Thin Film Semiconductor with Non-Conductive Polymer for Large-Area Crystalline Growth
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Solution Overview
Problem
Current solution-processed organic field-effect transistors (OFETs) based on polymer or soluble small-molecular semiconductors suffer from low carrier mobility due to grain boundaries and random molecular orientation, limiting their performance for large-area electronic devices, and existing methods for improving crystallinity, such as edge-casting, are restricted to small sizes as they cease when solvent evaporates.
Innovation Solution
A thin film semiconductor comprising a small-molecular semiconducting compound and a non-conductive polymer, specifically using poly(methylmethacrylate) with a solvent, allows controlled drying and stabilization of the growth process, enabling the formation of large-domain crystalline films through a modified edge-casting method, achieving high crystallinity and mobility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional solution processing methods (spin coating, drop casting) are used, then fabrication simplicity and ease of large-area coverage are achieved, but carrier mobility remains low (0.1 cm² V⁻¹ s⁻¹) due to grain boundaries and random molecular orientation
Solution Approach 1:
The invention changes the chemical composition parameter by introducing a non-conductive polymer as an additive to the small-molecular semiconductor solution. This modification alters the drying kinetics and molecular assembly process, enabling the formation of large single crystals with improved carrier mobility (5-10 cm² V⁻¹ s⁻¹) while maintaining solution processing simplicity
Solution Approach 2:
The invention creates a composite material system combining small-molecular semiconducting compound (0.1-1.0 wt.-%) with non-conductive polymer (1-10 wt.-%) in solution. The polymer matrix provides a controlled environment for crystal growth, resulting in large single-crystalline domains that maintain high carrier mobility while enabling simple large-area fabrication
2Reliability
If edge-casting method is used to improve crystallinity and carrier mobility to 5-10 cm² V⁻¹ s⁻¹, then molecular alignment is improved, but crystal size is limited to sub-millimeter dimensions due to complete solvent evaporation
Solution Approach 1:
The non-conductive polymer acts as an intermediary substance that modifies the solvent evaporation process. It controls the drying kinetics, creating a gradient that sustains crystal growth over larger areas. The polymer prevents complete and rapid evaporation, allowing continuous supply of semiconductor material to the crystal front, thereby enabling large-area single-crystalline film formation while maintaining high mobility
Solution Approach 2:
The invention changes the evaporation rate parameter by introducing the polymer additive, which modifies the solvent-polymer-semiconductor interaction. This controlled evaporation allows the crystal growth process to continue over larger distances before complete drying, transforming the crystal size from sub-millimeter to large-area dimensions while preserving the high crystallinity and carrier mobility
3Ease of manufacture
If polymer semiconductors are used to enable solution processing, then fabrication simplicity is improved, but carrier mobility remains insufficient due to inherent polymer structure limitations
Solution Approach 1:
The invention segments the functional roles: the small-molecular semiconductor provides the high-mobility charge transport pathways through its crystalline structure, while the polymer component provides the solution processing capability and forms the matrix. This segmentation allows each material to contribute its strengths, achieving both ease of manufacture and high reliability
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
This approach enables the growth of large-area single-crystalline organic semiconductor thin films with excellent crystallinity and carrier mobility of 5-10 cm^2 V^-1 s^-1, suitable for high-throughput, low-cost fabrication of large-area organic TFTs.
Implementation Method 1
the drying speed of the solvent can be controlled by mixing a non-conductive polymer with the organic semiconductor solution
Implementation Method 2
enabling the formation of large-domain crystalline films through a modified edge-casting method
Data Source
AI summary
A thin film semiconductor comprising a compound of formula I or II wherein: R1 and R2, at each occurrence, independently are selected from a C1-30 alkyl group, a C2-30 alkenyl group, a C2-30 alkynyl group and a C1-30 haloalkyl group, R3, R4, R5, and R6 independently are H or an electron-withdrawing group, wherein at least one of R3, R4, R5, and R6 is an electron-withdrawing group; and a non-conductive polymer.