| 1. |
- Liu, Jincheng, et al.
(författare)
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Gram-Scale Synthesis of Ultrathin Tungsten Oxide Nanowires and their Aspect Ratio-Dependent Photocatalytic Activity
- 2014
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Ingår i: Advanced Functional Materials. - : Wiley-VCH Verlag. - 1616-301X .- 1616-3028. ; 24:38, s. 6029-6037
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Tidskriftsartikel (refereegranskat)abstract
- Preparation of size-tunable ultrathin W18O49 nanowires by an alcohol-assisted solvothermal decomposition of tungstic acid is reported. The synthesis of ultrathin W18O49 nanowires can be achieved at large scale and low cost, while changing the molecular size of the used alcohols can control the nanowire morphology. With increasing the molecular size of the alcohol, the synthesized W18O49 nanowires have smaller diameters and longer lengths. The as-prepared blue W18O49 nanomaterials show a very strong visible light absorption caused by oxygen defects and an aspect ratio-dependent photocatalytic activity on the degradation of pollutant rhodamine B (RhB) under simulated solar light irradiation. It is found that the W18O49 nanowires with highest aspect ratio show the highest activity in the photodegradation of RhB, which could be related to their higher density of oxygen surface defects in combination with a higher adsorption capability of RhB. This new synthetic route of size tunable ultrathin W18O49 nanomaterials will enlarge their potential applications and can be possibly used in the pyrolyzing synthesis of other metal oxide nanomaterials.
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| 2. |
- Abdollahi Sani, Negar, et al.
(författare)
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All-printed diode operating at 1.6 GHz
- 2014
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 111:33, s. 11943-11948
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Tidskriftsartikel (refereegranskat)abstract
- Printed electronics are considered for wireless electronic tags and sensors within the future Internet-of-things (IoT) concept. As a consequence of the low charge carrier mobility of present printable organic and inorganic semiconductors, the operational frequency of printed rectifiers is not high enough to enable direct communication and powering between mobile phones and printed e-tags. Here, we report an all-printed diode operating up to 1.6 GHz. The device, based on two stacked layers of Si and NbSi2 particles, is manufactured on a flexible substrate at low temperature and in ambient atmosphere. The high charge carrier mobility of the Si microparticles allows device operation to occur in the charge injection-limited regime. The asymmetry of the oxide layers in the resulting device stack leads to rectification of tunneling current. Printed diodes were combined with antennas and electrochromic displays to form an all-printed e-tag. The harvested signal from a Global System for Mobile Communications mobile phone was used to update the display. Our findings demonstrate a new communication pathway for printed electronics within IoT applications.
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| 3. |
- Ali Abbasi, Mazhar, et al.
(författare)
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The determination of valence band offset and the current transport properties of the p-NiO/n-ZnO heterojunction
- 2013
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The electron transport in the electronic devices has significant influence on the device performance, thus current transport properties determination is highly demanded for a particular device. Herein, we report the facile hydrothermal growth method based fabrication of p-NiO/n-ZnO heterojunction. The material characterization was performed by scanning electron microscopy, X-ray diffraction, transmission electron microscopy and X-ray photo electron spectroscopy. These techniques provided the good crystal quality, pure phase of p-NiO and n-ZnO nanostructures respectively. The measured valance band offset of composite nanostructure is 2.25 eV and conduction band offset was found to be 2.58 eV. The current transport properties of the fabricated p-n junction are governed by three different I-V regions. The impedance spectroscopy was used for the determination of the role of grain boundaries at the interface.
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| 4. |
- Bao, Qinye, et al.
