Ion-Reconfigurable "N"-Shaped Antiambipolar Behavior in Organic Electrochemical Transistors

"N"-shaped negative differential transconductance (NDT) is crucial for advanced electronic applications, including neuromorphic circuits, multivalued logic, and Logic-in-Memory devices. Organic electrochemical transistors (OECTs) offer an energy-efficient platform for these technologies, yet achieving NDT behavior in single-material OECTs remains challenging. In this study, the realization of "N"-shaped transfer characteristics in OECTs is demonstrated by combining the p(C₄DPP-T) polymer with a potassium iodide (KI) electrolyte. The emergence of this unique behavior is attributed to the distinctive electrochemical properties of iodide, including its ability to participate in redox reactions and form triiodide species. Notably, this behavior emerges exclusively with iodide ions, while chloride, bromide and several other anions induce conventional monotonic p-type characteristics. By systematically tuning polymer microstructure, electrolyte concentration, and gate voltage scan rates, the intricate interplay among polymer-iodide interactions, and charge transport is uncovered, optimizing critical performance parameters such as the peak-to-valley ratio and the NDT range. Additionally, how iodine (I^-) concentration effectively facilitates ion-driven reconfigurability in OECT-based circuits, enabling transitions between binary and ternary logic states is illustrated. The results highlight an unprecedented tunability of NDT behavior in OECTs and hold immense promise for the advancement of NDT-OECTs in next-generation electronic and neuromorphic applications.