Subpixel Trench Cathode Structure for Uniform OLED Emission
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Solution Overview
Problem
Existing display devices face challenges in achieving improved cathode connectivity and uniform light emission across sub-pixels, particularly in high-integration displays like head-mounted devices, due to limitations in cathode thickness and structure design.
Innovation Solution
The display device incorporates a pixel define layer with trenches in the boundary regions between sub-pixels, featuring a cathode with varying thickness and a gentle slope over trenches, and an auxiliary electrode on the cathode to enhance connectivity, along with a deposition mask that allows precise material deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the cathode thickness is increased to improve connectivity in boundary regions, then cathode connectivity is improved, but the uniformity of light emission across sub-pixels deteriorates
Solution Approach 1:
The patent applies local quality by creating a multi-layer cathode structure where the first cathode layer has uniform thickness across all regions, while the second cathode layer is selectively formed only in boundary regions between sub-pixels. This allows the boundary regions to have increased local cathode thickness for improved connectivity, while the emission areas maintain uniform thickness for consistent light emission.
2Ease of manufacture
If the cathode structure is simplified to reduce manufacturing complexity, then ease of manufacture is improved, but cathode connectivity in boundary regions deteriorates
Solution Approach 1:
The patent segments the cathode into two distinct layers: a first cathode layer that provides uniform baseline coverage across all sub-pixels, and a second cathode layer that is segmented to appear only in boundary regions. This segmentation allows independent optimization of each layer's thickness and formation conditions, improving overall cathode connectivity while maintaining manufacturing feasibility through sequential deposition processes.
3Manufacturing precision
If the pixel define layer trenches are made deeper to improve sub-pixel isolation, then manufacturing precision is improved, but the cathode connectivity across trenches deteriorates
Solution Approach 1:
The patent resolves the conflict between trench depth and cathode connectivity by transitioning from a single-plane cathode to a multi-layer cathode structure in the vertical dimension. The first cathode layer fills the trenches to provide isolation, while the second cathode layer is deposited on top to bridge across the trench regions, ensuring connectivity is restored in the horizontal plane despite the deep trenches providing vertical isolation.
Data Source
AI summary
A display device includes: a pixel including one or more subpixels, the sub-pixels each having an emission area to emit light and the pixel having a non-emission area around the emission areas of the sub-pixels, a pixel define layer overlapping the non-emission area, defining trenches in a boundary region between adjacent sub-pixels of the sub-pixels and the trenches penetrating the pixel define layer, an emission structure on portions of the trenches and the pixel define layer, a cathode on the emission structure, and an auxiliary electrode on a portion of the cathode.