Composite Stacked Organic Semiconductors: Materials and Processing Towards Large Area Organic Electronics

摘要

Over the last three decades, organic semiconductors, both polymeric andudsmall-molecule compounds, have raised significant interest in academia and industryudin view of the attractive combination of their versatile optoelectronic properties,udlightness, flexibility and potential for low-cost and straight-forward manufacturingudthat makes them a valid alternative to conventional inorganic semiconductors.udThereby, 6,13-bis(triisopropylsilylethynyl) (TIPS) pentacene and other pentacene andudanthradithiophene derivatives are interesting candidate materials for electronicudapplications such as organic field-effect transistors (OFETs) as they feature highlyudpromising device performance and offer the possibility of processing them fromudsolution, originating from their good solubility in common solvents. However, theudsmall-molecule nature of these compounds often renders the control of the solid-stateudmorphology of architectures deposited from solution challenging, thus, resulting inudlow reproducibility of their transistor characteristics.udThis thesis explores possible pathways to control the thin-film microstructureudof such small molecules. By doing so, we aim to provide model systems that permitudthe elucidation of relevant electronic processes in these materials and to provideudarchitectures for future technological exploitation. A thorough analysis is presentedudincluding the influence of the selection of solvent, casting temperature, coatingudtechniques and the presence of small-molecular additives on the morphology of suchudsemiconducting small-molecule thin films. Various strategies for chemicaludmodification of TIPS pentacene are also discussed with focus of the effect of sidechainudsubstitution on the electronic properties of the resulting architectures. Furthermore, investigations into the supramolecular arrangements that can be realisedudwith some of those low-molecular-weight materials are presented and how this affectsudtheir optoelectronic features.