Publications Search Results

Now showing 1 - 10 of 42
  • Publication
    Transfer of the sputter technique for deposition of strongly thermochromic VO2-based coatings on ultrathin flexible glass to large-scale roll-to-roll device
    ( 2022-02-24)
    Rezek, Jiri
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    Vlček, Jaroslav
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    Čerstvý, Radomír
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    Houška, Jiří
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    The reversible semiconductor-to-metal transition of vanadium dioxide (VO2) makes VO2-based coatings a promising candidate for thermochromic smart windows, reducing the energy consumption of buildings. We report on transfer of the sputter technique for deposition of strongly thermochromic ZrO2/W-doped VO2/ZrO2 coatings on ultrathin (0.1 mm) flexible glass from a laboratory-scale device with three (V, W and Zr) planar magnetron targets to a large-scale roll-to-roll device with two (W-doped V and ZrO2) rotatable magnetron targets. The depositions were performed at a relatively low substrate surface temperature (330-350 °C) and without any substrate bias voltage. The W-doped VO2 layers were deposited using a reactive high-power impulse magnetron sputtering with a pulsed O2 flow control. We compare the process parameters used in both deposition devices and explain the basic principle of this sputter technique using the discharge characteristics measured during a large-scale roll-to-roll deposition. We characterize the design, structure (X-ray diffraction) and optical properties (spectrophotometry and spectroscopic ellipsometry) of the three-layer coatings. The coatings prepared on ultrathin flexible glass using the large-scale roll-to-roll device at a temperature close to 350 °C exhibit a low transition temperature of 22 °C, an integral luminous transmittance over 45% and a modulation of the solar energy transmittance approaching 10%. This is a promising first step to a cost-effective and high-rate preparation of large-area thermochromic VO2-based coatings for future smart-window applications.
  • Publication
    Electron beam cured acrylates as potential planarization layers
    ( 2021)
    Fichtner, Juliane
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    Mayer, Bernd
    In this study, electron beam (EB) curable acrylates are investigated for their use as planarization layers. Planarization layers can be used in multilayer thin film encapsulations for all kinds of flexible electronics, such as organic light emitting diodes (OLED), organic photovoltaics (OPV) and printed switching circuits, antennas, and sensors. Planarization layers cover particles and defects of the substrate and thus a plain smooth surface is created for optimized growing conditions of thin films, optimizing encapsulation properties. The thin film encapsulation prevents organic electronics from degradation due to invasive oxygen and water vapor. Several commercially available monomers and oligomers with different molar mass and number of reactive double bonds are investigated. The acrylates are deposited on polyethylene terephthalate (PET) web and glass substrates and cured by EB. The surfaces are analyzed using white light interferometry (WLI) and scanning electron microscopy (SEM). Density measurements and nanoindentation are also carried out to get information about the volume shrinkage and the elastic modulus. The correlation between chemical properties, degree of crosslinking, volume shrinkage and surface roughness are investigated. This work demonstrates that electron beam curing of acrylates is a promising method to generate smooth surfaces. It presents an increasing degree of crosslinking and volume shrinkage with decreasing molecular weight between crosslinks. Also, for comparable molecular weight between crosslinks, the volume shrinkage is higher for acrylates forming thermoplastics than for elastomers or duromers.
  • Publication
    Pulsed Magnetron Sputtering of Strongly Thermochromic VO2-Based Coatings with a Transition Temperature of 22 °C onto Ultrathin Flexible Glass
    ( 2020)
    Barta, Tomas
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    Vlcek, Jaroslav
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    Houska, Jiri
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    Cerstvy, Radomir
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    Haviar, Stanislav
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    The reversible semiconductor-to-metal transition of vanadium dioxide (VO2) makes VO2-based coatings a promising candidate for thermochromic smart windows, reducing the energy consumption of buildings. This paper deals with maximizing the application potential of these coatings in terms of their performance, an industry-friendly preparation technique, and an industrially relevant substrate. We present a scalable sputter deposition technique for the preparation of strongly thermochromic ZrO2/V0.984W0.016O2/ZrO2 coatings on ultrathin flexible glass and standard glass at a relatively low substrate surface temperature (330 °C) and without any substrate bias voltage. The V0.984W0.016O2 layers were deposited by a controlled high-power impulse magnetron sputtering of a V target, combined with a simultaneous pulsed dc magnetron sputtering of a W target. We explain the fundamental principles of this technique using the discharge characteristics measured for both discharges. We characterize the coating structure (X-ray diffraction) and a wide range of optical properties (spectrophotometry and spectroscopic ellipsometry). We find that the coatings combine a transition temperature of 22 °C, a luminous transmittance approaching 50%, a modulation of the solar energy transmittance over 10% and a temperature-independent color. The results in general, and the successful transfer from a standard glass to the ultrathin flexible glass in particular, are crucial for future applications of the coatings on smart windows.
