Organic mixed conductors for electrochemical transistors

Organic electrochemical transistors (OECTs) have emerged as a powerful platform for bioelectronic communication, enabling various technologies including neuromorphic devices, stimulation elements, and biosensors. These devices leverage the ionic-electronic coupling of organic semiconductors, known as organic mixed ionic-electronic conductors (OMIECs), to transduce signals across biotic and abiotic interfaces or mimic biological functions. The efficiency and behavior of this ionic-electronic communication are material- and electrolyte-dependent; therefore, the utility of OECTs depends on our control over OMIECs within a particular environment. Here we critically review material design considerations for the next generation of mixed conductors for OECT applications. Recent advances and strategies toward high-performance p- and n-type OMIECs are summarized. Important topics, such as batch-to-batch variability, assessing stability, processing methodologies, and alternative material platforms, are also covered—areas rarely discussed within the OMIEC community. Challenges and opportunities related to these topics are discussed, offering a practical guide to designing the next generation of OMIECs for bioelectronic applications.