Near-Infrared Light-Programmable Negative Differential Transconductance in Organic Electrochemical Transistors for Reconfigurable Logic

Organic electrochemical transistors offer advantages in low-power, ion-mediated electronics, yet their typically monotonic transfer characteristics limit their integration into advanced information-processing systems. Here, the emergence of optically induced negative differential transconductance (NDT) is reported in organic electrochemical transistors based on a near-infrared responsive polymer, p(C₄DPP-T), and a potassium iodide electrolyte. Under near-infrared illumination, the device exhibits a transition from a conventional monotonic transfer characteristic to a non-monotonic one with three conductance regions: a conventional binary on/off, a ternary on/partially on/off state, and an on/on/off, depending on light intensity. This unique response stems from the intrinsic material properties of the system, where near-infrared illumination generates holes in p(C₄DPP-T) and the potassium iodide electrolyte drives redox reactions. These coupled processes modulate channel doping, inducing NDT. Notably, NDT behavior is achieved without complex device architectures or p–n heterojunctions, which are typically required in conventional field-effect transistors. It is further shown that enlarging the gate–electrolyte interfacial area enhances the NDT response, yielding higher peak currents, sharper transitions, and improved peak-to-valley ratios. Finally, an optically reconfigurable logic circuit capable of switching between binary and ternary logic is realized without altering the device architecture, paving the way for the development of adaptive electronic circuits.