Polymer Field‐Effect Transistors Fabricated by the Sequential Gravure Printing of Polythiophene, Two Insulator Layers, and a Metal Ink Gate

Abstract The mass production technique of gravure contact printing is used to fabricate state‐of‐the art polymer field‐effect transistors (FETs). Using plastic substrates with prepatterned indium tin oxide source and drain contacts as required for display applications, four different layers are sequentially gravure‐printed: the semiconductor poly(3‐hexylthiophene‐2,5‐diyl) (P3HT), two insulator layers, and an Ag gate. A crosslinkable insulator and an Ag ink are developed which are both printable and highly robust. Printing in ambient and using this bottom‐contact/top‐gate geometry, an on/off ratio of >10 4 and a mobility of 0.04 cm 2 V −1 s −1 are achieved. This rivals the best top‐gate polymer FETs fabricated with these materials. Printing using low concentration, low viscosity ink formulations, and different P3HT molecular weights is demonstrated. The printing speed of 40 m min −1 on a flexible polymer substrate demonstrates that very high‐volume, reel‐to‐reel production of organic electronic devices is possible.