Ladder-Type Conjugated Polymers for High Mobility OTFTs
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Solution Overview
Problem
Current organic thin film transistors (OTFTs) using polymeric semiconductors have charge carrier mobilities significantly lower than their molecular semiconductor counterparts, with n-type polymers exhibiting particularly low mobility, and existing solutions like post-solution-casting modifications are not practical for general applications.
Innovation Solution
Development of new conjugated compounds with ladder-type moieties, such as indacene, indenofluorene, and tetraphenylene, and their analogs with heteroatoms, which are solution-processable and exhibit high n-type carrier mobility, ambipolar semiconducting activity, and improved stability, along with electron-withdrawing groups and alkyl chains for enhanced properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If polymeric semiconductors are used in OTFTs, then solution-processability and ease of manufacturing are improved, but charge carrier mobility deteriorates significantly compared to molecular semiconductors
Solution Approach 1:
The patent modifies the molecular structure of polymeric semiconductors by introducing ladder-type moieties (indacene, indenofluorene, tetraphenylene) with extended π-conjugation and planar geometries. These structural parameter changes enhance intermolecular π-stacking and charge transport pathways, achieving n-type carrier mobility exceeding 10^-5 cm²V⁻¹s⁻¹ while preserving solution-processability through appropriate side-chain engineering
Solution Approach 2:
The patent employs copolymerization strategies combining electron-deficient ladder-type units with electron-rich heteroaryl units (thiophene, selenophene, tellurophene). This composite approach creates ambipolar or n-type semiconducting polymers with optimized HOMO-LUMO levels and enhanced charge carrier mobility, resolving the contradiction between processability and performance
2Ease of manufacture
If conventional polymeric semiconductors are used, then processing advantages are maintained, but n-type carrier mobility remains extremely low (approaching only 10^-6 cm²V⁻¹s⁻¹)
Solution Approach 1:
The patent systematically varies key structural parameters including introducing heteroatoms (O, S, Se, Te) in the ladder-type core to modulate electron affinity and LUMO levels. This enables achievement of high n-type mobility (>10^-5 cm²V⁻¹s⁻¹) while maintaining solution-processability, eliminating the need for post-processing modifications
Solution Approach 2:
The patent divides the polymer structure into distinct functional segments: electron-deficient ladder-type semiconducting units for charge transport, heteroaryl units for ambipolar character, and solubilizing side chains for processing. This segmentation allows independent optimization of each function, achieving high n-type mobility without sacrificing solution-processability
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
These compounds demonstrate improved semiconducting performance, including high n-type carrier mobility and good current modulation characteristics, making them suitable for practical applications in OTFTs while maintaining processing advantages like solution-processability and stability.
Implementation Method 1
the highly π-conjugated and planar nature of these cores are believed to allow π-electron delocalization and to provide good intermolecular π-stacking
Implementation Method 2
one or more electron-withdrawing groups such as carbonyl groups and/or malononitrile groups can be introduced into the π-conjugated core. Such electron-deficient functionalities can contribute to low-lying LUMO levels, and promote semiconducting activity
Implementation Method 3
to aid solubility without causing disruption of the π-conjugation, alkyl chains (and similar groups such as alkenyl groups, alkynyl groups, haloalkyl groups, arylalkyl groups, heteroarylalkyl groups and so forth) can be introduced to modify the π-conjugated core or functional groups on the π-conjugated core
Data Source
AI summary
Disclosed are new conjugated compounds (e.g., monomers and polymers) that include ladder-type moieties which can be used for preparing semiconducting materials. Such conjugated compounds can exhibit high n-type carrier mobility and/or good current modulation characteristics. Compounds of the present teachings also can exhibit ambipolar semiconducting activity. In addition, the compounds of the present teachings can possess certain processing advantages such as solution-processability and/or good stability in ambient conditions.