LED Mirror Structure Layer for Light Extraction
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Solution Overview
Problem
Conventional light emitting diodes (LEDs) face challenges in achieving high light extraction efficiency due to limitations in reflecting light effectively, particularly in the structure and materials used in their design.
Innovation Solution
A light emitting device with a mirror structure layer composed of alternately stacked mirror layers of different refractive indices, where the thickness of each layer is optimized to enhance light reflection, combined with a light extraction structure on the substrate to improve light emission efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional single-layer mirror structure is used in LED, then the structure is simple, but the light extraction efficiency is insufficient
Solution Approach 1:
The mirror structure is divided into multiple alternating layers of high refractive index material (e.g., TiO2, SiO2) and low refractive index material (e.g., SiO2, MgF2). This segmentation creates a distributed Bragg reflector that achieves superior light extraction efficiency through constructive interference of reflected waves at each interface, resolving the contradiction between structural simplicity and extraction efficiency.
Solution Approach 2:
The patent employs composite mirror structures combining materials with different refractive indices (high-index TiO2/Si3N4 alternating with low-index SiO2/MgF2). This composite approach creates optical interference effects that significantly enhance light extraction efficiency compared to single-layer mirrors, while maintaining manageable manufacturing complexity through standardized deposition processes.
2Reliability
If mirror layers with large refractive index difference are used, then light reflection is enhanced, but manufacturing precision requirements increase
Solution Approach 1:
The patent optimizes the refractive index difference parameter between alternating layers to maximize reflection efficiency. By selecting materials with appropriate refractive index contrast (e.g., TiO2 with n≈2.4 and SiO2 with n≈1.46), the design achieves high extraction efficiency while the quarter-wavelength thickness formula (d = λ/4n) provides clear manufacturing targets that balance performance with fabrication capability.
Solution Approach 2:
Different regions of the mirror structure use materials with locally optimized refractive indices. The high-index layers (TiO2, Si3N4) are positioned to maximize reflection at specific interfaces, while low-index layers (SiO2, MgF2) provide spacing and additional reflection. This local optimization of material properties achieves high overall reflection efficiency with manageable precision requirements for each individual layer.
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 significantly enhances light extraction efficiency by optimizing the thickness and refractive index difference of the mirror layers and incorporating a light extraction structure, leading to improved reliability and performance in lighting systems.
Implementation Method 1
a mirror structure layer disposed under the light transmissive substrate and including a first mirror layer having a first refractive index and a second mirror layer having a second refractive index different from the first refractive index
Implementation Method 2
the first mirror layer and second mirror layer are alternately stacked on each other
Data Source
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AI summary
Disclosed are a light emitting diode, a light emitting diode package, and a lighting system. The light emitting diode (100) includes a light emitting structure (145) including a first conductive semiconductor layer (130), an active layer (140), and a second conductive semiconductor layer (150) on, a light transmissive substrate (110) having a refractive index lower than a refractive index of the first conductive semiconductor layer, and a mirror structure layer (120) having a structure in which a first mirror layer (121) having a first refractive index (111) and a second mirror layer (122) having a second refractive index (n2) different from the first refractive index are alternately stacked on each other. The first mirror layer has a thickness of W·λ/(4·n1·m), and the second mirror layer has a thickness of W·λ/(4·n2·m) in which W represents a weight constant in a range of about 1.05 to about 1.25, and m represents a natural number.