High Performance Vertical Organic Electrochemical Transistors

Since the initial demonstration of a working transistor in 1947, reduction in physical size (downscaling or miniaturization) of various inorganic transistors has led to better utilization of available substrate space while improving transistor performance and lowering power requirements and device cost.[1] Downscaling of transistors has enabled the advancement of a wide range of commonly used electronic devices.[2] Compared to traditional inorganic transistors, the development of transistors based on organic materials is at a relatively young phase. Downscaling of organic field-effect transistors (OFETs) has been primarily driven by active-matrix display technologies,[3] with much effort focused on understanding and optimizing organic semiconductor (OSC) morphology and charge transport properties.[4] An alternative organic transistor structure to the OFET, the organic electrochemical transistor (OECT), has also benefitted from OSC materials research, progressing significantly in the last decade. Whereas OFET current modulation relies on the field-effect, responding to charge accumulation at the dielectric interface of the channel, the current in OECTs is controlled by the injection of ions from an electrolyte into the bulk of the channel. This makes them particularly suitable for biointerfacing applications where documented advantages of organic technologies are numerous.[5], [6] Examples include neural implants,[7]–[14] in vitro arrays for biological assays,[15]–[21] and neuromorphic devices.[22]–[25] OECTs have reached a significant level of maturity and a major contemporary challenge is to pursue miniaturization for increasing density and improving performance