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  • 1.
    Aarnio, Harri
    et al.
    Abo Akad University.
    Sehati, Parisa
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry.
    Braun, Slawomir
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Nyman, Mathias
    Abo Akad University.
    de Jong, Michel P
    University of Twente.
    Fahlman, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Osterbacka, Ronald
    Abo Akad University.
    Spontaneous Charge Transfer and Dipole Formation at the Interface Between P3HT and PCBM2011In: ADVANCED ENERGY MATERIALS, ISSN 1614-6832, Vol. 1, no 5, p. 792-797Article in journal (Refereed)
    Abstract [en]

    In the pursuit of developing new materials for more efficient bulk-heterojunction solar cells, the blend poly (3-hexylthiophene):[ 6,6]-phenyl-C(61)-butyric acid methyl ester (P3HT:PCBM) serves as an important model system. The success of the P3HT: PCBM blend comes from efficient charge generation and transport with low recombination. There is not, however, a good microscopic picture of what causes these, hindering the development of new material systems. In this report UV photoelectron spectroscopy measurements on both regiorandom-(rra) and regioregular-(rr) P3HT are presented, and the results are interpreted using the Integer Charge Transfer model. The results suggest that spontaneous charge transfer from P3HT to PCBM occurs after heat treatment of P3HT: PCBM blends. The resulting formation of an interfacial dipole creates an extra barrier at the interface explaining the reduced (non-)geminate recombination with increased charge generation in heat treated rr-P3HT: PCBM blends. Extensive photoinduced absorption measurements using both above-and below-bandgap excitation light are presented, in good agreement with the suggested dipole formation.

  • 2.
    Abdollahi Sani, Negar
    et al.
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Robertsson, Mats
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Cooper, Philip
    De La Rue Plc, Overton, Hampshire, UK .
    Wang, Xin
    Acreo AB, Norrköping, Sweden.
    Svensson, Magnus
    Acreo AB, Norrköping, Sweden.
    Andersson Ersman, Peter
    Acreo AB, Norrköping, Sweden.
    Norberg, Petronella
    Acreo AB, Norrköping, Sweden.
    Nilsson, Marie
    Acreo AB, Norrköping, Sweden.
    Nilsson, David
    Acreo AB, Norrköping, Sweden.
    Liu, Xianjie
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Hesselbom, Hjalmar
    Hesselbom Innovation and Development HB, Huddinge, Sweden .
    Akesso, Laurent
    De La Rue Plc, Overton, Hampshire, UK .
    Fahlman, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Crispin, Xavier
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Engquist, Isak
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Berggren, Magnus
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology. Acreo AB, Norrköping, Sweden.
    Gustafsson, Goran
    Acreo AB, Norrköping, Sweden.
    All-printed diode operating at 1.6 GHz2014In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 111, no 33, p. 11943-11948Article in journal (Refereed)
    Abstract [en]

    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.

  • 3.
    Admassie, Shimelis
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Elfwing, Anders
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Jager, Edwin
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, The Institute of Technology.
    Bao, Qinye
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Inganäs, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    A renewable biopolymer cathode with multivalent metal ions for enhanced charge storage2014In: JOURNAL OF MATERIALS CHEMISTRY A, ISSN 2050-7488, Vol. 2, no 6, p. 1974-1979Article in journal (Refereed)
    Abstract [en]

    A ternary composite supercapacitor electrode consisting of phosphomolybdic acid (HMA), a renewable biopolymer, lignin, and polypyrrole was synthesized by a simple one-step simultaneous electrochemical deposition and characterized by electrochemical methods. It was found that the addition of HMA increased the specific capacitance of the polypyrrole-lignin composite from 477 to 682 F g(-1) ( at a discharge current of 1 A g(-1)) and also significantly improved the charge storage capacity from 6(to 128 mA h g(-1).

  • 4.
    Ali Abbasi, Mazhar
    et al.
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Hussain Ibupoto, Zafar
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Liu, Xianjie
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Nur, Omer
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Willander, Magnus
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    The determination of valence band offset and the current transport properties of the p-NiO/n-ZnO heterojunction2013Manuscript (preprint) (Other academic)
    Abstract [en]

    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.

  • 5.
    Alnoor, Hatim
    et al.
    Linköping University, Department of Science and Technology. Linköping University, Faculty of Science & Engineering.
    Chey, Chan Oeurn
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Pozina, Galia
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Liu, Xianjie
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Khranovskyy, Volodymyr
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Willander, Magnus
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Nour, Omer
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Effect of precursor solutions stirring on deep level defects concentration and spatial distribution in low temperature aqueous chemical synthesis of zinc oxide nanorods2015In: AIP Advances, ISSN 2158-3226, E-ISSN 2158-3226, Vol. 5, no 8, article id 087180Article in journal (Refereed)
    Abstract [en]

    Hexagonal c-axis oriented zinc oxide (ZnO) nanorods (NRs) with 120-300 nm diameters are synthesized via the low temperature aqueous chemical route at 80 degrees C on silver-coated glass substrates. The influence of varying the precursor solutions stirring durations on the concentration and spatial distributions of deep level defects in ZnO NRs is investigated. Room temperature micro-photoluminesnce (mu-PL) spectra were collected for all samples. Cathodoluminescence (CL) spectra of the as-synthesized NRs reveal a significant change in the intensity ratio of the near band edge emission (NBE) to the deep-level emission (DLE) peaks with increasing stirring durations. This is attributed to the variation in the concentration of the oxygen-deficiency with increasing stirring durations as suggested from the X-ray photoelectron spectroscopy analysis. Spatially resolved CL spectra taken along individual NRs revealed that stirring the precursor solutions for relatively short duration (1-3 h), which likely induced high super saturation under thermodynamic equilibrium during the synthesis process, is observed to favor the formation of point defects moving towards the tip of the NRs. In contrary, stirring for longer duration (5-15 h) will induce low super saturation favoring the formation of point defects located at the bottom of the NRs. These findings demonstrate that it is possible to control the concentration and spatial distribution of deep level defects in ZnO NRs by varying the stirring durations of the precursor solutions.

  • 6.
    Alnoor, Hatim
    et al.
    Linköping University, Department of Science and Technology. Linköping University, Faculty of Science & Engineering.
    Pozina, Galia
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Khranovskyy, Volodymyr
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Liu, Xianjie
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Iandolo, Donata
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Willander, Magnus
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Nur, Omer
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Influence of ZnO seed layer precursor molar ratio on the density of interface defects in low temperature aqueous chemically synthesized ZnO nanorods/GaN light-emitting diodes2016In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 119, no 16, p. 165702-Article in journal (Refereed)
    Abstract [en]

    Low temperature aqueous chemical synthesis (LT-ACS) of zinc oxide (ZnO) nanorods (NRs) has been attracting considerable research interest due to its great potential in the development of light-emitting diodes (LEDs). The influence of the molar ratio of the zinc acetate (ZnAc): KOH as a ZnO seed layer precursor on the density of interface defects and hence the presence of non-radiative recombination centers in LT-ACS of ZnO NRs/GaN LEDs has been systematically investigated. The material quality of the as-prepared seed layer as quantitatively deduced by the X-ray photoelectron spectroscopy is found to be influenced by the molar ratio. It is revealed by spatially resolved cathodoluminescence that the seed layer molar ratio plays a significant role in the formation and the density of defects at the n-ZnO NRs/p-GaN heterostructure interface. Consequently, LED devices processed using ZnO NRs synthesized with molar ratio of 1:5M exhibit stronger yellow emission (similar to 575 nm) compared to those based on 1:1 and 1:3M ratios as measured by the electroluminescence. Furthermore, seed layer molar ratio shows a quantitative dependence of the non-radiative defect densities as deduced from light-output current characteristics analysis. These results have implications on the development of high-efficiency ZnO-based LEDs and may also be helpful in understanding the effects of the ZnO seed layer on defect-related non-radiative recombination. Published by AIP Publishing.

  • 7.
    Alnoor, Hatim
    et al.
    Linköping University, Department of Science and Technology. Linköping University, Faculty of Science & Engineering.
    Savoyant, Adrien
    Aix Marseille University, France.
    Liu, Xianjie
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Pozina, Galia
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Willander, Magnus
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Nur, Omer
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    An effective low-temperature solution synthesis of Co-doped [0001]-oriented ZnO nanorods2017In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 121, no 21, article id 215102Article in journal (Refereed)
    Abstract [en]

    We demonstrate an efficient possibility to synthesize vertically aligned pure zinc oxide (ZnO) and Co-doped ZnO nanorods (NRs) using the low-temperature aqueous chemical synthesis (90 degrees C). Two different mixing methods of the synthesis solutions were investigated for the Co-doped samples. The synthesized samples were compared to pure ZnO NRs regarding the Co incorporation and crystal quality. Electron paramagnetic resonance (EPR) measurements confirmed the substitution of Co2+ inside the ZnO NRs, giving a highly anisotropic magnetic Co2+ signal. The substitution of Zn2+ by Co2+ was observed to be combined with a drastic reduction in the core-defect (CD) signal (g similar to 1.956) which is seen in pure ZnO NRs. As revealed by the cathodoluminescence (CL), the incorporation of Co causes a slight red-shift of the UV peak position combined with an enhancement in the intensity of the defect-related yellow-orange emission compared to pure ZnO NRs. Furthermore, the EPR and the CL measurements allow a possible model of the defect configuration in the samples. It is proposed that the as-synthesized pure ZnO NRs likely contain Zn interstitial (Zn-i(+)) as CDs and oxygen vacancy (V-O) or oxygen interstitial (O-i) as surface defects. As a result, Co was found to likely occupy the Zn-i(+), leading to the observed CDs reduction and hence enhancing the crystal quality. These results open the possibility of synthesis of highly crystalline quality ZnO NRs-based diluted magnetic semiconductors using the low-temperature aqueous chemical method. Published by AIP Publishing.

  • 8.
    Andersson, Mattias
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics.
    Osikowicz, Wojciech
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry.
    Jakobsson, Fredrik L.E.
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Berggren, Magnus
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
    Lindgren, L.
    Polymer Chemistry, Department of Materials and Surface Chemistry, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden.
    Andersson, M.R.
    Polymer Chemistry, Department of Materials and Surface Chemistry, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden.
    Inganäs, Olle
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics.
    Intrinsic and extrinsic influences on the temperature dependence of mobility in conjugated polymers2008In: Organic electronics, ISSN 1566-1199, E-ISSN 1878-5530, Vol. 9, no 5, p. 569-574Article in journal (Refereed)
    Abstract [en]

    The temperature dependence of charge carrier mobility in conjugated polymers and their blends with fullerenes is investigated with different electrical methods, through field effect transistor (FET), space charge limited current (SCLC) and charge extraction (CELIV) measurements. Simple models, such as the Gaussian disorder model (GDM), are shown to accurately predict the temperature behavior, and a good correlation between the different measurement methods is obtained. Inconsistent charge carrier concentrations in the modeling are explained through intrinsic non-equilibrium effects, and are responsible for the limited applicability of existing numerical models. A severe extrinsic influence from water in FETs with a hydrophilic insulator interface is also demonstrated. The presence of water leads to a significant overestimate of the disorder in the materials from measurements close to room temperature and erratic behavior in the 150-350 K range. To circumvent this problem it is shown to be necessary to measure under ultra high vacuum (UHV) conditions. © 2008 Elsevier B.V. All rights reserved.

