Structure-Property Relationships of Organic Electrochemical Transistors Based on the Conjugated Polyelectrolyte PCPDTBTSO3- Na (CPE-Na)

This dissertation is concerned with the fabrication and characterization of organic electrochemical transistors (OECTs) made from polyelectrolytes based on the material PCPDTBT-SO3-Na (CPE-Na). OECTs are electrolyte-gated transistors that allow the electrolyte to permeate into the bulk of the film and directly changes the doping state of the bulk of the semiconducting layer. The relationship between the molecular structure of the polyelectrolytes and the material properties are explored in the lens of optimizing device characteristics in OECTs. The first chapter of this thesis focuses on the development of OECTs made using PCPDTBT-SO3-K (CPE-K) as the active layer. While the large majority of OECT research still utilizes poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) as the active layer, a few new OECT materials have been recently reported. CPE-K has been used in the past for applications such as DNA-detection, thermoelectric devices and as interlayers in organic photovoltaic devices. Conjugated polyelectrolytes (CPEs) represent a promising and unique class of materials which are characterized by their conjugated carbon backbone and pendant ionic chains. Their water solubility in addition to their electronic and ionic conductivity makes them an ideal candidate for OECT applications. Using various spectroscopic and electric characterization techniques, CPE-K was fully characterized so that it could be accurately compared to other OECT materials reported in the literature. In fact, CPE-K is among the short list of high-performance OECT materials. The techniques used in this work was used to shed light on the operational mechanism of CPE-based OECTs. In addition, the effective use of interdigitated contacts was used to increase the transconductance of OECT devices.The second portion of this thesis expands on the work of CPE OECTs, by exploring their structure-property-relationship. A series of CPE-Na polymers with varying sidechain lengths were synt