Reflective Electrode Layer for Light Extraction in LEDs
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Solution Overview
Problem
Conventional light emitting devices, such as LEDs, face challenges in achieving high luminance and light extraction efficiency due to limitations in electrode bonding and reflectivity, leading to reduced performance in applications requiring high luminance.
Innovation Solution
A light emitting device design featuring a reflective electrode layer and a bonding electrode layer with a superior bonding force to the semiconductor layer, enhancing light reflectivity and extraction efficiency while preventing peeling-off, achieved through specific layer structures and materials like chromium, aluminum, and gold.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a conventional single-layer electrode structure is used, then the device structure is simple, but the bonding strength to semiconductor layer is insufficient and light reflectivity is low
Solution Approach 1:
The electrode is divided into multiple functional layers: a bonding electrode layer (first electrode layer) that provides strong adhesion to the semiconductor layer, and a reflective electrode layer (second electrode layer) that provides high light reflectivity. This segmentation allows each layer to optimize its specific function rather than requiring a single layer to perform both functions simultaneously.
Solution Approach 2:
The electrode uses a composite structure combining different materials with complementary properties. The bonding electrode layer uses materials with superior bonding characteristics to the semiconductor layer, while the reflective electrode layer uses materials with high light reflectivity. This composite approach achieves both strong bonding and high reflectivity that cannot be obtained with a single material.
2Strength
If the electrode layer is made thicker to improve bonding, then bonding strength increases, but light extraction efficiency decreases due to increased absorption
Solution Approach 1:
By segmenting the electrode into a thin bonding layer and a reflective layer, the bonding layer can be kept sufficiently thin to allow light transmission while still providing adequate bonding strength. The reflective layer then compensates for any light loss by reflecting transmitted light back through the semiconductor layer, improving overall light extraction efficiency.
Solution Approach 2:
The bonding electrode layer acts as an intermediary between the semiconductor layer and the reflective electrode layer. It provides the necessary bonding interface while being thin enough to allow light transmission, and simultaneously supports the reflective layer that enhances light extraction. This intermediary structure resolves the conflict between bonding requirements and light transmission requirements.
3Loss of energy
If a reflective electrode layer is added to improve light reflectivity, then light extraction efficiency increases, but the electrode structure becomes more complex
Solution Approach 1:
The electrode structure is segmented into distinct functional layers: the bonding electrode layer for adhesion and the reflective electrode layer for light reflection. This segmentation makes the complexity manageable by organizing it into modular functional units, where each layer can be independently optimized and manufactured.
Solution Approach 2:
The multi-layer electrode structure serves multiple functions simultaneously: electrical conduction, mechanical bonding, and optical reflection. By integrating these functions into a single electrode assembly with multiple layers, the overall device complexity is managed while achieving superior performance in all three areas compared to single-layer electrodes.
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 proposed design significantly improves light reflectivity and extraction efficiency by about 5% or more, maintaining strong bonding between the electrode and semiconductor layer, thus enhancing the overall luminous performance of the light emitting device.
Implementation Method 1
a reflective electrode layer disposed over the second semiconductor layer
Implementation Method 2
a bonding electrode layer disposed in at least a partial region of an outer side surface of the reflective electrode layer while coming into contact with the second semiconductor layer
Data Source
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AI summary
A light emitting device is disclosed. The light emitting device includes an electrode, which includes a reflective electrode layer disposed over a second semiconductor layer and a bonding electrode layer disposed in at least a partial region of an outer side surface of the reflective electrode layer while coming into contact with the second semiconductor layer. Thus, it may be possible to enhance bonding reliability between the electrode and the semiconductor layer.