(författare)
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Effects of ultraviolet soaking on surface electronic structures of solution processed ZnO nanoparticle films in polymer solar cells
- 2014
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry. - 2050-7488. ; 2:41, s. 17676-17682
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Tidskriftsartikel (refereegranskat)abstract
- We systematically show the effect of UV-light soaking on surface electronic structures and chemical states of solution processed ZnO nanoparticle (ZnONP) films in UHV, dry air and UV-ozone. UV exposure in UHV induces a slight decrease in work function and surface-desorption of chemisorbed oxygen, whereas UV exposure in the presence of oxygen causes an increase in work function due to oxygen atom vacancy filling in the ZnO matrix. We demonstrate that UV-light soaking in combination with vacuum or oxygen can tune the work function of the ZnONP films over a range exceeding 1 eV. Based on photovoltaic performance and diode measurements, we conclude that the oxygen atom vacancy filling occurs mainly at the surface of the ZnONP films and that the films consequently retain their n-type behavior despite a significant increase in the measured work function.
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| 5. |
- Bao, Qinye, et al.
(författare)
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Oxygen- and Water-Based Degradation in [6,6]-Phenyl-C-61-Butyric Acid Methyl Ester (PCBM) Films
- 2014
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Ingår i: Advanced Energy Materials. - : Wiley-VCH Verlag. - 1614-6832 .- 1614-6840. ; 4:6
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Tidskriftsartikel (refereegranskat)abstract
- Effects of in situ oxygen/water exposure on the energetics of [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) films are presented. For oxygen exposure, the work function is downshifted by ≈0.15 eV compared to the ideal integer charge transfer (ICT) curve for pristine PCBM, which is incompatible with significant introduction of electron trap states or p-doping. Water induces the highest occupied molecular orbital (HOMO) structure to undergo strong, irreversible modifications accompanied by a chemical interaction with PCBM.
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| 6. |
- Bao, Qinye, et al.
(författare)
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Trap-Assisted Recombination via Integer Charge Transfer States in Organic Bulk Heterojunction Photovoltaics
- 2014
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Ingår i: Advanced Functional Materials. - : Wiley-VCH Verlag. - 1616-301X .- 1616-3028. ; 24:40, s. 6309-6316
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Tidskriftsartikel (refereegranskat)abstract
- Organic photovoltaics are under intense development and significant focus has been placed on tuning the donor ionization potential and acceptor electron affinity to optimize open circuit voltage. Here, it is shown that for a series of regioregular-poly(3-hexylthiophene): fullerene bulk heterojunction (BHJ) organic photovoltaic devices with pinned electrodes, integer charge transfer states present in the dark and created as a consequence of Fermi level equilibrium at BHJ have a profound effect on open circuit voltage. The integer charge transfer state formation causes vacuum level misalignment that yields a roughly constant effective donor ionization potential to acceptor electron affinity energy difference at the donor-acceptor interface, even though there is a large variation in electron affinity for the fullerene series. The large variation in open circuit voltage for the corresponding device series instead is found to be a consequence of trap-assisted recombination via integer charge transfer states. Based on the results, novel design rules for optimizing open circuit voltage and performance of organic bulk heterojunction solar cells are proposed.
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| 7. |
- Boerrnert, Felix, et al.
(författare)
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Single-wall-carbon-nanotube/single-carbon-chain molecular junctions
- 2010
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 81:8, s. 085439-1-085439-5
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Tidskriftsartikel (refereegranskat)abstract
- Stable junctions between a single carbon chain and two single-wall carbon nanotubes were produced via coalescence of functionalized fullerenes filled into a single-wall carbon nanotube and directly imaged by in situ transmission electron microscopy. First principles quantum chemical calculations support the observed stability of such molecular junctions. They also show that short carbon chains bound to other carbon structures are cumulenes and stable semiconductors due to Peierls-like distortion. Junctions like this can be regarded as archetypical building blocks for all-carbon molecular electronics.
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| 8. |
- Braun, Slawomir, et al.
