Mesh Auxiliary Electrodes for Top-Emission OLED Voltage Uniformity
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Solution Overview
Problem
In top emission organic light emitting displays, the high resistivity of transparent cathode electrodes leads to voltage differences between pixels, causing non-uniform brightness and deteriorating picture quality due to voltage drops across the display region.
Innovation Solution
The implementation of mesh-type auxiliary electrodes coupled to cathode electrodes through contact regions formed by steps at the lower parts of the auxiliary electrodes, ensuring uniform voltage maintenance across the display and facilitating manufacturing processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If transparent electrode material such as ITO or IZO is used for cathode electrodes to enable top emission structure, then light emission in the direction of encapsulating substrate is achieved with higher aperture ratio, but high resistivity causes voltage difference between pixels leading to non-uniform brightness
Solution Approach 1:
The patent introduces mesh-type auxiliary electrodes that divide the cathode electrode structure into multiple conductive paths. These auxiliary electrodes are positioned between the transparent cathode electrode and the organic light emission layer, creating a segmented conductive network that distributes voltage more uniformly across different pixel regions, thereby reducing voltage drop and improving picture quality uniformity while maintaining the top emission structure's high aperture ratio
Solution Approach 2:
The patent introduces auxiliary electrodes as an intermediary conductive layer between the transparent cathode electrode and the organic light emission layer. This intermediary structure serves to equalize voltage distribution across the display region by providing additional conductive pathways, thereby mitigating the high resistivity issue of transparent electrode materials without compromising the top emission configuration
2Reliability
If mesh type auxiliary electrodes are introduced to maintain uniform voltages, then voltage uniformity and picture quality are improved, but device structure becomes more complex
Solution Approach 1:
The auxiliary electrodes are configured in a mesh pattern that segments the cathode electrode region into multiple zones. This segmentation approach provides multiple conductive pathways for voltage distribution while using simple geometric shapes (intersecting lines) that can be manufactured using standard photolithography techniques, thus achieving voltage uniformity without excessive structural complexity
Solution Approach 2:
The auxiliary electrodes serve multiple functions simultaneously: they act as conductive pathways for voltage distribution, provide structural support for the organic light emission layer, and define the pixel boundaries. This multi-functionality reduces the need for additional separate components, thereby improving voltage uniformity while limiting the increase in device complexity
Data Source
AI summary
A top emission organic light emitting display and a method of manufacturing the same. The organic light emitting display includes a substrate, a plurality of thin film transistors (TFT) on the substrate, a plurality of first electrodes coupled to the plurality of TFTs, auxiliary electrodes having a mesh structure defining areas where the plurality of first electrodes are located, a pixel defining layer on a substantially entire area of the substrate and patterned to expose the first electrodes and the auxiliary electrodes, an organic light emission layer on the substantially entire area of the substrate including the exposed first electrodes and auxiliary electrodes, and second electrodes on the organic light emission layer. Steps are formed at lower parts of the auxiliary electrodes, and the second electrodes are coupled to the auxiliary electrodes through contact regions in which the auxiliary electrodes are exposed due to the steps.