Award Date

12-1-2017

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry and Biochemistry

First Committee Member

Clemens Heske

Second Committee Member

Dong-Chan Lee

Third Committee Member

Kathleen Robins

Fourth Committee Member

Daniel Gerrity

Number of Pages

121

Abstract

Solution-processed materials are appealing for use in printable electronics as a means to lower production costs, but precise control of the process is crucial for achieving the desired properties in the final materials and their interfaces. Electronic interface properties depend on both the involved materials and their fabrication processes, impacting the development and commercialization of these materials. Analyzing the chemical and electronic structure of these materials, particularly at the surfaces and interfaces, is important not only for insuring that the materials have the desired properties, but also for understanding the effects of the fabrication process and how to modify properties via processing for specific applications. To gain such insights into the chemical and electronic properties at the surface, photoelectron spectroscopy and inverse photoemission spectroscopy have proven to be powerful techniques.

In the first part of this research, indium-based transparent conductive oxides (TCOs) were prepared by spin-coating precursor solutions of metal-acetylacetonate coordination complexes onto glass substrates. The precursor films were converted into TCO films by annealing in ambient air or in dry nitrogen. These were characterized with X-ray Photoelectron Spectroscopy (XPS), Ultraviolet Photoelectron Spectroscopy (UPS), and Inverse Photoemission Spectroscopy (IPES). The observed surface chemistries and electronic structures are reported, and the effects of ambient environment, low-energy (50 eV) ion treatments, and heating in ultra-high vacuum (UHV) will be discussed.

The second part of this dissertation explores the surfaces of, and the interface between, two materials widely used in printable organic electronics: indium tin oxide (ITO) and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS). Spin coating was used to fabricate thin films of both ITO and PEDOT:PSS, which were then characterized using XPS, UPS, and IPES. Inhomogeneities in the PEDOT:PSS films involving differing ratios of PEDOT to PSS were observed using XPS, and the work function at different points on individual samples was measured. The impact of these findings on the surface electronic properties and the implications for printable electronic devices will be discussed.

Keywords

conductive polymer; metal oxides; organic electronics; printable electronics; solution-processed materials; thin films

Disciplines

Chemistry | Engineering Science and Materials | Materials Science and Engineering | Physical Chemistry

Language

English


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