Alkali Metal Common Electrode Oxidation Prevention
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Solution Overview
Problem
In EL display devices, the contact resistance between electrical supply wiring and the common electrode increases due to the formation of alkali metal or alkaline earth metal oxides, leading to voltage drop and reduced electron injection efficiency.
Innovation Solution
The common electrode is made of alkali metal or alkaline earth metal, and a protective layer is applied to prevent oxidation, maintaining low contact resistance and improving electron injection properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the common electrode is made of alkali metal or alkaline earth metal to improve electron injection efficiency, then the electron injection property is improved, but contact resistance increases due to oxide formation
Solution Approach 1:
An organic electron transport layer is introduced as an intermediary between the alkali metal/alkaline earth metal common electrode and the light-emitting layer. This layer prevents direct oxidation of the common electrode by ITO while facilitating electron transport, thus resolving the contradiction between improving electron injection efficiency and preventing contact resistance increase due to oxide formation
Solution Approach 2:
The patent uses a composite structure combining alkali metal or alkaline earth metal with organic electron transport materials. This composite approach allows the common electrode to maintain low work function for efficient electron injection while the organic layer prevents oxidation and maintains low contact resistance
2Manufacturing precision
If electrical supply wiring is provided to suppress voltage drop in the common electrode, then voltage uniformity is improved, but contact resistance between wiring and common electrode increases due to oxide formation
Solution Approach 1:
The organic electron transport layer serves as a mediator between the electrical supply wiring and the alkali metal/alkaline earth metal common electrode, preventing oxide formation at the interface while enabling effective electrical connection. This resolves the contradiction between achieving voltage uniformity through wiring and preventing contact resistance increase
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 prevents the formation of insulating oxides, maintaining high conductivity and improving electron injection efficiency, thus reducing voltage drop and enhancing the performance of the light-emitting layer.
Implementation Method 1
a protective layer located on or above the common electrode, and preventing oxidization of the common electrode
Implementation Method 2
the property of electron injection can be improved through the doping with alkali metal or alkaline earth metal
Data Source
AI summary
An EL display device of the present invention includes a plurality of pixel electrodes, wiring, a common electrode, a plurality of light-emitting layer portions, and a protective layer. The pixel electrodes are formed in one-to-one correspondence with a plurality of pixels. The wiring is formed in at least one of a plurality of intervals between the pixels. The common electrode is formed above each of the pixel electrodes and is in electrical connection with the wiring. The common electrode is made of alkali metal or alkaline earth metal. The light-emitting layer portions are each located between a corresponding one of the pixel electrodes and the common electrode. The protective layer is located on the common electrode, preventing oxidization thereof. The EL display device suppresses voltage drop in the common electrode, while also suppressing reduction in a property of electron injection to the light-emitting layer portions.