Photonic Crystal Light Directivity Control in Semiconductor LEDs
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Solution Overview
Problem
Semiconductor light emitting devices face challenges in adjusting the directivity angle of emitted light, particularly when used in applications like projectors and vehicle headlights, where a broader light distribution is desired.
Innovation Solution
A semiconductor light emitting device is constructed with a supporting substrate, a wavelength conversion layer containing semiconductor nanoparticles, and a photonic crystal layer with alternating refractive indices arranged in a two-dimensional cyclic pattern, which reduces the directivity angle of emitted light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a photonic crystal structure is formed on the surface of the semiconductor light emitting element to adjust the directivity angle, then the light directivity can be controlled, but the device complexity increases
Solution Approach 1:
The patent changes the physical parameters of the photonic crystal structure, specifically the pitch between holes and hole depth, to control the directivity angle of emitted light. By adjusting these parameters, the light extraction efficiency and emission pattern can be optimized without requiring complex additional components
Solution Approach 2:
The photonic crystal structure is applied locally on the light emitting surface rather than throughout the entire device. This localized application provides directivity control exactly where needed (at the light emission interface) while keeping the rest of the device structure simple and manageable
2Illumination intensity
If the directivity angle is decreased for projector and headlight applications, then broader light distribution is achieved, but the manufacturing precision requirements increase
Solution Approach 1:
The patent transitions from controlling light in one dimension to two dimensions by creating a periodic array of holes arranged in a specific pattern on the surface. This two-dimensional photonic crystal structure enables precise control over light extraction angles and distribution patterns, achieving broad illumination while maintaining manufacturability through standardized patterning techniques
3Adaptability or versatility
If a wavelength conversion layer with semiconductor nanoparticles is added, then light wavelength conversion is achieved, but the device complexity increases
Solution Approach 1:
The wavelength conversion layer is merged with the photonic crystal structure by integrating the nanoparticle-containing layer directly onto the photonic crystal surface. This combination allows simultaneous wavelength conversion and light direction control in a single integrated structure, avoiding the need for separate conversion and direction control components
Solution Approach 2:
The photonic crystal structure serves multiple functions: it controls light directivity, enhances light extraction efficiency, and works in conjunction with the wavelength conversion layer to enable both color conversion and beam shaping. This multi-functionality reduces the need for additional separate components
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 device achieves a reduced directivity angle of approximately 30°, enabling broader light distribution while maintaining efficient light emission, effectively addressing the need for adjustable light patterns in various applications.
Implementation Method 1
a photonic crystal layer that is disposed on the optical semiconductor laminate, and that has first portions having a first refractive index and second portions having a second refractive index different from the first refractive index, the first portions and the second portions being arranged in a two-dimensional cyclic pattern
Implementation Method 2
a photonic crystal layer that is disposed on the optical semiconductor laminate, and that has first portions having a first refractive index and second portions having a second refractive index different from the first refractive index, the first portions and the second portions being arranged in a two-dimensional cyclic pattern
Implementation Method 3
a wavelength conversion layer that is disposed on the supporting substrate, and contains semiconductor nanoparticles developing a quantum size effect
Implementation Method 4
a supporting substrate that has light reflecting characteristics
Data Source
AI summary
A semiconductor light emitting device comprises a supporting substrate that has light reflecting characteristics; a wavelength conversion layer that is disposed on the supporting substrate, and contains semiconductor nanoparticles developing a quantum size effect; an optical semiconductor laminate that is disposed on the wavelength conversion layer and has light emitting characteristics; and a photonic crystal layer that is disposed on the optical semiconductor laminate, and that has first portions having a first refractive index and second portions having a second refractive index different from the first refractive index, the first portions and the second portions being arranged in a two-dimensional cyclic pattern.