Inkjet-Printing-Based Soft-Etching Technique for High-Speed Polymer Ambipolar Integrated Circuits

Here, we report the so-called soft-etching process based on an inkjet-printing technique for realizing high-performance printed and flexible organic electronic circuits with conjugated polymer semiconductors. The soft-etching process consists of selective etching of the gate made of a dielectric polymer and deposition of another gate dielectric layer. The method enables the use of a more desirable polymer dielectric layer for the p-channel and n-channel organic field-effect transistors (OFETs) in complementary integrated circuits. We fabricated high-performance ambipolar complementary inverters and ring oscillators (ROs) using poly­([<i>N</i>,<i>N</i>′-bis­(2-octyldodecyl)-naphthalene-1,4,5,8-bis­(dicarboximide)-2,6-diyl]-alt-5,5′-(2,2′-bithiophene)) (P­(NDI2OD-T2)) as the active layer as well as poly­(vinylidenefluoride-trifluoroethylene) (P­(VDF-TrFE)) and polystyrene ((PS)/P­(VDF-TrFE)) as dielectric materials for the p-channel (pull-up transistor) and n-channel (pull-down transistor) OFETs, respectively. The PS dielectric polymer was selectively etched by inkjetting of <i>n</i>-butyl acetate as an orthogonal solvent for P­(NDI2OD-T2). Employing this methodology, the five-stage ambipolar ROs with P­(NDI2OD-T2) exhibited an oscillation frequency of ∼16.7 kHz, which was much higher than that of non-soft-etched ROs with a single dielectric layer (P­(VDF-TrFE); ∼3 kHz)