Macroscopically Oriented Polymer Fibers for High Mobility FETs
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Solution Overview
Problem
Current methods for fabricating field-effect transistors using conjugated polymers face challenges in achieving high charge mobilities due to difficulties in forming long-range ordered polymer structures, which are essential for improved electrical properties.
Innovation Solution
The synthesis of directionally aligned polymer fibers from conjugated polymers, where the longitudinal axes of the polymers are substantially aligned, forming a bundle with non-random orientation, enhances the field-effect saturation mobility by creating an organic semiconductor film that can transport charge effectively between source and drain electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional solution processing methods are used to fabricate polymer-based FETs, then low-cost production and ease of manufacture are achieved, but long-range ordered polymer structures cannot be formed, resulting in limited charge mobility
Solution Approach 1:
The substrate surface is pre-treated with self-assembled monolayers (SAMs) before polymer deposition to create specific surface properties that guide polymer orientation. This preliminary surface modification enables the polymer chains to align in desired directions during subsequent solution processing, achieving long-range order without complex fabrication steps
Solution Approach 2:
Self-assembled monolayers serve as an intermediary layer between the substrate and polymer semiconductor. The SAMs mediate the interaction by providing controlled surface energy and molecular recognition sites that direct polymer chain orientation and promote long-range ordering during solution-based fabrication
2Productivity
If polymer chains are randomly oriented in the active layer, then simple fabrication processes are used, but charge transport is limited due to lack of long-range order
Solution Approach 1:
The invention creates local orientational order within the polymer active layer by controlling chain alignment in specific regions. The polymer chains are oriented parallel to each other and to the substrate surface in the channel region, while maintaining solution processing simplicity. This local ordering significantly enhances charge transport along the chain direction
3Reliability
If high molecular weight polymers are used to improve charge mobility, then better charge transport is achieved, but film formation and processing difficulty increase
Solution Approach 1:
The invention changes the surface energy parameters of the substrate through SAM modification to optimize polymer deposition. By adjusting the surface properties rather than polymer molecular weight, high charge mobility is achieved while maintaining good film formation and processability of the polymer semiconductor
Data Source
AI summary
Embodiments of the invention include methods and materials for preparing organic semiconducting layers, for example one used in an organic semiconductor device including a substrate with a nanostructured surface and an organic semiconductor film overlying the nanostructured surface. The semiconductor film is typically formed from macroscopically ordered polymer fibers made from selected conjugate polymer compounds. Such polymer fibers synthesized from selected conjugated polymer compounds and directionally aligned in organic semiconductor devices can provide these devices improved functional properties, including for example, unexpectedly high field effect saturation mobilities.