LED Light Extraction via Current Blocking and Protection Layers
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Solution Overview
Problem
Despite the advantages of LEDs over traditional lighting technologies, there is a need for further improvements in light emitting diode (LED) efficiency and operational voltage reduction to enhance their performance in various applications.
Innovation Solution
The proposed solution involves a light emitting device structure that includes a conductive support substrate, a bonding layer, a reflective layer, an ohmic contact layer, a current blocking layer, a protection layer, and electrodes that overlap the current blocking and protection layers, with the protection layer being made of a material with lower conductivity than the reflective or ohmic contact layers, or an electric insulation material, to improve light extraction efficiency and reduce operational voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional LED structure is used, then the device is simple to manufacture, but the light extraction efficiency is insufficient and operational voltage is high
Solution Approach 1:
The LED structure is divided into multiple functional layers including a bonding layer, reflective layer, ohmic contact layer, current blocking layer, and protection layer. Each layer performs a specific function to collectively improve light extraction efficiency while maintaining manufacturing feasibility through standardized layer-by-layer fabrication processes.
Solution Approach 2:
Different regions of the LED structure are assigned different material properties and functions. For example, the reflective layer has high reflectivity to redirect light, the current blocking layer has specific conductivity to control current flow, and the protection layer has insulating properties. This local differentiation optimizes overall performance without complicating the global manufacturing process.
2Device complexity
If a conventional LED structure is used, then the device structure is simple, but the operational voltage is high
Solution Approach 1:
The electrical conduction path is segmented into multiple layers with controlled conductivity. The ohmic contact layer provides low-resistance contact, while the current blocking layer selectively restricts current flow. This segmentation enables better electrical control and reduced operational voltage without requiring a complete redesign of the overall device structure.
Solution Approach 2:
The conductivity parameters of different layers are optimized to achieve the desired electrical characteristics. By adjusting the conductivity of the bonding layer, reflective layer, and protection layer, the operational voltage is reduced while maintaining a relatively simple structural configuration that can be manufactured with existing processes.
3Reliability
If the protection layer is made of highly conductive material, then electrical contact is improved, but light extraction efficiency decreases
Solution Approach 1:
The protection layer is designed with specific insulating properties to prevent unwanted current leakage and improve light extraction efficiency. Rather than making the entire structure highly conductive, localized electrical contact is achieved through the ohmic contact layer, allowing the protection layer to focus on its primary function of protecting the structure and enhancing light extraction.
Solution Approach 2:
The ohmic contact layer acts as an intermediary between the reflective layer and the protection layer, providing the necessary electrical conductivity while allowing the protection layer to maintain its insulating properties for optimal light extraction. This intermediary layer resolves the conflict between electrical contact requirements and light extraction 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
This configuration enhances light output and reduces operational voltage, resulting in improved light efficiency and reliability for LEDs, as demonstrated by an 8% increase in light output compared to comparative arrangements.
Implementation Method 1
a reflective layer 160 on the bonding layer 170
Implementation Method 2
an ohmic contact layer 150 on the reflective layer 160
Data Source
AI summary
A light emitting device including a contact layer, a blocking layer over the contact layer, a protection layer adjacent the blocking layer, a light emitter over the blocking layer, and an electrode layer coupled to the light emitter. The electrode layer overlaps the blocking layer and protection layer, and the blocking layer has an electrical conductivity that substantially blocks flow of current from the light emitter in a direction towards the contact layer. In addition, the protection layer may be conductive to allow current to flow to the light emitter or non-conductive to block current from flowing from the light emitter towards the contact layer.