Circular Organic Semiconductor Layer for Uniform TFT Characteristics
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Solution Overview
Problem
Conventional silicon thin film transistors are costly and fragile, and their high-temperature fabrication makes them unsuitable for plastic substrates, while organic thin film transistors face issues with the 'coffee stain effect' and imperfect contact between the organic semiconductor layer and electrodes, leading to non-uniform transistor characteristics and poor image reproduction in flat panel displays.
Innovation Solution
The organic thin film transistor features a circular organic semiconductor layer with edge portions of the source and drain electrodes having curved concave shapes, ensuring full contact and uniform characteristics, which can be achieved through various deposition methods, including fine metal mask deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If inkjet printing method is used to form organic semiconductor layer, then patterning process is simplified, but coffee stain effect occurs causing non-uniform thickness
Solution Approach 1:
The patent applies circular geometry to the organic semiconductor layer pattern, which fundamentally changes the inkjet printing dynamics. The circular shape creates symmetric capillary flow patterns that prevent the coffee stain effect, achieving uniform thickness distribution across the entire layer while maintaining the simplicity of inkjet printing deposition
2Manufacturing precision
If conventional wet and/or dry etching processes are used to pattern organic semiconductor layer, then patterning is achieved, but organic semiconductor layer is seriously damaged
Solution Approach 1:
The patent performs preliminary patterning by controlling the inkjet printing deposition itself to form the desired pattern directly, eliminating the need for subsequent etching processes. The organic semiconductor layer is deposited in the exact pattern required, preventing any damage from chemical or physical etching while maintaining manufacturing precision
3Area of stationary object
If organic semiconductor layer is formed with rectangular shape, then coverage area is maximized, but edge and center thicknesses vary significantly
Solution Approach 1:
The patent replaces rectangular geometry with circular geometry for the organic semiconductor layer. This curvature-based design creates uniform radial flow patterns during inkjet printing, ensuring consistent thickness from edge to center while maximizing the effective coverage area within the deposition zone
4Reliability
If conventional silicon thin film transistor is used, then high performance is achieved, but manufacturing cost is high and device is fragile
Solution Approach 1:
The patent changes the fundamental material parameter from inorganic silicon to organic semiconductor materials, enabling low-temperature processing on plastic substrates. This material substitution maintains transistor performance while dramatically reducing manufacturing cost and improving flexibility, allowing deployment on flexible displays and wearable devices
Data Source
AI summary
An organic thin film transistor comprising an organic semiconductor layer that does not cause a coffee stain effect and can prevent an imperfect contact with source and drain electrodes, and a flat panel display apparatus comprising the organic thin film transistor are provided. The organic thin film transistor comprises a gate electrode; source and drain electrodes insulated from the gate electrode; and an organic semiconductor layer insulated from the gate electrode and contacts the source and drain electrodes, wherein the organic semiconductor layer has a circular shape when viewed through a substrate on which the organic thin film transistor is formed, and an edge portion of at least one of the source and drain electrodes contacting the organic semiconductor layer having a curved shape that is concave toward the organic semiconductor layer.