Auxiliary Cathode Layer for Top-Emitting OLED Array Substrates
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Solution Overview
Problem
Current top-emitting OLED devices with transparent cathodes, such as Mg:Ag and IZO, suffer from high sheet resistance, leading to non-uniform display brightness and quality, especially in large-sized screens.
Innovation Solution
An array substrate design featuring a substrate with an anode layer, pixel defining layer, auxiliary cathode layer, spacer layer, organic light-emitting layer, and cathode layer, where the cathode layer laps with the auxiliary cathode layer, utilizing a metal conductive auxiliary cathode material with low sheet resistance and an inverted trapezoidal spacer structure to ensure uniformity and prevent short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If transparent cathode materials such as Mg:Ag and IZO are used in top-emitting OLED devices, then the opening ratio can be increased, but the sheet resistance becomes high leading to non-uniform display brightness
Solution Approach 1:
The cathode structure is divided into two separate layers: an auxiliary cathode layer (first cathode layer) and a main cathode layer (second cathode layer). The auxiliary cathode layer is positioned at the bottom and provides low sheet resistance, while the main cathode layer is positioned at the top and provides transparency. This segmentation allows each layer to optimize its function independently, resolving the contradiction between low resistance and high transparency.
Solution Approach 2:
The patent uses a composite cathode structure combining different materials with complementary properties. The auxiliary cathode layer uses materials optimized for low sheet resistance, while the main cathode layer uses materials optimized for transparency. This composite approach allows the system to achieve both low overall resistance and high transparency simultaneously.
2Use of energy by moving object
If the cathode layer is made transparent to increase opening ratio, then light emission efficiency improves, but sheet resistance increases causing non-uniform brightness distribution
Solution Approach 1:
The cathode is segmented into functional layers where the auxiliary cathode layer handles electrical conduction (low resistance requirement) and the main cathode layer handles light emission (transparency requirement). This segmentation allows optimization of light emission efficiency through the transparent main cathode while maintaining brightness uniformity through the low-resistance auxiliary cathode layer.
Solution Approach 2:
Different regions of the cathode structure have different material compositions and properties. The auxiliary cathode layer has high electrical conductivity for uniform current distribution, while the main cathode layer has high transparency for efficient light emission. This local quality differentiation resolves the contradiction between emission efficiency and brightness uniformity.
3Device complexity
If a single-layer cathode structure is used, then the device structure is simple, but it cannot simultaneously achieve low sheet resistance and high transparency
Solution Approach 1:
Rather than using a single-layer structure, the cathode is segmented into multiple functional layers. The auxiliary cathode layer provides low sheet resistance while the main cathode layer provides transparency. Although this increases structural complexity, it enables the simultaneous achievement of both low resistance and high transparency, which is impossible with a single layer.
Solution Approach 2:
The patent employs composite cathode materials arranged in layers, where each material is selected for its specific property (conductivity or transparency). This composite structure overcomes the limitations of single-material single-layer designs, achieving both low sheet resistance and high transparency despite increased structural complexity.
Data Source
AI summary
The present invention provides an array substrate, a method for manufacturing the same and a display device. The array substrate includes a substrate; a anode layer and a pixel defining layer on the substrate; an auxiliary cathode layer on the pixel defining layer; a spacer layer on the auxiliary cathode layer; an organic light-emitting layer covering the anode layer, the pixel defining layer, and the spacer layer; a cathode layer covering the organic light-emitting layer, wherein the cathode layer laps with the auxiliary cathode layer on the pixel defining layer. Since the auxiliary cathode layer disposed on the pixel defining layer corresponds to the non-display area, the material with low resistivity can be selected for the auxiliary cathode layer. Thus the uniformity of the display brightness and the like of the screen can be improved, thereby improving the display quality of the screen.