Characterization of Screen-Printed Organic Electrochemical Transistors to Detect Cations of Different Sizes.

Laura Contat-Rodrigo,Clara Pérez-Fuster,Eduardo García-Breijo,José Lidón-Roger,Annalisa Bonfiglio

doi:10.3390/s16101599

Abstract

A novel screen-printing fabrication method was used to prepare organic electrochemical transistors (OECTs) based on poly(3,4-ethylenedioxythiophene) doped with polysterene sulfonate (PEDOT:PSS). Initially, three types of these screen-printed OECTs with a different channel and gate areas ratio were compared in terms of output characteristics, transfer characteristics, and current modulation in a phosphate buffered saline (PBS) solution. Results confirm that transistors with a gate electrode larger than the channel exhibit higher modulation. OECTs with this geometry were therefore chosen to investigate their ion-sensitive properties in aqueous solutions of cations of different sizes (sodium and rhodamine B). The effect of the gate electrode was additionally studied by comparing these all-PEDOT:PSS transistors with OECTs with the same geometry but with a non-polarizable metal gate (Ag). The operation of the all-PEDOT:PSS OECTs yields a response that is not dependent on a Na+ or rhodamine concentration. The weak modulation of these transistors can be explained assuming that PEDOT:PSS behaves like a supercapacitor. In contrast, the operation of Ag-Gate OECTs yields a response that is dependent on ion concentration due to the redox reaction taking place at the gate electrode with Cl− counter-ions. This indicates that, for cation detection, the response is maximized in OECTs with non-polarizable gate electrodes.

Highlights

Organic electronics has been extensively developed since the discovery of conducting polymers in the late 1970s [1,2] due to the unique features that these materials can offer, such as low-cost fabrication, low temperature processing, mechanical flexibility, ionic conductivity, and facile chemical modification [3]
In organic electrochemical transistors (OECTs) based on PEDOT:PSS, the gate electrode plays an important role with respect to its ion-sensitive properties
The device geometry is another critical issue to the ion-sensitive behavior of OECTs based on PEDOT:PSS

Summary

Introduction

Organic electronics has been extensively developed since the discovery of conducting polymers in the late 1970s [1,2] due to the unique features that these materials can offer, such as low-cost fabrication, low temperature processing, mechanical flexibility, ionic conductivity, and facile chemical modification [3]. Many electronic devices based on organic semiconductors have been developed, including organic light emitting diodes (OLEDs) [4], organic photovoltaics (OPVs) [5], and organic thin film transistors (OTFTs) [6,7]. Among the latter, organic electrochemical transistors (OECTs) have attracted considerable interest in recent years for their application as organic semiconductor devices in many fields, especially for chemical and biological sensing due to their ability to operate in aqueous environments [8,9]. The Sensors 2016, 16, 1599; doi:10.3390/s16101599 www.mdpi.com/journal/sensors

Methods

Results

Conclusion