WLED Phosphor Segmentation for Absorption Loss Reduction
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Solution Overview
Problem
White light-emitting diodes (WLEDs) face challenges in achieving high light-emitting efficiency due to absorption issues between phosphors, where longer wavelength phosphors absorb light from shorter wavelength phosphors, leading to reduced color uniformity and rendering index.
Innovation Solution
A light-emitting element comprising a semiconductor stack with two wavelength conversion materials, where the first material converts the initial light to a second light and the second material converts the combined light to a third light, both mixed to produce a white light with specific chromaticity coordinates, using a method of uniformly spreading phosphors to minimize absorption and optimize light extraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If two different phosphors are mixed and spread together, then the color rendering index and light-emitting efficiency are improved, but absorption occurs between phosphors where longer wavelength phosphors absorb shorter wavelength light, reducing overall light-emitting efficiency
Solution Approach 1:
The patent divides the phosphor spreading process into two separate steps: first spreading the yellow phosphor layer, then spreading the red phosphor layer on top. This segmentation prevents direct contact and absorption between different phosphor particles, eliminating the harmful absorption effect while maintaining good color rendering index and light-emitting efficiency.
2Manufacturing precision
If phosphor spreading methods are improved to enhance color uniformity and light extraction, then color uniformity and rendering index are improved, but the device complexity and manufacturing process complexity increase
Solution Approach 1:
The patent segments the phosphor application into two separate spreading operations with distinct material compositions and thicknesses. The yellow phosphor layer (5-15 μm) is spread first, followed by the red phosphor layer (3-8 μm). This segmented approach achieves superior color uniformity and light extraction while maintaining relatively simple manufacturing processes.
Solution Approach 2:
The patent applies different phosphor materials with specific properties to different locations and layers: the yellow phosphor (Y3Al5O12:Ce) forms the base layer with specific emission characteristics, while the red phosphor (CaAlSiN3:Eu) forms the top layer with complementary emission properties. This local quality differentiation optimizes color uniformity and light extraction efficiency.
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
This approach enhances light-emitting efficiency, reduces phosphor usage, and improves color uniformity and rendering index by adjusting the amount and type of phosphors to achieve desired chromaticity coordinates, resulting in a brighter and more cost-effective WLED.
Implementation Method 1
a first wavelength conversion material on the semiconductor light-emitting stack converting the first light to emit a second light
Implementation Method 2
a second wavelength conversion material on the first wavelength conversion material converting the second light to emit a third light
Data Source
AI summary
The present application discloses a light-emitting element comprising a semiconductor light-emitting stack emitting a first light which has a first color coordinate, a first wavelength conversion material on the semiconductor light-emitting stack converting the first light to emit a second light, and a second wavelength conversion material on the first wavelength conversion material converting the second light to emit a third light. The first light and the second light are mixed to be a fourth light having a second color coordinate. The third light and the fourth light are mixed to be a fifth light having a third color coordinate, and the second color coordinate locates at the top right of the first color coordinate and the third color coordinate locates at the top right of the second color coordinate.