Ultrathin-Film Small Molecule Mixed Conductors Exhibiting Ion-Tunable Ambipolarity for High-Performance Organic Electrochemical Transistors and Multivalued Logic Inverters.

Single-component, ultrathin ambipolar organic electrochemical transistors (OECTs) combined with multivalued logic (MVL) circuits offer new opportunities for advancing next-generation bioelectronic systems due to their low-power consumption, manufacturing simplicity, and high-density integration, central to which is the evolution of ambipolar organic mixed ionic-electronic conductors (OMIECs) as channel materials. However, small-molecule analogues remain unexplored to date for lack of well-defined molecular strategies. Herein, first two acceptor-donor-acceptor-donor-acceptor-type vinyl-linked bis-diketopyrrolopyrrole-core ambipolar small-molecule OMIECs are developed featuring multiple conformational locks. It is discovered that grafting shortened glycolated sidechains produces stronger solid-state aggregation, tighter lamellar stacking, and higher crystallinity, consequently elevating the ambipolar µC* figure-of-merit by over fourfold. Furthermore, the skillful manipulation of anionic species to facilitate oxidation doping enables significant increasement in p-type µC* (170 F cm^-1 V^-1 s^-1) and a record-high n-type µC* of 360 F cm^-1 V^-1 s^-1, especially at a channel thickness of sub-10 nm. Crucially, single-component OECT-based inverters constructed therefrom are for the first time demonstrated to accommodate ternary/quaternary logic, achieving a remarkable gain of 135 V/V. This work not only provides an effective molecular design strategy for creating high-performing ultrathin-film ambipolar small-molecule OMIECs, highlighting ionic doping effect on ambipolarity, but also demonstrates their potential in MVL circuits for organic bioelectronics applications.