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C60 Field-Effect Transistors: Effects of Polymerization on electronic Properties and Device Performance.
Umeå University, Faculty of Science and Technology, Physics.
Umeå University, Faculty of Science and Technology, Physics.
Umeå University, Faculty of Science and Technology, Physics.
2007 (English)In: Physical Review B, Vol. 75, no 7, 075203- p.Article in journal (Refereed) Published
Abstract [en]

We have investigated thin-film field-effect transistors (TFTs) with C60 as the active material, and we report the effects of photo-induced polymerization of the C60 film. We find that the effects of a complete polymerization for a typical top-contact C60 TFT is as follows: the electron mobility (μn) at room temperature drops slightly from 0.074 to 0.068 cm2/Vs, the activation energy of μn decreases from 0.10 meV to 0.09 meV, and the threshold voltage for TFT operation decreases markedly by ~15 %. The latter observation suggests that the effective number of electron traps in the C60 film decreases following polymerization. Considering that the polymerization was achieved with a low-energy HeNe laser, it is conceivable that the polymerization approach could be of interest for applications, e.g., organic bulk-heterojunction solar cells, where a stabilized C60 morphology attained with benign means is desired

Place, publisher, year, edition, pages
2007. Vol. 75, no 7, 075203- p.
URN: urn:nbn:se:umu:diva-11904OAI: diva2:151575
Available from: 2007-12-13 Created: 2007-12-13 Last updated: 2011-01-11Bibliographically approved
In thesis
1. Photo-polymerization as a tool for engineering the active material in organic field-effect transistors
Open this publication in new window or tab >>Photo-polymerization as a tool for engineering the active material in organic field-effect transistors
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The emergence of organic semiconductors is exciting since it promises to open up for straightforward and low-cost fabrication of a wide range of efficient and novel electronic devices. However, in order for this promise to become reality it is critical that new and functional fabrication techniques are developed. This thesis demonstrates the conceptualization, development, realization and implementation of a particularly straightforward and scalable fabrication process: the photo-induced and resist-free imprint patterning technique.Initial experiments revealed that some members of a group of carbon-cage molecular semiconductors – termed fullerenes – can be photochemically modified into dimeric or polymeric structures during exposure to laser light, and, importantly, that the exposed fullerene material retains its good electron-transport property while its solubility in common organic solvents is drastically lowered. With this information at hand, it was possible to design and create well-defined patterns in a solution-deposited fullerene film by exposing selected film areas to laser light and then developing the entire film in a tuned developer solution. An electronically active fullerene pattern emerges at the locations defined by the incident laser beam, and the patterning technique was successfully utilized for the fabrication of arrays of efficient field-effect transistors.In a later stage, the capacity of the photo-induced and resist-free imprint technique was demonstrated to encompass the fabrication of ubiquitous and useful CMOS circuits. These are based on a combination of p-type and n-type transistors, and a blend between a p-type organic semiconductor and an n-type fullerene compound was designed so that the latter dominated. By solution-depositing the blend film on an array of transistor structures, exposing selected transistors to laser light, and then developing the entire transistor array in a developer solution, it was possible to establish a desired combination of (non-exposed) p-type transistors and (exposed) n-type transistors. We finally utilized this combination of transistors for the fabrication of a CMOS circuit in the form of well a-functional organic inverter stage.

Place, publisher, year, edition, pages
Umeå: Print & Media, 2009. 50 p.
Field-effect transistor, photo-polymerization, PCBM, C60, Fullerene
National Category
Physical Sciences
Research subject
Solid State Physics
urn:nbn:se:umu:diva-22127 (URN)978-91-7264-779-4 (ISBN)
Public defence
2009-05-20, NA430, SE-90187 Umea, Umea, 13:00 (English)
Available from: 2009-04-24 Created: 2009-04-23 Last updated: 2009-04-24Bibliographically approved

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