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Fabricating designed fullerene nanostructures for functional electronic devices
Umeå University, Faculty of Science and Technology, Department of Physics. (Organic Photonics and Electronics Group)
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

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.
Keyword [en]
Organic electronics, Organic field-effect transistor, Organic photovoltaics, Fullerene C60, PCBM, Photochemical transformation, Resist-free lithography, C60 Nanorod, Solution processable
National Category
Physical Chemistry Nano Technology
Research subject
nanomaterials; Physical Chemistry; Physics; Materials Science
Identifiers
URN: urn:nbn:se:umu:diva-97294ISBN: 978-91-7601-187-4 (print)OAI: oai:DiVA.org:umu-97294DiVA: diva2:771376
Public defence
2015-01-20, N300, Naturvetarhuset, Umeå universitet, Universitetsvägen, 901 87 Umeå, Umeå, 10:00 (English)
Opponent
Supervisors
Available from: 2014-12-19 Created: 2014-12-12 Last updated: 2014-12-18Bibliographically approved
List of papers
1. Palladium nanocrystals supported on photo-transformed C-60 nanorods: effect of crystal morphology and electron mobility on the electrocatalytic activity towards ethanol oxidation
Open this publication in new window or tab >>Palladium nanocrystals supported on photo-transformed C-60 nanorods: effect of crystal morphology and electron mobility on the electrocatalytic activity towards ethanol oxidation
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2014 (English)In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 73, 34-40 p.Article in journal (Refereed) Published
Abstract [en]

We report on the synthesis and decoration of high-aspect-ratio crystalline C-60 nanorods (NRs) by functionalized palladium nanoparticles with an average size of 4.78 +/- 0.66 nm. In their pristine form, C-60 NRs suffer from partial damage in the solution-based decoration process resulting in poor crystallinity. However, by modifying the NR surface via in situ photochemical transformation in the liquid state, we are able to prepare highly stable NRs that retain their crystalline structure during the decoration process. Our method thus opens up for the synthesis of highly crystalline nanocomposite hybrids comprising Pd nanoparticles and C-60 NRs. Bys measuring the electron mobility of different C-60 NRs, we relate both the effect of electron mobility and crystallinity to the final electrocatalytic performance of the synthesized hybrid structures. We show that the photo-transformed C-60 NRs exhibit highly advantageous properties for ethanol oxidation based on both a better crystallinity and a higher bulk conductivity. These findings give important information in the search for efficient catalyst support.

National Category
Physical Chemistry Nano Technology
Identifiers
urn:nbn:se:umu:diva-97292 (URN)10.1016/j.carbon.2014.02.028 (DOI)000335096300004 ()
Available from: 2014-12-12 Created: 2014-12-12 Last updated: 2017-12-05Bibliographically approved
2. Solution-Based Phototransformation of C-60 Nanorods: Towards Improved Electronic Devices
Open this publication in new window or tab >>Solution-Based Phototransformation of C-60 Nanorods: Towards Improved Electronic Devices
2013 (English)In: Particle & particle systems characterization, ISSN 0934-0866, E-ISSN 1521-4117, Vol. 30, no 8, 715-720 p.Article in journal (Refereed) Published
Abstract [en]

A modified liquid-liquid interface precipitation synthesis of C-60 nanorods, effects and opportunities following an in situ photochemical transformation in the liquid state, and an electronic characterization using a field-effect transistor (FET) geometry are reported. The nanorods feature a high aspect ratio of approximate to 10(3) and a notably small average diameter of 172 nm. Interestingly, it is found that a decreased nanorod diameter appears to correlate with distinctly improved electronic properties, and an average electron mobility of 0.30 cm(2) V-1 s(-1), as measured in a FET geometry, is reported for as-grown nanorods, with the peak value being an impressive 1.0 cm(2) V-1 s(-1). A photoexposure using green laser light ( = 532 nm) is demonstrated to result in the formation of a polymer-C-60 shell encapsulating a monomer-C-60 bulk; such photo-transformed nanorods exhibit an electron mobility of 4.7 x 10(-3) cm(2) V-1 s(-1). It is notable that the utilized FET geometry only probes the polymer-C-60 nanorod surface shell, and that the monomer-C-60 bulk is anticipated to exhibit a higher mobility. Importantly, photoexposed nanorods can be conveniently processed as a stabile dispersion in common hydrophobic solvents, and this finding is attributed to the insoluble character of the polymer-C-60 shell.

Place, publisher, year, edition, pages
Wiley-VCH Verlagsgesellschaft, 2013
Keyword
C-60 nanorods, nanowhiskers, field-effect transistors, liquid-liquid-interface precipitation, photopolymerization, Raman spectroscopy
National Category
Physical Chemistry Nano Technology
Identifiers
urn:nbn:se:umu:diva-84136 (URN)10.1002/ppsc.201300016 (DOI)000327250400012 ()
Available from: 2013-12-17 Created: 2013-12-16 Last updated: 2017-12-06Bibliographically approved
3. An Arylene-Vinylene Based Donor-Acceptor-Donor Small Molecule for the DonorCompound in High-Voltage Organic Solar Cells
Open this publication in new window or tab >>An Arylene-Vinylene Based Donor-Acceptor-Donor Small Molecule for the DonorCompound in High-Voltage Organic Solar Cells
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(English)Article in journal (Other academic) Submitted
Abstract [en]

ne"> A donor-acceptor-donor (D-A-D) molecule has been designed and synthesized for use as the electron-donating material in solution-processed small-molecule organic solar cells (OSCs). The D-A-D molecule comprises a central electron-accepting (2Z,2´Z)-2,2´-(2,5-bis(octyloxy)- 1,4-phenylene)bis(3-(thiophen-2-yl)acrylonitrile) (ZOPTAN) core, which is chemically connected to two peripheral and electron-donating triphenylamine (TPA) units. The ZOPTAN-TPA molecule features a low HOMO level of5.2 eV and an optical energy gap of 2.1 eV. Champion OSCs based on a solution-processed and non-annealed active-material blend of [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) and ZOPTAN-TPA in a mass ratio of 2:1 exhibits a power conversion efficiency of 1.9 % and a high open-circuit voltage of 1.0 V.

