Garnet-Type Mn4+ Fluoride for Humidity-Stable LED Red Emission
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Solution Overview
Problem
Existing light emitting diode (LED) devices using Mn4+-activated fluoride compounds face issues with toxicity and sensitivity to humid environments, leading to short shelf times and performance degradation.
Innovation Solution
Development of LED devices with wavelength converting elements containing Mn4+-activated fluoride compounds with a garnet-type crystal structure, which are less toxic and less sensitive to humidity, utilizing a specific composition such as {A3}[B2-x-yMnxMgy](Li3)F12-dOd, where A, B, and C represent metal ions in specific sites within the garnet structure, and the presence of Mn4+ and F− ions for red spectral emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If Mn4+-activated fluoride compounds are used in wavelength converting elements, then red spectral emission and warm white light production are achieved, but toxicity and sensitivity to humid environments increase
Solution Approach 1:
The patent changes the crystal structure parameter from conventional fluoride compounds to garnet-type structure, which fundamentally alters the material's properties. This structural parameter change reduces humidity sensitivity while preserving the Mn4+-activated red emission characteristics, allowing the material to maintain its luminescent function while becoming more stable in humid environments.
Solution Approach 2:
The invention uses composite material design by incorporating Mn4+ ions into the garnet-type fluoride compound matrix. This composite approach combines the host garnet structure (which provides humidity stability) with the Mn4+ activator (which provides red emission), achieving both desired luminescence and improved environmental stability.
2Illumination intensity
If Mn4+-activated fluoride compounds are used in wavelength converting elements, then red spectral emission and warm white light production are achieved, but toxicity increases
Solution Approach 1:
The patent changes the chemical composition parameters by adopting garnet-type structure with specific metal ion combinations (A, B, C sites in the garnet structure). This compositional change replaces more toxic conventional fluoride compounds with less toxic garnet-based materials while maintaining the Mn4+-activated red emission properties needed for warm white light production.
3Illumination intensity
If conventional fluoride compounds are used, then red emission is achieved, but shelf life and device performance duration decrease due to surface decomposition in humid air
Solution Approach 1:
The patent changes the crystal structure parameter to garnet-type, which provides inherent stability against surface decomposition in humid environments. This structural parameter change extends the shelf life and operational duration of the wavelength converting elements while maintaining effective red emission for warm white light generation.
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 new compounds exhibit improved stability and reduced toxicity, enabling the production of warm white light with enhanced performance and longer shelf life in LED devices, while also allowing for the formation of ceramic platelets or resin-based wavelength converting elements for efficient light conversion.
Implementation Method 1
wavelength converting element containing a Mn4+-activated fluoride compound... converting a part of the light generated by a blue/UV LED
Implementation Method 2
Prolonged exposure of these materials to (humid) air causes formation of a thin water film on the surface of the material, leading to (surface) decomposition. This disadvantageous property affects both the pure materials... and the LED devices in which they are applied
Implementation Method 3
These luminescent materials appear to show a narrow band or line emission in the red spectral region (600-660 nm) of the electromagnetic spectrum
Data Source
AI summary
The invention provides a light emitting diode device comprising a light emitting diode arranged on a substrate and a wavelength converting element. The wavelength converting element contains as a luminescent material a Mn4+-activated fluoride compound having a garnet-type crystal structure. The Mn4+-activated fluoride compound preferably answers the general formula {A3}[B2-x-yMnxMgy](Li3)F12-dOd, in which formula A stands for at least one element selected from the series consisting of Na+ and K+ and B stands for at least one element selected from the series consisting of Al3+, B3+, Sc3+, Fe3+, Cr3+, Ti4+ and In3+, and in which formula x ranges between 0.02 and 0.2, y ranges between 0.0 (and incl. 0.0) and 0.4 and d ranges between 0 (and incl. 0) and 1. Said compound is most preferably {Na3}[Al2-x-yMnxMgy](Li3)F12-dOd.