Fabricating designed fullerene nanostructures for functional electronic devices
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
A long-term goal within the field of organic electronics has been to developflexible and functional devices, which can be processed and patterned withlow-cost and energy-efficient solution-based methods. This thesis presents anumber of functional paths towards the attainment of this goal via thedevelopment and demonstration of novel fabrication and patterningmethods involving the important organic-semiconductor family termedfullerenes.Fullerenes are soccer-shaped small molecules, with two often-employedexamples being the symmetric C60 molecule and its more soluble derivative[6,6]-phenyl-C61-butyric acid methyl ester (PCBM). We show that PCBM canbe photochemically transformed into a dimeric state in a bi-excited reactionprocess, and that the exposed material features a significantly reducedsolubility in common solvents as well as an effectively retained electronmobility. This attractive combination of material properties allows for adirect and resist-free lithographic patterning of electronic PCBM films downto a smallest feature size of 1 µm, using a simple and scalable two-stepprocess constituting light exposure and solution development. In a furtherdevelopment, it was shown that the two-step method was useful also in thearea-selective transformation of fullerene/conjugated-polymer blend films,as demonstrated through the realization of a functional complementary logiccircuit comprising a 5-stage ring oscillator.In another project, we have synthesized highly flexible, single-crystal C60nanorods with a solution-based self-assembly process termed liquid-liquidinterfacial precipitation. The 1-dimensional nanorods can be deposited fromtheir synthesis solution and employed as the active material in field-effecttransistor devices. Here, it was revealed that the as-fabricated nanorods canfeature an impressive electron mobility of 1.0 cm2 V-1 s-1, which is on par withthe performance of a work horse in the transistor field, viz. vacuumdeposited amorphous Si. We further demonstrated that the processability ofthe nanorods can be improved by a tuned light-exposure treatment, duringwhich the nanorod shell is polymerized while the high-mobility interior bulkis left intact. This has the desired consequence that stabile nanoroddispersions can be prepared in a wide range of solvents, and we anticipatethat functional electronic devices based on solution-processable nanorodscan be realized in a near future.
Place, publisher, year, edition, pages
Umeå: Umeå universitet , 2014. , 71 p.
Organic electronics, Organic field-effect transistor, Organic photovoltaics, Fullerene C60, PCBM, Photochemical transformation, Resist-free lithography, C60 Nanorod, Solution processable
Physical Chemistry Nano Technology
Research subject nanomaterials; Physical Chemistry; Physics; Materials Science
IdentifiersURN: urn:nbn:se:umu:diva-97294ISBN: 978-91-7601-187-4OAI: oai:DiVA.org:umu-97294DiVA: diva2:771376
2015-01-20, N300, Naturvetarhuset, Umeå universitet, Universitetsvägen, 901 87 Umeå, Umeå, 10:00 (English)
Janssen, René, Professor
Edman, Ludvig, Professor
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