.