Ambipolar Organic Polymer Semiconductor for Charge Mobility
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Solution Overview
Problem
Current organic thin film transistors (OTFTs) face challenges in achieving high charge mobility and low leakage current, particularly with polymer-based materials, which are essential for commercialization and mass production, as they often exhibit undesirable properties compared to low-molecular-weight materials, and there is a need for ambipolar transistors with both p-type and n-type semiconductor properties for CMOS circuit development.
Innovation Solution
An organic polymer semiconductor with a quinoxaline ring and aromatic rings in the main chain, allowing for both p-type and n-type semiconductor properties, is developed, which is synthesized through copolymerization of specific monomers using palladium and nickel catalysts, and used in the active layer of ambipolar OTFTs to enhance charge mobility and reduce leakage current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If polymer-based organic semiconductor material is used in OTFTs, then processibility is improved and fabrication cost is decreased through solution process, but charge mobility becomes undesirable compared to low-molecular-weight material
Solution Approach 1:
The patent employs a composite molecular structure combining thiophene units (providing charge transport capability) with fluorinated aromatic units (providing structural stability and solubility). This composite approach at the molecular level enables the polymer to achieve both good processibility through solution processing and enhanced charge mobility of 0.01-0.04 cm²/Vs, resolving the contradiction between ease of manufacture and device performance.
Solution Approach 2:
The patent systematically varies molecular parameters including the type of aromatic units (fluorinated vs non-fluorinated), chain length, and side group configurations to optimize both processibility and charge mobility. By adjusting these molecular parameters, the material achieves optimal balance between solution processability and transistor performance, enabling charge mobility in the range of 0.01-0.04 cm²/Vs while maintaining ease of fabrication.
2Ease of manufacture
If F8T2 polythiophene material is used, then solution processability is achieved, but charge mobility is limited to about 0.01-0.02 cm2/Vs
Solution Approach 1:
The patent modifies the molecular parameters of polythiophene by introducing fluorinated aromatic units and varying chain structures. This parameter optimization enhances the charge mobility from the original 0.01-0.02 cm²/Vs (as seen in F8T2) to 0.01-0.04 cm²/Vs, while preserving the solution processability that enables low-cost fabrication through printing and coating techniques.
3Reliability
If low-molecular-weight organic semiconductor material is used, then charge mobility is increased to about 3.2-5.0 cm2/Vs with pentacene monocrystals, but vacuum deposition process is required which increases fabrication complexity
Solution Approach 1:
The patent adopts a polymer-based material that can be processed through simple solution methods (printing, coating) rather than complex vacuum deposition. While the charge mobility (0.01-0.04 cm²/Vs) is lower than pentacene monocrystals (3.2-5.0 cm²/Vs), the dramatic simplification of fabrication processes and reduction in equipment requirements makes the overall system more practical for commercial applications, effectively trading some performance for manufacturing simplicity.
4Reliability
If regioregular polythiophene P3HT is used, then charge mobility is about 0.01 cm2/Vs, but cut-off leakage current is increased which decreases on/off ratio to about 400 or less
Solution Approach 1:
The patent introduces fluorinated aromatic units into the polythiophene structure, which modifies the electronic properties and energy level alignment. This structural parameter change effectively reduces the cut-off leakage current while maintaining charge mobility in the range of 0.01-0.04 cm²/Vs, thereby improving the on/off ratio beyond the 400:1 limitation observed in P3HT-based devices.
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
The ambipolar OTFTs demonstrate improved charge mobility and reduced leakage current, making them suitable for electronic devices, and the polymer semiconductor exhibits both p-type and n-type transistor properties, facilitating the fabrication of various electronic devices such as LCDs and integrated circuits.
Implementation Method 1
an organic polymer semiconductor, which may include an aromatic ring derivative having p-type semiconductor properties and a heteroaromatic ring having n-type semiconductor properties in the main chain thereof, and which thus may exhibit both p-type transistor properties and n-type transistor properties
Implementation Method 2
which is synthesized through copolymerization of specific monomers using palladium and nickel catalysts
Data Source
AI summary
Disclosed are an organic polymer semiconductor, an ambipolar organic thin film transistor using the same, an electronic device comprising the ambipolar organic thin film transistor and methods of fabricating the same. Example embodiments relate to an organic polymer semiconductor, which may include an aromatic ring derivative having p-type semiconductor properties and a heteroaromatic ring having n-type semiconductor properties in the main chain thereof, and which thus may exhibit both p-type transistor properties and n-type transistor properties when used in the organic active layer of an electronic device, e.g., an organic thin film transistor, an ambipolar organic thin film transistor using such an organic polymer semiconductor, an electronic device comprising the ambipolar organic thin film transistor and methods of fabricating the same.