Mn4+-Doped Oxyfluoride Red Phosphors for Narrow-Band LED Conversion
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Solution Overview
Problem
Conventional red-emitting luminophores in white light-emitting conversion LEDs suffer from inefficiency due to broad emission bands that result in a significant reduction in photon count in the desired red spectral region, leading to lower color rendering index and luminous efficacy, as the human eye is less sensitive to longer wavelengths.
Innovation Solution
Development of Mn4+-doped oxo fluorides with empirical formulas such as K3MoOF7:Mn4+ and K2NaNbO2F4:Mn4+, which exhibit narrow emission bands and peak wavelengths between 625 nm to 635 nm, optimizing photon emission in the red spectral region for improved color rendering and luminous efficacy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional red-emitting luminophores (Eu2+ or Ce3+) are used, then the emission band is broad, but this leads to severe reduction in efficiency of the conversion LED in relation to eye sensitivity
Solution Approach 1:
The patent changes the activator ion from Eu2+ or Ce3+ to Mn4+, which fundamentally alters the emission mechanism from broad band to narrow line emission. This parameter change in the activator ion identity resolves the contradiction by enabling narrow emission lines that match the eye sensitivity curve, thereby improving luminous efficacy while maintaining ease of manufacture through established doping techniques
Solution Approach 2:
The patent substitutes the emission mechanism from broadband phosphorescence (Eu2+/Ce3+) to line emission (Mn4+). This substitution of the emission mechanism resolves the contradiction by replacing a mechanism that inherently produces broad emission with one that produces narrow emission lines, improving eye sensitivity matching and luminous efficacy
2Loss of energy
If the emission spectrum is shifted to shorter wavelength by variations in chemical composition, then the overlap with eye sensitivity curve increases, but this leads to a reduction in the photon count in the desired red spectral region
Solution Approach 1:
The patent changes the activator ion from Eu2+ or Ce3+ to Mn4+, which fundamentally alters the emission mechanism from broad band to narrow line emission. This parameter change resolves the contradiction by enabling precise positioning of emission lines at wavelengths that match eye sensitivity peaks, thereby simultaneously improving luminous efficacy and maintaining high photon count in the red spectral region
Solution Approach 2:
The patent applies local quality by concentrating emission intensity at specific wavelengths (620-640 nm) where the eye sensitivity curve has high values, rather than distributing photons across a broad spectrum. This localized emission approach resolves the contradiction by maximizing the overlap with eye sensitivity at critical wavelengths while maintaining total photon output
3Loss of energy
If Mn4+-doped compounds are used, then the emission spectrum features narrow lines with small FWHM values, but the emission peak is typically at longer wavelengths with lower eye sensitivity
Solution Approach 1:
The patent changes the host matrix from conventional oxides or fluorides to oxo fluorides with specific empirical formulas (A3M*OxF9-2x or A3MOxF8-2x). This parameter change in the host composition resolves the contradiction by enabling Mn4+ emission lines to be positioned at shorter wavelengths (620-640 nm) that match the eye sensitivity curve, thereby simultaneously achieving narrow emission lines and high eye sensitivity
4Quantity of substance
If high wavelength red radiation is used to achieve deep red emission, then the color rendering index improves, but the luminous efficacy decreases due to lower eye sensitivity
Solution Approach 1:
The patent changes the activator ion to Mn4+ and the host to oxo fluorides, which positions the emission lines at 620-640 nm. This parameter change resolves the contradiction by finding an optimal balance point where the emission lines are sufficiently red to provide good color rendering (R9 > 90) while remaining at wavelengths where the eye sensitivity curve still has high values, thereby maintaining luminous efficacy
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
These luminophores achieve high color rendering index and luminous efficacy by minimizing inefficient photon conversion in the long-wave red region, making them suitable for high-efficiency white LEDs and large color space representation.
Implementation Method 1
the red component of the white overall radiation is produced by the conversion of blue primary light from a semiconductor layer sequence to longer-wave red radiation by means of an inorganic luminophore
Data Source
AI summary
A luminophore having the empirical formula A3M*OxF9-2x:Mn4+ where A may be or include Li, Na, Rb, K, Cs, or combinations thereof. M* may be or include Cr, Mo, W, or combinations thereof. x may be or include 0<x<4.5.