Halogen-Substituted Oxynitride Phosphor for LED Brightness
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Solution Overview
Problem
Conventional phosphors used in light-emitting elements, such as those combining a GaN blue LED and a yellow phosphor, suffer from reduced brightness at elevated temperatures and do not provide sufficient emission brightness.
Innovation Solution
A green-light-emitting phosphor with a specific composition, represented by formulas like M1-aSi2O2-1/2nXnN2:Eua, where M is strontium, barium, or calcium, X is chlorine or bromine, and a and n are within specific ranges, is developed to enhance brightness by substituting oxygen with halogen elements and optimizing the amount of europium as an activator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional yellow phosphors are used in combination with GaN blue LED, then white light can be generated, but the brightness lowers when temperature rises
Solution Approach 1:
The patent changes the chemical composition parameters of the phosphor by substituting oxygen atoms with halogen atoms (Cl, Br, I) in the oxynitride phosphor structure M2Si2O2N2. This compositional parameter change results in improved thermal stability and maintained brightness at elevated temperatures, resolving the contradiction between brightness and thermal stability.
Solution Approach 2:
The patent creates a composite phosphor material with the formula M2-a-bSi2O2-xN2-yHalxHy:Eu, where Hal represents halogen elements. This composite structure combining oxynitride with halogen substitution provides both the desired brightness and thermal stability, overcoming the limitations of conventional yellow phosphors.
2Reliability
If nitride phosphors and oxynitride phosphors are used to improve thermal stability, then temperature resistance is enhanced, but emission brightness is insufficient
Solution Approach 1:
The patent modifies the oxynitride phosphor structure by substituting oxygen with halogen elements, changing the chemical composition parameters. This parameter change simultaneously improves thermal stability and enhances emission brightness, resolving the contradiction between reliability and illumination intensity.
Solution Approach 2:
The patent introduces halogen substitution at specific positions in the phosphor structure (substituting oxygen atoms), creating local compositional variations. This local quality change in the crystal structure leads to improved optical properties and thermal stability without compromising the overall structure.
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 phosphor composition achieves higher emission brightness and improved thermal stability, allowing for the creation of white-light-emitting elements with enhanced color-rendering properties when combined with light-emitting semiconductor elements.
Implementation Method 1
a phosphor which absorbs visible light in a short-wavelength region such as blue light and ultraviolet light and emits visible light of a longer wavelength such as green light
Implementation Method 2
a phosphor as a conversion material absorbs visible light in a blue light region emitted from a GaN blue LED and emits yellow light
Data Source
AI summary
A green-light-emitting phosphor of a high emission brightness when excited by blue light emitted from a blue LED is provided. The green-light-emitting phosphor is represented by a formula M1-aSi2O2-1/2nXnN2:Eua, wherein M is at least one element of strontium (Sr), barium (Ba) and calcium (Ca); X is at least one element of chlorine (Cl) and bromine (Br); a is 0.005≦a≦0.15 and n is 0.02≦n≦0.2. Substitution of a part of the oxygen (O) in a matrix with at least one halogen element of chlorine (Cl) and bromine (Br) gives a green-light-emitting phosphor of higher brightness.