Wavelength Conversion Coating for Uniform White LED Color
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Solution Overview
Problem
Semiconductor light-emitting devices face challenges in maintaining high mechanical, thermal, and chemical stability, especially when emitting white color light, and existing wavelength conversion members exhibit significant color coordinate deviation with orientation angle, affecting light-flux characteristics.
Innovation Solution
A semiconductor light-emitting device with a wavelength conversion member having a slanted sidewall and a coating layer with alternately stacked oxide and magnesium fluoride (MgF2) layers, functioning as a distributed Bragg reflector, improves light extraction efficiency and reduces color coordinate deviation across viewing angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional wavelength conversion member is used, then the device structure is simple, but color coordinate deviation occurs with orientation angle changes
Solution Approach 1:
The wavelength conversion member is segmented into multiple functional layers: a base layer containing phosphors and inorganic oxide particles, and a coating layer with alternately stacked high-refractive-index and low-refractive-index layers. This segmentation allows each layer to perform its specific function while collectively achieving uniform color coordinates across different orientation angles.
Solution Approach 2:
The invention uses composite materials in the coating layer, combining materials with different refractive indices (high-refractive-index material and low-refractive-index material) in alternating layers. This composite structure creates optical interference effects that compensate for color coordinate deviations, maintaining uniformity across different viewing angles.
2Productivity
If the sidewall is vertical, then the manufacturing process is simpler, but light extraction efficiency is reduced
Solution Approach 1:
The sidewall of the wavelength conversion member is designed with an asymmetric profile, featuring a slanted portion adjacent to the first surface and a vertical portion adjacent to the second surface. This asymmetric geometry optimizes light extraction by directing light at different angles from different portions of the sidewall, improving overall efficiency while remaining manufacturable.
3Manufacturing precision
If a single-layer coating is used, then the device complexity is low, but color coordinate uniformity across viewing angles is poor
Solution Approach 1:
The coating layer employs a periodic structure with alternately stacked high-refractive-index and low-refractive-index layers. This periodic arrangement creates constructive and destructive interference patterns for different wavelengths and angles of light, effectively compensating for color coordinate deviations across various viewing angles and maintaining uniformity.
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 enhances light-flux characteristics and maintains uniform color coordinates regardless of orientation, improving the stability and performance of white light emission in semiconductor light-emitting devices.
Implementation Method 1
a coating layer arranged on the second surface of the wavelength conversion member, the coating layer including a first material layer and a second material layer alternately stacked on the second surface, wherein the first material layer includes an oxide, and the second material layer includes magnesium fluoride (MgF2), wherein the first material layer and the second material layer function as a distributed Bragg reflector (DBR)
Implementation Method 2
the first material layer and the second material layer function as a distributed Bragg reflector (DBR)
Implementation Method 3
a portion of the sidewall adjacent to the first surface is slanted with respect to the first surface
Data Source
AI summary
A semiconductor light-emitting device includes a light emitting structure, a wavelength conversion member arranged on an upper surface of the light emitting structure, the wavelength conversion member including a first surface in contact with the light emitting structure, a second surface opposite to the first surface, and a sidewall, wherein the first surface entirely covers the upper surface of the light emitting structure, and a portion of the sidewall adjacent to the first surface is slanted with respect to the first surface, and a coating layer arranged on the second surface of the wavelength conversion member, the coating layer including a first material layer and a second material layer alternately stacked on the second surface, wherein the first material layer includes an oxide, and the second material layer includes magnesium fluoride (MgF2), wherein the second material layer is arranged at an uppermost surface of the coating layer.