Multi-Layer Electrode Structure for Organic EL Display Voltage Drop
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Solution Overview
Problem
Existing organic electroluminescence (EL) display units face issues with voltage drop and display image quality due to foreign matter causing short paths between electrodes, which are difficult to repair, especially with thick transparent electrically conductive films.
Innovation Solution
A display unit structure with a second electrode comprising a transparent first electrically conductive film, a high-resistivity layer, and a second electrically conductive film, where the first electrically conductive film is insulated or ablated locally to cut short paths, and the high-resistivity layer is used to prevent further short circuits, allowing for lower resistance without increasing film thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a thick transparent electrically conductive film is used for the electrode, then the resistance is reduced and voltage drop is suppressed, but the ability to repair dark spots caused by foreign matter is lost
Solution Approach 1:
The electrode is divided into multiple layers: a first transparent electrically conductive film (thick, low resistance) and a second transparent electrically conductive film (thin, repairable). This segmentation allows each layer to fulfill different functions - the first layer provides low resistance while the second layer enables dark spot repair through reverse bias application.
Solution Approach 2:
The second transparent electrically conductive film is designed with locally varied thickness or material properties, allowing certain regions to be more susceptible to reverse bias effects for dark spot repair while maintaining overall electrical conductivity. This enables localized repair action without affecting the entire electrode's low resistance characteristic.
2Loss of energy
If a thick transparent electrically conductive film is used for the electrode, then lower resistance is achieved, but the electrode structure becomes more complex with multiple layers
Solution Approach 1:
The multi-layer electrode structure serves multiple functions simultaneously: electrical conduction, dark spot repair capability, and potentially optical function. The first thick layer provides low resistance conduction while the second thin layer enables repair operations, making the electrode structure universally functional rather than requiring separate components for each function.
3Reliability
If foreign matter is present in the organic layer, then short paths are generated between electrodes causing dark spots, but the existing repair method is ineffective with thick conductive films
Solution Approach 1:
The second thin transparent electrically conductive film is prepared in advance with properties that enable reverse bias repair. This preliminary preparation ensures that when dark spots occur due to foreign matter, the repair mechanism is already in place and functional, allowing effective repair before the product leaves the manufacturing line.
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 reduces the impact of dark spots on display image quality by minimizing voltage drop and preventing additional short circuits, thereby enhancing the overall image quality and reliability of the organic EL display unit.
Implementation Method 1
applying a reverse bias between electrodes to ablate an electrode material with heat generation due to a reverse bias current
Implementation Method 2
forming, on the first electrically conductive film with the dark spot portion being repaired, a high-resistivity layer having higher electric resistance than the first electrically conductive film
Data Source
AI summary
A display unit includes a first electrode, an organic layer, and a second electrode. The first electrode, the organic layer, and the second electrode are provided in this order on a substrate. The organic layer includes a light-emitting layer. The second electrode includes, in order from the organic layer, a first electrically conductive film, a high-resistivity layer, and a second electrically conductive film. The first electrically conductive film is transparent and includes an insulated or ablated local part. The high-resistivity layer has higher electric resistance than the first electrically conductive film. The second electrically conductive film is provided on the high-resistivity layer.