Wavelength Conversion Structure for Uniform White LED Emission
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Solution Overview
Problem
Semiconductor light-emitting devices face challenges in achieving high mechanical, thermal, and chemical stability for high-power white color light emission, particularly in maintaining uniform color coordinates and light flux across various orientation angles.
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, to enhance light extraction efficiency and maintain uniform color coordinates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional wavelength conversion member with vertical sidewalls is used, then the device structure is simple, but the color coordinates deviate at different orientation angles and light flux is uneven
Solution Approach 1:
The wavelength conversion member is designed with an asymmetric cross-sectional shape where the sidewalls are slanted relative to the base. This asymmetric geometry compensates for angular deviations in light emission, maintaining uniform color coordinates and light flux distribution across different viewing angles by redirecting oblique light paths
Solution Approach 2:
The solution transitions from a simple vertical sidewall structure to a slanted sidewall configuration, effectively changing the geometric dimensioning of the wavelength conversion member. This dimensional modification introduces angular compensation capabilities that resolve the color uniformity issue across different orientation angles
2Loss of energy
If no coating layer is applied on the wavelength conversion member, then the device structure is simpler, but light extraction efficiency is reduced
Solution Approach 1:
A multi-layer coating structure is applied on the wavelength conversion member, combining different materials with complementary optical properties. This composite coating system enhances light extraction efficiency by managing reflection and transmission characteristics at the interfaces between the wavelength conversion member and surrounding media
Solution Approach 2:
The coating layer acts as an optical intermediary between the wavelength conversion member and the external environment. It mediates the interaction of light with the wavelength conversion member surface, improving light extraction by reducing parasitic reflections and enhancing coupling 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
The solution improves light-flux characteristics and reduces color coordinates deviation across angles, achieving stable and uniform white color light emission.
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 (MgF 2 ), wherein the second material layer is arranged at an uppermost surface of the coating layer
Implementation Method 2
the first material layer has a first refractive index, and the second material layer has a second refractive index, wherein the second refractive index is less than the first refractive index
Implementation Method 3
a portion of the sidewall adjacent to the first surface is slanted with respect to the first surface
Implementation Method 4
white color light elements include wavelength conversion members such as phosphor on blue light-emitting devices
Data Source
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AI summary
A semiconductor light-emitting device (100, 100A) includes a light emitting structure (110), a wavelength conversion member (120) arranged on an upper surface (110U) of the light emitting structure, the wavelength conversion member including a first surface (120F1) in contact with the light emitting structure, a second surface (120F2) opposite to the first surface, and a sidewall (120S), wherein the first surface entirely covers the upper surface of the light emitting structure, and a portion (120_IS) of the sidewall adjacent to the first surface is slanted with respect to the first surface, and a coating layer (130) arranged on the second surface of the wavelength conversion member, the coating layer including a first material layer (132) and a second material layer (134) 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 (134) is arranged at an uppermost surface (130U) of the coating layer.