Green-Emitting LED Using High-Temperature-Stable Oxynitridosilicate Phosphor
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Solution Overview
Problem
Current green-emitting LEDs face inefficiencies and significant temperature drift in color locus, with existing phosphors offering limited stability and high thermal sensitivity, hindering the achievement of high-efficiency green emission.
Innovation Solution
A luminescence conversion LED utilizing a high-temperature-stable oxynitridosilicate phosphor, specifically SrSi2O2N2:Eu, with a majority HT phase, excited over a broad band from 200 to 480 nm, providing enhanced stability and efficiency, and capable of maintaining color locus stability under varying conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional phosphors (BAM derivatives and sulfides) are used for green emission, then green light can be produced, but quantum efficiency remains low and color locus shows strong temperature drift
Solution Approach 1:
The patent changes the chemical composition parameters of the phosphor material by using oxynitridosilicate with specific cations (Mg, Ca, Sr, Ba) and europium doping, which fundamentally alters the material's excitation and emission characteristics to achieve both high efficiency and thermal stability
Solution Approach 2:
The invention uses a composite phosphor system combining oxynitridosilicate host material with europium activator ions, creating a material that exhibits superior quantum efficiency and color stability compared to conventional single-phase phosphors
2Illumination intensity
If phosphors are used for green emission, then color can be converted, but the phosphors show strong temperature drift in color locus
Solution Approach 1:
The patent modifies the phosphor's thermal response characteristics by selecting specific cations (Mg, Ca, Sr, Ba) in the oxynitridosilicate structure, which have different thermal expansion coefficients and bonding strengths that collectively reduce color drift with temperature changes
3Productivity
If existing phosphors are used, then green light emission is achieved, but efficiency cannot exceed that of direct-emitting LEDs
Solution Approach 1:
The invention optimizes the phosphor's bandgap and absorption coefficients by controlling the cation composition and europium doping concentration, enabling more efficient energy transfer from the blue LED chip to the green emission, thereby minimizing conversion losses
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 solution achieves quantum efficiencies of 80% to over 90%, with stable green emission and minimal temperature dependence, significantly outperforming previous phosphor-based LEDs in efficiency and color stability, allowing for reliable operation across different temperatures.
Implementation Method 1
a layer of a phosphor which is arranged in front of the primary radiation source and completely or partially converts the radiation of the chip into green light
Data Source
AI summary
Phosphor from the class of the oxynitridosilicates, having a cation M which is doped with divalent europium and having the empirical formula M(1-c)Si2O2N2:Dc, where M=Sr or M=Sr(1-x-y)BaYCax with x+y<0.5 is used, the oxynitridosilicate completely or predominantly comprising the high-temperature-stable modification HT.