OLED Pixel Defining Layer Thickness Gradient for Spin Coating
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Solution Overview
Problem
The spin deposition method for forming a common electrode in organic light emitting diode displays often results in non-deposition areas, leading to damage of the emission layer due to filler infiltration, which deteriorates display quality and reliability as the damaged regions expand over time.
Innovation Solution
The organic light emitting diode display design includes a pixel defining layer with varying thicknesses, gradually decreasing from the center to the peripheral areas, ensuring the side slope of the layer does not impede metal particle deposition, thus preventing non-deposition areas and enhancing film quality of the common electrode formed by spin deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the common electrode is formed by spin deposition method, then manufacturing cost is reduced, but non-deposition areas are generated in the peripheral portion of the display area
Solution Approach 1:
The pixel defining layer is designed with different thicknesses in different regions: a first thickness in the central area and a second thickness (smaller than the first) in the peripheral area. This local variation in thickness allows the layer to accommodate the deposition characteristics of the spin deposition method, ensuring uniform metal particle deposition across the entire display area while maintaining cost-effectiveness.
Solution Approach 2:
The thickness parameter of the pixel defining layer is changed based on position within the display area. By reducing the thickness in the peripheral portion compared to the central area, the deposition barrier is reduced at the edges, enabling metal particles to deposit uniformly across the entire surface without forming non-deposition areas.
2Device complexity
If the pixel defining layer has uniform thickness, then manufacturing process is simplified, but metal particle deposition is impeded in peripheral areas
Solution Approach 1:
The pixel defining layer transitions from uniform thickness to position-dependent thickness, with a first thickness in the central area and a second reduced thickness in the peripheral area. This local differentiation resolves the deposition impairment while maintaining relatively simple manufacturing processes.
3Strength
If the pixel defining layer has large thickness in peripheral area, then structural support is improved, but filler infiltration damages the emission layer
Solution Approach 1:
The pixel defining layer is designed with a first thickness in the central area providing structural support and a second reduced thickness in the peripheral area preventing deposition barriers. This local differentiation ensures both structural integrity and emission layer protection.
Solution Approach 2:
The reduced thickness in the peripheral area, which might seem to reduce structural support, actually prevents the formation of deposition barriers that would lead to non-deposition areas. This converts a potential structural weakness into a benefit by ensuring complete electrode coverage and preventing filler infiltration.
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 prevents damage to the emission layer by ensuring even deposition of the common electrode, improving display quality and reliability by eliminating abnormal deposition areas and reducing manufacturing costs.
Implementation Method 1
The common electrode may be formed by a spin deposition method. The spin deposition method is a method of disposing a deposition source below the center of the substrate and depositing the common electrode while rotating the substrate.
Data Source
AI summary
An organic light emitting diode display including: a plurality of pixel electrodes formed in a display area of a substrate; a pixel defining layer having an opening exposing a part of each of the plurality of pixel electrodes and formed in the display area; a plurality of emission layers formed on the plurality of pixel electrodes; and a common electrode formed on the pixel defining layer and the plurality of emission layers. The pixel defining layer is formed with a smaller thickness farther from the center of the display area.