Inkjet-Printed OLED Wells for High Fill Factor Displays
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Solution Overview
Problem
High-resolution OLED displays face challenges in precision droplet placement and uniformity during inkjet printing, leading to reduced fill factor and increased manufacturing costs, as well as undesirable visual artifacts and reduced pixel lifetime due to confinement well size limitations and droplet spreading.
Innovation Solution
The method involves creating a substantially continuous active OLED layer with a non-planar topography over confinement wells defined by electrodes, using larger confinement wells that span multiple sub-pixels to accommodate conventional inkjet droplet sizes and printing accuracies, and optimizing the deposition process to maintain uniformity and precision, thereby increasing the active area and reducing non-active regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional inkjet printing is used with standard confinement wells, then manufacturing process is simpler, but droplet placement precision deteriorates at high pixel densities
Solution Approach 1:
The confinement well is segmented into multiple zones with different surface properties. The well includes a hydrophobic region that repels the OLED ink droplet and a hydrophilic region that attracts and confines the droplet, creating distinct functional areas within the same structure to improve placement precision
Solution Approach 2:
Different regions of the confinement well are assigned different surface energies - the center region has hydrophobic characteristics to prevent droplet spreading, while the peripheral regions have hydrophilic characteristics to guide droplet placement, creating local quality variations that enhance precision
2Productivity
If confinement well area is reduced to increase pixel density, then pixel density improves, but droplet uniformity deteriorates
Solution Approach 1:
The solution moves from controlling droplet placement in two dimensions (x,y position) to three dimensions by incorporating vertical surface energy gradients. The confinement well uses varying surface energies at different heights and positions to guide droplet formation and placement, enabling precise control in high-density configurations
Solution Approach 2:
The surface energy parameters of the confinement well are dynamically optimized by creating regions with different hydrophobicity levels. This parameter variation allows the well to maintain optimal droplet confinement and uniformity even when the well area is reduced for high pixel density
3Device complexity
If conventional confinement structures are used, then device structure is simpler, but fill factor deteriorates due to edge non-uniformities
Solution Approach 1:
The harmful edge non-uniformities are extracted and isolated from the active emission area by designing the hydrophobic region to extend beyond the intended droplet placement zone. This extraction prevents non-uniformities from encroaching on the active area, maintaining high fill factor without requiring complex additional structures
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 approach enhances the fill factor of OLED pixels, improves the reliability of droplet placement, and reduces visual artifacts, resulting in higher resolution and longer display lifetime while maintaining manufacturing efficiency.
Implementation Method 1
Inkjet printing uses droplets of ink containing OLED layer material and one or more carrier liquids ejected from a nozzle at a high speed to produce one or more active OLED layers
Implementation Method 2
Light emission can occur through photoemission as the charge carriers relax back to normal energy states
Data Source
AI summary
A method of manufacturing an organic light-emitting diode display comprising a substrate having a well-defined by a confinement structure, the well containing a first electrode and a second electrode spaced from each other, wherein the method may comprise depositing a light-emissive material in the well via ink-jet printing, thereby forming a substantially continuous light-emissive material layer in the well from the deposited light-emissive material, the light-emissive material layer spanning and contained within boundaries of the well, wherein a surface of the light-emissive material layer that faces away from the substrate has a non-planar topography. The method may further comprise positioning a common electrode over the light-emissive material layer.