Undercut Bank Structure Isolates OLED Pixels
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Solution Overview
Problem
Excessive lithium (Li) in the organic light-emission layer of electro-luminescent display devices can cause current transfer to neighboring pixels, leading to light emission defects due to its high conductivity properties.
Innovation Solution
An undercut structure is formed under the edge of the bank using a dummy pattern that can be selectively etched relative to the anode, cutting off inter-pixel connections of the organic light-emission layer, thereby preventing Li from moving to adjacent pixels and reducing manufacturing costs by eliminating the need for additional masks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If the amount of lithium (Li) in the organic light-emission layer is increased to extend device lifespan, then the lifespan is improved, but light emission defects occur in neighboring pixels due to current transfer caused by high conductivity of Li
Solution Approach 1:
The patent introduces an undercut structure that segments the organic light-emission layer into isolated pixel regions. This segmentation prevents lithium ions from migrating between adjacent pixels, thereby eliminating light emission defects while allowing increased lithium content for extended device lifespan.
Solution Approach 2:
The undercut structure acts as an intermediary barrier between adjacent pixels. By creating a physical discontinuity in the organic light-emission layer at the pixel boundaries, it mediates the lithium ion migration issue, blocking the harmful current transfer while maintaining the beneficial high conductivity within each pixel.
2Object-affected harmful factors
If an undercut structure is formed to prevent Li migration between pixels, then light emission defects are suppressed, but manufacturing complexity increases due to additional masks
Solution Approach 1:
The patent merges the formation of the dummy pattern and the undercut structure into a single etching process. The dummy pattern serves dual purposes: as an etch mask to create the undercut structure and as a sacrificial layer that is later removed. This merging eliminates the need for separate masking steps, reducing manufacturing complexity while maintaining the effectiveness of the undercut structure in preventing Li migration.
Solution Approach 2:
The dummy pattern performs self-service by acting as both the etch mask and the sacrificial material. The same dummy pattern that defines the undercut structure is subsequently removed to complete the formation process, eliminating the need for additional masks and simplifying the manufacturing process.
3Ease of manufacture
If the organic light-emission layer is deposited on the entire surface of the substrate, then manufacturing is simplified, but inter-pixel connections are created that allow Li to transfer to neighboring pixels
Solution Approach 1:
The patent applies segmentation by creating an undercut structure that divides the continuous organic light-emission layer into discrete pixel regions. This segmentation maintains the simplicity of full-surface deposition while preventing harmful inter-pixel connections, as the undercut physically isolates each pixel's organic layer from its neighbors.
Solution Approach 2:
The patent solves the inter-pixel connection problem by transitioning from a two-dimensional surface pattern to a three-dimensional undercut structure. By creating a vertical discontinuity at the pixel boundaries, the organic light-emission layer is effectively segmented in the depth dimension, preventing lateral Li migration while maintaining continuous coverage on the substrate surface.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution effectively suppresses light emission defects caused by excessive Li while increasing the lifespan of the electro-luminescent display device and simplifies the manufacturing process by eliminating the need for extra masks.
Implementation Method 1
a dummy pattern disposed under an edge of the bank and forming an undercut structure within the bank
Implementation Method 2
When a hole from the anode and an electron from the cathode are injected into the light-emission layer, the injected hole and electron recombine into an exciton to emit light from the light-emission layer
Implementation Method 3
The host generates an exciton from an electron and a hole and transfers energy to the dopant. The dopant is an organic dye material contained in a small amount and receives the energy from the host and converts the energy into light
Data Source
AI summary
An electro-luminescent display device includes an anode disposed on a substrate; a bank having an opening that exposes a portion of the anode and having an undercut structure adjacent to the opening; a dummy pattern disposed at the undercut structure of the bank; an organic light-emission layer disposed on the anode and electrically disconnected with at least one of adjacent pixels; and a cathode disposed on the organic light-emission layer.