OLED Cathode Layer IR Drop Reduction via Composite Structure
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Solution Overview
Problem
In organic light emitting diode (OLED) display panels, the IR drop across different regions of the cathode leads to non-uniformity of voltage levels and display illuminance due to high resistance, which is exacerbated by the difficulty in handling nano-silver ink used for the auxiliary cathode, causing issues with line width and glomeration.
Innovation Solution
A display substrate with a unitary cathode layer, an organic auxiliary cathode layer made of organic conductive polymer material, and a metallic auxiliary cathode layer limited in a groove defined by the organic auxiliary cathode layer, connected to the unitary cathode layer, which maintains high light transmittance and avoids IR drop and glomeration issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional cathode layer is used in OLED display panels, then the structure is simple, but the high resistance causes IR drop across different regions leading to non-uniform voltage levels and display illuminance
Solution Approach 1:
The cathode is divided into multiple segments: a base cathode layer, an organic auxiliary cathode layer with conductive polymer material, and a metallic auxiliary cathode layer with electrode bars. This segmentation allows each layer to perform specific functions - the base layer provides structural support while the auxiliary layers reduce resistance and eliminate IR drop, achieving uniform voltage distribution across different regions of the display panel
Solution Approach 2:
The invention uses a composite cathode structure combining organic conductive polymer material in the organic auxiliary cathode layer with metallic material (such as nano-silver) in the metallic auxiliary cathode layer. This composite approach leverages the advantages of both materials - the organic layer provides flexibility and coverage while the metallic layer provides high conductivity - to achieve low resistance and uniform voltage levels throughout the cathode structure
2Reliability
If nano-silver ink is used for the auxiliary cathode to reduce resistance, then the conductivity improves, but the handling difficulty causes issues with line width control and glomeration
Solution Approach 1:
The organic auxiliary cathode layer made of conductive polymer material serves as an intermediary between the base cathode layer and the metallic auxiliary cathode layer. This intermediate layer facilitates the deposition of metallic material, enables precise control of line width through patterning processes, and prevents glomeration by providing a controlled interface for metallic particle deposition, thereby simplifying the manufacturing process while maintaining high conductivity
Solution Approach 2:
The metallic auxiliary cathode layer is selectively deposited in the inter-subpixel region rather than uniformly across the entire cathode area. This localized application of high-conductivity metallic material optimizes its function in regions where current density is highest and where it can most effectively reduce IR drop, while avoiding unnecessary material deposition in other areas, thus improving manufacturability and reducing waste
3Reliability
If the auxiliary cathode layer is extended throughout the display area to reduce IR drop, then the voltage uniformity improves, but the light transmittance may be compromised
Solution Approach 1:
The metallic auxiliary cathode layer is strategically positioned only in the inter-subpixel region where it is needed for current distribution and IR drop compensation. The organic auxiliary cathode layer extends into the subpixel region but maintains optical transparency. This localized quality approach ensures that the high-conductivity metallic layer is present where it most effectively reduces IR drop while minimizing its impact on light transmittance in the light-emitting subpixel areas
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
The solution achieves uniform voltage levels and high light transmittance by controlling the line width and preventing glomeration, resulting in improved display illuminance and substrate performance.
Implementation Method 1
an organic auxiliary cathode layer electrically connected to the unitary cathode layer, the organic auxiliary cathode layer comprising an organic conductive polymer material
Implementation Method 2
a metallic auxiliary cathode layer limited in a groove defined by the organic auxiliary cathode layer and in direct contact with the organic auxiliary cathode layer and in direct contact with the unitary cathode layer
Data Source
AI summary
A display substrate includes a base substrate; a plurality of light emitting blocks on the base substrate, a respective one of the plurality of light emitting blocks in a subpixel region; a unitary cathode layer electrically connected to the plurality of light emitting blocks, the unitary cathode layer extending substantially throughout a display area of the display substrate; an organic auxiliary cathode layer electrically connected to the unitary cathode layer, the organic auxiliary cathode layer including an organic conductive polymer material; and a metallic auxiliary cathode layer limited in a groove defined by the organic auxiliary cathode layer and in direct contact with the organic auxiliary cathode layer and in direct contact with the unitary cathode layer. The metallic auxiliary cathode layer is limited in an inter-subpixel region of the display substrate. The organic auxiliary cathode layer is at least partially in the inter-subpixel region of the display substrate.