(författare)
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Fermi level equilibrium at donor-acceptor interfaces in multi-layered thin film stack of TTF and TCNQ
- 2010
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Ingår i: Organic electronics. - Amsterdam, Netherlands : Elsevier BV. - 1566-1199 .- 1878-5530. ; 11:2, s. 212-217
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Tidskriftsartikel (refereegranskat)abstract
- Organic hetero-junctions in multi-layered thin film stacks comprising alternate layers of the molecular donor-tetrathiafulvalene (TTF) and the acceptor - tetracyanoquinodimethane (TCNQ), have been studied by ultraviolet photoelectron spectroscopy ( UPS). We show that the energy level alignment at the organic-organic interfaces in the stacks depends only upon the relative energy structure of the donor and acceptor molecules, in particular, the molecular integer charge transfer (ICT) states. The observed interfacial dipoles, across the multi-layered organic stacks, correspond to the difference in energy between the positive and the negative charge transfer states of the molecules constituting the interface. Consequently, Fermi level across the multi-layer system is pinned to those states, since the energetic conditions for the charge transfer across the interface are fulfilled. Hence the energy level alignment at donor - acceptor interfaces studied can be rationalized on the basis of integer charge transfer model (ICT-model). Moreover, we present the photoelectron spectra where 0.85 eV shift of the highest occupied molecular orbital (HOMO) of TTF during formation of TCNQ over-layer is directly observed. These studies contribute to the understanding of the nature of the offset between the frontier electronic levels of the donor and acceptor components which is of high importance in the engineering of efficient organic solar cells.
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| 9. |
- Briones-Leon, Antonio, et al.
(författare)
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Orbital and spin magnetic moments of ferrocene encapsulated in metallicity sorted single-walled carbon nanotubes
- 2012
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Ingår i: Physica status solidi. B, Basic research. - : Wiley-VCH Verlag Berlin. - 0370-1972 .- 1521-3951. ; 249:12, s. 2424-2427
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Tidskriftsartikel (refereegranskat)abstract
- The nature of the electronic and local magnetic properties of ferrocene (FeCp2) filled single-walled carbon nanotubes (SWCNT) has been investigated by X-ray absorption spectroscopy (XAS) and magnetic circular dichroism (XMCD). Metallic, semiconducting, and unsorted ferrocene-filled tubes have been studied in different conditions of temperature and magnetic field. XMCD signal becomes evident with the application of a magnetic field at low temperature. We find that the molecular states of ferrocene interact with SWCNT of different metallicities. A paramagnetic behavior of encapsulated ferrocene is observed from the magnetic field dependent XMCD measurements which is consistent with theoretical predictions.
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| 10. |
- Briones-Leon, Antonio, et al.
(författare)
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Orbital and spin magnetic moments of transforming one-dimensional iron inside metallic and semiconducting carbon nanotubes
- 2013
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - : American Physical Society. - 1098-0121 .- 1550-235X. ; 87:19
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Tidskriftsartikel (refereegranskat)abstract
- The orbital and spin magnetic properties of iron inside metallic and semiconducting carbon nanotubes are studied by means of local x-ray magnetic circular dichroism (XMCD) and bulk superconducting quantum interference device (SQUID). The iron-nanotube hybrids are initially ferrocene filled single-walled carbon nanotubes (SWCNT) of different metallicities. We show that the ferrocene's molecular orbitals interact differently with the SWCNT of different metallicities with no significant XMCD response. At elevated temperatures the ferrocene molecules react with each other to form cementite nanoclusters. The XMCD at various magnetic fields reveal that the orbital and/or spin magnetic moments of the encapsulated iron are altered drastically as the transformation to the 1D clusters takes place. The orbital and spin magnetic moments are both found to be larger in filled semiconducting nanotubes than in the metallic sample. This could mean that the magnetic polarization of the encapsulated material depends on the metallicity of the tubes. From a comparison between the iron 3d magnetic moments and the bulk magnetism measured by SQUID, we conclude that the delocalized magnetisms dominate the magnetic properties of these 1D hybrid nanostructures.
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