Stacked Semiconductor Light Emitting Element for Uniform Polychromatic Emission
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Solution Overview
Problem
Current semiconductor light emitting elements face challenges in achieving uniform color rendition and efficient light emission due to issues like color breakup and limited light extraction efficiency, particularly when multiple LEDs with different wavelengths are stacked.
Innovation Solution
The semiconductor light emitting element incorporates a specific structure with a light reflecting layer and multiple light emitting units of different peak wavelengths, where the first light transmitting layer is thick enough to ensure efficient light extraction and the light reflecting layer is connected to one of the semiconductor layers, facilitating heat dissipation and reducing color breakup by emitting light uniformly in all directions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If multiple LEDs with different wavelengths are stacked to achieve polychromatic light emission, then the color rendition is improved, but color breakup occurs and light extraction efficiency decreases
Solution Approach 1:
The patent transitions from planar lateral arrangement of multiple LEDs to a vertical stacked configuration along the light propagation direction. This dimensional change allows multiple light emitting units with different peak wavelengths to be arranged in the thickness direction, enabling polychromatic light emission while maintaining color uniformity through optimized optical path design and light extraction structures at each interface.
Solution Approach 2:
The light emitting element is segmented into multiple independent light emitting units, each with specific semiconductor layers and light emitting layers having different peak wavelengths. Each unit can be independently designed and optimized, with light extraction structures positioned at different interfaces to extract light from different wavelength ranges, thereby preventing color breakup while achieving comprehensive color rendition.
2Illumination intensity
If multiple LEDs with different wavelengths are stacked to achieve polychromatic light emission, then the color rendition is improved, but light extraction efficiency is limited
Solution Approach 1:
Light extraction structures are introduced as intermediary elements at the interfaces between different light emitting units and between the uppermost unit and the external environment. These structures serve as mediators to facilitate efficient light extraction by reducing total internal reflection and guiding light from different wavelength ranges to the extraction surfaces, thereby improving overall light extraction efficiency while maintaining polychromatic emission.
Solution Approach 2:
Different light extraction structures are positioned at different locations and interfaces within the stacked configuration. Each light extraction structure is optimized for the specific wavelength range and optical properties of the adjacent light emitting unit, allowing localized optimization of light extraction efficiency for each wavelength component while achieving uniform polychromatic light emission overall.
3Loss of energy
If the first light transmitting layer is made thick to ensure efficient light extraction, then light extraction efficiency is improved, but device complexity increases
Solution Approach 1:
The first light transmitting layer is designed to serve multiple functions simultaneously: it acts as a light extraction medium for the first light emitting unit, provides mechanical support and structural integrity for the stacked configuration, and facilitates heat dissipation from the underlying semiconductor layers. This multi-functionality allows the layer to be relatively thick for efficient light extraction without proportionally increasing device complexity, as the same structure fulfills multiple critical roles.
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 configuration results in highly efficient and uniform polychromatic light emission with improved heat dissipation, reducing color breakup and enhancing light extraction efficiency, making the semiconductor light emitting element more practical and productive.
Implementation Method 1
a first light emitting layer (13), configured to emit a first light (L10) of a first peak wavelength
Implementation Method 2
a light reflecting layer (40)... The first light (L10) emitted from the first light emitting layer (13) is reflected by the light reflecting layer (40)
Implementation Method 3
a first light transmitting layer (15), provided between the second semiconductor layer (12) and the light reflecting layer (40)... A thickness of the first light transmitting layer (15) is not less than 10 times a distance (t2) between the second light emitting layer (23) and the light reflecting layer (40)
Data Source
AI summary
According to one embodiment, a semiconductor light emitting element includes a light reflecting layer, first second, third and fourth semiconductor layers, first and second light emitting layers, and a first light transmitting layer. The second semiconductor layer is provided between the first semiconductor layer and the light reflecting layer. The first light emitting layer is provided between the first and second semiconductor layers. The first light transmitting layer is provided between the second semiconductor layer and the light reflecting layer. The third semiconductor layer is provided between the first light transmitting layer and the light reflecting layer. The fourth semiconductor layer is provided between the third semiconductor layer and the light reflecting layer. The second light emitting layer is provided between the third and fourth semiconductor layers. The light reflecting layer is electrically connected to one selected from the third and fourth semiconductor layers.