National Category
Materials Chemistry
Identifiers
urn:nbn:se:umu:diva-97293 (URN)
Available from: 2014-12-12 Created: 2014-12-12 Last updated: 2014-12-17
4. On the fabrication of crystalline C-60 nanorod transistors from solution
Open this publication in new window or tab >>On the fabrication of crystalline C-60 nanorod transistors from solution
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2012 (English)In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 23, no 34, 344015- p.Article in journal (Refereed) Published
Abstract [en]

Flexible and high-aspect-ratio C-60 nanorods are synthesized using a liquid-liquid interfacial precipitation process. As-grown nanorods are shown to exhibit a hexagonal close-packed single-crystal structure, with m-dichlorobenzene solvent molecules incorporated into the crystalline structure in a C-60:m-dichlorobenzene ratio of 3.2. An annealing step at 200 degrees C transforms the nanorods into a solvent-free face-centred-cubic polycrystalline structure. The nanorods are deposited onto field-effect transistor structures using two solvent-based techniques: drop-casting and dip-coating. We find that dip-coating deposition results in a preferred alignment of non-bundled nanorods and a satisfying transistor performance. The latter is quantified by the attainment of an electron mobility of 0.08 cm(2) V-1 s(-1) and an on/off ratio of >10(4) for a single-crystal nanorod transistor, fabricated with a solution-based and low-temperature process that is compatible with flexible substrates.

Place, publisher, year, edition, pages
Bristol: Institute of Physics Publishing (IOPP), 2012
National Category
Physical Sciences
Identifiers
urn:nbn:se:umu:diva-60080 (URN)10.1088/0957-4484/23/34/344015 (DOI)000307812000016 ()
Available from: 2012-10-08 Created: 2012-10-01 Last updated: 2017-12-07Bibliographically approved
5. Complementary ring oscillator fabricated via direct laser-exposure and solution-processing of a single-layer organic film
Open this publication in new window or tab >>Complementary ring oscillator fabricated via direct laser-exposure and solution-processing of a single-layer organic film
2012 (English)In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 520, no 7, 3009-3012 p.Article in journal (Refereed) Published
Abstract [en]

A complementary ring oscillator is realized by exposing a solution-processed single-layer organic film to area-selective laser-light exposure and solution development. The pristine film comprises a blend of two organic semiconductors: p-type poly(3-hexylthiophene-2,5-diyl) (P3HT) and n-type [6,6]-phenyl C-61 butyric acid methyl ester (PCBM). The exposure transforms PCBM into an insoluble form, and the subsequent development selectively removes the non-exposed PCBM while leaving exposed PCBM and P3HT intact. The 5-step ring oscillator exhibits a frequency of 10 mHz, a power delay product of 2.0 mu J, and an energy delay product of 22 mu Js. Opportunities for performance improvements of the scalable fabrication technique are highlighted in an accompanying analysis.

Keyword
CMOS, Ring-oscillator, Inverter, Organic thin-film transistor, Patterning, Energy delay product, P3HT, PCBM
National Category
Physical Sciences
Identifiers
urn:nbn:se:umu:diva-55400 (URN)10.1016/j.tsf.2011.12.048 (DOI)000301085100107 ()
Available from: 2012-05-15 Created: 2012-05-14 Last updated: 2017-12-07Bibliographically approved
6. Direct UV patterning of electronically active fullerene films
Open this publication in new window or tab >>Direct UV patterning of electronically active fullerene films
2011 (English)In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 21, no 19, 3723-3728 p.Article in journal (Refereed) Published
Abstract [en]

We utilize UV light for the attainment of high-resolution, electronically active patterns in [6,6]-phenyl C61-butyric acid methyl ester (PCBM) films. The patterns are created by directly exposing selected parts of a solution-cast PCBM film to UV light, and thereafter developing the film by immersing it in a tuned developer solution. We demonstrate that it is possible to attain complex, large-area PCBM structures with a smallest demonstrated-feature size of 1 μm by this method, and that the patterned PCBM material exhibits a high average electron mobility (1.2 × 10−2 cm2 V−1 s−1) in transistor experiments. The employment of UV light for direct patterning of PCBM for electronic applications is attractive, because PCBM exhibits high absorption in the UV range, and no sacrificial photoresist is needed. The patterning is achieved through the transformation by UV light of the soluble PCBM monomers into insoluble dimers with retained attractive electronic properties.

Place, publisher, year, edition, pages
Weinheim, Germany: Wiley-VCH Verlag GmbH, 2011
Keyword
Resist-free patterning, UV light, organic semiconductors, fullerenes, organic field-effect transistors
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:umu:diva-48545 (URN)10.1002/adfm.201100568 (DOI)000295224900015 ()
Available from: 2011-10-21 Created: 2011-10-21 Last updated: 2017-12-08Bibliographically approved

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