  • 9.
    Andersson, Peter
    et al.
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Robinson, Nathaniel D.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Berggren, Magnus
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Diodes Based on Blends of Molecular Switches and Conjugated Polymers2005In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, ISSN 0379-6779, Vol. 150, no 3, p. 217-221Article in journal (Refereed)
    Abstract [en]

    Here we report polymer diodes based on a conjugated polymer host and a dispersed molecular switch. In this case, the molecular switch is a photochromic (PC) molecule that can be reversibly switched between low and high energy gap states, triggered by exposure to ultra-violet and visible light, respectively. While dispersed inside the conjugated polymer bulk and switched to its low energy gap state, the PC molecules act as traps for holes. Solid-state blends of this PC material and conjugated polymers have been demonstrated in diodes. The state of the PC molecule controls the current density versus voltage (JV) characteristics of the resulting diode. Both poly(2-methoxy-5(2′-ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PPV) and poly(3-hexylthiophene-2,5-diyl) (P3HT) host materials have been studied. The two conjugated polymers resulted in differing JV switching characteristics. A more pronounced JV switch is observed with MEH-PPV than with P3HT. We postulate that the PC material, while switched to its low energy gap state, act as traps in both the conjugated polymers but at different trap depth energies.

  • 10.
    Andersson, Peter
    et al.
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Robinson, Nathaniel D.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Berggren, Magnus
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Switchable Charge Traps in Polymer Diodes2005In: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 17, no 14, p. 1798-1803Article in journal (Refereed)
  • 11.
    Atxabal, Ainhoa
    et al.
    CIC NanoGUNE, Spain.
    Braun, Slawomir
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Arnold, Thorsten
    Technical University of Dresden, Germany.
    Sun, Xiangnan
    National Centre Nanosci and Technology, Peoples R China.
    Parui, Subir
    CIC NanoGUNE, Spain.
    Liu, Xianjie
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Gozalvez, Cristian
    University of Basque Country UPV EHU, Spain.
    Llopis, Roger
    CIC NanoGUNE, Spain.
    Mateo-Alonso, Aurelio
    University of Basque Country UPV EHU, Spain; Basque Fdn Science, Spain.
    Casanova, Felix
    CIC NanoGUNE, Spain; Basque Fdn Science, Spain.
    Ortmann, Frank
    Technical University of Dresden, Germany.
    Fahlman, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Hueso, Luis E.
    CIC NanoGUNE, Spain; Basque Fdn Science, Spain.
    Energy Level Alignment at Metal/Solution-Processed Organic Semiconductor Interfaces2017In: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 29, no 19, article id 1606901Article in journal (Refereed)
    Abstract [en]

    Energy barriers between the metal Fermi energy and the molecular levels of organic semiconductor devoted to charge transport play a fundamental role in the performance of organic electronic devices. Typically, techniques such as electron photoemission spectroscopy, Kelvin probe measurements, and in-device hot-electron spectroscopy have been applied to study these interfacial energy barriers. However, so far there has not been any direct method available for the determination of energy barriers at metal interfaces with n-type polymeric semiconductors. This study measures and compares metal/solution-processed electron-transporting polymer interface energy barriers by in-device hot-electron spectroscopy and ultraviolet photoemission spectroscopy. It not only demonstrates in-device hot-electron spectroscopy as a direct and reliable technique for these studies but also brings it closer to technological applications by working ex situ under ambient conditions. Moreover, this study determines that the contamination layer coming from air exposure does not play any significant role on the energy barrier alignment for charge transport. The theoretical model developed for this work confirms all the experimental observations.

  • 12.
    Bantikassegn, W.
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, Faculty of Science & Engineering.
    Dannetun, Per
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Inganäs, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, Faculty of Science & Engineering.
    Salaneck, William R.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
    Absence of Schottky barrier formation in junctions of Al and polypyrrole-polyelectrolyte polymer complexes1993In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 224, no 2, p. 232-236Article in journal (Refereed)
    Abstract [en]

    Thin films of conducting polypyrrole doped with large polymeric anions of polystyrene-sulphonate are electrochemically prepared to study the metal/polymer junctions. Aluminium and gold contacts are vacuum deposited to form metal/polymer/gold sandwich structures for current-voltage characterization. Photoelectron spectroscopy, using UV and X-ray photons, is carried out to investigate the possible causes of current limitation in the Al/PPy(PSS) junction.

  • 13.
    Bao, Qinye
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Interface Phenomena in Organic Electronics2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Organic electronics based on organic semiconductors offer tremendous advantages compared to traditional inorganic counterparts such as low temperature processing, light weight, low manufacturing cost, high throughput and mechanical flexibility. Many key electronic processes in organic electronic devices, e.g. charge injection/extraction, charge recombination and exciton dissociation, occur at interfaces, significantly controlling performance and function. Understanding/modeling the interface energetics at organic-electrode/organic-organic heterojunctions is one of the crucial issues for organic electronic technologies to provide a route for improving device efficiency, which is the aim of the research presented in this thesis.

    Integer charge transfer (ICT) states pre-existed in the dark and created as a consequence of Fermi level equilibrium at donor-acceptor interface have a profound effect on open circuit voltage in organic bulk heterojunction photovoltaics. ICT 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.

    Doping and insertion of interlayer are two established methods for enhancing charge injection/extraction properties at organic-electrode interface. By studying the energy level alignment behavior at low to intermediate doping levels for molecule-doped conjugated polymer/electrode interfaces, we deduce that two combined processes govern the interface energetics: (i) equilibration of the Fermi level due to oxidation (or reduction) of polymer sites at the interface as per the ICT model and (ii) a double dipole step induced by image charge from the dopant-polymer charge transfer complex that causes a shift of the work function. Such behavior is expected to hold in general for low to intermediate level doped organic semiconductor systems. The unified model is further extended to be suitable for conjugated electrolyte/electrode  interfaces, revealing the design rules for achieving the smallest charge injection/extraction barrier for both thin tunneling and thick charge transporting conjugated electrolyte interlayers.

    To probe into the energy level spatial extension at interfaces, we employ the original approach of building and characterizing multilayers composed of a well-defined number of polymer monolayers with the Langmuir-Shäfer method to control polymer film uniformity and thicknesses, avoiding the problems associated with spin-coating ultrathin films. The disordered/amorphous films feature smaller, and in fact negligible, energy level bending compared to the more well-ordered films, in contradiction with existing models. It is found that that energy level bending depends on the ICT state distribution rather than the density of states of the neutral polymer chains in relation to the Fermi energy, thus taking into account the Coulomb energy associated with charging the polymer chain and transferring a charge across the interface. Based on this work, a general model for energy level bending in absence of significant doping of conjugated polymer films is proposed.

    Organic semiconductors are sensitive to ambient atmosphere that can influence the energetics. The degradation effects of common PCBM film induced by oxygen and water are found to be completely different. Upon exposure to oxygen, the work function is down-shifted by ~ 0.15 eV compared to the ICT curve of the pristine PCBM film, originating from the weak interaction between the fullerene part of PCBM and oxygen, and this can be reversed by thermal treatment in vacuum. The down-shift in energetics will cause a loss in open circuit voltage at electrode interface, but aids free charge generation at donor-acceptor interface. Upon exposure to water, there is irreversible extensive broadening and bleaching of the valence electronic structure features as well as a substantial decrease of work function and ionization potential, severely degrading the transport properties.

    Overall, the research results in this thesis thus give a deeper understanding of interface phenomena in organic electronics, especially regard to organic solar cells, aimed to further improve the device operation efficiency and lifetime.

    List of papers
    1. Trap-Assisted Recombination via Integer Charge Transfer States in Organic Bulk Heterojunction Photovoltaics
    Open this publication in new window or tab >>Trap-Assisted Recombination via Integer Charge Transfer States in Organic Bulk Heterojunction Photovoltaics
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    2014 (English)In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 24, no 40, p. 6309-6316Article in journal (Refereed) Published
    Abstract [en]

    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.

    Place, publisher, year, edition, pages
    Wiley-VCH Verlag, 2014
    National Category
    Physical Sciences Chemical Sciences
    Identifiers
    urn:nbn:se:liu:diva-112635 (URN)10.1002/adfm.201401513 (DOI)000344249900007 ()
    Note

    Funding Agencies|Swedish Energy Agency [34142-1]; European Commission [287594]; Academy of Finland [137093]; Swedish Research Council Linnaeus grant LiLi-NFM; Waldemar von Frenckell Foundation; Swedish Cultural Foundation in Finland; Advanced Functional Materials Center at Linkoping University

    Available from: 2014-12-08 Created: 2014-12-05 Last updated: 2017-12-05
    2. Oxygen- and Water-Based Degradation in [6,6]-Phenyl-C-61-Butyric Acid Methyl Ester (PCBM) Films
    Open this publication in new window or tab >>Oxygen- and Water-Based Degradation in [6,6]-Phenyl-C-61-Butyric Acid Methyl Ester (PCBM) Films
    2014 (English)In: ADVANCED ENERGY MATERIALS, ISSN 1614-6832, Vol. 4, no 6Article in journal (Refereed) Published
    Abstract [en]

    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.

    Place, publisher, year, edition, pages
    Wiley-VCH Verlag, 2014
    Keywords
    electronic structure; integer charge transfer; oxygen; water exposure; degradation; photoelectron spectroscopy
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-106975 (URN)10.1002/aenm.201301272 (DOI)000334790000005 ()
    Available from: 2014-06-04 Created: 2014-06-02 Last updated: 2015-06-05
    3. The energetics of the semiconducting polymer-electrode interface for solution-processed electronics
    Open this publication in new window or tab >>The energetics of the semiconducting polymer-electrode interface for solution-processed electronics
    Show others...
    (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    The semiconductor-electrode interface impacts the function and the performance of (opto-)electronic devices. For printed organic electronics the electrode surface is not atomically clean leading to weakly interacting interfaces. As a result, solution-processed organic ultra-thin films on electrodes typically form islands due to de-wetting. It has therefore been utterly difficult to achieve homogenous ultrathin conjugated polymer films. This has made the investigation of the correct energetics of the conjugated polymer-electrode interface impossible. Also, this has hampered the development of devices including ultra-thin conjugated polymer layers. Here, we report Langmuir-Shäfer-manufactured homogenous mono- and multilayers of semiconducting polymers on metal electrodes and track the energy level bending using photoelectron spectroscopy. The amorphous films display an abrupt energy level bending that does not extend beyond the first monolayer. Our findings provide new insights of the energetics of the polymer-electrode interface and opens up for new high-performing devices based on ultra-thin semiconducting polymers.

