Top-Emissive OLED Auxiliary Cathode Under-Cut Structure
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Solution Overview
Problem
In large-area organic light-emitting diode displays, the high surface resistance of cathodes made from transparent conductive materials like indium tin oxide or indium zinc oxide leads to uneven voltage distribution and brightness across the screen, affecting image quality.
Innovation Solution
A top-emissive light-emitting diode display design featuring an auxiliary cathode with an under-cut structure that connects to the cathode, reducing surface resistance by using a metal material for the auxiliary cathode and connecting terminal, and simplifying the manufacturing process by reducing the number of mask processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a transparent conductive material is used for the cathode, then the display structure is achieved, but the surface resistance increases leading to uneven voltage distribution
Solution Approach 1:
The cathode system is segmented into two parts: a transparent conductive cathode material and a separate auxiliary cathode made of low-resistivity metal. The auxiliary cathode is divided into multiple regions (first auxiliary cathode, second auxiliary cathode, third auxiliary cathode) that are selectively connected to different pixel electrodes, creating a distributed voltage compensation network across the display panel.
Solution Approach 2:
The auxiliary cathode acts as an intermediary element between the power supply and the pixel electrodes. It provides an additional low-resistance conduction path that mediates the voltage distribution across the display, compensating for the high resistance of the transparent conductive cathode material without interfering with the optical properties of the cathode.
2Reliability
If an auxiliary cathode is added to reduce surface resistance, then voltage distribution improves, but device complexity increases
Solution Approach 1:
The auxiliary cathode structure is merged with the existing pixel electrode formation process. The same conductive material and deposition techniques used for creating pixel electrodes are also used to form the auxiliary cathode regions, combining two functions into a single integrated structure rather than adding completely separate components.
Solution Approach 2:
The auxiliary cathode serves multiple functions: it provides low-resistance voltage distribution, defines pixel boundaries, and works in conjunction with the transparent conductive cathode material. This multi-functionality reduces the need for additional separate structures and simplifies the overall device architecture.
3Manufacturing precision
If mask processes are used to define auxiliary cathode regions, then precision is achieved, but manufacturing time increases
Solution Approach 1:
The auxiliary cathode regions are formed simultaneously with the pixel electrodes during the same deposition process. By preparing the auxiliary cathode structure in advance as part of the base layer formation, the need for subsequent mask processes to define these regions is eliminated, reducing manufacturing steps while maintaining precision through controlled deposition patterns.
Data Source
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AI summary
The present invention relates to a top-emissive organic light-emitting diode display. The organic light-emitting diode comprises a substrate (SUB), an auxiliary cathode (ACT), a passivation film (PAS), a planarization film (OC), an under-cut opening (OH), a connecting terminal (CT), an under-area (UA), a bank (BN), an organic emission layer (OL), and a cathode (CAT). The auxiliary cathode (ACT) is placed on the substrate (SUB). The passivation film (PAS) covers the auxiliary cathode (ACT). The planarization film (OC) is stacked on the passivation film (PAS). The under-cut opening (OH) is formed in the passivation film (PAS) and the planarization film (OC) and exposes one end of the auxiliary cathode (ACT). The connecting terminal (CT) makes contact with the top surface of the one end exposed through the under-cut opening (OH) and protrudes into the under-cut opening (OH), being longer in length than the one end of the auxiliary cathode (ACT). The under-area (UA) is formed between the end of the connecting terminal (CT) and the one end of the auxiliary cathode (ACT). The bank (BN) lies on the planarization film (OC) and exposes the entire under-cut opening (OH) in a larger size than the under-cut opening (OH). The organic emission layer (OL) covers the surface of the connecting terminal (CT) in the under-cut opening (OH), and is not applied to the under-area (UA) and exposes the side of the connecting terminal (CT). The cathode (CAT) is stacked on the organic emission layer (OL), makes contact with the side of the connecting terminal (CT) not covered by the organic emission layer (OL), and extends all the way to the under-area (UA).