No abstract

No abstract

Organic electrochemical transistors (OECTs) have exhibited promising performance as transducers and amplifiers of low potentials due to their exceptional transconductance, enabled by the volumetric charging of organic mixed ionic/electronic conductors (OMIECs) employed as the channel material. OECT performance in aqueous electrolytes as well as the OMIECs’ redox activity has spurred a myriad of studies employing OECTs as chemical transducers. However, the OECT's large (potentiometrically derived) transconductance is not fully leveraged in common approaches that directly conduct chemical reactions amperometrically within the OECT electrolyte with direct charge transfer between the analyte and the OMIEC, which results in sub‐unity transduction of gate to drain current. Hence, amperometric OECTs do not truly display current gains in the traditional sense, falling short of the expected transistor performance. This study demonstrates an alternative device architecture that separates chemical transduction and amplification processes on two different electrochemical cells. This approach fully utilizes the OECT's large transconductance to achieve current gains of 103 and current modulations of four orders of magnitude. This transduction mechanism represents a general approach enabling high‐gain chemical OECT transducers.

consumption and sensing as well as high-energy-density batteries for energy storage. Recently, interest in developing systems that interface seamlessly with the human body (e.g., wearables, braincomputer interfaces, and soft robots) has driven the development of soft, organic, and biomimetic materials that emulate the functions of their inorganic counterparts. Beyond emulation, these materials are unique because they provide an opportunity to embody such multifunctional properties within the material itself, rather than relying on device design. These multifunctional properties are intrinsic to organic mixed ionic electronic conductors (OMIECs), that is, once synthesized and processed, OMIECs can serve as the active component of multiple devices (be it transistors, sensors, energy-storage devices, etc.), where essentially the material is the device.OMIECs generally consist of a conjugated backbone for electronic conduction as well as sidechains to facilitate ionic intercalation from the operational electrolyte and to aid in solvation in processing solvents. [1] Organic chemistry provides a large toolbox in the molecular design of the backbone, side chains, and other additives, resulting in an almost infinite design space for the corresponding materials properties: energy levels, electronic and ionic conductivity, optical, volume, and moduli. Additionally, one or more of these properties can be modified during device operation, thereby transducing an input (e.g., ionic) into an output (e.g., electronic), allowing OMIECs to be used for a variety of applications including sensors, transistors, optoelectronic devices, energy-storage electrodes, and actuators. The multifunctionality of OMIECs is illustrated in Figure 1 to highlight their versatility in design and their ability to respond to a variety of stimuli.The underlying and unifying phenomena behind these property changes arise from the large modulation in electronic and ionic charge density in the bulk of the OMIEC. This modulation in turn results in second-order effects such as modulations in electrochemical potential (electron energy levels), electronic and ionic transport, capacitance, free volume, optical bandgap, and modulus. Tuning these properties throughout the bulk of the material enables new design parameters that were previously untapped in traditional electronic devices where Organic mixed ionic-electronic conductors (OMIECs) have gained recent interest and rapid development due to their versatility in diverse applications ranging from sensing, actuation and computation to energy harvesting/ storage, and information transfer. Their multifunctional properties arise from their ability to simultaneously participate in redox reactions as well as modulation of ionic and electronic charge density throughout the bulk of the material. Most importantly, the ability to access charge states with deep modulation through a large extent of its density of states and physical volume of the material enables OMIEC-based devices to display exciting new characteristics...