    Keywords
    Energy level bending, conjugated polymer, Langmuir-Shäfer, organic electronics
    National Category
    Physical Sciences Electrical Engineering, Electronic Engineering, Information Engineering
    Identifiers
    urn:nbn:se:liu:diva-118913 (URN)
    Available from: 2015-06-05 Created: 2015-06-05 Last updated: 2017-02-03
    4. Energetics at Doped Conjugated Polymer/Electrode Interfaces
    Open this publication in new window or tab >>Energetics at Doped Conjugated Polymer/Electrode Interfaces
    Show others...
    2015 (English)In: ADVANCED MATERIALS INTERFACES, ISSN 2196-7350, Vol. 2, no 2Article in journal (Refereed) Published
    Abstract [en]

    n/a

    Place, publisher, year, edition, pages
    Wiley: 12 months, 2015
    National Category
    Physical Sciences Biological Sciences
    Identifiers
    urn:nbn:se:liu:diva-114420 (URN)10.1002/admi.201400403 (DOI)000348287700008 ()
    Note

    Funding Agencies|EU [287594]; Swedish Research Council Linnaeus grant LiLi-NFM; Swedish Research Council [2013-4022]; Goran Gustafsson Foundation for Research in Natural Sciences and Medicine; Advanced Functional Materials Center at Linkoping University

    Available from: 2015-03-02 Created: 2015-02-20 Last updated: 2015-06-05
    5. Regular Energetics at Conjugated Electrolyte/Electrode Modifier for Organic Electronics and Their Implications of Design Rules
    Open this publication in new window or tab >>Regular Energetics at Conjugated Electrolyte/Electrode Modifier for Organic Electronics and Their Implications of Design Rules
    Show others...
    2015 (English)In: Advanced Materials Interfaces, ISSN 2196-7350, Vol. 2, no 12, p. 1-6, article id 1500204Article in journal (Refereed) Published
    Abstract [en]

    Regular energetics at a conjugated electrolyte/electrode modifier are found and controlled by equilibration of the Fermi level and an additional interface double dipole step induced by ionic functionality. Based on the results, design rules for conjugated electrolyte/electrode modifiers to achieve the smallest charge injection/exaction barrier and break through the current thickness limitation are proposed.

    Place, publisher, year, edition, pages
    John Wiley & Sons, 2015
    Keywords
    Conjugated electrolyte, electrode modifier, energetics, organic electronics
    National Category
    Physical Sciences Electrical Engineering, Electronic Engineering, Information Engineering
    Identifiers
    urn:nbn:se:liu:diva-118917 (URN)10.1002/admi.201500204 (DOI)000360057500011 ()
    Note

    On the day of the defence date the status of this article was Manuscript.

    Available from: 2015-06-05 Created: 2015-06-05 Last updated: 2017-03-16Bibliographically approved
    6. Effects of ultraviolet soaking on surface electronic structures of solution processed ZnO nanoparticle films in polymer solar cells
    Open this publication in new window or tab >>Effects of ultraviolet soaking on surface electronic structures of solution processed ZnO nanoparticle films in polymer solar cells
    Show others...
    2014 (English)In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 2, no 41, p. 17676-17682Article in journal (Refereed) Published
    Abstract [en]

    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.

    Place, publisher, year, edition, pages
    Royal Society of Chemistry, 2014
    National Category
    Physical Sciences Biological Sciences
    Identifiers
    urn:nbn:se:liu:diva-112033 (URN)10.1039/c4ta02695k (DOI)000342763300057 ()
    Note

    Funding Agencies|EU [287594]; Swedish Research Council Linnaeus grant LiLi-NFM

    Available from: 2014-11-17 Created: 2014-11-13 Last updated: 2017-12-05
  • 14.
    Bao, Qinye
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Fabiano, Simone
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Andersson, Mattias
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Braun, Slawomir
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Sun, Zhengyi
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Crispin, Xavier
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Berggren, Magnus
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Liu, Xianjie
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Fahlman, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Energy Level Bending in Ultrathin Polymer Layers Obtained through Langmuir-Shafer Deposition2016In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 26, no 7, p. 1077-1084Article in journal (Refereed)
    Abstract [en]

    The semiconductor-electrode interface impacts the function and the performance of (opto) electronic devices. For printed organic electronics the electrode surface is not atomically clean leading to weakly interacting interfaces. As a result, solution-processed organic ultrathin films on electrodes typically form islands due to dewetting. It has therefore been utterly difficult to achieve homogenous ultrathin conjugated polymer films. This has made the investigation of the correct energetics of the conjugated polymer-electrode interface impossible. Also, this has hampered the development of devices including ultrathin conjugated polymer layers. Here, LangmuirShafer-manufactured homogenous mono-and multilayers of semiconducting polymers on metal electrodes are reported and the energy level bending using photoelectron spectroscopy is tracked. The amorphous films display an abrupt energy level bending that does not extend beyond the first monolayer. These findings provide new insights of the energetics of the polymer-electrode interface and opens up for new high-performing devices based on ultrathin semiconducting polymers.

  • 15.
    Bao, Qinye
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Fabiano, Simone
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Andersson, Mattias
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Braun, Slawomir
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Sun, Zhengyi
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Crispin, Xavier
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Berggren, Magnus
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Liu, Xianjie
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Fahlman, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    The energetics of the semiconducting polymer-electrode interface for solution-processed electronicsManuscript (preprint) (Other academic)
    Abstract [en]

    The semiconductor-electrode interface impacts the function and the performance of (opto-)electronic devices. For printed organic electronics the electrode surface is not atomically clean leading to weakly interacting interfaces. As a result, solution-processed organic ultra-thin films on electrodes typically form islands due to de-wetting. It has therefore been utterly difficult to achieve homogenous ultrathin conjugated polymer films. This has made the investigation of the correct energetics of the conjugated polymer-electrode interface impossible. Also, this has hampered the development of devices including ultra-thin conjugated polymer layers. Here, we report Langmuir-Shäfer-manufactured homogenous mono- and multilayers of semiconducting polymers on metal electrodes and track the energy level bending using photoelectron spectroscopy. The amorphous films display an abrupt energy level bending that does not extend beyond the first monolayer. Our findings provide new insights of the energetics of the polymer-electrode interface and opens up for new high-performing devices based on ultra-thin semiconducting polymers.

  • 16.
    Bao, Qinye
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Liu, Xianjie
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Braun, Slawomir
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Fahlman, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Oxygen- and Water-Based Degradation in [6,6]-Phenyl-C-61-Butyric Acid Methyl Ester (PCBM) Films2014In: ADVANCED ENERGY MATERIALS, ISSN 1614-6832, Vol. 4, no 6Article in journal (Refereed)
    Abstract [en]

    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.

  • 17.
    Bao, Qinye
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Liu, Xianjie
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Braun, Slawomir
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Fahlman, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Energetics at Doped Conjugated Polymer/Electrode Interfaces2015In: ADVANCED MATERIALS INTERFACES, ISSN 2196-7350, Vol. 2, no 2Article in journal (Refereed)
    Abstract [en]

    n/a

  • 18.
    Bao, Qinye
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering. East China Normal University, Peoples R China.
    Liu, Xianjie
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Braun, Slawomir
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Li, Yanqing
    Soochow University, Peoples R China.
    Tang, Jianxin
    Soochow University, Peoples R China.
    Duan, Chungang
    East China Normal University, Peoples R China.
    Fahlman, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Energy Level Alignment of N-Doping Fullerenes and Fullerene Derivatives Using Air-Stable Dopant2017In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 9, no 40, p. 35476-35482Article in journal (Refereed)
    Abstract [en]

    Doping has been proved to be one of the powerful technologies to achieve significant improvement in the performance of organic electronic devices. Herein, we systematically map out the interface properties of solution-processed air-stable n-type (4(1,3-dimethyl-2,3-dihydro-1H-benzoimidazol-2-yl)phenyl) doping fullerenes and fullerene derivatives and establish a universal energy level alignment scheme for this class of n-doped system. At low doping levels at which the charge-transfer doping induces mainly bound charges, the energy level alignment of the n-doping organic semiconductor can be described by combining integer charger transfer-induced shifts with a so-called double-dipole step. At high doping levels, significant densities of free charges are generated and the charge flows between the organic film and the conducting electrodes equilibrating the Fermi level in a classic "depletion layer" scheme. Moreover, we demonstrate that the model holds for both n- and p-doping of pi-backbone molecules and polymers. With the results, we provide wide guidance for identifying the application of the current organic n-type doping technology in organic electronics.

    The full text will be freely available from 2018-09-20 15:19
  • 19.
    Bao, Qinye
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering. East China Normal Univ, Peoples R China; Soochow Univ, Peoples R China.
    Liu, Xianjie
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Braun, Slawomir
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Yang, Jianming
    East China Normal Univ, Peoples R China.
    Li, Yanqing
    Soochow Univ, Peoples R China.
    Tang, Jianxin
    Soochow Univ, Peoples R China.
    Duan, Chungang
    East China Normal Univ, Peoples R China.
    Fahlman, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    The Effect of Oxygen Uptake on Charge Injection Barriers in Conjugated Polymer Films2018In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 10, no 7, p. 6491-6497Article in journal (Refereed)
    Abstract [en]

    The energy offset between the electrode Fermi level and organic semiconductor transport levels is a key parameter controlling the charge injection barrier and hence efficiency of organic electronic devices. Here, we systematically explore the effect of in situ oxygen exposure on energetics in n-type conjugated polymer P(NDI2OD-T2) films. The analysis reveals that an interfacial potential step is introduced for a series of P(NDI2OD-T2) electrode contacts, causing a nearly constant downshift of the vacuum level, while the ionization energies versus vacuum level remain constant. These findings are attributed to the establishment of a so-called double-dipole step via motion of charged molecules and will modify the charge injection barriers at electrode contact. We further demonstrate that the same behavior occurs when oxygen interacts with p-type polymer TQ1 films, indicating it is possible to be a universal effect for organic semiconductOrs.

