Display Device Pixel Defining Layers Prevent Lateral Leakage
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Solution Overview
Problem
Display devices face issues with color mixing and luminance deterioration due to lateral leakage current between adjacent pixels caused by common organic layers, leading to defects in image display.
Innovation Solution
A display device design featuring separate pixel areas with distinct emission layers and charge generating layers, including n-type and p-type charge generating layers, and hole transport regions, which are strategically positioned and overlapped to prevent lateral current leakage, along with a manufacturing method using specific masks to form these layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If an organic layer is formed commonly over all pixels through an open mask, then the manufacturing process is simplified, but lateral leakage current occurs between adjacent pixels causing color mixing and luminance defects
Solution Approach 1:
The patent divides the common organic layer into separate pixel-level organic layers by forming pixel-defining layers over each pixel area. This segmentation prevents lateral leakage current between adjacent pixels while maintaining the benefit of forming organic layers over multiple pixels. The pixel-defining layers create isolated regions for each pixel, eliminating the color mixing issue caused by continuous organic layers.
2Reliability
If separate pixel-defining layers are formed over each pixel area, then lateral leakage current is prevented, but the manufacturing process complexity increases
Solution Approach 1:
The patent merges the formation of pixel-defining layers with the formation of emission layers by using the same shadow mask for both purposes. The shadow mask defines both the pixel areas and the emission layer patterns simultaneously, reducing the number of separate manufacturing steps. This merging approach minimizes process complexity while achieving the reliability benefit of preventing lateral leakage current.
3Reliability
If emission layers are formed separately for each pixel using a shadow mask, then color mixing is prevented, but mask sagging defects occur
Solution Approach 1:
The patent introduces pixel-defining layers as intermediary structures between the substrate and the emission layers. These pixel-defining layers serve as a mediator that defines pixel boundaries and prevents lateral leakage current, eliminating the need for shadow masks during emission layer formation. This intermediary approach maintains color mixing prevention while avoiding mask sagging defects by using a deposition method that does not require shadow masks for the critical emission layer formation.
Data Source
AI summary
A display device includes a base layer including first and second pixel areas, and a non-pixel area, a first electrode on base layer, a first light emitting stack on first electrode and including a first emission layer, a n-type charge generating layer on first light emitting stack, a p-type charge generating layer on the n-type charge generating layer, a second light emitting stack including a hole transport region on the p-type charge generating layer, and a second emission layer on hole transport region, and a second electrode on the second light emitting stack.