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Liquid-crystalline semiconducting polymers with high charge-carrier mobility

Abstract

Organic semiconductors that can be fabricated by simple processing techniques and possess excellent electrical performance, are key requirements in the progress of organic electronics. Both high semiconductor charge-carrier mobility, optimized through understanding and control of the semiconductor microstructure, and stability of the semiconductor to ambient electrochemical oxidative processes are required. We report on new semiconducting liquid-crystalline thieno[3,2-b ]thiophene polymers, the enhancement in charge-carrier mobility achieved through highly organized morphology from processing in the mesophase, and the effects of exposure to both ambient and low-humidity air on the performance of transistor devices. Relatively large crystalline domain sizes on the length scale of lithographically accessible channel lengths (200 nm) were exhibited in thin films, thus offering the potential for fabrication of single-crystal polymer transistors. Good transistor stability under static storage and operation in a low-humidity air environment was demonstrated, with charge-carrier field-effect mobilities of 0.2–0.6 cm2 V−1 s−1 achieved under nitrogen.

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Figure 1: Chemical structure of poly(2,5-bis(3-alkylthiophen-2-yl) thieno[3,2-b]thiophene).
Figure 2: AFM images of polymer C12 (annealed at 180 C).
Figure 3: X-ray scattering pattern of polymer C12 (annealed at 180 C).
Figure 4: Field-effect transistor device characteristics in N2 atmosphere with polymer C14 semiconductor.
Figure 5: Stability of FET devices.

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Acknowledgements

Portions of this research were carried out at the Stanford Synchrotron Radiation Laboratory, a user facility operated by Stanford University on behalf of the US Department of Energy, Office of Basic Energy Sciences.

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Correspondence to Iain McCulloch.

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McCulloch, I., Heeney, M., Bailey, C. et al. Liquid-crystalline semiconducting polymers with high charge-carrier mobility. Nature Mater 5, 328–333 (2006). https://doi.org/10.1038/nmat1612

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