OLED Electrode Head-Neck Geometry for Uniform Deposition
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Solution Overview
Problem
The existing organic light emitting display devices face display quality deterioration due to thickness deviations in the organic emission layer, leading to luminance non-uniformity and reduced lifespan, particularly when using the solution process for large-area patterning.
Innovation Solution
The design includes a substrate with sub-pixels arranged in a column and row direction, featuring first and second banks with specific openings to expose electrodes, allowing for uniform organic light-emitting material deposition and preventing color mixing by alternating the widths of head and neck portions of the electrodes, ensuring proper material spreading and confinement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the solution process is used for large-area patterning, then material use rate increases and thermal stability improves, but thickness non-uniformity occurs leading to display quality deterioration
Solution Approach 1:
The electrode structure is divided into different regions with different widths: a head portion with a first width and a neck portion with a second width. This local variation in geometry allows different regions to serve different functions - the wider head portion ensures sufficient material deposition area, while the narrower neck portion controls material spreading to prevent thickness non-uniformity and color mixing between adjacent sub-pixels.
2Illumination intensity
If the emission layer thickness is increased to improve luminance, then display brightness improves, but thickness deviation causes color mixing between sub-pixels
Solution Approach 1:
The electrode structure employs asymmetric design where the head portion and neck portion have different widths. The neck portion with smaller width acts as a constraint region that prevents organic light-emitting material from spreading into adjacent sub-pixels, while the head portion provides adequate area for light emission. This asymmetric geometry simultaneously achieves high luminance and effective color separation.
3Area of stationary object
If a large-area mask is used for patterning, then large-area display can be realized, but the mask bends causing deposition at incorrect positions
Solution Approach 1:
The invention eliminates the mask component entirely by using a solution process with controlled electrode geometry. Instead of relying on a large-area mask that bends and causes positioning errors, the pattern is defined by the electrode structure itself (head and neck portions) formed through a maskless solution process, thereby extracting the problematic mask element from the system while maintaining large-area patterning capability.
Data Source
AI summary
An organic light emitting display device comprises a substrate on which a plurality of sub-pixels are arranged in a column direction and a row direction; a plurality of first electrodes respectively allocated to the plurality of sub-pixels; a first bank disposed between the plurality of first electrodes neighboring in the column direction and having a plurality of first openings that exposes the plurality of first electrodes arranged in the row direction; a second bank disposed between the plurality of first electrodes neighboring in the row direction and having a plurality of second openings that exposes the plurality of first electrodes arranged in the column direction, wherein each of the plurality of first electrodes includes a head portion having a first width in the row direction and a neck portion having a second width less than the first width and extending from one side of the head portion in the column direction, wherein the head portion of the first electrodes arranged in an odd column neighbors the neck portion of the first electrodes arranged in an even column along the row direction, and wherein the neck portion of the first electrodes arranged in an odd column neighbors the head portion of the first electrodes arranged in an even column along the row direction.