Composite Phosphor for Stable LED Color Rendering
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Solution Overview
Problem
Current conversion LEDs for general lighting and backlighting face issues with wavelength fluctuations in semiconductor chips, leading to inconsistent color rendering and efficiency, particularly due to the use of phosphors like yttrium aluminum garnet and β-SiAlON, which have limited color space coverage and efficiency, and the instability and toxicity of quantum dots.
Innovation Solution
A phosphor with a specific molecular formula, including elements like Eu, Ce, and Yb, is developed to improve the emission properties, allowing for adjustable peak wavelength and full width at half maximum, enhancing color purity and efficiency while being environmentally friendly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional phosphors like yttrium aluminum garnet or β-SiAlON are used, then the conversion LED can be manufactured with existing processes, but the color space coverage is limited and efficiency is reduced
Solution Approach 1:
The patent employs a composite phosphor system combining multiple phosphor materials (β-SiAlON with specific rare earth doping, and additional phosphors such as garnet or nitride phosphors) to achieve both narrowband emission for color space coverage and compatibility with existing manufacturing processes. This composite approach allows each phosphor component to contribute specific properties, resolving the contradiction between manufacturability and color space coverage.
2Illumination intensity
If β-SiAlON phosphor with narrowband emission is used, then color rendering is more saturated, but internal and external quantum efficiency are poor and production costs are very high
Solution Approach 1:
The patent applies local quality by using β-SiAlON phosphor selectively in specific wavelength regions where narrowband emission is most beneficial for color saturation, while combining it with other phosphor materials in different spectral regions. This localized application of the expensive narrowband phosphor reduces overall production costs while maintaining color saturation where it matters most.
Solution Approach 2:
The patent modifies the composition parameters of β-SiAlON phosphor by optimizing rare earth metal doping concentrations and stoichiometric ratios to improve quantum efficiency. Additionally, the patent adjusts the ratio of different phosphor materials in the composite system to balance color saturation performance with manufacturing cost, effectively using parameter changes to resolve the contradiction.
3Reliability
If semiconductor chips are sorted with narrow tolerances to avoid wavelength fluctuations, then the quality of conversion LEDs is improved, but the manufacturing complexity and cost increase
Solution Approach 1:
The patent applies preliminary action by pre-compensating for wavelength variations through careful selection and combination of phosphor materials with complementary emission characteristics. The phosphor composition is designed to compensate for potential semiconductor chip wavelength shifts, reducing the need for stringent sorting and binning operations while maintaining color consistency.
4Illumination intensity
If quantum dots are used for conversion, then narrowband emission is achieved, but stability is very poor and toxicity is high
Solution Approach 1:
The patent replaces unstable quantum dots with solid-state phosphor materials that, while having different emission characteristics, provide long-term stability and reliability. The phosphor materials are designed to deliver sufficient narrowband emission performance without the stability and toxicity issues of quantum dots, effectively substituting a reliable but different technology approach.
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 achieves stable and efficient conversion of primary radiation into secondary radiation with improved color rendering and efficiency, suitable for various applications including 'color on demand' scenarios, with reduced production costs and environmental impact.
Implementation Method 1
a phosphor configured at least partly to convert the electromagnetic primary radiation into an electromagnetic secondary radiation
Data Source
AI summary
A lighting device is specified. The lighting device comprises a phosphor having the general molecular formula (MA)a(MB)b(MC)c(MD)d(TA)e(TB)f(TC)g(TD)h(TE)i(TF)j(XA)k(XB)l(XC)m(XD)n:E. In this case, MA is selected from a group of monovalent metals, MB is selected from a group of divalent metals, MC is selected from a group of trivalent metals, MD is selected from a group of tetravalent metals, TA is selected from a group of monovalent metals, TB is selected from a group of divalent metals, TC is selected from a group of trivalent metals, TD is selected from a group of tetravalent metals, TE is selected from a group of pentavalent elements, TF is selected from a group of hexavalent elements, XA is selected from a group of elements which comprises halogens, XB is selected from a group of elements which comprises O, S and combinations thereof, XC=N and XD=C and E=Eu, Ce, Yb and/or Mn. The following furthermore hold true: a+b+c+d=t; e+f+g+h+i+j=u; k+l+m+n=v; a+2b+3c+4d+e+2f+3g+4h+5i+6j−k−2l−3m−4n=w; 0.8≤t≤1; −3.5≤u≤4; 3.5≤v≤4; (−0.2)≤w≤0.2 and 0≤m<0.875 v and/or v≥1>0.125 v.