    The full text will be freely available from 2019-01-29 12:54
  • 20.
    Bao, Qinye
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Liu, Xianjie
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Wang, Ergang
    Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Göteborg, Sweden.
    Fang, Junfeng
    Ningbo Institute of Material Technology and Engineering, Chinese Academy of Science, Ningbo, PR China.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering. State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou, P. R. China.
    Braun, Slawomirslama19
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Fahlman, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Regular Energetics at Conjugated Electrolyte/Electrode Modifier for Organic Electronics and Their Implications of Design Rules2015In: Advanced Materials Interfaces, ISSN 2196-7350, Vol. 2, no 12, p. 1-6, article id 1500204Article in journal (Refereed)
    Abstract [en]

    Regular energetics at a conjugated electrolyte/electrode modifier are found and controlled by equilibration of the Fermi level and an additional interface double dipole step induced by ionic functionality. Based on the results, design rules for conjugated electrolyte/electrode modifiers to achieve the smallest charge injection/exaction barrier and break through the current thickness limitation are proposed.

  • 21.
    Bao, Qinye
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Liu, Xianjie
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Xia, Yuxin
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Kauffmann, Louis-Dominique
    GenesInk, France.
    Margeat, Olivier
    Aix Marseille University, France.
    Ackermann, Jorg
    Aix Marseille University, France.
    Fahlman, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Effects of ultraviolet soaking on surface electronic structures of solution processed ZnO nanoparticle films in polymer solar cells2014In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 2, no 41, p. 17676-17682Article in journal (Refereed)
    Abstract [en]

    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.

  • 22.
    Bao, Qinye
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Sandberg, Oskar
    Abo Akad University, Finland.
    Dagnelund, Daniel
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Sanden, Simon
    Abo Akad University, Finland.
    Braun, Slawomir
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Aarnio, Harri
    Abo Akad University, Finland.
    Liu, Xianjie
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Osterbacka, Ronald
    Abo Akad University, Finland.
    Fahlman, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Trap-Assisted Recombination via Integer Charge Transfer States in Organic Bulk Heterojunction Photovoltaics2014In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 24, no 40, p. 6309-6316Article in journal (Refereed)
    Abstract [en]

    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.

  • 23.
    Ben Dkhil, Sadok
    et al.
    Aix Marseille University, France.
    Duche, David
    University of Toulon and Var, France.
    Gaceur, Meriem
    Aix Marseille University, France.
    Thakur, Anil K.
    Aix Marseille University, France.
    Bencheikh Aboura, Fatima
    University of Toulon and Var, France.
    Escoubas, Ludovic
    University of Toulon and Var, France.
    Simon, Jean-Jacques
    University of Toulon and Var, France.
    Guerrero, Antonio
    University of Jaume 1, Spain.
    Bisquert, Juan
    University of Jaume 1, Spain; King Abdulaziz University, Saudi Arabia.
    Garcia-Belmonte, Germa
    University of Jaume 1, Spain.
    Bao, Qinye
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Fahlman, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Videlot-Ackermann, Christine
    Aix Marseille University, France.
    Margeat, Olivier
    Aix Marseille University, France.
    Ackermann, Joerg
    Aix Marseille University, France.
    Interplay of Optical, Morphological, and Electronic Effects of ZnO Optical Spacers in Highly Efficient Polymer Solar Cells2014In: ADVANCED ENERGY MATERIALS, ISSN 1614-6832, Vol. 4, no 18, p. 1400805-Article in journal (Refereed)
    Abstract [en]

    Optical spacers based on metal oxide layers have been intensively studied in poly(3-hexylthiophene) (P3HT) based polymer solar cells for optimizing light distribution inside the device, but to date, the potential of such a metal oxide spacer to improve the electronic performance of the polymer solar cells simultaneously has not yet be investigated. Here, a detailed study of performance improvement in high efficient polymer solar cells by insertion of solution-processed ZnO optical spacer using ethanolamine surface modification is reported. Insertion of the modified ZnO optical spacer strongly improves the performance of polymer solar cells even in the absence of an increase in light absorption. The electric improvements of the device are related to improved electron extraction, reduced contact barrier, and reduced recombination at the cathode. Importantly, it is shown for the first time that the morphology of optical spacer layer is a crucial parameter to obtain highly efficient solar cells in normal device structures. By optimizing optical spacer effects, contact resistance, and morphology of ZnO optical spacers, poly[[4,8-bis[(2-ethylhexyl) oxy] benzo[1,2-b: 4,5-b] dithiophene-2,6diyl] [3-fluoro-2-[(2-ethylhexyl) carbonyl] thieno[3,4-b] thiophenediyl]] (PTB7):[6,6]-phenyl-C71-butyric acid (PC70 BM) bulk heterojunction solar cells with conversion efficiency of 7.6% are obtained in normal device structures with all-solution-processed interlayers.

  • 24.
    Ben Dkhil, Sadok
    et al.
    Aix Marseille University, France.
    Gaceur, Meriem
    Aix Marseille University, France.
    Karim Diallo, Abdou
    Aix Marseille University, France.
    Didane, Yahia
    Aix Marseille University, France.
    Liu, Xianjie
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Fahlman, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Margeat, Olivier
    Aix Marseille University, France.
    Ackermann, Jorg
    Aix Marseille University, France.
    Videlot-Ackermann, Christine
    Aix Marseille University, France.
    Reduction of Charge-Carrier Recombination at ZnO Polymer Blend Interfaces in PTB7-Based Bulk Heterojunction Solar Cells Using Regular Device Structure: Impact of ZnO Nanoparticle Size and Surfactant2017In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 9, no 20, p. 17257-17265Article in journal (Refereed)
    Abstract [en]

    Cathode interfacial layers, also called electron extraction layers (EELs), based on zinc oxide (ZnO) have been studied in polymer-blend solar cells toward optimization of the opto-electric properties. Bulk heterojunction solar cells based on poly( {4, 8-bis [(2- ethylhexyl) oxy]b enzo [1,2- b :4,5-b dithiophene-2,6-diyl}{3-fluoro-2-[(2-ethylhexyl)carbonyl]- thieno[3,4-b]thiophenediy1}) (PTB7) and [6,6]-phenyl-C71-butyric acid methyl ester (PC70BM) were realized in regular structure with all-solution-processed interlayers. A pair of commercially available surfactants, ethanolamine (EA) and ethylene glycol (EG), were used to modify the surface of ZnO nanoparticles (NPs) in alcohol-based dispersion. The influence of ZnO particle size was also studied by preparing dispersions of two NP diameters (6 versus 11 nm). Here, we show that performance improvement can be obtained in polymer solar cells via the use of solution-processed ZnO EELs based on surface-modified nanoparticles. By the optimizing of the ZnO dispersion, surfactant ratio, and the resulting morphology of EELs, PTB7/PC70BM solar cells with a power-conversion efficiency of 8.2% could be obtained using small sized EG-modified ZnO NPs that allow the clear enhancement of the performance of solution processed photovoltaic devices compared to state-of-the-art ZnO-based cathode layers.

  • 25.
    Bengtsson, Katarina
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Additive manufacturing methods and materials for electrokinetic systems2015Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Fabrication of miniaturized devices is usually time-consuming, costly, and the materials commonly used limit the structures that are possible to create. The techniques most often used to make microsystems involve multiple steps, where each step takes considerable time, and if only a few systems are to be made, the price per device becomes excessive. This thesis describes how a simple syringebased 3D-printer, in combination with an appropriate choice of materials, can reduce the delay between design and prototype and simplify fabrication of microsystems. This thesis suggest two types of materials that we propose be used in combination with 3D-printing to further develop microsystems for biology and biochemistry.

    Analytical applications in biology and biochemistry often contain electrodes, such as in gel electrophoresis. Faradaic (electrochemical) reactions have to occur at the metal electrodes to allow electron-to-ion transduction through an electrolyte-based system to drive a current when a potential is applied to the electrodes in an electrolyte-based system. These electrochemical reactions at the electrodes, such as water electrolysis, are usually problematic when miniaturizing devices and analytical systems. An alternative to metal electrodes can be electrochemicallyactive conducting polymers, e.g. poly(3,4-ethylenedioxythiophene) (PEDOT), which can be used to reduce electrolysis when driving a current through water-based systems. Paper 1 describes gel electrophoresis where the platinum electrodes were replaced with the conductive polymer PEDOT, without affecting the separation.

    Manufacturing and prototyping of microsystems can be simplified by using 3Dprinting in combination with a sacrificial material. A sacrificial template material can further simplify bottom-up manufacturing of more complicated forms such as protruding and overhanging structures. We showed in paper 2 that polyethylene glycol (PEG), in combination with a carbonate-based plasticizer, functions well as a 3D-printable sacrificial template material. PEG2000 with between 20 wt% and 30 wt% ethylene carbonate or propylene carbonate has properties advantageous for 3D-printing, such as shear-thinning rheology, mechanical and chemical stability, and easy dissolution in water.

    List of papers
    1. Conducting Polymer Electrodes for Gel Electrophoresis
    Open this publication in new window or tab >>Conducting Polymer Electrodes for Gel Electrophoresis
    2014 (English)In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 9, no 2, p. 0089416-Article in journal (Refereed) Published
    Abstract [en]

    In nearly all cases, electrophoresis in gels is driven via the electrolysis of water at the electrodes, where the process consumes water and produces electrochemical by-products. We have previously demonstrated that p-conjugated polymers such as poly(3,4-ethylenedioxythiophene) (PEDOT) can be placed between traditional metal electrodes and an electrolyte to mitigate electrolysis in liquid (capillary electroosmosis/electrophoresis) systems. In this report, we extend our previous result to gel electrophoresis, and show that electrodes containing PEDOT can be used with a commercial polyacrylamide gel electrophoresis system with minimal impact to the resulting gel image or the ionic transport measured during a separation.

    Place, publisher, year, edition, pages
    Public Library of Science, 2014
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-105901 (URN)10.1371/journal.pone.0089416 (DOI)000331711900141 ()
    Available from: 2014-04-14 Created: 2014-04-12 Last updated: 2017-12-05Bibliographically approved
    2. Plasticized polyethylene glycol as sacrificial support and template material for syringe-based 3D-printing
    Open this publication in new window or tab >>Plasticized polyethylene glycol as sacrificial support and template material for syringe-based 3D-printing
    2015 (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    Syringe-based 3D-printing is a powerful additive manufacturing method for fabricating short runs (small volumes) of components from multiple materials with a wide range of viscosities. However, objects that are hollow or not in complete contact with the printer’s stage are difficult to fabricate. Using a sacrificial template as a supporting layer enables bottom-up construction of complex structures. Template materials based on polyethylene glycol (PEG) plasticized with organic carbonates to tune their rheological (shear-thinning) and thermal (crystallization) properties have been evaluated, including results from rheometry, differential scanning calorimetry, dissolution rate, chemical compatibility with  polydimethylsiloxane (PDMS), and general functionality in a syringe-based 3D-printer. A family of such blends yields material that is easily printed, is stable over time, is soluble in water, and can support other materials and larger structures without collapsing. These mixtures are proposed for use with other extrudable or mouldable materials to enable 3D-printed devices with complex unsupported geometries.

