Complementary Inverter Based on n-Type and p-Type OFETs with the Same Ambipolar Organic Semiconductor and ITO S/D Electrodes

Bottom-gate and bottom-contact n-type and p-type organic field-effect transistors (OFETs) are simultaneously obtained by combining the ambipolar semiconductor film of diketopyrrolopyrrole-based conjugated polymer (P4FTVT-C32) with indium tin oxide (ITO) source/drain (S/D) electrodes. P4FTVT-C32 thin film exhibits n-type unipolar property with the low work functional (WF) ITO S/D electrodes modified by polyethylenimine ethoxylated (PEIE) and it exhibits p-type unipolar property with the high WF ITO S/D electrodes modified by HCl:InCl3. Hence, complementary inverters with transition voltages near V-DD/2 and the maximum gain of 138 converting "1" state input into "0" state output are achieved by two different modifications via screen printing on ITO electrodes and then, only one-time bar coating of P4FTVT-C32. To further improve the performance and the uniformity of the OFET devices, the modification of octadecyltrichlorosilane (OTS) is also introduced. This work provides an easy-handling method for the fabrication of low-cost, high performance organic electronic devices and integrated circuits.