Ion Gel-Gated Quasi-Solid-State Vertical Organic Electrochemical Transistor and Inverter

Parallel-type organic electrochemical transistors (p-OECTs) with aqueous electrolyte gate dielectrics have been widely studied for transducing biological signals into electrical signals. However, aqueous liquid electrolyte-based p-OECTs suffer from poor device stability, low transconductance (g_m), and limited applications. In this study, a quasi-solid-state ion gel-gated vertical-type OECT (v-OECT) and NOT logic gate are successfully demonstrated by combining both p-type and n-type v-OECTs for the first time. Indacenodithiophene (IDT) polymers with alkyl (PIDTC16-BT) and oligoethylene glycol (OEG) substituents (PIDTPEG-BT) are studied as a channel material, and an ionic liquid in a crosslinked polymer matrix is adopted as a quasi-solid electrolyte. Compared to aqueous devices, an enlarged electrochemical window and improved operational stability are observed. Notably, the v-OECTs have a significantly larger channel area (50 × 50 µm²) and shorter channel length (≈30 nm), yielding a dramatically increased g_m. As-spun PIDTC16-BT films exhibit a noticeably higher g_m of 72.8 mS than that of previous p-OECTs along with superior device stability, despite a low volumetric capacitance. In the case of v-OECTs, face-on intermolecular packing is required to increase the carrier transport in a vertical direction. Logic gates are successfully demonstrated using p- and n-type v-OECTs, suggesting the potential of OECT-based next-generation electronics.