    Keywords
    3D-Printing, polyethylene glycol, organic carbonates, sacrificial template, extrusion
    National Category
    Physical Sciences Physical Chemistry
    Identifiers
    urn:nbn:se:liu:diva-121250 (URN)
    Available from: 2015-09-10 Created: 2015-09-10 Last updated: 2015-09-10Bibliographically approved
  • 26.
    Bengtsson, Katarina
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Electrokinetic devices from polymeric materials2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    There are multiple applications for polymers: our bodies are built of them, plastic bags and boxes used for storage are composed of them, as are the shells for electronics, TVs, computers, clothes etc. Many polymers are cheap, and easy to manufacture and process which make them suitable for disposable systems. The choice of polymer to construct an object will therefore highly influence the properties of the object itself. The focus of this thesis is the application of commonly used polymers to solve some challenges regarding integration of electrodes in electrokinetic devices and 3D printing.

    The first part of this thesis regards electrokinetic systems and the electrodes’ impact on the system. Electrokinetic systems require Faradaic (electrochemical) reactions at the electrodes to maintain an electric field in an electrolyte. The electrochemical reactions at the electrodes allow electron-to-ion transduction at the electrode-electrolyte interface, necessary to drive a current at the applied potential through the system, which thereby either cause flow (electroosmosis) or separation (electrophoresis). These electrochemical reactions at the electrodes, such as water electrolysis, are usually problematic in analytical systems and systems applied in biology. One solution to reduce the impact of water electrolysis is by replacing metal electrodes with electrochemically active polymers, e.g. poly(3,4-ethylenedioxythiophene) (PEDOT). Paper 1 demonstrates that PEDOT electrodes can replace platinum electrodes in a gel electrophoretic setup. Paper 2 reports an all-plastic, planar, flexible electroosmotic pump which continuously transports water from one side to the other using potentials as low as 0.3 V. This electroosmotic pump was further developed in paper 3, where it was made into a compact and modular setup, compatible with commercial microfluidic devices. We demonstrated that the pump could maintain an alternating flow for at least 96 h, with a sufficient flow of cell medium to keep cells alive for the same period of time.

    The second part of the thesis describes the use of 3D printers for manufacturing prototypes and the material requirements for 3D printing. Protruding and over-hanging structures are more challenging to print using a 3D printer and usually require supporting material during the printing process. In paper 4, we showed that polyethylene glycol (PEG), in combination with a carbonate-based plasticizer, functions well as a 3D printable sacrificial template material. PEG2000 with between 20 and 30 wt% dimethyl carbonate or propylene carbonate have good shear-thinning rheology, mechanical and chemical stability, and water solubility, which are advantageous for a supporting material used in 3D printing.

    The advances presented in this thesis have solved some of the challenges regarding electrokinetic systems and prototype manufacturing. Hopefully this will contribute to the development of robust, disposable, low-cost, and autonomous electrokinetic devices.

    List of papers
    1. Conducting Polymer Electrodes for Gel Electrophoresis
    Open this publication in new window or tab >>Conducting Polymer Electrodes for Gel Electrophoresis
    2014 (English)In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 9, no 2, p. 0089416-Article in journal (Refereed) Published
    Abstract [en]

    In nearly all cases, electrophoresis in gels is driven via the electrolysis of water at the electrodes, where the process consumes water and produces electrochemical by-products. We have previously demonstrated that p-conjugated polymers such as poly(3,4-ethylenedioxythiophene) (PEDOT) can be placed between traditional metal electrodes and an electrolyte to mitigate electrolysis in liquid (capillary electroosmosis/electrophoresis) systems. In this report, we extend our previous result to gel electrophoresis, and show that electrodes containing PEDOT can be used with a commercial polyacrylamide gel electrophoresis system with minimal impact to the resulting gel image or the ionic transport measured during a separation.

    Place, publisher, year, edition, pages
    Public Library of Science, 2014
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-105901 (URN)10.1371/journal.pone.0089416 (DOI)000331711900141 ()
    Available from: 2014-04-14 Created: 2014-04-12 Last updated: 2017-12-05Bibliographically approved
  • 27.
    Bengtsson, Katarina
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering. LunaMicro AB, Linköping, Sweden.
    Christoffersson, Jonas
    Linköping University, Department of Physics, Chemistry and Biology, Biotechnology. Linköping University, Faculty of Science & Engineering.
    Mandenius, Carl-Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Biotechnology. Linköping University, Faculty of Science & Engineering.
    Robinson, Nathaniel D
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering. LunaMicro AB, Linköping, Sweden.
    A clip-on electroosmotic pump for oscillating flow in microfluidic cell culture devices2018In: Microfluidics and Nanofluidics, ISSN 1613-4982, E-ISSN 1613-4990, Vol. 22, no 3, article id 27Article in journal (Refereed)
    Abstract [en]

    Recent advances in microfluidic devices put a high demand on small, robust and reliable pumps suitable for high-throughput applications. Here we demonstrate a compact, low-cost, directly attachable (clip-on) electroosmotic pump that couples with standard Luer connectors on a microfluidic device. The pump is easy to make and consists of a porous polycarbonate membrane and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) electrodes. The soft electrode and membrane materials make it possible to incorporate the pump into a standard syringe filter holder, which in turn can be attached to commercial chips. The pump is less than half the size of the microscope slide used for many commercial lab-on-a-chip devices, meaning that these pumps can be used to control fluid flow in individual reactors in highly parallelized chemistry and biology experiments. Flow rates at various electric current and device dimensions are reported. We demonstrate the feasibility and safety of the pump for biological experiments by exposing endothelial cells to oscillating shear stress (up to 5 dyn/cm2) and by controlling the movement of both micro- and macroparticles, generating steady or oscillatory flow rates up to ± 400 μL/min.

  • 28.
    Bengtsson, Katarina
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Mindemark, Jonas
    Department of Chemistry – Ångström Laboratory, Uppsala University, Uppsala, Sweden.
    Brandell, Daniel
    Department of Chemistry – Ångström Laboratory, Uppsala University, Uppsala, Sweden.
    Robinson, Nathaniel D
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Plasticized polyethylene glycol as sacrificial support and template material for syringe-based 3D-printing2015Manuscript (preprint) (Other academic)
    Abstract [en]

    Syringe-based 3D-printing is a powerful additive manufacturing method for fabricating short runs (small volumes) of components from multiple materials with a wide range of viscosities. However, objects that are hollow or not in complete contact with the printer’s stage are difficult to fabricate. Using a sacrificial template as a supporting layer enables bottom-up construction of complex structures. Template materials based on polyethylene glycol (PEG) plasticized with organic carbonates to tune their rheological (shear-thinning) and thermal (crystallization) properties have been evaluated, including results from rheometry, differential scanning calorimetry, dissolution rate, chemical compatibility with  polydimethylsiloxane (PDMS), and general functionality in a syringe-based 3D-printer. A family of such blends yields material that is easily printed, is stable over time, is soluble in water, and can support other materials and larger structures without collapsing. These mixtures are proposed for use with other extrudable or mouldable materials to enable 3D-printed devices with complex unsupported geometries.

  • 29.
    Bengtsson, Katarina
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Nilsson, Sara
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Robinson, Nathaniel D
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Conducting Polymer Electrodes for Gel Electrophoresis2014In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 9, no 2, p. 0089416-Article in journal (Refereed)
    Abstract [en]

    In nearly all cases, electrophoresis in gels is driven via the electrolysis of water at the electrodes, where the process consumes water and produces electrochemical by-products. We have previously demonstrated that p-conjugated polymers such as poly(3,4-ethylenedioxythiophene) (PEDOT) can be placed between traditional metal electrodes and an electrolyte to mitigate electrolysis in liquid (capillary electroosmosis/electrophoresis) systems. In this report, we extend our previous result to gel electrophoresis, and show that electrodes containing PEDOT can be used with a commercial polyacrylamide gel electrophoresis system with minimal impact to the resulting gel image or the ionic transport measured during a separation.

  • 30.
    Bengtsson, Katarina
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering. LunaMicro AB, Linkoping, Sweden.
    Robinson, Nathaniel D
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering. LunaMicro AB, Linkoping, Sweden.
    A large-area, all-plastic, flexible electroosmotic pump2017In: Microfluidics and Nanofluidics, ISSN 1613-4982, E-ISSN 1613-4990, Vol. 21, no 12, article id 178Article in journal (Refereed)
    Abstract [en]

    A large-area, fabric-like pump would potentially have applications, for example, in controlling water transport through a garment, such as a rain jacket, regardless of the external temperature and humidity. This paper presents an all-plastic, flexible electroosmotic pump, constructed from commercially available materials: A polycarbonate membrane combined with the electrochemically active polymer poly(3,4-ethylenedioxythiophene) polystyrene sulfonate that actively transports water using an electric potential that can be supplied by a small battery. By using electrochemically active polymer electrodes instead of metal electrodes, the electrochemical reaction that drives flow avoids the oxygen and hydrogen gas production or pH changes associated with water electrolysis. We observe a water mass flux up to 23 mg min(-1) per cm(2) polycarbonate membrane (porosity 10-15%), at an applied potential of 5 V, and a limiting operating pressure of 0.3 kPa V-1, similar to previously reported membrane-based electroosmotic pumps.

