Defect Structures and Properties of Liquid Crystalline Polymer Semiconductors

Regents Of The University Of Michigan - Ann Arbor, Ann Arbor MI

Investigators

Abstract

ABSTRACT: Defect Structures and Properties of Liquid Crystalline Polymer Semiconductors, DMR-0802655, Prof. David C. Martin, The University of Michigan, Department of Materials Science and Engineering. TECHNICAL SUMMARY Polymer and organic molecular semiconductors are of considerable interest for creating inexpensive electronic devices. Previous studies of polycrystalline organic molecular films have shown evidence that grain boundary defects play an important role in limiting the performance of these materials. However the detailed relationship between the microstructure and macroscopic properties of these materials remains obscure and controversial. Liquid crystalline polymer and organic molecular semiconductors are of particular current interest, because it is expected that the more modest distortions near grain boundaries and other defects in the solid-state may not lead to the large reductions in properties seen in polycrystalline films. The microstructure of liquid crystalline polymer and organic molecular semiconductors will be investigated using an array of instruments and techniques including optical microscopy, wide angle X-ray diffraction, small angle X-ray diffraction, scanned probe microscopy, scanning electron microscopy, transmission electron microscopy, low voltage electron microscopy, and high resolution electron microscopy. These microstructural details will be correlated with information about sample performance on thin-film transistor devices, and with impedance spectroscopy of the carrier transport. The fundamental scientific challenge is to determine if and how the increased order provided by liquid crystalline order makes it possible to create films that have better performance than either the amorphous or polycrystalline structures seen in other organic molecular solids. NON-TECHNICAL SUMMARY There is considerable interest and future potential in developing new materials for all-organic "plastic" electronics. Examples of such devices include soft, flexible computers and displays printed on flexible substrates, and biomedical components that can be directly implanted into the body. However there are many important questions about these materials that are not yet known, such as the detailed relationship between their local structure and the properties that they exhibit when used in devices. This research project will make it possible to develop improved materials that can be easily and inexpensively processed and manufactured into components. This project will provide for financial support for graduate students from Materials Science, Macromolecular Science, and Biomedical Engineering. Research opportunities for undergraduate students will be provided through the University Research Opportunity Program, the Sarah Marian Parker Women in Engineering and the Minority Engineering Programs. We also have summer students from high schools in the Ann Arbor area. Established collaborations and interactions will be continued with colleagues at the University of Michigan, the University of Kentucky, Georgia Tech, the Fraunhofer Institute in Bremen, Germany, the National Institute of Science and Technology, Chulalongkorn University in Bangkok, Thailand, the University of Wollongong, Australia, and Suwan University in Seoul, South Korea. Industrial interactions will be extended with companies including Ford Motor Company (Dearborn, MI), Cochlear (Australia), BioControl (Israel), Plexon (Dallas, TX), Biotectix (Quincy, MA) and NeuroNexus (Ann Arbor, MI).