Flexible low-voltage organic thin-film transistors and PMOS inverters: the effect of channel width on noise margin

Abstract

Low-operating-voltage (<2 V) organic thin-film transistors (OTFTs) and P-channel metal-oxide-semiconductor (PMOS) inverter circuits are fabricated on a 125 µm-thick flexible polyethylene naphthalate substrate using a blend of 2,7-dihexyl-dithieno[2,3-d;2′,3′-d′]benzo[1,2-b;4,5-b′]dithiophene and polystyrene as an active p-type organic semiconducting material. All three electrodes (gate, source, and drain) are inkjet-printed, while the active semiconducting material is deposited by a dispenser system to achieve a saturation mobility of 0.32 cm2 V−1 s−1 at V GS = −2 V. Two different PMOS inverters are fabricated, for which the signal gain peak values are resolved for an ultra-low supply voltage, V DD = −0.5 V. We achieve a signal gain of 2.73 at V DD = −0.5 V. The effect of channel width is demonstrated for both OTFTs and PMOS devices. The ‘on’ current increases with channel width, and the switching point of the PMOS inverters shifts toward the middle of the voltage transfer characteristics, and hence improves the noise margin.