Comparison of conductor and dielectric inks in printed organic complementary transistors

Two types of printable conductor and a bilayer gate dielectric are evaluated for use in all-additive, inkjet-printed complementary OTFTs. The Ag nanoparticle ink based on nonpolar alkyl amine surfactant enables good charge injection into p-channel devices, but this ink also leaves residual surfactant that modifies the transistor back-channel and shifts the turn-on voltage to negative values. The Ag ink based on polar solvent requires dopant modification to improve charge injection to p-channel devices, but this ink allows the OTFT turn-on voltage to be close to 0 V. The reverse trend is observed for n-channel OTFTs. For gate insulator, a bilayer dielectric is demonstrated to combine the advantages of two types of insulator materials, in which a fluoropolymer reduces dipolar disorder at the semiconductor-dielectric interface, while a high-k PVDF terpolymer dielectric facilitates high gate capacitance. The dielectric is incorporated into an inverter and a three-stage ring-oscillator, and the resulting circuits were demonstrated to operate at supply voltage as low as 2 V, with bias stress levels comparable to circuits with other types of dielectrics.