  • 31.
    Bergenti, I.
    et al.
    ISMN-Bo CNR, via Gobetti 101, 40129 Bologna, Italy.
    Dediu, V.
    ISMN-Bo CNR, via Gobetti 101, 40129 Bologna, Italy.
    Arisi, E.
    ISMN-Bo CNR, via Gobetti 101, 40129 Bologna, Italy.
    Cavallini, M.
    ISMN-Bo CNR, via Gobetti 101, 40129 Bologna, Italy.
    Biscarini, F.
    ISMN-Bo CNR, via Gobetti 101, 40129 Bologna, Italy.
    Taliani, C.
    ISMN-Bo CNR, via Gobetti 101, 40129 Bologna, Italy.
    de Jong, Michel P
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Dennis, C.L.
    Clarendon Laboratory, University of Oxford, Parks Road, Oxford, OX1 3PU, United Kingdom.
    Gregg, J.F.
    Clarendon Laboratory, University of Oxford, Parks Road, Oxford, OX1 3PU, United Kingdom.
    Solzi, M.
    Department of Physics, INFM, Parco Area delle Scienze 7/a, 43100 Parma, Italy.
    Natali, M.
    ICIS CNR, Corso Stati Uniti 4, 35127 Padova, Italy.
    Spin polarized La0.7Sr0.3MnO3 thin films on silicon2007In: Journal of Magnetism and Magnetic Materials, ISSN 0304-8853, E-ISSN 1873-4766, Vol. 312, no 2, p. 453-457Article in journal (Refereed)
    Abstract [en]

    La0.7Sr0.3MnO3 polycrystalline manganite thin films were grown on silicon (Si) substrates covered by SiOx amorphous native oxide. Curie temperatures of about 325 K were achieved for 70-nm-thick films. Strong room temperature XMCD signal was detected indicating high spin polarization at the surface. Cross-sectional TEM images show sharp interface between SiOx and manganite without signature of chemical reaction at the interface. Unusual sharp splitting of the manganite film was observed: on the top of a transition layer characterized by low crystalline order, a magnetically robust layer is formed. © 2007 Elsevier B.V. All rights reserved.

  • 32.
    Bergenti, I.
    et al.
    ISMN CNR, via P. Gobetti 101, 40129 Bologna, Italy.
    Dediu, V.
    ISMN CNR, via P. Gobetti 101, 40129 Bologna, Italy.
    Arisi, E.
    ISMN CNR, via P. Gobetti 101, 40129 Bologna, Italy.
    Cavallini, M.
    ISMN CNR, via P. Gobetti 101, 40129 Bologna, Italy.
    Moulin, J.F.
    ISMN CNR, via P. Gobetti 101, 40129 Bologna, Italy.
    Biscarini, F.
    ISMN CNR, via P. Gobetti 101, 40129 Bologna, Italy.
    de Jong, Michel P
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Dennis, C.
    Clarendon Laboratory, University of Oxford, Parks Road, Oxford, OX1 3PU, United Kingdom.
    Gregg, J.
    Clarendon Laboratory, University of Oxford, Parks Road, Oxford, OX1 3PU, United Kingdom.
    Structural and magnetic properties of thin manganite films grown on silicon substrates2005In: Progress in Solid State Chemistry, ISSN 0079-6786, E-ISSN 1873-1643, Vol. 33, no 2-4 SPEC. ISS., p. 293-298Article in journal (Refereed)
    Abstract [en]

    Polycrystalline La0.7Sr0.3MnO3 manganite thin films were grown on silicon substrates covered by SiOx amorphous native oxide. Unusual splitting of the manganite layer was found: on the top of an intermediate layer characterised by lower crystalline order, a magnetic robust layer is formed. Curie temperatures of about 325 K were achieved for 70 nm thick films. A strong room temperature XMCD signal was detected indicating high spin polarisation near the surface. © 2005 Elsevier Ltd. All rights reserved.

  • 33.
    Berggren, Magnus
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
    Nilsson, David
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
    Chen, Miaoxiang
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
    Andersson, Peter
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
    Kugler, T.
    Acreo AB, Bredgatan 34, SE-602 21 Norrköping, Sweden.
    Malmstrom, A.
    Malmström, A., Acreo AB, Bredgatan 34, SE-602 21 Norrköping, Sweden.
    Hall, J.
    Acreo AB, Bredgatan 34, SE-602 21 Norrköping, Sweden.
    Remonen, T.
    Acreo AB, Bredgatan 34, SE-602 21 Norrköping, Sweden.
    Robinson, Nathaniel D
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry.
    Polymer based electrochemical devices for logic functions and paper displays2003Conference paper (Other academic)
    Abstract [en]

    Here, we report on devices based on patterned thin films of the conducting polymer system poly(3,4-ethylenedioxythiophene) doped with poly(styrene sulphonic acid) (PEDOT:PSS) combined with patterns of solid electrolyte. The key device functionalities base on the updating of the RedOx state of PEDOT. This results in control of the electronic properties of this conjugated polymer, i.e. the conductivity and optical properties are updated. Based on this we have achieved electric current rectifiers, transistors and display cells. Also, matrix addressed displays will be presented. Electrochemical switching is taking place when the oxidation and reduction potentials are overcome respectively. Therefore, these devices operate at voltage levels less then 2 Volts. Low voltage operation is achieved in devices not requiring any extremely narrow dimensions, as is the case for field effect driven devices. All devices reported can or has been made using standard printing techniques on flexible carriers.

  • 34.
    Bergström, Gunnar
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biotechnology. Linköping University, The Institute of Technology.
    Nilsson, K.
    Percell Biolytica AB, Åstorp, Sweden.
    Mandenius, Carl-Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Biotechnology. Linköping University, The Institute of Technology.
    Robinson, Nathaniel D
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Macroporous microcarriers for introducing cells into a microfluidic chip2014In: Lab on a Chip, ISSN 1473-0197, E-ISSN 1473-0189, Vol. 14, no 18, p. 3502-3504Article in journal (Refereed)
    Abstract [en]

    Macroporous gelatin beads (CultiSpher™ microcarriers) provide a convenient method for rapidly and reliably introducing cells cultured ex situ into a microfluidic device, where the spheres create a 3D environment for continued cell proliferation. We demonstrate the usefulness of this technique with a proof-of-concept viability analysis of cardiac cells after treatment with doxorubicin. © 2014 the Partner Organisations.

  • 35.
    Bhatt, Pramod
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Carlegrim, Elin
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Kanciurzewska, A
    Adam Mickiewicz University Poznan.
    de Jong, M. P.
    University of Twente.
    Fahlman, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Electronic structure of thin film iron-tetracyanoethylene: Fe(TCNE)x2009In: Applied Physics A: Materials Science & Processing, ISSN 0947-8396, E-ISSN 1432-0630, Vol. 95, no 1, p. 131-138Article in journal (Refereed)
    Abstract [en]

    Thin film iron-tetracyanoethylene Fe(TCNE) x , x∼2, as determined by photoelectron spectroscopy, was grown in situ under ultra-high vacuum conditions using a recently developed physical vapor deposition-based technique for fabrication of oxygen- and precursor-free organic-based molecular magnets. Photoelectron spectroscopy results show no spurious trace elements in the films, and the iron is of Fe2+ valency. The highest occupied molecular orbital of Fe(TCNE) x is located at ∼1.7 eV vs. Fermi level and is derived mainly from the TCNE singly occupied molecular orbital according to photoelectron spectroscopy and resonant photoelectron spectroscopy results. The Fe(3d)-derived states appear at higher binding energy, ∼4.5 eV, which is in contrast to V(TCNE)2 where the highest occupied molecular orbital is mainly derived from V(3d) states. Fitting ligand field multiplet and charge transfer multiplet calculations to the Fe L-edge near edge X-ray absorption fine structure spectrum yields a high-spin Fe2+ (3d6) configuration with a crystal field parameter 10Dq∼0.6 eV for the Fe(TCNE) x system. We propose that the significantly weaker Fe-TCNE ligand interaction as compared to the room temperature magnet V(TCNE)2 (10Dq∼2.3 eV) is a strongly contributing factor to the substantially lower magnetic ordering temperature (T C ) seen for Fe(TCNE) x -type magnets.

  • 36.
    Bhatt, Pramod
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Kanciurzewska, Anna
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Carlegrim, Elin
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Kapilashrami, Mukes
    Division of Engineering Material Physics, Royal Institute of Technology, Stockholm, Sweden.
    Belova, Liubov
    Division of Engineering Material Physics, Royal Institute of Technology, Stockholm, Sweden.
    Rao, K V
    Division of Engineering Material Physics, Royal Institute of Technology, Stockholm, Sweden.
    Fahlman, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Ferromagnetism above room temperature in nickel–tetracyanoethylene thin films2009In: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 19, no 36, p. 6610-6615Article in journal (Refereed)
    Abstract [en]

    Room temperature ferromagnetic ordering is reported in Ni–tetracyanoethylene (TCNE) thin films fabricated on Au substrates using physical vapor deposition (PVD) under ultra high vacuum conditions. This technique enables the preparation of very clean films without having any kind of contamination from oxygen-containing species, solvents or precursor molecules. Film stoichiometry was obtained from X-ray photoelectron spectroscopy (XPS) measurements. XPS derived stoichiometry points to a 1 : 2 ratio between Ni and TCNE resulting in Ni(TCNE)x, x ≈ 2. No evidence of pure Ni metal in the in situ grown films was present in the XPS or the ultraviolet photoelectron spectroscopy (UPS) measurements within the detection limits of the techniques.

  • 37. Birgerson, J.
    et al.
    Janssen, F.J.J.
    Department of Applied Physics, Dutch Polymer Institute, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, Netherlands.
    Denier, van der Gon A.W.
    Tsukahara, Y.
    Dept. of Chem. and Mat. Technology, Kyoto Institute of Technology, Kyoto 606-8585, Japan.
    Kaeriyama, K.
    Dept. of Chem. and Mat. Technology, Kyoto Institute of Technology, Kyoto 606-8585, Japan.
    Salaneck, William R
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Doped polymeric cathodes for PPV/Al based LEDs2002In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 132, no 1, p. 57-61Article in journal (Refereed)
    Abstract [en]

    The effect of Li-doping in poly(para-phenylenevinylene) (PPV) based light emitting devices has been studied. In a standard structure with an indium tin oxide (ITO) anode, poly(3,4-ethylenedioxythiophene) doped with poly(4-styrenesulfonate) (PEDOT-PSS)-layer and an active PPV-layer, the effects of a thin (around 1 Å) Li-layer and a thin layer, (50 Å), of a large bandgap polymer, poly(2,5-diheptyl-1,4-phenylene-alt-1,4-naphthylene) (P14NHP) between the PPV and the aluminum cathode have been studied in terms of IV-characteristics and efficiency. The Li-atoms dope the interfacial layer of the PPV as seen by photoelectron spectroscopy. A thin layer of Li improves the charge balance by decreasing the energy barrier for injection of electrons for the Al/Li/PPV/PEDOT-PSS/ITO device. The efficient electron injection originates from a Fermi level alignment between the doped polymer and the aluminum cathode, which reduces the energy barrier. A thin layer of the large bandgap polymer P14NHP, between the PPV and Al contact, increases the light output and efficiency by blocking the holes. In addition, it may also reduce the light quenching by moving the region of recombination away from the Al-contact. The addition of a Li-layer on top of P14NHP leads to an increase of the quantum efficiency, because of better electron injection. © 2002 Elsevier Science B.V. All rights reserved.

