High‐Performance Vertical Organic Electrochemical Transistors

Abstract

Organic electrochemical transistors (OECTs) are promising transducers for biointerfacing due to their high transconductance, biocompatibility, and availability in a variety of form factors. Most OECTs reported to date, however, utilize rather large channels, limiting the transistor performance and resulting in a low transistor density. This is typically a consequence of limitations associated with traditional fabrication methods and with 2D substrates. Here, the fabrication and characterization of OECTs with vertically stacked contacts, which overcome these limitations, is reported. The resulting vertical transistors exhibit a reduced footprint, increased intrinsic transconductance of up to 57 mS, and a geometry-normalized transconductance of 814 S m . The fabrication process is straightforward and compatible with sensitive organic materials, and allows exceptional control over the transistor channel length. This novel 3D fabrication method is particularly suited for applications where high density is needed, such as in implantable devices.

Vertical, electrolyte-gated organic transistors show continuous operation in the MA cm−2 regime and artificial synaptic behaviour

“…Finally, our transistors show large transconductances of above 5000 S/m (see Supplementary Fig. 2b) -larger than for example SWCNT network FETs 3 or PEDOT:PSS FETs 14,43 . A more detailed comparison of transconductances is given in Table T1.…”

Energetic Control of Redox‐Active Polymers toward Safe Organic Bioelectronic Materials

“…These materials, also called organic mixed ionic/electronic conductors (OMIECs), can exchange ions with aqueous electrolytes when electronic charge carriers are injected, transported, and stored in the bulk of the material. [ 1 ] Recent developments of OMIECs based on redox‐active conjugated polymers [ 2–8 ] and novel device concepts [ 9,10 ] have opened up new pathways for bioelectronic devices including integrated circuits for electroencephalogram (EEG) monitoring [ 9 ] or low‐power voltage amplifiers based on organic electrochemical transistors (OECTs). [ 11 ] Specifically, the OECT has drawn significant attention in the field of organic bioelectronics.…”

Active Materials for Organic Electrochemical Transistors

“…Some efforts have been made to understand and improve the bioelectronic interface and achieve a better interaction with cells and tissues. Examples toward this direction include i) the integration of model lipid membranes to study the effect of ion transport in synthetic biomembranes located between the gate and the active layer, ii) the realization of a functional active layer surface for effective bio‐recognition of biological species, and iii) the development of new form factors to prevent scar tissue formation for in vivo bioelectronic applications as well as to improve OECTs' performance …”

“…The opportunity to use the OECT as a sensitive bidirectional interface with biological systems has generated a growing interest in the scientific community toward the design of materials and device architectures aimed to improve OECT performance and biointegration . Concurrently, the desire to enhance the fundamental knowledge on OECT operation on one hand has stimulated the rational design of active materials aimed to elucidate key structure–property relations .…”