Abstract
Organic electrochemical transistors (OECTs) from poly(3,4-ethylenedioxythiophene) doped with polystyrene sulfonate (PEDOT:PSS) are used as amplifying transducers for bioelectronics. Although the impact on performance of device geometry parameters such as channel area and thickness has been widely explored, the overlap between the semiconductor film and the source and drain contacts has not been considered. Here we vary this overlap and explore its impact on transconductance and noise. We show that increasing contact overlap does not alter the magnitude of the steady-state transconductance but it does decreases the cut-off frequency. Noise was found to be independent of contact overlap and to vary according to the charge noise model. The results show that high-quality contacts can be established in PEDOT:PSS OECTs with minimal overlap.
Highlights
Organic electrochemical transistors (OECTs) are attracting a great deal of attention for applications in electronics and bioelectronics[1]
The results show that high quality contacts can be established in PEDOT:PSS OECTs with minimal overlap
A systematic decrease in the cut-off frequency fc=gm,max/√2 is observed as the overlap increases: The OECT with 70% contact overlap is ~300 Hz slower than the one with 10% contact overlap
Summary
Organic electrochemical transistors (OECTs) are attracting a great deal of attention for applications in electronics and bioelectronics[1]. Their operation relies on the injection of ions from an electrolyte into the volume of a semiconducting polymer. Small metal cations can be readily injected in this material from a variety of electrolytes under the influence of an applied gate voltage, leading to large changes in the drain current. The figure-of-merit that characterises the ability of transistors to transduce a signal is the transconductance gm, defined as the first derivative of the drain current Id over the gate voltage Vg. OECTs have been shown to exhibit a very high transconductance, due to the volumetric changes in the conductivity of the channel [9]. Fluctuations in the hole density inside the channel are assumed to be responsible for this behaviour[18]
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