OLED Pixel Bank Structure for Uniform Emission Layer Flatness
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Solution Overview
Problem
The existing technologies face challenges in achieving uniform thickness and improving flatness of the emission layer in organic light emitting elements manufactured through a solution process, which affects the light emission efficiency.
Innovation Solution
A display device is designed with a substrate, banks, and an emission layer. The banks include a hydrophilic first bank, a hydrophobic second bank, and a hydrophobic third bank with a T shape, which helps in forming an emission layer with a higher edge portion surface height than the central portion, thereby improving flatness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a solution process is used to form the emission layer, then the manufacturing complexity is reduced, but the thickness uniformity and flatness of the emission layer deteriorate
Solution Approach 1:
The bank structure is segmented into multiple layers (first bank, second bank, third bank) with different heights, creating a stepped configuration. This segmentation allows different regions of the emission layer to be formed under controlled conditions, improving thickness uniformity while maintaining the simplicity of the solution process.
Solution Approach 2:
Different regions of the bank structure are given different heights and properties (hydrophilic first bank, hydrophobic second and third banks). This local differentiation creates specific microenvironments for emission layer formation in different areas, enabling better control over thickness distribution and flatness throughout the pixel region.
2Device complexity
If a simple bank structure is used, then the device complexity is reduced, but the emission layer flatness deteriorates
Solution Approach 1:
The bank is divided into three distinct banks with progressively different heights, where the first bank has the lowest height, the second bank has intermediate height, and the third bank has the highest height. This segmented approach creates a stepped structure that provides better control over emission layer formation, improving flatness without requiring overly complex manufacturing processes.
Solution Approach 2:
The bank structure extends in the vertical dimension with three different height levels, creating a three-dimensional stepped configuration. This dimensional approach allows the emission layer to be formed with better flatness control by providing gradual height transitions, avoiding the need for complex lateral structures.
3Ease of manufacture
If the emission layer thickness is not uniform, then the manufacturing process is simpler, but the light emission efficiency deteriorates
Solution Approach 1:
The multi-level bank structure segments the emission area into different zones with controlled thickness variations. The stepped configuration ensures that the emission layer forms with more uniform thickness across different regions, which directly improves light emission efficiency while maintaining the simplicity of solution-based manufacturing.
Solution Approach 2:
Different banks with different heights create local variations in the formation environment for the emission layer. This local quality control ensures that each region of the emission layer achieves optimal thickness and flatness for its specific location, thereby improving overall light emission efficiency without complicating the manufacturing process.
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
The proposed solution enhances the surface flatness of the emission layer, leading to improved light emission efficiency and performance of the organic light emitting element.
Implementation Method 1
The first bank may be hydrophilic, and each of the second bank and the third bank may have a hydrophobic upper surface
Implementation Method 2
The first bank may be hydrophilic, and each of the second bank and the third bank may have a hydrophobic upper surface
Implementation Method 3
an edge portion of the emission layer may be formed inside the first hole and may have a surface height higher than that of a central portion of the emission layer
Data Source
AI summary
A display device includes a substrate on which a plurality of pixels are disposed; a bank defining emission areas of the plurality of pixels; and an emission layer formed in each of the emission areas, wherein the bank includes a first bank extended in row and column directions; a second bank disposed on the first bank and extended in the column direction to separate adjacent pixel columns; and a third bank disposed on the second bank, wherein the first bank is hydrophilic, and each of the second bank and the third bank has a hydrophobic upper surface.