Micro-LED Electrode Layout for Self-Assembly and Light Extraction
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Solution Overview
Problem
Current display devices face challenges in improving the yield of the self-assembly process of light emitting diodes (LEDs) and minimizing light extraction efficiency losses due to electrode placement and design, particularly with ohmic contact electrodes and side electrodes.
Innovation Solution
The solution involves forming a substrate with spaced low potential power lines and using a magnet to self-assemble LEDs with specific semiconductor layers and electrodes, including a side electrode on an insulating film and an ohmic contact electrode, to enhance assembly yield and light extraction efficiency by optimizing electrode placement and design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a side electrode is formed on the first insulating film to enable self-assembly of the light emitting diode, then the self-assembly process yield is improved, but the light extraction efficiency is reduced due to the electrode blocking light
Solution Approach 1:
The side electrode is positioned only at the side surface of the first semiconductor layer rather than covering the entire bottom surface, creating a localized electrode configuration that enables self-assembly while minimizing light blocking. This local placement allows the majority of the bottom surface to remain open for light extraction.
Solution Approach 2:
The electrode configuration transitions from a conventional bottom-only electrode to a side electrode positioned on the first insulating film. This dimensional change from horizontal (bottom surface) to vertical (side surface) positioning enables self-assembly functionality while preserving light extraction pathways at the bottom surface.
2Reliability
If an ohmic contact electrode is formed in the lower part of the light emitting diode to improve electrical contact, then the resistance is reduced, but the light extraction efficiency is lowered due to the electrode blocking light
Solution Approach 1:
The electrical contact function is segmented between the side electrode (which provides primary contact and enables self-assembly) and the ohmic contact electrode (which provides additional contact at the bottom). This segmentation allows the ohmic contact electrode to be smaller and less intrusive, blocking less light while still achieving low resistance.
Solution Approach 2:
The first insulating film acts as an intermediary that positions the side electrode at the side surface, allowing electrical contact to be achieved without requiring a large bottom electrode. This intermediary structure enables the ohmic contact electrode to be minimized in size, reducing its light blocking effect.
3Manufacturing precision
If the light emitting diode is self-assembled using an electric field between spaced power lines, then the assembly precision is improved, but the device complexity increases due to additional electrodes and insulating films
Solution Approach 1:
The side electrode serves multiple functions: it enables self-assembly of the light emitting diode through electric field interaction, provides electrical contact, and positions the device during manufacturing. This multi-functionality reduces the need for separate components, offsetting the added complexity with functional consolidation.
Solution Approach 2:
The first insulating film is formed in advance to enclose the side surface of the first semiconductor layer before the side electrode is deposited. This preliminary action prepares the surface for precise electrode placement, enabling accurate self-assembly while organizing the manufacturing sequence to manage complexity systematically.
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 approach improves the yield of the self-assembly process, reduces light extraction efficiency losses, and enhances the overall performance of the display device by minimizing electrode interference and maximizing luminance.
Implementation Method 1
moving the plurality of light emitting diodes to the substrate using a magnet
Implementation Method 2
applying a voltage to the pair of low potential power lines and forming an electric field between the pair of low potential power lines, the plurality of light emitting diodes self-assembled on the substrate between the pair of low potential power lines responsive to the electric field
Data Source
AI summary
A display device includes a substrate in which a plurality of sub pixels are defined; a pair of low potential power lines are in a sub pixel of the plurality of sub pixels; and a plurality of light emitting diodes that overlap an area between the pair of low potential power lines. Each of the plurality of light emitting diodes includes a first semiconductor layer; an emission layer; a second semiconductor layer; a first insulating film that encloses side surfaces of the first semiconductor layer, the emission layer, and the second semiconductor layer; a side electrode on the first insulating film; and a first electrode that is in contact with a bottom surface of the first semiconductor layer and a lower part of the side electrode.