Green Phosphor Particle Size Control for Absorption
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Solution Overview
Problem
Current green emitting phosphors, such as SrGa2S4:Eu, have limitations in luminescent efficiency due to poor absorption ratios, which affect their external quantum efficiency, and struggle to improve color rendering properties in white LEDs, particularly when illuminating red objects or human skin.
Innovation Solution
A green emitting phosphor with a specific particle size distribution, characterized by a D10 of 4.5 μm to 30 μm, is developed, using a host material containing Ga, S, and elements like Sr, Ba, and Ca, with a luminescent center of Eu2+, to enhance absorption ratio and external quantum efficiency, allowing for improved light emission and color rendering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional green emitting phosphors (SrGa2S4:Eu) are used, then the phosphor can emit green light, but the absorption ratio is poor and external quantum efficiency is limited
Solution Approach 1:
The patent applies parameter changes by precisely controlling the particle size distribution parameters (D10 between 4.5-30 μm, D50 between 15-50 μm, D90 between 50-150 μm) of the phosphor particles. This parameter optimization directly improves the absorption ratio to 65% or greater and achieves external quantum efficiency of 30% or more, resolving the contradiction between energy absorption and manufacturing control.
2Device complexity
If white LEDs combine blue LED and YAG:Ce phosphor, then the structure is simple, but color rendering properties are poor
Solution Approach 1:
The patent employs composite materials by combining the green emitting phosphor (containing Ga, S, Sr/Ba/Ca, and Eu luminescent center) with red and blue phosphors in a multi-phosphor system. This composite approach enables excellent color rendering properties while maintaining reasonable device structure, as the green phosphor fills the spectral gap between red and blue emissions.
3Loss of energy
If the particle size is reduced to improve absorption, then the absorption ratio increases, but the manufacturing precision becomes more difficult to control
Solution Approach 1:
The patent resolves this contradiction by optimizing multiple particle size parameters simultaneously: D10 (4.5-30 μm) for absorption, D50 (15-50 μm) for overall performance, and D90 (50-150 μm) for manufacturing control. This multi-parameter approach achieves absorption ratio of 65% or greater while maintaining controllable manufacturing precision through defined size ranges.
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 phosphor achieves an absorption ratio of 65% or greater and external quantum efficiency of 30% or more, enhancing light extraction efficiency and color rendering capabilities, particularly when excited by near-ultraviolet to blue light, effectively addressing the limitations of previous phosphors.
Implementation Method 1
a green emitting phosphor... emitting a green light by way of an excitation light with a wavelength in the near-ultraviolet region to blue region
Data Source
AI summary
A green emitting phosphor exhibiting an excellent absorption ratio is provided. A green emitting phosphor containing a crystal represented by MGa2S4:Eu2+, wherein M is an element comprising one species or a combination of two or more species among Sr, Ba and Ca, and Eu2+ is a luminescent center, and wherein the particle diameter at 10%, D10, 4.5 μm to 30 μm in the volume-based particle size distribution measured and obtained by the laser diffraction/diffusion particle size distribution measurement method.