OLED Cathode Lower Auxiliary Wiring for Voltage Drop and Aperture Ratio
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Solution Overview
Problem
The technical challenge in organic light-emitting display (OLED) devices is luminance non-uniformity due to increased electrical resistance of the cathode, which worsens with larger device sizes, and this is exacerbated by the need for auxiliary wiring that reduces the light-emitting area and aperture ratio.
Innovation Solution
Incorporating a lower auxiliary wiring electrically connected to the cathode between the organic light-emitting element and the planarization layer to minimize voltage drop and parasitic capacitance, while maintaining a sufficient light-emitting area and aperture ratio by positioning it between the anode and the planarization layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a separate auxiliary wiring is formed on the same plane with an anode, then voltage drop is minimized, but light-emitting area and aperture ratio are decreased
Solution Approach 1:
The auxiliary wiring is moved from the same plane as the anode to a lower layer (between the anode and planarization layer), utilizing vertical spatial arrangement. This dimensional change allows the auxiliary wiring to provide electrical connection without occupying horizontal space that would reduce the light-emitting area, thus resolving the contradiction between voltage drop minimization and aperture ratio maintenance.
2Illumination intensity
If cathode thickness is reduced to improve transmittance, then light emission is enhanced, but electrical resistance increases causing voltage drop
Solution Approach 1:
An auxiliary wiring is introduced as an intermediary element to provide an additional electrical connection path to the cathode. This mediator reduces the overall electrical resistance by creating parallel conduction paths, allowing the cathode to maintain thin thickness for high transmittance while the auxiliary wiring compensates for the increased resistance through alternative current flow routes.
3Area of stationary object
If device size is increased, then display area is expanded, but luminance non-uniformity worsens due to increased voltage drop
Solution Approach 1:
The electrical connection system is segmented by adding auxiliary wiring that creates multiple independent connection paths to different regions of the cathode. This segmentation allows each region to have its own optimized electrical connection, compensating for the increased voltage drop that occurs in larger devices and maintaining uniform luminance across the expanded display area.
Data Source
AI summary
An organic light-emitting display device according to one embodiment of the present disclosure includes a substrate, a thin-film transistor formed on the substrate, a planarization layer formed on the thin-film transistor, an organic light-emitting element formed on the planarization layer, the emitting element including an organic light-emitting layer and a cathode, and a lower auxiliary wiring between the organic light-emitting element and the planarization layer, the wiring electrically connected with the cathode.