SiON Buffer and Encapsulation Layers for OLED TFT Reliability
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Solution Overview
Problem
The reliability of thin film transistors (TFTs) in organic light emitting display devices is compromised due to hydrogen penetration through the display panel, leading to degraded characteristics and increased weight and volume of the devices.
Innovation Solution
An organic light emitting display device is designed with a base substrate, a first buffer layer made of silicon oxynitride (SiON), and an encapsulation layer also made of SiON, where the buffer layer and encapsulation layer are in contact to prevent water penetration and enhance the adhesion between them, thereby protecting the TFTs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the gate driver and data driver are separately manufactured and connected to the display panel, then the device functionality is achieved, but the volume and weight of the display device increase
Solution Approach 1:
The gate driver and data driver are integrated into the display panel itself, merging previously separate components into a unified structure. This integration reduces the overall device volume and weight while maintaining all necessary driving functions through shared substrate and circuitry architecture
2Volume of moving object
If the gate driver is built into one side of the display panel in a GIP structure, then the volume and weight are reduced, but the characteristic of TFTs is degraded due to hydrogen penetration
Solution Approach 1:
A multilayer encapsulation structure comprising alternating inorganic and organic layers is employed. The inorganic layers (such as SiO2, Si3N4, SiON) provide barrier properties against hydrogen penetration, while the organic layers provide sealing and adhesion functions. This composite material approach effectively blocks hydrogen from reaching the TFTs while maintaining the compact GIP structure
Solution Approach 2:
Thin film encapsulation layers are deposited over the TFTs and driver circuits to create a protective barrier. These thin films conformally cover the device surfaces and interfaces, providing effective hydrogen blocking without significantly increasing device thickness or volume
3Ease of manufacture
If the encapsulation layer and buffer layer are made of different materials, then the manufacturing process is simplified, but water penetration occurs and TFT reliability is compromised
Solution Approach 1:
The encapsulation structure uses a composite of inorganic and organic materials in alternating layers. The inorganic layers provide impermeability to water vapor, while the organic layers provide flexibility and adhesion. This composite approach creates effective water barriers without complicating the manufacturing process, as both material types can be deposited using standard thin film fabrication techniques
Data Source
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AI summary
An organic light emitting display device is presented which prevents water from penetrating through an outermost side of a display panel, thereby enhancing reliability of first thin film transistors (TFTs). The organic light emitting display device includes a base substrate (110), a first buffer layer (130) disposed on the base substrate, a TFT (T1) disposed on the first buffer layer in a display area, a second TFT (T2) disposed on the first buffer layer in a non-display area, an organic light emitting diode (OLED) disposed on the first TFT, and an encapsulation layer (180) disposed on the OLED, the second TFT, and the first buffer layer. The first buffer layer and the encapsulation layer each include the same material, for example, silicon oxynitride (SiON).