  • Publication
    Roll to Roll Deposition of Transparent Electrodes on Permeation Barrier Coatings
    The European project PI-SCALE has set an objective to create a virtual pilot manufacturing line for various types of OLED lighting devices. An important part of this virtual pilot line is the roll-to-roll sputtering of the anode layer. An indium tinoxide (ITO) layer with a sheet resistance below 30 Osq (ohm/square) was sputtered onto a continuously moving polyethylene terephthalate (PET) film substrate using a rotatable magnetron. The sputtering performance of a bonded ITO target was compared to the performance of a plasma sprayed ITO target. It was demonstrated that the variation of the hydrogen content of the sputtering gas atmosphere can serve as a powerful parameter for the optimization of the layer properties. This gas was varied between zero and ten percent of the total gas flow. The PET film was equipped with a planarizing layer and a permeation barrier coating on top of it. It was shown how the permeation barrier is prevented from getting deteriorated by conveying the film. The removal of a protective interleaf film directly before entering the sputtering zone turned out to be decisive for the layer quality. The same holds true for the application of a protective interleaf immediately after leaving the sputtering zone. By applying these two steps, the permeation barrier could be kept below 1×10-3 g/m2day, which is the lower limit of the applied coulometric measurement device.
  • Publication
    Quantifying Performance of Permeation Barrier - Encapsulation Systems for Flexible and Glass-Based Electronics and their Application to Perovskite Solar Cells
    ( 2019)
    Castro-Hermosa, Sergio
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    Dagar, Janardan
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    Brown, Thomas M.
    Effective transparent barrier/encapsulation systems represent a key enabling technology for large‐area electronics. Securing stability to the environment is vital. Here, the effects of architectures, application processes, and water vapor transmission rates (WVTR) of transparent flexible ultra‐high permeation barrier films (UHPBF) applied to substrates with adhesive resins are unraveled for attaining long lifetime, and compared with polyethylene terephthalate and glass barriers. How strongly performance of barrier/adhesive systems depends on barrier orientation, adhesion, manipulation, defects, and storage procedures is quantified via calcium tests. Furthermore, it is found that introducing an additional adhesion‐promoting layer on the standard UHPBF stack reduces WVTRs by a factor of 5 compared to barriers without it. Finally, barriers are used for sealing and encapsulation of perovskite solar cells (PSCs) enabling the extraction of a relationship between WVTRs of barrier/adhesive systems and degradation rates (DR) of PSCs. DR fall exponentially when WVTRs decrease from 101 to 10−3 g m−2 d−1. Outside that range any gains or losses are mitigated by tailing of the sigmoid curve relating the two parameters. Results highlight important factors which will help those developing strategies relating to encapsulation, barrier, adhesive and sealant systems and stable optoelectronic devices on glass and flexible substrates.
  • Publication
    Slot-die processing and encapsulation of non-fullerene based ITO-free organic solar cells and modules
    ( 2019)
    Destouesse, E.
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    Lamminaho, J.
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    Rubahn, H.-G.
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    Madsen, M.
    Organic photovoltaic (OPV) devices have shown remarkable performance progress in recent years, reaching current record power conversion efficiency (PCE) values of 16.4% for single junction and 17.3% for multi junction devices, owing mostly to the impressive developments made within synthesis of new non-fullerene acceptors. This progress places organic solar cells at the forefront of thin-film photovoltaic technology. However, in order to meet industrial demands and reach high performance values in industrial settings, further research and development efforts within roll-to-roll (R2R) and sheet-to-sheet (S2S) processing of OPV devices under ambient conditions are required. Furthermore, OPV modules being manufactured through such up-scaled processing techniques should ideally be developed from low cost materials, and show good stability towards various different operational stress conditions. In this work, we demonstrate combined R2R and S2S development of ITO-free OPV devices, which are based on the non-fullerene material system PBDB-T:ITIC. The devices are processed from R2R vacuum sputtering and S2S slot-die coating at ambient conditions, and reach cell PCE values of 5.5%. In addition, we introduce a correlation between different barrier films, both commercial and sputtered inorganic coatings on ultra-clean PET, and the lifetime of the developed devices. The results therefore demonstrate an important step in the development of OPV devices from R2R and S2S processes in industrial settings.
