Two-dimensional crystal growth of thermally converted organic semiconductors at the surface of ionic liquid and high-mobility organic field-effect transistors

We report a novel solution-crystallization method to grow two-dimensional platelet-shaped single-crystals of well-known insoluble organic semiconductors via thermal conversion of their precursor molecules dissolved in ionic liquids (ILs). By optimizing conditions of the crystal growth regarding physical properties of ILs such as density and viscosity, we successfully and reproducibly obtained thin platelets of pentacene and dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene (DNTT) single-crystals, with which nearly the best performing field-effect transistors are constructed for the two compounds. The prompt and simple technique has opened the way to use practically insoluble organic semiconductor materials for high-performance printed electronics, which enables mass-producible and large-area organic circuitry devices.

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► We develop a novel solution-crystallized method to grow 2D crystals in ionic liquids.
► We convert soluble precursors to insoluble organic materials via thermal conversion.
► We obtain the single-crystals of well-known pentacene and DNTT semiconductors.
► These obtained crystals nearly exhibit the best-reported FET performance.
► The simple technique has opened the way to use practically insoluble materials.