Narrow-Band Dark Red Phosphor for High-Efficiency White LEDs
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Solution Overview
Problem
Current white light-emitting diode (LED) phosphors lack effective solid phosphors that emit in the dark red region of the electromagnetic spectrum with narrow half-value widths and high quantum efficiency, leading to inefficiencies due to emission outside the visible range.
Innovation Solution
A phosphor comprising an inorganic compound with specific activators like Eu2+ and crystallizing in a structure similar to K2Zn6O7, with empirical formulas such as M4−xEuxLiAl11N14, which exhibits efficient emission in the dark red region with minimal emission outside the visible spectrum, achieved through precise control of lattice parameters and composition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If phosphor (Sr,Ba)2Si5N8:Eu2+ is used to achieve orange to red emission, then emission wavelength can be shifted into the red region, but long-term stability is reduced and half-value width is large
Solution Approach 1:
The patent changes the crystal structure parameter from the original (Sr,Ba)2Si5N8 structure to a new structure with space group Pnnm and specific lattice parameters (a=10.4291(7) Å, b=10.4309(7) Å, c=3.2349(2) Å). This structural parameter change enables red emission with improved stability while maintaining the Eu2+ activator.
2Illumination intensity
If phosphor (Sr,Ca)AlSiN3:Eu2+ is used to achieve dark red emission, then emission in the dark red region is obtained, but half-value width is very broad extending into non-visible region, reducing luminescence efficiency
Solution Approach 1:
The patent modifies the crystal structure parameters to achieve a half-value width of less than 70 nm, significantly narrower than the broad emission of (Sr,Ca)AlSiN3:Eu2+. The new structure with space group Pnnm and specific lattice parameters confines the emission within the visible region, reducing energy loss and improving luminescence efficiency.
3Loss of energy
If phosphor SrLiAl3N4:Eu2+ is used to achieve narrow-band dark red emission, then half-value width is small and emission outside visible region is minimal, but quantum efficiency is lower
Solution Approach 1:
The patent creates a composite phosphor material with the formula M4−xEuxLiAl11N14, combining the beneficial narrow emission bandwidth of SrLiAl3N4:Eu2+ with enhanced quantum efficiency through the new crystal structure. The composite structure with space group Pnnm and specific stoichiometry achieves both high quantum efficiency and intense red emission.
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 a higher quantum efficiency and reduced emission in non-visible regions, ensuring high luminescence efficiency and stable emission over the service life of LEDs, with a dominant wavelength greater than 620 nm and a half-value width less than 70 nm.
Implementation Method 1
The phosphor comprises an inorganic compound, which comprises at least one activator E and N and/or O in its empirical formula... E is responsible for the wavelength of the emitted radiation of the phosphor
Data Source
AI summary
A phosphor is disclosed. In an embodiment the phosphor includes an inorganic compound having at least one activator E and N and/or O in its empirical formula, wherein E is selected from the group consisting of Mn, Cr, Ni, Ce, Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Yb, Tm, Li, Na, K, Rb, Cs and combinations thereof, and wherein the inorganic compound crystallizes in a crystal structure with the same atomic sequence as in K2Zn6O7.