Organic Light-Emitting Display Device with Rare-Earth Capping Layer
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Solution Overview
Problem
Metal wirings in organic light-emitting display devices, particularly cathode electrodes made of Ag, are prone to oxidation, leading to reduced luminance and defective pixels due to their high reactivity with oxygen and moisture.
Innovation Solution
A metal wiring structure and organic light-emitting display device design that incorporates a capping layer containing a rare-earth material with higher oxidizing power than the metal wiring, which prevents oxidation by reacting with oxygen and moisture, maintaining high light transmittance and low resistance values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a thin cathode electrode is used to improve light transmittance, then light transmittance is improved, but resistance value increases leading to reduced luminance
Solution Approach 1:
The cathode electrode is constructed as a composite structure with a thin Ag layer (50-200 nm) providing high light transmittance and low resistance, combined with an organic capping layer containing rare-earth materials that prevent oxidation. This composite approach allows the Ag layer to be thin enough for high transmittance while maintaining low resistance and preventing degradation through oxidation protection.
2Illumination intensity
If Ag is used for the cathode electrode to improve luminance, then luminance is improved, but oxidation occurs leading to defective pixels
Solution Approach 1:
The organic capping layer containing rare-earth materials acts as an intermediary protective barrier between the Ag cathode electrode and the oxidizing environment. This capping layer selectively protects the Ag from oxidation while allowing the Ag to maintain its high reflectivity and low resistance properties, thus preserving luminance performance.
Solution Approach 2:
The organic capping layer creates a protective environment around the Ag cathode electrode, effectively isolating it from oxygen and moisture in the surrounding atmosphere. This protective encapsulation prevents oxidation reactions that would otherwise degrade the Ag electrode and cause pixel defects.
3Reliability
If a capping layer is added to prevent oxidation, then oxidation resistance is improved, but device complexity increases
Solution Approach 1:
The organic capping layer is implemented as a thin film structure that provides oxidation protection without adding significant structural complexity. The thin film approach allows the protective function to be integrated into the existing device architecture with minimal additional layers and processing steps.
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 effectively suppresses oxidation of the cathode electrode, preventing defective pixels and ensuring high luminance and low resistance values, thereby enhancing the performance and reliability of the organic light-emitting display devices.
Implementation Method 1
a capping layer formed on the metal wiring and containing an organic material and a rare-earth material which has higher oxidizing power than the material that forms the metal wiring
Data Source
AI summary
An organic light-emitting display device comprises a substrate, an anode electrode formed on the substrate, an organic layer formed on the anode electrode, a cathode electrode formed on the organic layer, and an organic capping layer formed on the cathode electrode and containing a capping organic material and a rare-earth material which has higher oxidizing power than the material which forms the cathode electrode.