Segmented Cathode Structure for OLED Voltage Drop Reduction
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Solution Overview
Problem
Conventional large-sized organic light emitting diode displays face issues with display uniformity due to voltage drops caused by varying resistances in the common cathode, leading to a need for large driving currents that can shorten the lifespan of electronic devices.
Innovation Solution
The design replaces the conventional common cathode with isolated small-sized cathodes and auxiliary electrodes, where each light emitting structure includes a substrate with an auxiliary electrode, insulating layers, a first electrode, an organic light-emitting layer, and a patterned structure layer that surrounds the cathode, reducing the cathode area and minimizing voltage drops.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a common cathode is used for all organic light emitting diodes in a large-sized display, then the display can be manufactured with a simpler structure, but voltage drops occur due to varying resistances in different locations of the common cathode, degrading display uniformity
Solution Approach 1:
The patent divides the common cathode into multiple independent small-sized cathodes, each corresponding to a specific light emitting diode or group of diodes. This segmentation eliminates the varying resistance issues of a large common cathode while maintaining manufacturing simplicity through the use of auxiliary electrodes that can be formed using the same deposition processes.
Solution Approach 2:
The patent introduces auxiliary electrodes as intermediary elements that are electrically connected to the small-sized cathodes through conductive structures. These auxiliary electrodes serve as the new common cathode interface, allowing simplified manufacturing while the small cathodes provide the localized current control needed for display uniformity.
2Productivity
If a common cathode with large area is used to drive all organic light emitting diodes, then all diodes can be driven simultaneously, but large driving current is required which shortens the lifespan of the electronic device
Solution Approach 1:
The patent segments the total driving current into multiple smaller currents, each flowing through individual small-sized cathodes. This distribution of current load reduces the stress on any single cathode and the overall system, thereby extending device lifespan while maintaining the ability to drive all diodes simultaneously through parallel operation.
Solution Approach 2:
The patent applies different current densities locally to different regions of the display through the small-sized cathodes. Each cathode is optimized for its specific location and the diodes it drives, allowing efficient current utilization and reducing the total current requirement compared to a single large common cathode.
Data Source
AI summary
A light emitting device includes a substrate, and a plurality of light emitting structures disposed thereon. Each of the light emitting structures includes an auxiliary electrode disposed on the substrate, a first insulating layer disposed on the substrate and covering the auxiliary electrode, an electrode disposed on the first insulating layer, a second insulating layer disposed on the first insulating layer and having a first opening exposing the electrode, an organic light emitting layer disposed in the first opening, a cathode disposed on the organic light emitting layer, at least a conductive structure penetrating through the first insulating layer and the second insulating layer, and a closed ring structure disposed on the second insulating layer and around the cathode, wherein a thickness of the closed ring structure is larger than that of the cathode.