Sub-anode Structure for OLED Hole Injection
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Solution Overview
Problem
Conventional organic light emitting displays face challenges in maximizing the hole injection effect, which is crucial for efficient light emission, due to limitations in the work function between the anode and hole injection layer.
Innovation Solution
The introduction of a sub-anode formed with metallic oxide and nickel (Ni) improves the hole injection effect by providing a high work function and low surface resistance, with the sub-anode being thinner than the anode and formed using a dual target DC sputtering system, allowing for optimized layer structure and improved transmittance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional anode structure is used, then the device structure is simple, but the hole injection effect is insufficient due to limited work function
Solution Approach 1:
The anode is segmented into two distinct layers: a conventional anode layer and a sub-anode layer formed with metallic oxide and nickel. This segmentation allows each layer to perform its specific function - the conventional anode provides basic electrical connection while the sub-anode with higher work function material enhances hole injection into the hole injection layer, thereby resolving the contradiction between structural simplicity and hole injection effectiveness.
Solution Approach 2:
The sub-anode is constructed using composite materials comprising metallic oxide and nickel, which together provide a high work function necessary for effective hole injection. This composite material approach enables the anode structure to achieve superior hole injection characteristics without requiring complex multi-step fabrication processes, thus balancing reliability improvement with manufacturing feasibility.
2Reliability
If a sub-anode is added to improve hole injection, then the hole injection effect and luminance are improved, but the manufacturing process becomes more complex
Solution Approach 1:
The formation of the sub-anode layer is merged with the existing sputtering process used for depositing the hole injection layer. By using a dual target DC sputtering system, the sub-anode (metallic oxide and nickel) and the hole injection layer are deposited in a single continuous process without requiring separate fabrication steps. This merging of processes improves luminance characteristics through enhanced hole injection while minimizing the increase in manufacturing complexity.
3Reliability
If a thicker anode is used to improve electrical connection, then the electrical conductivity is improved, but the light transmittance is reduced
Solution Approach 1:
Instead of increasing the thickness of the conventional anode layer in the vertical dimension (which would improve conductivity but reduce transmittance), the solution adds a new functional dimension by introducing a sub-anode layer with specific optical and electrical properties. The sub-anode is designed to be thin enough to maintain high light transmittance while providing the necessary electrical conductivity and work function enhancement, thus resolving the contradiction by operating in a different structural dimension.
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 configuration enhances the hole injection effect, leading to improved current density and luminance characteristics in organic light emitting displays.
Implementation Method 1
formed using a dual target DC sputtering system
Data Source
AI summary
An organic light emitting display is provided. The organic light emitting display comprises: a substrate; an anode that is positioned on the substrate; a sub-anode that is positioned on the anode and that is formed with a metallic oxide and nickel (Ni); an organic light emitting layer that is positioned on the sub-anode; and a cathode that is positioned on the organic light emitting layer.