Top-Emitting OLED Electrode Structure for Uniform Brightness
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Solution Overview
Problem
Large-sized top-emitting OLED display devices face issues with voltage drop due to high cathode resistance, leading to uneven brightness and poor brightness uniformity, characterized by bright edges and dark centers.
Innovation Solution
The display panel design includes a second electrode connected to a first electrode, with the second electrode being closer to the base substrate, reducing the sheet resistance of the first electrode and improving light extraction efficiency and display uniformity. This design also features an inorganic layer with varying thickness portions and encapsulation thin films to protect the light-emitting element and enhance manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a top-emitting OLED structure is used, then the aperture ratio and light emission efficiency are improved, but the cathode resistance causes voltage drop and brightness non-uniformity
Solution Approach 1:
The cathode is divided into multiple segments: a first cathode layer and a second cathode layer. The first cathode layer has higher transparency and lower resistance, while the second cathode layer provides additional cathodic function. This segmentation allows the cathode to simultaneously achieve low resistance and high transparency, resolving the contradiction between brightness uniformity and cathode resistance.
Solution Approach 2:
The patent employs composite material structures in the cathode design, combining different materials with complementary properties. The first cathode layer uses materials with high transparency and low resistance characteristics, while the second cathode layer supplements the cathodic function. This composite approach enables the cathode to overcome the inherent trade-off between resistance and transparency.
2Reliability
If the inorganic layer thickness is increased to improve encapsulation, then the protection against moisture and oxygen is enhanced, but the device thickness and manufacturing complexity increase
Solution Approach 1:
The inorganic layer is designed with different thicknesses at different locations: a first inorganic layer portion with greater thickness for enhanced encapsulation protection, and a second inorganic layer portion with smaller thickness. This local quality variation allows the structure to provide maximum protection where needed while minimizing overall complexity and thickness elsewhere in the device.
3Reliability
If the first encapsulation thin film is in contact with both electrodes, then the encapsulation coverage is improved, but the manufacturing precision requirements increase
Solution Approach 1:
The first encapsulation thin film is formed to contact both the first electrode and the second electrode in advance, establishing comprehensive encapsulation coverage before subsequent processing steps. This preliminary action ensures that the encapsulation structure is already in place to protect both electrodes, and the manufacturing process is designed to accommodate this configuration, thereby managing precision requirements.
Data Source
AI summary
Provided are a display panel and a manufacturing method therefor, and a display device. The display panel, including: a base substrate; and a plurality of sub-pixels, located on the base substrate, including a pixel circuit and a light-emitting element, wherein the light-emitting element is connected to the pixel circuit, the pixel circuit is configured to drive the light-emitting element; the light-emitting element includes: a first electrode; and a second electrode, electrically connected to the first electrode, the first electrode is closer to the base substrate than the second electrode.