  • Patent
    Vorrichtung zum Beschichten eines bandförmigen Substrates
    Die Erfindung betrifft eine Vorrichtung zum Beschichten eines bandförmigen Substrates, umfassend eine Beschichtungseinrichtung und eine Kühleinrichtung mit zumindest einem Oberflächenbereich, welchen das bandförmige Substrat zum Zeitpunkt des Beschichtens zumindest teilweise berührt. Dabei besteht eine Randschicht des Oberflächenbereichs der Kühleinrichtung, aus einem Kunststoff, welcher eine säulenförmige Struktur aufweist, wobei die Säulen der säulenförmigen Struktur mit einer Säulenhöhe im Bereich von 50 µm bis 500 µm und mit einem Säulenquerschnitt im Bereich von 300 µmbis 10.000 µmausgebildet sind.
  • Publication
    Vacuum coating on polymer films for outdoor applications
    This paper discusses functionalization of ETFE webs by vacuum roll-to-roll deposition of permeation barrier layers and highly conductive transparent electrodes for outdoor applications. A 100 nm thick gas barrier layer (zinc-tin-oxide - ZTO) and a 60nm thick transparent conductive layer stack(indium-tin-oxide - ITO 25 nm - Ag 10 nm -ITO 25 nm) achieve a water vapor transmission rate of 0.01 g/m²d (at38°C/90% r.h.) and sheet resistance of< 6 O/sq on a commercial grade ETFE film. However, the elastic properties of ETFE as well as its creep-behavior require specific attention during roll-to-roll processing and for design of the functional layer stacks. Inconsequence, layer thicknesses and material selection must be balanced between functional performance and the ability to survive deformation of the polymer web. This paper compares functional performance and crack formation under strain load of different layer stacks on both PET and ETFE substrates.
  • Publication
    Nanostructuring of polymer surfaces by magnetron plasma treatment
    ( 2018) ;
    Fichtner, Juliane
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    Stochastic nanostructured polymer surfaces exhibit superior properties like enhanced antireflective behavior and soil- resistance as well as improved adhesion to adhesives and other coatings. This paper investigates the modification of surface chemistry and topography of different widely used polymers by means of a roll-to-roll reactive dual magnetron plasma etching process. The etching process induces formation of stochastic nanostructures on the surfaces. Structure shapes, texture and application relevant properties depend on the composition, morphology and crystallinity of the treated polymers. The impact on optical transmission and hydrophobic behavior of the surfaces are discussed. Nanostructured varnish coatings allow surface modification of inorganic surfaces that may not be etched directly in a plasma treatment. This paper therefore characterizes plasma etching of acrylic based varnish coatings on polymer webs. Structure formation is investigated in relation to surface active additive content in varnish material. Finally, the outdoor stability of a nanostructured ethylene tetrafluoroethylene (ETFE) surface is shown in a 24 month outdoor weathering test in central Europe.
  • Publication
    Effect of humidity on the residual stress in silicon-containing plasma polymeric coatings
    ( 2018) ;
    Mulder, Guus
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    Hosson, Jeff de
    Residual stress measurements of thin films are common practice in device technology and are extremely important in particular for the characterization of thin film coatings. A largely ignored stress contribution is the difference in coefficient of hygroscopic expansion between the coating and substrate. This paper presents a rather novel approach to accurately evaluate the residual stress and coefficient of hygroscopic expansion of strongly curved specimens. Silicon-containing plasma polymer coatings with different carbon contents were deposited using hollow cathode arc discharge based PECVD. Samples of different layer composition were produced comprising silicon-containing plasma-polymer layers with a high carbon concentration and more ""inorganic"" SiO2 like layers with lower carbon concentration. All coatings show a compressive stress state. The highest stress was measured in the coating with the highest carbon content (239 ± 6 MPa) and decreases to 94 ± 31 MPa at lower carbon contents. Variation of the humidity showed that all coatings expand under influence of increasing relative humidity. The most inorganic coatings exhibits the highest expansion coefficient of 29.2 ± 2·10−6 (% r.h.)−1. The results obtained were compared with the results from contact angle measurements. An increase in the hygroscopic expansion corresponds with an increasing hydrophilicity of the coatings.