OLED Pixel Defining Layer Edge Light Control
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Solution Overview
Problem
Organic light-emitting display apparatuses using the printing method face challenges in achieving uniform light emission due to non-uniform thickness of the organic emission layer, particularly at the edge regions, leading to reduced light extraction efficiency and quality.
Innovation Solution
The formation of a thin pixel defining layer using a second conductive pattern and insulating layer with a controlled thickness, which prevents light emission from the edge regions and enhances the uniformity of the emissive layer, thereby improving light extraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a printing method is used to form the organic emission layer, then the manufacturing process is simplified and productivity is improved, but the thickness of the organic emission layer becomes non-uniform at edge regions, leading to reduced manufacturing precision
Solution Approach 1:
The patent applies local quality by creating a pixel defining layer with non-uniform thickness distribution - thinner at edge regions and thicker in central regions. This localized thickness variation compensates for the printing method's tendency to produce non-uniform emission layers, ensuring uniform optical properties across the entire emission area while maintaining the simplicity of printing fabrication.
2Loss of energy
If the organic emission layer thickness is adjusted to form a resonance structure, then light extraction efficiency is improved, but it becomes difficult to apply this approach to printing methods
Solution Approach 1:
The pixel defining layer serves as an intermediary structure that enables resonance-based light extraction enhancement in printing-based OLEDs. Instead of directly controlling emission layer thickness for resonance, the pixel defining layer with its specific thickness profile (10-100 nm) acts as a mediator that creates the necessary optical resonance conditions, making the approach compatible with printing fabrication methods.
3Ease of manufacture
If the pixel defining layer is formed with conventional thickness, then the structure is robust and easy to manufacture, but light emits from edge regions, reducing light quality and extraction efficiency
Solution Approach 1:
The patent applies parameter changes by precisely controlling the pixel defining layer thickness within 10-100 nm, with thinner regions at edges and thicker regions in the center. This parameter optimization prevents edge light emission while maintaining structural simplicity and manufacturability, achieving both good light quality and ease of fabrication.
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 ensures improved light quality and extraction efficiency by minimizing non-uniform emission, enhancing the overall performance of the organic light-emitting device.
Implementation Method 1
most of the photons emitted in an arbitrary direction cannot reach an actual observer due to total internal reflection of the organic light-emitting device
Data Source
AI summary
Disclosed is an organic light-emitting device. The organic light-emitting device includes a first pixel electrode that is disposed on a substrate, a first conductive film that is formed on the substrate to cover the first pixel electrode, a second conductive pattern and an insulating layer that are sequentially formed on the first conductive film and include an opening which exposes a portion of a top of the first conductive film, a hole injection layer that is formed on the opening and the insulating layer to cover the exposed first conductive film, a hole transport layer that is formed in a partial region of the hole injection layer and the opening, and an emissive layer that is formed on the hole transport layer.