Pyrrole Based Donor-acceptor Building Blocks for Organic Field-effect Transistors




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The class of organic semiconductors is a definite contender for replacing high-cost silicon semiconductors owing to unique advantages such as solution processability, flexibility, lightweight, low cost, and the ability to do multiple structural modifications. Hence, a remarkable amount of scientific research has been carried out to improve the electronic properties of these materials. Throughout the past two decades, many improvements in the field have achieved by designing novel building blocks. There remains the possibility, however, for performance improvement through areas that has paid less attention in both conventional and non-conventional building blocks. Because of the appealing performance of organic semiconductors, it is highly desirable to seek and develop new building blocks for the next generation of organic electronics. In this dissertation, the fundamentals, history, and recent developments of conventional and nonconventional materials are covered briefly in the first chapter. Operation principles, charge transport of organic field effect transistors is introduced. Compared to conventional thiophenebased -electron donor materials, promising non-conventional pyrrole-based donor materials employed in organic field effect transistors are discussed and summarized. Chapter 2 describes the effect on organic field effect transistor (OFET) properties of a donor-acceptor polymer consist of a branched ester functionalized bithiophene copolymerized with thiophene vinyl thiophene donor. The influence on frontier molecular orbital energy levels, UV-vis absorption, electrochemical properties, OFET parameters and morphological effects were investigated. In chapter 3, the effect of furan spacer group on a thieno[3,2-b]pyrrole and diketopyrrolopyrrole based copolymer is discussed. Upon changing similar flanking groups, the polymer showed a high hole mobility of 0.42 cm2 /V s while the on-to-off ratio exhibited a drastic improvement 105 . Chapter 4 describes the incorporation of selenium hetero atom in the pyrrole fused rings to yield seleno[3,2-b]pyrrole based small molecules replacing thieno[3,2-b]pyrrole to extend the knowledge of OFETs activity of seleno[3,2-b]pyrrole in banana shaped small molecules. They exhibited moderate charge carrier properties 10-2 cm2 /V s hole mobility. In the Chapter 5 (attached as an appendix), a study on oxidative degradation of polypropylene mesh in Escherichia coli (E. coli.) environment is disscussed. Medical implants of polypropylene (PP) mesh have demonstrated biodegradation inside the body. Among the many possible factors, bacterial colonization is believed to be one of the causes for biodegradation. To gain insights on this hypothesis PP mesh samples were tested in Luria-Bertani broth containing E. coli and the experimental results demonstrated qualitative and quantitative bioerosion, confirming the oxidative degradation in vitro.



Chemistry, Organic, Chemistry, Polymer, Chemistry, General