OLED Pixel Bank Structure for High-Resolution Short-Circuit Prevention
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Solution Overview
Problem
Existing display devices face challenges in providing high-resolution images and preventing short-circuits between the anode and cathode.
Innovation Solution
The display device incorporates a bank structure with multiple layers, including a tip protruding towards the non-emission area, and a pixel defining layer that separates the anode and light emitting layer, along with a cathode configuration that avoids direct contact, allowing for deposition processes without a fine metal mask.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional single-layer bank structure is used, then the manufacturing process is simpler, but the image resolution is insufficient and short-circuits may occur between anode and cathode
Solution Approach 1:
The bank structure is divided into multiple layers (first bank layer, second bank layer, third bank layer) with each layer serving specific functions. The first and second bank layers provide structural support and define emission areas, while the third bank layer with protruding tips prevents short-circuits and enables precise patterning during deposition processes, thereby achieving high image resolution without requiring complex fine metal masks.
Solution Approach 2:
The third bank layer includes tips that protrude in the thickness direction beyond the first and second bank layers. This dimensional extension creates physical barriers that prevent short-circuits between anode and cathode while also serving as deposition guides during fabrication, solving both reliability and precision issues simultaneously.
2Reliability
If the light emitting layer is spaced apart from the anode over the anode contact hole, then short-circuits are prevented, but the manufacturing process becomes more complex
Solution Approach 1:
The pixel defining layer is formed in advance to cover the anode contact hole before depositing the light emitting layer. This preliminary action creates a pre-defined pathway that guides subsequent deposition processes, allowing the light emitting layer to be deposited uniformly without requiring complex fine metal masks while ensuring the anode contact hole remains exposed for proper electrical connection.
Solution Approach 2:
The pixel defining layer acts as an intermediary structure between the anode and the light emitting layer. It selectively covers the anode contact hole to prevent short-circuits while leaving openings that allow the light emitting layer to contact the anode in appropriate regions, thereby simplifying the overall fabrication process.
3Manufacturing precision
If a fine metal mask is used for deposition, then precise patterning is achieved, but the manufacturing cost and complexity increase
Solution Approach 1:
The third bank layer with its protruding tips serves a dual function: it prevents short-circuits between anode and cathode, and simultaneously acts as a self-aligned deposition guide. During deposition processes, the protruding tips naturally define the deposition boundaries without requiring external fine metal masks, thereby achieving precise patterning while simplifying the fabrication process.
Data Source
AI summary
A display device includes a substrate including an emission area and a non-emission area surrounding the emission area; a bank structure located on the emission area of the substrate and comprising a tip protruding toward the non-emission area; an anode contact hole penetrating the bank structure; an anode located on the bank structure and electrically connected to a transistor located on the substrate through the anode contact hole; a pixel defining layer located on the anode; and a light emitting layer located on the pixel defining layer, wherein the light emitting layer is spaced apart from the anode with the pixel defining layer therebetween in a portion overlapping the anode contact hole in a plan view and contacts the anode in a portion not overlapping the anode contact hole in the plan view.