Green Phosphor Particles for LED Brightness via Wet Dispersion
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Solution Overview
Problem
The existing SrGa2S4:Eu phosphor for white LEDs experiences concentration quenching when doped with excessive europium, leading to reduced brightness due to saturation of the emission center, which has not been effectively addressed.
Innovation Solution
The development of green-emitting phosphor particles composed of (Sr,Ba,Ca)1-xGa2S4:Eux, where 0.10≤x≤0.20, using a wet method to disperse europium uniformly and prevent local high concentration regions, maintaining high internal quantum efficiency even with increased absorption efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If europium doping concentration is increased to amplify brightness, then absorption efficiency is improved, but internal quantum efficiency is reduced due to concentration quenching
Solution Approach 1:
The patent changes the chemical composition parameters by introducing Ba and Ca elements into the SrGa2S4 host lattice, creating (Sr,Ba,Ca)1-xGa2S4. This compositional modification alters the crystal field environment of Eu3+ ions, enabling high internal quantum efficiency (≥80%) to be maintained even at high europium concentrations (x≥0.10), thus resolving the contradiction between brightness and internal quantum efficiency
Solution Approach 2:
The patent creates a composite phosphor system by combining Sr, Ba, and Ca elements with Ga2S4 host and Eu3+ activator. The multi-element composition (Sr,Ba,Ca)1-xGa2S4:Eu3+ synergistically improves both absorption efficiency and internal quantum efficiency, allowing the material to achieve high brightness without suffering from concentration quenching
2Quantity of substance
If europium doping concentration is increased to improve absorption efficiency, then absorption efficiency is improved, but brightness is reduced due to saturation of emission center
Solution Approach 1:
The patent modifies the host lattice composition by incorporating Ba and Ca elements, which changes the optical and electronic properties of the phosphor. This parameter change enables the material to maintain high brightness output even when europium concentration is increased to improve absorption efficiency, breaking the conventional trade-off relationship
3Quantity of substance
If conventional SrGa2S4:Eu phosphor is used with high europium concentration, then absorption efficiency is improved, but concentration quenching occurs reducing internal quantum efficiency
Solution Approach 1:
The patent develops a composite phosphor material (Sr,Ba,Ca)1-xGa2S4:Eu3+ that combines multiple alkaline earth elements. This composite structure creates a more favorable crystal field for Eu3+ ions, enabling the material to achieve both high absorption efficiency and high internal quantum efficiency simultaneously, even at elevated europium concentrations where conventional phosphors would suffer from concentration quenching
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 green-emitting phosphor particles maintain high internal quantum efficiency and absorption efficiency, preventing concentration quenching and ensuring consistent brightness, as demonstrated by the manufacturing methods and applications in color conversion sheets, light-emitting devices, and image display devices.
Implementation Method 1
green-emitting phosphor particles which are excited by the light emitted from the light source
Data Source
AI summary
A method for manufacturing green-emitting phosphor particles including the steps of producing a powder containing europium and strontium from a solution containing a europium compound and a strontium compound, mixing the resulting powder and a powdered gallium compound, and performing firing.