Oxide TFT Pixel Layout With Overlap for Higher Aperture Ratio
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Solution Overview
Problem
Existing light-emitting display devices face challenges in achieving a high aperture ratio, which is essential for higher definition displays such as 3D or 4K2K displays, especially when using thin film transistors with oxide semiconductors.
Innovation Solution
The light-emitting display device incorporates a pixel structure with a thin film transistor that includes an oxide semiconductor layer extended beyond the edge of the scan line region, allowing the light-emitting element and the oxide semiconductor layer to overlap, thereby increasing the aperture ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the oxide semiconductor layer is extended beyond the edge of the scan line region to increase aperture ratio, then the aperture ratio is improved, but the risk of electrical short circuit between the light-emitting element and scan line increases
Solution Approach 1:
The gate insulating film serves as an intermediary insulating layer between the oxide semiconductor layer and the scan line. This gate insulating film is positioned between the light-emitting element and the scan line, providing electrical insulation while allowing the oxide semiconductor layer to extend beyond the scan line edge to increase aperture ratio.
Solution Approach 2:
The patent utilizes the vertical dimension by extending the oxide semiconductor layer in the planar direction beyond the scan line edge, while maintaining electrical insulation through the gate insulating film. This dimensional approach allows the light-emitting element to overlap with the oxide semiconductor layer in the vertical direction, increasing aperture ratio without causing short circuits.
2Area of moving object
If a conventional thin film transistor structure is used, then the manufacturing process is simpler, but the aperture ratio is reduced
Solution Approach 1:
The patent increases aperture ratio by utilizing the vertical overlapping dimension. The light-emitting element is positioned to overlap with the oxide semiconductor layer in the vertical direction, effectively using the Z-axis to increase the light-emitting area without expanding the planar footprint, thus improving aperture ratio while maintaining a compact pixel structure.
Solution Approach 2:
The oxide semiconductor layer serves multiple functions: it acts as the channel region of the thin film transistor for switching control, and simultaneously serves as part of the light-emitting structure that can overlap with the light-emitting element. This multi-functionality increases aperture ratio without significantly complicating the pixel structure.
3Speed
If amorphous silicon is used for the thin film transistor channel, then the substrate area can be larger, but the field effect mobility is low
Solution Approach 1:
The patent changes the material parameter from amorphous silicon to oxide semiconductor, which fundamentally alters the field effect mobility characteristic. Oxide semiconductors inherently provide higher field effect mobility compared to amorphous silicon, enabling faster switching speeds and better performance in high-definition displays while maintaining compatibility with large substrate manufacturing.
Data Source
AI summary
An object is to provide a light-emitting display device in which a pixel including a thin film transistor using an oxide semiconductor has a high aperture ratio. The light-emitting display device includes a plurality of pixels each including a thin film transistor and a light-emitting element. The pixel is electrically connected to a first wiring functioning as a scan line. The thin film transistor includes an oxide semiconductor layer over the first wiring with a gate insulating film therebetween. The oxide semiconductor layer is extended beyond the edge of a region where the first wiring is provided. The light-emitting element and the oxide semiconductor layer overlap with each other.