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 (gm), 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 gm. As‐spun PIDTC16‐BT films exhibit a noticeably higher gm 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. A quasi‐solid‐state ion‐gel gated vertical organic electrochemical transistor (OECT) and logic gate are successfully demonstrated. A noticeably high transconductance, enlarged electrochemical window, and superior device stability are measured compared to typical aqueous electrolyte‐gated parallel OECTs.