Organic Light Emitting Device Sub-Bank Uniformity
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Solution Overview
Problem
In organic light emitting devices, the functional layer formed in the groove region between banks is not uniform in thickness, leading to increased current density and degradation in regions with smaller thickness, particularly affecting blue light emitting elements.
Innovation Solution
The introduction of a sub-bank within the groove region, with a height equal to or smaller than the column banks, ensures that the functional layer is uniform across both sides of the sub-bank, reducing the groove region's opening width and maintaining consistent thickness distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the groove region opening width is increased to reduce current density in blue light emitting elements, then the current density is reduced and element degradation is prevented, but the functional layer thickness becomes non-uniform causing brightness unevenness
Solution Approach 1:
The groove region is divided into multiple sub-regions by introducing partition walls (sub-banks) that extend from the bottom of the groove toward the opening. This segmentation allows the functional layer to be formed more uniformly across each sub-region while maintaining the overall larger opening width needed for current density control.
Solution Approach 2:
Different regions of the groove are given different local structures through the partition walls. The partition walls create localized zones with controlled geometry that ensure uniform functional layer formation in each zone, while the overall groove dimensions maintain the required opening width for current density management.
2Manufacturing precision
If the groove region opening width is kept small to maintain uniform functional layer thickness, then the functional layer thickness is uniform, but the current density increases causing element degradation
Solution Approach 1:
By dividing the groove into multiple sub-regions with partition walls, the effective width of each sub-region is reduced, allowing uniform functional layer formation without requiring the entire groove opening to be small. This maintains thickness uniformity while preserving overall groove dimensions for current density control.
Solution Approach 2:
The partition walls extend in the vertical dimension from the groove bottom upward, creating a three-dimensional structure that controls functional layer formation without constraining the horizontal opening width. This dimensional approach allows simultaneous achievement of uniform thickness and adequate opening width.
3Ease of manufacture
If banks are added to define pixel regions in the row direction, then pixel regions are properly defined, but the device complexity increases
Solution Approach 1:
The partition walls serve dual functions: they define pixel regions in the row direction and simultaneously act as sub-banks for functional layer formation in the groove regions. This merging of functions reduces the need for separate structures, thereby reducing overall device complexity while maintaining manufacturing ease.
Data Source
AI summary
A light emitting device includes: a base substrate; banks extending in a direction along a surface of the base substrate; and light emitting elements extending along the direction in groove regions defined by the banks. Each light emitting element includes one or more functional layers between a pair of electrodes. Within at least one of the groove regions: a sub-bank extends along the one direction and has a height equal to or smaller than a height of the banks; for each of the one or more functional layers in the groove regions, portions of each of the one or more functional layers on each side of the sub-bank are made of a same material; and a thickness of the one or more functional layers is smaller than a height of the sub-bank.