Thermally Evaporated Silicon Phthalocyanine and Thioxanthene Benzanthrone Based Organic Thin-Film Transistors

Abstract

Since their infancy began approximately 50 years ago, carbon-based ‘organic’ semiconductors (OSCs) have redefined the possibilities of electronics through their unique material properties such as solubility, chemical sensitivity, sublimability and flexibility. The enormous amount of organic synthetic tools available can produce a nearly endless number of tailor-made OSCs for a wide variety of applications, including already established technology such as organic light-emitting diodes (OLEDs). An increasing demand for smart-technology and data creates a particular need for low-cost electronic communication tools, sensors, and processors. In this area, organic thin-film transistors (OTFTs) excel, demonstrating potential for chemical and biological sensing, large area and printed electronics, artificial skin and smart packaging. Despite this potential, OTFT technology is still developing, with a number of consistent issues hampering widespread commercial utilization. Lack of available OSCs with good performance and low synthetic complexity is one such problem, especially for electron conducting OSCs required for complex circuit components such as inverters. Although metal phthalocyanines (MPcs) are well-known, stable molecules demonstrated in high-performance OTFTs, few are successful as n-type or ambipolar OSCs that transport electrons. The work presented in this thesis documents the first use of silicon phthalocyanines (SiPcs) in n-type OTFTs along with a thioxanthene benzanthrone, 14H-anthra[2,1,9-mna]thioxanthen-14-one (Red GG), a simple base molecule in a relatively unexplored class of compounds never before characterized for p-type OTFTs. The report within documents a number of strategies aimed at understanding and improving the performance of these molecules for this application. In particular, the chapters examine dielectric, architectural and contact modification as part of the OTFT fabrication process, while considering characterization environment, bias stress and contact resistance in their analysis. The results serve as a basis for continued development of SiPcs and Red GG derivatives for OTFT-based applications.