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Title: Composite stacked organic semiconductors : materials and processing towards large area organic electronics
Author: Yu, Liyang
ISNI:       0000 0004 2732 1082
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2012
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Over the last three decades, organic semiconductors, both polymeric and small-molecule compounds, have raised significant interest in academia and industry in view of the attractive combination of their versatile optoelectronic properties, lightness, flexibility and potential for low-cost and straight-forward manufacturing that makes them a valid alternative to conventional inorganic semiconductors. Thereby, 6,13-bis(triisopropylsilylethynyl) (TIPS) pentacene and other pentacene and anthradithiophene derivatives are interesting candidate materials for electronic applications such as organic field-effect transistors (OFETs) as they feature highly promising device performance and offer the possibility of processing them from solution, originating from their good solubility in common solvents. However, the small-molecule nature of these compounds often renders the control of the solid-state morphology of architectures deposited from solution challenging, thus, resulting in low reproducibility of their transistor characteristics. This thesis explores possible pathways to control the thin-film microstructure of such small molecules. By doing so, we aim to provide model systems that permit the elucidation of relevant electronic processes in these materials and to provide architectures for future technological exploitation. A thorough analysis is presented including the influence of the selection of solvent, casting temperature, coating techniques and the presence of small-molecular additives on the morphology of such semiconducting small-molecule thin films. Various strategies for chemical modification of TIPS pentacene are also discussed with focus of the effect of sidechain substitution on the electronic properties of the resulting architectures. Furthermore, investigations into the supramolecular arrangements that can be realised with some of those low-molecular-weight materials are presented and how this affects their optoelectronic features.
Supervisor: Stingelin, Natalie Sponsor: Dutch Polymer Institute
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral