A Multifunctional aromatic polythiourea gate insulator with dual cross-linking network for organic field-effect transistors
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We synthesized a multifuntional aromatic polythiourea(PTU) gate dielectric with dual covalent and noncovalent interactions for organic field-effect transistors(OFETs). Aromatic PTU was successfully polymerized using condensation reaction of 1,1’-thiocarbonyldiimidazole and 4,4’-oxidianiline monomers. For crosslinking network, photo-radical reaction is possible between thiyl radical group in crosslinker, pentaerythritol tetrakis(3-mercaptopropionate), and thiourea group in PTU, and micrometer-sized patterns can be fabricated using a conventional photolithography process. Crosslinked PTU(c-PTU) thin film exhibited dielectric constant of 4.10 at 1 kHz and excellent leakage current density properties. We fabricated dinaphtho[2,3-b:2’,3’-f]thieno[3,2-b]thiophene(DNTT) OFETs with the 200 nm-thick c-PTU gate insulator. DNTT OFETs with metal-oxide assisted surface treatment(MAST) of c-PTU gate insulator showed enhanced transfer properties of 1.03 cm2/Vs and an on/off ratio of 1.48 x 106.