  • 38. Birgerson, J.
    et al.
    Johansson, N.
    Pohl, A.
    Logdlund, M.
    Lögdlund, M., ACREO AB, Bredgatan 34, S-602 21 Norrköping, Sweden.
    Tsukahara, Y.
    Dept. of Chem. and Mat. Technology, Kyoto Institute of Technology, Kyoto 606-8585, Japan.
    Kaeriyama, K.
    Dept. of Chem. and Mat. Technology, Kyoto Institute of Technology, Kyoto 606-8585, Japan.
    Salaneck, William R
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Electronic structure of some conjugated polymers for electron transport2001In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 122, no 1, p. 67-72Article in journal (Refereed)
    Abstract [en]

    The chemical and electronic structure of three different, strictly alternating copolymers, poly(2,5-diheptyl-1,4-phenylene-alt-1,4-naphthylene) (P14NHP), poly(2,5-diheptyl-1,4-phenylene-alt-2,6-naphthylene) (P26NHP) and poly(2,5-diheptyl-1,4-phenylene-alt-9,10-anthrylene) (P910AHP), have been studied by photoelectron spectroscopy and optical absorption spectroscopy. The experimental results have been analyzed using the results of quantum chemical calculations. In the geometrical structure of all three of the polymers there are large torsion angles between the phenylene unit and the naphthylene or anthrylene units. These large torsion angles lead to localization of the p-electron wave functions, and minimal conjugation along the polymer backbone. For all three polymers, the highest occupied molecular orbital is completely localized to the naphthylene or anthrylene unit. The frontier molecular orbital wave functions are very reminiscent of the highest occupied orbitals of the isolated naphthalene or anthracene molecules. The optical absorption spectra of all three polymers verify the existence of large optical band gaps, consistent with the large torsion angels. The first several optical transitions in the polymers are also very reminiscent of the transitions in single naphthalene and anthracene molecules.

  • 39. Birgerson, J.
    et al.
    Keil, M.
    Luo, Y.
    Theoretical Chemistry, Royal Institute of Technology, S-100 44 Stockholm, Sweden.
    Svensson, S.
    Department of Physics, Uppsala University, S-751 21 Uppsala, Sweden.
    Agren, H.
    Ågren, H., Theoretical Chemistry, Royal Institute of Technology, S-100 44 Stockholm, Sweden.
    Salaneck, William R
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    A study of the electronic structure of ethylenedioxythiophene in gas phase using NEXAFS and quantum chemical calculations2004In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 392, no 1-3, p. 100-104Article in journal (Refereed)
    Abstract [en]

    Near-edge X-ray absorption fine structure spectroscopy spectra of ethylenedioxythiophene has been recorded in gas phase at the carbon K-edge, sulphur L-edge and oxygen, K-edge. The experimental data has been interpreted with the help of a modified density functional code deMon. The good agreement between the calculated spectra and the measured one allows us to assign all observed resonances. The existence of p* resonances in both the measured and the calculated OK-edge adsorption spectrum demonstrate that the delocalized p-system of the thiophene part of the molecule is extended up to the oxygen atoms of the molecule. © 2004 Elsevier B.V. All rights reserved.

  • 40.
    Boerrnert, Felix
    et al.
    Leibniz-Institut für Festkörper- und Werkstoffforschung Dresden e. V., Dresden, Germany.
    Boerrnert, Carina
    Max-Planck-Institut für Chemische Physik fester Stoffe, Dresden, Germany.
    Gorantla, Sandeep
    Leibniz-Institut für Festkörper- und Werkstoffforschung Dresden e. V., Dresden, Germany.
    Liu, Xianjie
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Bachmatiuk, Alicja
    Leibniz-Institut für Festkörper- und Werkstoffforschung Dresden e. V., Dresden, Germany.
    Joswig, Jan-Ole
    Technische Universität Dresden, Dresden, Germany.
    Wagner, Frank P
    Max-Planck-Institut für Chemische Physik fester Stoffe, Dresden, Germany.
    Schaeffel, Franziska
    Leibniz-Institut für Festkörper- und Werkstoffforschung Dresden e. V., Dresden, Germany.
    Warner, Jamie H
    University of Oxford, Oxford, United Kingdom.
    Schoenfelder, Ronny
    Leibniz-Institut für Festkörper- und Werkstoffforschung Dresden e. V., Dresden, Germany.
    Rellinghaus, Bernd
    Leibniz-Institut für Festkörper- und Werkstoffforschung Dresden e. V., Dresden, Germany.
    Gemming, Thomas
    Leibniz-Institut für Festkörper- und Werkstoffforschung Dresden e. V., Dresden, Germany.
    Thomas, Juergen
    Leibniz-Institut für Festkörper- und Werkstoffforschung Dresden e. V., Dresden, Germany.
    Knupfer, Martin
    Leibniz-Institut für Festkörper- und Werkstoffforschung Dresden e. V., Dresden, Germany.
    Buechner, Bernd
    Leibniz-Institut für Festkörper- und Werkstoffforschung Dresden e. V., Dresden, Germany.
    Ruemmeli, Mark H
    Leibniz-Institut für Festkörper- und Werkstoffforschung Dresden e. V., Dresden, Germany and Technische Universität Dresden, Dresden, Germany.
    Single-wall-carbon-nanotube/single-carbon-chain molecular junctions2010In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 81, no 8, p. 085439-1-085439-5Article in journal (Refereed)
    Abstract [en]

    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.

  • 41.
    Braun, Slawomir
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry . Linköping University, The Institute of Technology.
    Studies of Materials and Interfaces for Organic Electronics2007Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Organic electronics is a rapidly evolving field with vast number of applications having high potential for commercial success. Although a great progress has been made, many organic electronic applications: organic light-emitting diodes (OLEDs), organic fieldeffect transistors (OFETs), organic solar cells, etc; still require further optimization to fulfill the requirements for successful commercialization. For many applications, available at this time organic materials do not provide satisfactory performance and stability, which hinders the possibility of a large-scale production. Therefore, the key ingredient needed for a successful improvement in performance and stability of organic electronic devices is in-depth knowledge of physical and chemical properties of molecular and polymeric materials. Since many applications encompass several thin film layers made of organics, and often also inorganic materials, the understanding of both organic-organic and hybrid interfaces is yet another important issue necessary for the successful development of organic electronics.

    The research presented in this thesis is based mainly on photoelectron spectroscopy, which is an experimental technique especially suited to study both surfaces and interfaces of materials. In the thesis, the properties of one of the most successful polymeric materials, poly(3,4-ethylenedioxythiophene), often abbreviated as PEDOT, have been extensively studied. The research was done in close cooperation with an industrial partner – AGFA Gevaert, Belgium. The study was focused on the exploration of the intrinsic properties of the material, such as stability, morphology and conductivity. In addition, however, a possibility of alternation of these properties was also explored. This thesis reports also about investigations of the properties of various organic-organic and hybrid interfaces. The energy level alignment at such interfaces plays important role in charge injection and performance of the thin film organic-based devices. The conditions for different energy level alignment regimes at the various interfaces have been studied. The studies on interfaces were performed in close collaboration with the R&D division of DuPont Corporation, USA. This work led to the significant advances in understanding of the interface energetics and properties of industryrelevant organic materials, as represented not only by published scientific papers, but also patent applications.

    List of papers
    1. Light Induced Damage in Poly(3,4-ethylenedioxythiophene) and its Derivatives Studied by Photoelectron Spectroscopy
    Open this publication in new window or tab >>Light Induced Damage in Poly(3,4-ethylenedioxythiophene) and its Derivatives Studied by Photoelectron Spectroscopy
    Show others...
    2004 (English)In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 141, no 1-2, p. 67-73Article in journal (Refereed) Published
    Abstract [en]

    Poly(3,4-ethylenedioxythiophene), usually known as PEDOT, and derivatives have attracted significant interest because of their high electrical conductivity. This electric property, however, deteriorates upon exposure to solar radiation. X-ray photoelectron spectroscopy (XPS) has been used to study the UV-light-induced chemical changes in doped PEDOT, as well as in both neutral and doped forms of its alkylated derivative—PEDOT-C14H29. Analysis of the XPS data indicates an oxidation of the sulfur in the thiophene ring. Apparently, photo-oxidation leads to the formation of sulfon groups, SO2, resulting in a disruption of π-conjugation in PEDOT, which there by diminishes the conductivity of the organic layer. This hypothesis is supported by the results of a study of model molecules for pristine and the oxidized PEDOT unit: 3,4 ethylenedioxythiophene (EDOT) and 3,4 ethylenedioxythiophene and S-dioxide (EDOT-SO2), respectively.

    Place, publisher, year, edition, pages
    Elsevier, 2004
    Keywords
    Poly(3, 4-ethylenedioxythiophene), X-ray photoelectron spectroscopy, Degradation, Photo-oxidation, Sulfon
    National Category
    Materials Chemistry
    Identifiers
    urn:nbn:se:liu:diva-14580 (URN)10.1016/j.synthmet.2003.08.017 (DOI)000220273400012 ()
    Available from: 2007-07-03 Created: 2007-07-03 Last updated: 2017-12-13Bibliographically approved
    2. Conductivity, Morphology, Interfacial Chemistry, and Stability of Poly(3,4- ethylene dioxythiophene)–Poly(styrene sulfonate): A Photoelectron Spectroscopy Study
    Open this publication in new window or tab >>Conductivity, Morphology, Interfacial Chemistry, and Stability of Poly(3,4- ethylene dioxythiophene)–Poly(styrene sulfonate): A Photoelectron Spectroscopy Study
    Show others...
    2003 (English)In: Journal of Polymer Science Part B: Polymer Physics, ISSN 0887-6266, E-ISSN 1099-0488, Vol. 41, no 21, p. 2561-2583Article, review/survey (Refereed) Published
    Abstract [en]

    X-ray photoelectron spectroscopy (XPS) has been used to characterize poly(3,4-ethylene dioxythiophene)-poly(styrene sulfonate) (PEDT/PSS), one of the most common electrically conducting organic polymers. A correlation has been established between the composition, morphology, and polymerization mechanism, on the one hand, and the electric conductivity of PEDT/PSS, on the other hand. XPS has been used to identify interfacial reactions occurring at the polymer-on-ITO and polymer-on-glass interfaces, as well as chemical changes within the polymer blend induced by electrical stress and exposure to ultraviolet light.

