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Searching for Relationships between Liquid Crystalline [1]benzothieno[3,2-b][1]benzothiophene Structure and Phases, and Semiconductor Properties.

Record Type:	Language materials, manuscript : Monograph/item
Title/Author:	Searching for Relationships between Liquid Crystalline [1]benzothieno[3,2-b][1]benzothiophene Structure and Phases, and Semiconductor Properties./
Author:	Wei, Dayan.
Description:	1 online resource (175 pages)
Notes:	Source: Dissertations Abstracts International, Volume: 80-03, Section: B.
Contained By:	Dissertations Abstracts International80-03B.
Subject:	Chemistry. -
Online resource:	click for full text (PQDT)
ISBN:	9780438382862

Searching for Relationships between Liquid Crystalline [1]benzothieno[3,2-b][1]benzothiophene Structure and Phases, and Semiconductor Properties.
Wei, Dayan.

Searching for Relationships between Liquid Crystalline [1]benzothieno[3,2-b][1]benzothiophene Structure and Phases, and Semiconductor Properties. - 1 online resource (175 pages)

Source: Dissertations Abstracts International, Volume: 80-03, Section: B.

Thesis (Ph.D.)--University of Colorado at Boulder, 2018.

Includes bibliographical references

Organic semiconducting materials that are more affordable, flexible and biocompatible than traditional silicon semiconductors have drawn considerable attention over the last thirty years. Organic semiconducting materials have been extensively studied for applications including organic photovoltaics (OPVs), organic light-emitting diodes (OLEDs), and organic field effect transistors (OFETs). The biggest challenges for this relatively new technology are the achievement of good electrical performance, and the development of a theoretical and experimental understanding of how charges are transferred in organic semiconductors, this being very different from the charge transfer mechanisms of their inorganic semiconductor counterparts. The work presented here focuses on a well-known small molecular organic semiconductor system: derivatives of [1]benzothieno[3,2-b][1]benzothiophene (BTBT). The main goal of this work is developing an understanding of the relationship of semiconductor behavior and mesophases in organic semiconductors, and working towards improving their electrical performance through rational chemical structure design, taking advantage of the unique, high-quality macroscopic "alignability" of molecules attainable in liquid crystal phases. First, systematic molecular structural variation of the BTBT derivatives achievable by directed synthesis was carried out to study the key structure-property relationships. As expected, molecular electronic energy levels, solubility, crystallinity, molecular packing are all important in determining semiconductor properties. Here, we are able to identify some general design rules for optimizing desirable semiconductor properties in BTBT-based LCs. In this regard, the liquid crystalline properties of all the synthesized BTBT derivatives were characterized by polarized light microscopy (PLM), differential scanning calorimetry (DSC), and X-ray diffraction (XRD). We also assessed the alignment quality obtained for BTBT derivatives in planar-anchoring sandwich cells as a function of their various liquid crystal phases. It was found that one of the derivatives provides nicely uniform planar alignment, thought to be due to the very rare presence of a nematic liquid crystal phase in the phase sequence of BTBT derivatives. Uniform molecular alignment is expected, other things being equal, to optimize semiconductor charge carrier mobility. Finally, devices were fabricated using structures that combine key features of planar-anchoring liquid crystal sandwich cells, and OFETs, allowing alignment of the BTBT derivatives and testing of their electrical performance of the aligned films. It was discovered that the BTBT derivative showing the highest quality alignment performed better than the other less aligned BTBT derivatives. With this highly aligned semiconductor film, it proved possible to observe the anisotropy of the intralayer charge transfer versus interlayer charge transfer. Overall, through rational chemical structure and device engineering, a thorough structure-property study of BTBT derivatives in the context of OFET construction was enabled. This led to optimization of electrical performance by optimization of the liquid crystal phase alignment, which may have wide applicability for optimization of liquid crystalline organic semiconductors.

Electronic reproduction.
Ann Arbor, Mich. :
ProQuest,
2024

Mode of access: World Wide Web

ISBN: 9780438382862Subjects--Topical Terms:

593913
Chemistry.
Subjects--Index Terms:

Liquid crystalline [1]benzothieno[3,2-b][1]benzothiopheneIndex Terms--Genre/Form:

554714
Electronic books.

Searching for Relationships between Liquid Crystalline [1]benzothieno[3,2-b][1]benzothiophene Structure and Phases, and Semiconductor Properties.
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520 $a Organic semiconducting materials that are more affordable, flexible and biocompatible than traditional silicon semiconductors have drawn considerable attention over the last thirty years. Organic semiconducting materials have been extensively studied for applications including organic photovoltaics (OPVs), organic light-emitting diodes (OLEDs), and organic field effect transistors (OFETs). The biggest challenges for this relatively new technology are the achievement of good electrical performance, and the development of a theoretical and experimental understanding of how charges are transferred in organic semiconductors, this being very different from the charge transfer mechanisms of their inorganic semiconductor counterparts. The work presented here focuses on a well-known small molecular organic semiconductor system: derivatives of [1]benzothieno[3,2-b][1]benzothiophene (BTBT). The main goal of this work is developing an understanding of the relationship of semiconductor behavior and mesophases in organic semiconductors, and working towards improving their electrical performance through rational chemical structure design, taking advantage of the unique, high-quality macroscopic "alignability" of molecules attainable in liquid crystal phases. First, systematic molecular structural variation of the BTBT derivatives achievable by directed synthesis was carried out to study the key structure-property relationships. As expected, molecular electronic energy levels, solubility, crystallinity, molecular packing are all important in determining semiconductor properties. Here, we are able to identify some general design rules for optimizing desirable semiconductor properties in BTBT-based LCs. In this regard, the liquid crystalline properties of all the synthesized BTBT derivatives were characterized by polarized light microscopy (PLM), differential scanning calorimetry (DSC), and X-ray diffraction (XRD). We also assessed the alignment quality obtained for BTBT derivatives in planar-anchoring sandwich cells as a function of their various liquid crystal phases. It was found that one of the derivatives provides nicely uniform planar alignment, thought to be due to the very rare presence of a nematic liquid crystal phase in the phase sequence of BTBT derivatives. Uniform molecular alignment is expected, other things being equal, to optimize semiconductor charge carrier mobility. Finally, devices were fabricated using structures that combine key features of planar-anchoring liquid crystal sandwich cells, and OFETs, allowing alignment of the BTBT derivatives and testing of their electrical performance of the aligned films. It was discovered that the BTBT derivative showing the highest quality alignment performed better than the other less aligned BTBT derivatives. With this highly aligned semiconductor film, it proved possible to observe the anisotropy of the intralayer charge transfer versus interlayer charge transfer. Overall, through rational chemical structure and device engineering, a thorough structure-property study of BTBT derivatives in the context of OFET construction was enabled. This led to optimization of electrical performance by optimization of the liquid crystal phase alignment, which may have wide applicability for optimization of liquid crystalline organic semiconductors.
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