Auxiliary Electrode Layer for OLED Voltage Uniformity
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Solution Overview
Problem
Existing organic electroluminescence (EL) display devices face issues with non-uniform voltage distribution across the second electrode, leading to variations in luminance and deteriorated display quality due to high electrical resistivity of light-transmissive conductive materials, and challenges in reliably connecting the second electrode and auxiliary electrode, as well as addressing foreign materials incorporated into the organic layer.
Innovation Solution
A display device configuration with a contact portion and auxiliary electrode layer formed to ensure reliable electrical connection between the second electrode and auxiliary electrode, using a layered structure with specific etching rates and materials to prevent oxidation and reduce contact resistance, and a method for repairing by laser irradiation to separate affected electrode portions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If a light-transmissive conductive material (e.g., IZO) is used for the second electrode to achieve top emission type display, then the aperture ratio is improved, but the electrical resistivity increases causing non-uniform voltage distribution and luminance variation
Solution Approach 1:
The second electrode is divided into a main electrode region and an auxiliary electrode extending from it. This segmentation allows the main electrode to maintain light transparency while the auxiliary electrode provides additional conductive pathways to distribute voltage more uniformly across the electrode plane, reducing the impact of high resistivity in light-transmissive materials.
Solution Approach 2:
An auxiliary electrode acts as an intermediary conductive element that bridges the high-resistivity light-transmissive second electrode and the low-resistivity first electrode. This intermediary structure enables better voltage distribution without compromising the light-emission properties of the main second electrode.
2Reliability
If an auxiliary electrode is formed using the same material as the first electrode (e.g., Al or Al alloy) to improve electrical connection, then the conductivity is improved, but the surface oxidizes during manufacturing increasing contact resistance
Solution Approach 1:
The auxiliary electrode is formed using a composite material structure consisting of a first auxiliary electrode layer (Al or Al alloy for low resistivity) and a second auxiliary electrode layer (oxidation-resistant material) covering it. This composite structure combines the advantages of both materials: high conductivity from the aluminum layer and oxidation resistance from the protective outer layer.
Solution Approach 2:
The second auxiliary electrode layer is specifically designed to be resistant to oxidation, creating a protective environment for the underlying aluminum-based first auxiliary electrode layer. This protective layer prevents direct exposure of the reactive aluminum to oxygen during manufacturing and operation, maintaining low contact resistance.
3Ease of manufacture
If foreign materials are incorporated into the organic layer, then the manufacturing process is simplified, but short-circuiting between electrodes occurs requiring complex repair procedures
Solution Approach 1:
The repair method involves extracting or removing only the affected portion of the first electrode that contains foreign materials causing short-circuits, rather than removing entire electrodes or complex assemblies. This targeted extraction simplifies the repair process while restoring proper device function.
Solution Approach 2:
The repair approach applies local treatment by targeting only the specific region where foreign materials are incorporated into the organic layer. By focusing repair efforts on the localized defective area rather than the entire device, the process becomes simpler and more efficient.
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 solution ensures reliable electrical connection and reduced power consumption, improves display quality by maintaining low resistance and preventing short-circuiting, and simplifies the repair process by minimizing the target area for laser irradiation.
Implementation Method 1
a first portion of the first electrode surrounding the window portion is irradiated with a laser beam, thereby the affected portion is separated from the other portions
Data Source
AI summary
A display device includes light emitting elements that are arranged in a two-dimensional matrix, in which the light emitting elements include a drive circuit which is provided on a substrate, a first insulating layer which covers the drive circuit and the substrate, a light emitting portion in which a first electrode, an organic layer having a light emitting layer, and a second electrode are laminated, and a second insulating layer which covers the first electrode.