    Place, publisher, year, edition, pages
    John Wiley & Sons, 2003
    Keywords
    ESCA/XPS, poly(3, 4-ethylene dioxythiophene), conductivity, degradation, interfacial chemistry, conducting polymers
    National Category
    Polymer Chemistry Polymer Technologies
    Identifiers
    urn:nbn:se:liu:diva-14581 (URN)10.1002/polb.10659 (DOI)000185967300009 ()
    Available from: 2007-07-03 Created: 2007-07-03 Last updated: 2017-12-13Bibliographically approved
    3. Energy level alignment regimes at hybrid organic–organic and inorganic–organic interfaces
    Open this publication in new window or tab >>Energy level alignment regimes at hybrid organic–organic and inorganic–organic interfaces
    2007 (English)In: Organic Electronics, ISSN 1566-1199, Vol. 8, no 1, p. 14-20Article in journal (Refereed) Published
    Abstract [en]

    Ultraviolet photoelectron spectroscopy has been used to determine the energy level alignment at interfaces of molecular hole-transporting materials and various conductive substrates. Depending on the work function of the substrate, s, a transition between two different energy level alignment regimes has been observed: namely vacuum level alignment and Fermi level pinning. The transition is associated with spontaneous positive charge transfer across the interface to the organic semiconductors above a certain material-specific threshold value of s. The charge transfer results in formation of an interfacial dipole of a magnitude that scales with s. In the vacuum level alignment regime, the hole-injection barriers scale linearly with s, while in the Fermi level pinning regime, these barriers are constant and independent of s.

    Keywords
    Energy level alignment; OLED; Hole-transporting materials; Interfaces; Photoelectron spectroscopy; Hole-injection barrier
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-14582 (URN)10.1016/j.orgel.2006.10.006 (DOI)
    Note
    Original Publication: Slawomir Braun, Wojciech Osikowicz, Ying Wang and William R. Salaneck, Energy level alignment regimes at hybrid organic–organic and inorganic–organic interfaces, 2007, Organic Electronics, (8), 1, 14-20. http://dx.doi.org/10.1016/j.orgel.2006.10.006 Copyright: Elsevier Science B.V., Amsterdam. http://www.elsevier.com/ Available from: 2007-07-03 Created: 2007-07-03 Last updated: 2010-05-19
    4. Fermi level pinning at interfaces with tetrafluorotetracyanoquinodimethane (F4-TCNQ): The role of integer charge transfer states
    Open this publication in new window or tab >>Fermi level pinning at interfaces with tetrafluorotetracyanoquinodimethane (F4-TCNQ): The role of integer charge transfer states
    2007 (English)In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 438, no 4-6, p. 259-262Article in journal (Refereed) Published
    Abstract [en]

    The energy level alignment of vacuum deposited molecular films of tetrafluorotetracyanoquinodimethane (F4-TCNQ) on various substrates has been studied by photoelectron spectroscopy. The interfaces studied span the work function range from 3.45 to 5.8 eV. In this range, the Fermi level of the substrate is pinned in proximity to LUMO level. This indicates that a charge transfer mechanism is responsible for the observed alignment scheme. The photoelectron emission study of sub-monolayer of F4-TCNQ revealed presence of electrons in the charge transfer states at the interface. In this context the electronic structure of neutral and negatively charged F4-TCNQ has been studied theoretically and by photoelectron spectroscopy.

    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-14583 (URN)10.1016/j.cplett.2007.03.005 (DOI)
    Available from: 2007-07-03 Created: 2007-07-03 Last updated: 2017-12-13
    5. Energy level alignment of organic interfaces under reversal of deposition sequence: the role of Fermi level pinning
    Open this publication in new window or tab >>Energy level alignment of organic interfaces under reversal of deposition sequence: the role of Fermi level pinning
    2007 (English)Article in journal (Refereed) Submitted
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-14584 (URN)
    Available from: 2007-07-03 Created: 2007-07-03
  • 42.
    Braun, Slawomir
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry . Linköping University, The Institute of Technology.
    de Jong, Michel P.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry . Linköping University, The Institute of Technology.
    Salaneck, William R.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry . Linköping University, The Institute of Technology.
    Energy level alignment of organic interfaces under reversal of deposition sequence: the role of Fermi level pinning2007Article in journal (Refereed)
  • 43.
    Braun, Slawomir
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    de Jong, M.P.
    Osikowicz, Wojciech
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Salaneck, William R
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Influence of the electrode work function on the energy level alignment at organic-organic interfaces2007In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 91, no 20Article in journal (Refereed)
    Abstract [en]

    The energy level alignment at interfaces, in stacks comprising of (4, 4′ -N, N′ -dicarbazolyl-biphenyl) (CBP), (4,4, 4″ -tris[3-methyl-phenyl(phenyl)amino]-triphenylamine) (m -MTDATA), and a conductive substrate, has been studied. We show that the alignment of energy levels depends on the equilibration of the chemical potential throughout the layer stack, while any electronic coupling between the individual layers is of lesser importance. This behavior is expected to occur for a broad class of weakly interacting interfaces and can have profound consequences for the design of organic electronic devices. © 2007 American Institute of Physics.

  • 44.
    Braun, Slawomir
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Liu, Xianjie
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Salaneck, William R
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Fahlman, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Fermi level equilibrium at donor-acceptor interfaces in multi-layered thin film stack of TTF and TCNQ2010In: Organic electronics, ISSN 1566-1199, E-ISSN 1878-5530, Vol. 11, no 2, p. 212-217Article in journal (Refereed)
    Abstract [en]

    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.

  • 45.
    Braun, Slawomir
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry . Linköping University, The Institute of Technology.
    Osikowicz, Wojciech
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry . Linköping University, The Institute of Technology.
    Wang, Ying
    E. I. DuPont de Nemours and Co., Inc., Experimental Station, Wilmington, DE, United States.
    Salaneck, William R.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry . Linköping University, The Institute of Technology.
    Energy level alignment regimes at hybrid organic–organic and inorganic–organic interfaces2007In: Organic Electronics, ISSN 1566-1199, Vol. 8, no 1, p. 14-20Article in journal (Refereed)
    Abstract [en]

    Ultraviolet photoelectron spectroscopy has been used to determine the energy level alignment at interfaces of molecular hole-transporting materials and various conductive substrates. Depending on the work function of the substrate, s, a transition between two different energy level alignment regimes has been observed: namely vacuum level alignment and Fermi level pinning. The transition is associated with spontaneous positive charge transfer across the interface to the organic semiconductors above a certain material-specific threshold value of s. The charge transfer results in formation of an interfacial dipole of a magnitude that scales with s. In the vacuum level alignment regime, the hole-injection barriers scale linearly with s, while in the Fermi level pinning regime, these barriers are constant and independent of s.

  • 46.
    Braun, Slawomir
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry . Linköping University, The Institute of Technology.
    Salaneck, William R.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry . Linköping University, The Institute of Technology.
    Fermi level pinning at interfaces with tetrafluorotetracyanoquinodimethane (F4-TCNQ): The role of integer charge transfer states2007In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 438, no 4-6, p. 259-262Article in journal (Refereed)
    Abstract [en]

    The energy level alignment of vacuum deposited molecular films of tetrafluorotetracyanoquinodimethane (F4-TCNQ) on various substrates has been studied by photoelectron spectroscopy. The interfaces studied span the work function range from 3.45 to 5.8 eV. In this range, the Fermi level of the substrate is pinned in proximity to LUMO level. This indicates that a charge transfer mechanism is responsible for the observed alignment scheme. The photoelectron emission study of sub-monolayer of F4-TCNQ revealed presence of electrons in the charge transfer states at the interface. In this context the electronic structure of neutral and negatively charged F4-TCNQ has been studied theoretically and by photoelectron spectroscopy.

  • 47.
    Braun, Slawomir
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry . Linköping University, The Institute of Technology.
    Salaneck, William R
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry . Linköping University, The Institute of Technology.
    Fahlman, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry . Linköping University, The Institute of Technology.
    Energy-Level Alignment at Organic/Metal and Organic/Organic Interfaces2009In: ADVANCED MATERIALS, ISSN 0935-9648, Vol. 21, no 14-15, p. 1450-1472Article, review/survey (Refereed)
    Abstract [en]

    In this Review, we summarize recent work on modeling of organic/metal and organic/organic interfaces. Some of the models discussed have a semiempirical approach, that is, experimentally derived values are used in combination with theory, and others rely completely of calculations. The models are categorized according to the types of interfaces they apply to, and the strength of the interaction at the interface has been used as the main factor. We explain the basics of the models, their use, and give examples on how the models correlate with experimental results. We stress that given the complexity of organic/metal and organic/organic interface formation, it is crucial to know the exact way in which the interface was formed before choosing the model that is applicable, as none of the models presented covers the whole range of interface interaction strengths (weak physisorption to strong chemisorption).

  • 48. Bredas, JL
    et al.
    Marder, SR
    Salaneck, William R
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Alan J. Heeger, Alan G. MacDiarmid, and Hideki Shirakawa - Tribute2002In: Macromolecules, ISSN 0024-9297, E-ISSN 1520-5835, Vol. 35, no 4, p. 1137-1139Other (Other academic)
  • 49.
    Briones-Leon, Antonio
    et al.
    University of Vienna, Austria.
    Ayala, Paola
    University of Vienna, Austria.
    Liu, Xianjie
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Yanagi, Kazuhiro
    Tokyo Metropolitan University, Japan.
    Weschke, Eugen
    Helmholtz Zentrum Berlin Mat and Energie, Germany.
    Eisterer, Michael
    Vienna University of Technology, Austria.
    Jiang, Hua
    Aalto University, Finland.
    Kataura, Hiromichi
    Nat Institute Adv Ind Science and Technology AIST, Japan.
    Pichler, Thomas
    University of Vienna, Austria.
    Shiozawa, Hidetsugu
    University of Vienna, Austria.
    Orbital and spin magnetic moments of transforming one-dimensional iron inside metallic and semiconducting carbon nanotubes2013In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 87, no 19Article in journal (Refereed)
    Abstract [en]

    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.

  • 50.
    Briones-Leon, Antonio
    et al.
    University of Vienna, Austria .
    Liu, Xianjie
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Ayala, Paola
    University of Vienna, Austria .
    Kataura, Hiromichi
    National Institute Adv Ind Science and Technology, Japan .
    Yanagi, Kazuhiro
    Tokyo Metropolitan University, Japan .
    Weschke, Eugen
    Helmholtz Zentrum Berlin Fr Mat and Energie, Germany .
    Pichler, Thomas
    University of Vienna, Austria .
    Shiozawa, Hidetsugu
    University of Vienna, Austria .
    Orbital and spin magnetic moments of ferrocene encapsulated in metallicity sorted single-walled carbon nanotubes2012In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 249, no 12, p. 2424-2427Article in journal (Refereed)
    Abstract [en]

    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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