Electronic Processes and Phenomena in Organic Materials: A Materials Scientist’s Point of View

Presented on July 12, 2013 from 4:00 to 5:00 pm in the Molecular Science and Engineering Building (MoSE) room G011.Runtime: 62:17 minutes.Natalie Stingelin(-Stutzmann) is a Reader in Organic Functional Materials at the Department of Materials, Imperial College London. She also holds a part-time Senior Researcher position (20%) at the Swiss Federal Institute of Technology (ETH) Zurich, Switzerland (since 2003), and has been an External Senior Fellow at the Freiburg Institute for Advanced Studies(FRIAS), Albert- Ludwigs-Universität Freiburg (since 2010). Prior to these appointments, she conducted research at the Cavendish Laboratory at the University of Cambridge, the Philips Research Laboratories, Eindhoven, and as junior staff at Queen Mary University of London. She obtained the degree of Engineer in Materials Science in 1997 from ETH Zürich, and her PhD in 2001, for which she was awarded the ETH Medal. She has published more than 90 papers, has 4 granted patents and 4 patent applications. Her current research interests encompass the broad field of organic functional materials, including organic electronics, multifunctional inorganic/organic hybrids, and smart, advanced optical systems based on organic matter. She is an Associate Editor of the Journal of Materials Chemistry and received a €1.2 Million ERC Starting Independent Researcher Award in 2011.In the past decade, significant progress has been made in the fabrication of organic semiconductor thin-film devices predominantly due to important improvements of existing materials and the creation of a wealth of novel compounds. Many challenges, however, still exist. Key to commercial success is to make it technological practice to exploit the touted potential for low-cost manufacturing of these functional materials. This requires intimate knowledge of relevant structure/processing/performance interrelations. Here, examples are given of how materials scientists ‘tools’ may be utilized to gain further understanding of this interesting class of materials and how the physical organization, from the molecular scale to the macroscale, of functional organic matter such as polymer semiconductors can be controlled. To this end, we present a survey on the principles of structure development from the liquid phase of this materials family with focus on how to manipulate their phase transformations and solid-state order to tailor and tune the final ‘morphology’ towards technological and practical applications

Going against the grain: the dematurity of the European textile industry

Proceedings of the 5th International Ph.D. School on Innovation and Economic Development, Globelics Academy 2008, Tampere, 2nd of June 13th of June, 2008.The paper investigates the process of transition of the European textile industry away from being a mature industry towards a more knowledge-based one. The European industry has fallen into what Abernathy (1978, 1983) termed the 'maturity trap' due to a number of different factors; firm inertia, the fragmentation of markets, increasing competition and regional and national business cultures. However, the findings also suggest that a number of companies have successfully circumvented maturity-trap and indeed shifted their capabilities from mature businesses to ferment phase. There is now a concerted effort at the EU and national level to rescue the European industry from the maturity trap based on innovation and entrepreneurial management at the level of the firm

Organic thin-film electronics from vitreous solution-processed rubrene hypereutectics

Electronic devices based on single crystals of organic semiconductors provide powerful means for studying intrinsic charge-transport phenomena and their fundamental electronic limits. However, for technological exploitation, it is imperative not to be confined to the tedious growth and cumbersome manipulation of molecular crystals—which generally show notoriously poor mechanical properties—but to be able to process such materials into robust architectures by simple and efficient means. Here, we advance a general route for facile fabrication of thin-film devices from solution. The key beneficial feature of our process—and the principal difference from existing vapour deposition and solution-processing schemes—is the incorporation of a glass-inducing diluent that enables controlled crystallization from an initial vitreous state of the organic semiconductor, formed in a selected area of the phase diagram of the two constituents. We find that the vitrifying diluent does not adversely affect device performance. Indeed, our environmentally stable, discrete rubrene-based transistors rival amorphous silicon devices, reaching saturated mobilities of up to 0.7 cm2 V−1 s−1, ON–OFF ratios of ≥10e6 and subthreshold slopes as steep as 0.5 V per decade. A nearly temperature-independent device mobility, indicative of a high crystalline quality of our solution-processed, rubrene-based films, corroborates these findings. Inverter and ring-oscillator structures are also demonstrated.

Multicomponent semiconducting polymer systems with low crystallization-induced percolation threshold

Blends and other multicomponent systems are used in various polymer applications to meet multiple requirements that cannot be fulfilled by a single material. In polymer optoelectronic devices it is often desirable to combine the semiconducting properties of the conjugated species with the excellent mechanical properties of certain commodity polymers. Here we investigate bicomponent blends comprising semicrystalline regioregular poly(3-hexylthiophene) and selected semicrystalline commodity polymers, and show that, owing to a highly favourable, crystallization-induced phase segregation of the two components, during which the semiconductor is predominantly expelled to the surfaces of cast films, we can obtain vertically stratified structures in a one-step process. Incorporating these as active layers in polymer field-effect transistors, we find that the concentration of the semiconductor can be reduced to values as low as 3 wt% without any degradation in device performance. This is in stark contrast to blends containing an amorphous insulating polymer, for which significant reduction in electrical performance was reported. Crystalline-crystalline/semiconducting-insulating multicomponent systems offer expanded flexibility for realizing high-performance semiconducting architectures at drastically reduced materials cost with improved mechanical properties and environmental stability, without the need to design all performance requirements into the active semiconducting polymer itself