OLED Cathode Segmentation for Uniform Brightness
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Solution Overview
Problem
Top emission type OLED display devices face issues with non-uniform brightness due to increased resistance of the cathode, which limits their ability to achieve large size and high definition while maintaining uniform brightness.
Innovation Solution
The implementation of a thin film transistor, a first electrode connected to the drain electrode, an auxiliary electrode on the same layer, a bank layer with transmissive holes, and a residual layer with increasing thickness from the central portion to the edge portion, along with a second electrode on the light emitting layer and residual layer, helps in reducing the resistance and ensuring uniform brightness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a top emission type OLED display device is used to achieve large size and high definition, then the aperture ratio is improved, but the cathode resistance increases causing non-uniform brightness
Solution Approach 1:
The cathode is divided into multiple segments (first cathode, second cathode, third cathode) arranged in a grid pattern. Each segment connects to different data lines, allowing independent control and current distribution. This segmentation reduces the effective resistance path for each segment while maintaining overall high aperture ratio, thereby achieving both large size/high definition and uniform brightness.
Solution Approach 2:
The invention transitions from a single-layer cathode structure to a multi-layer three-dimensional cathode structure. The first cathode is positioned at a lower level while the second and third cathodes are positioned at higher levels, creating vertical stacking. This dimensional change allows current to flow through multiple pathways and reduces resistance without increasing the planar area, thus maintaining high aperture ratio while improving brightness uniformity.
2Reliability
If the cathode resistance is reduced to achieve uniform brightness, then the brightness uniformity is improved, but the device complexity increases
Solution Approach 1:
Multiple cathode segments (first, second, and third cathodes) are merged into a unified three-dimensional structure where they share common support elements and are integrated with the same pixel circuitry. This merging approach reduces the number of independent components and simplifies the overall device architecture while achieving low resistance through the multi-path current flow.
Solution Approach 2:
The multi-layer cathode structure serves multiple functions simultaneously: it provides current distribution pathways (reducing resistance), maintains high aperture ratio through vertical stacking, and enables independent pixel control through connection to different data lines. This multi-functionality reduces device complexity by consolidating multiple requirements into a single integrated structure.
Data Source
AI summary
An organic light emitting diode display device includes a substrate; a thin film transistor on the substrate; a first electrode on the thin film transistor and connected to a drain electrode of the thin film transistor; an auxiliary electrode on a same layer as the first electrode; a bank layer covering edges of the first electrode and edges of the auxiliary electrode and having a transmissive hole corresponding to the first electrode and an auxiliary contact hole corresponding to the auxiliary electrode; a light emitting layer on the first electrode in the transmissive hole; a residual layer on the auxiliary electrode in the auxiliary contact hole, wherein a thickness of a central portion of the residual layer is smaller than a thickness of an edge portion of the residual layer; and a second electrode on the light emitting layer and the residual layer.