OLED Pixel Electrode Structure for Ag Particle Prevention
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Solution Overview
Problem
Current OLED displays face challenges in achieving high light efficiency and display quality due to issues such as dark point defects caused by Ag particle reprecipitation during etching and outgassing from organic insulating layers, which affect the lifetime and reliability of the devices.
Innovation Solution
The OLED display design incorporates a semi-transmissive metal layer with transparent conductive oxide layers, a light characteristics adjusting layer, and a specific structure for the pixel electrode and insulating layers to prevent Ag particle reprecipitation and outgassing, including a fourth insulating layer that covers the end portions of the pixel electrode in a closed loop, reducing the influence of electrical fields and minimizing organic insulating material exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a semi-transmissive metal layer (Ag) is used in the pixel electrode to improve light efficiency, then light efficiency is improved, but Ag particle reprecipitation occurs during etching causing dark point defects
Solution Approach 1:
A light characteristics adjusting layer composed of transparent conductive oxide is introduced between the pixel electrode and the first insulating layer. This intermediary layer prevents direct contact between Ag particles in the etchant and the semi-transmissive metal layer, thereby preventing Ag particle reprecipitation and dark point defects while maintaining light efficiency
Solution Approach 2:
The patent uses a sacrificial protective structure during the etching process. The light characteristics adjusting layer serves as a protective barrier that can be removed or modified after serving its protective function, allowing the Ag-based pixel electrode to maintain its light efficiency without suffering from Ag particle reprecipitation
2Reliability
If organic insulating layers are used to cover the pixel electrode to prevent Ag particle reprecipitation, then dark point defects are reduced, but outgassing occurs affecting device lifetime
Solution Approach 1:
The patent changes the material parameter of the protective layer from organic insulating material to transparent conductive oxide. This material substitution eliminates outgassing issues while maintaining the protective function against Ag particle reprecipitation, thereby extending device lifetime
Solution Approach 2:
The light characteristics adjusting layer serves as a temporary protective barrier during the critical etching process. After serving its protective function, it can be removed or integrated into the final structure, having fulfilled its purpose of preventing dark point defects without causing long-term outgassing problems
3Reliability
If the pixel electrode is extended outside the opening in the third insulating layer to improve electrical connection, then electrical conductivity is improved, but exposure to electrical fields increases causing instability
Solution Approach 1:
The patent applies different functional zones to the pixel electrode structure. The portion within the opening provides electrical connection, while the portion covered by the fourth insulating layer provides electrical field shielding. This local differentiation allows the electrode to simultaneously achieve good electrical connection and stability
4Manufacturing precision
If multiple insulating layers are added to protect the pixel electrode structure, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The light characteristics adjusting layer serves multiple functions simultaneously: it acts as a protective barrier during etching, adjusts light emission characteristics, provides electrical field shielding, and serves as an adhesive layer. This multi-functionality reduces the need for separate protective layers, thereby managing device complexity
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 design significantly reduces dark point defects and improves light efficiency while extending the OLED display's lifetime by preventing Ag particle reprecipitation and minimizing outgassing, resulting in enhanced display quality and reliability.
Implementation Method 1
OLED displays are self-emissive and emit light when holes injected from the hole injection electrode and electrons injected from the electron injection electrode recombine and decay in the organic emitting layer
Implementation Method 2
This design significantly reduces dark point defects and improves light efficiency while extending the OLED display's lifetime by preventing Ag particle reprecipitation
Implementation Method 3
a fourth insulating layer that covers the end portions of the pixel electrode in a closed loop, reducing the influence of electrical fields and minimizing organic insulating material exposure
Implementation Method 4
a light characteristics adjusting layer, and a specific structure for the pixel electrode and insulating layers to prevent Ag particle reprecipitation and outgassing
Data Source
AI summary
An organic light-emitting diode (OLED) display is disclosed. In one aspect, the OLED display includes a thin film transistor comprising an active layer, a gate electrode, a source electrode, and a drain electrode. A first insulating layer is formed at least between the active layer and the gate electrode and a second insulating layer formed at least between the gate, source, and drain electrodes. The OLED display also includes a third insulating layer covering the source and drain electrodes and a pixel electrode including a first portion formed in first and second openings respectively defined in the second and third insulating layers and a second portion formed outside of the second opening. A pixel defining layer is formed over the second portion of the pixel electrode and the third insulating layer and has a third opening. The third opening has an area greater than that of the second opening.