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Redox-tunable structural colour images by UV-patterned conducting polymer nanofilms on metal surfaces
Linköping University, Faculty of Science & Engineering. Linköping University, Department of Science and Technology, Laboratory of Organic Electronics.ORCID iD: 0000-0002-7410-2531
Linköping University, Department of Science and Technology, Laboratory of Organic Electronics. Linköping University, Faculty of Science & Engineering.ORCID iD: 0000-0003-1365-7469
Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.ORCID iD: 0000-0002-7626-1181
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

Precise manipulation of light-matter interaction has enabled a wide variety of approaches to create bright and vivid structural colours. Techniques utilizing photonic crystals, Fabry-Pérot cavities, plasmonics, or high-refractive index dielectric metasurfaces have been studied for applications ranging from optical coatings to reflective displays. However, complicated fabrication procedures for sub-wavelength nanostructures, limited active areas, and inherent absence of tunability of these approaches significantly impede their further development towards flexible, large-scale, and switchable devices compatible with facile and cost-effective production. Herein, we present a simple and efficient method to generate structural colours based on nanoscale conducting polymer films prepared on metallic surfaces via vapour phase polymerization and ultraviolet (UV) light patterning. Varying the UV dose enables synergistic control of both nanoscale film thickness and polymer permittivity, which generates controllable colours from violet to red. Together with greyscale photomasks this enables fabrication of high-resolution colour images using single exposure steps. We further demonstrate spatiotemporal tuning of the structurally coloured surfaces and images via electrochemical modulation of the polymer redox state. The simple structure, facile fabrication, wide colour gamut, and dynamic colour tuning make this concept competitive for future multi-functional and smart displays.

National Category
Materials Chemistry
Identifiers
URN: urn:nbn:se:liu:diva-173349OAI: oai:DiVA.org:liu-173349DiVA, id: diva2:1529028
Available from: 2021-02-17 Created: 2021-02-17 Last updated: 2023-12-28Bibliographically approved
In thesis
1. Optics of Conducting Polymer Thin Films and Nanostructures
Open this publication in new window or tab >>Optics of Conducting Polymer Thin Films and Nanostructures
2021 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Intrinsically conducting polymers forms a category of doped conjugated polymers that can conduct electricity. Since their discovery in the late 1970s, they have been widely applied in many fields, ranging from optoelectronic devices to biosensors. The most common type of conducting polymers is poly(3,4-ethylenedioxythiophene), or PEDOT. PEDOT has been popularly used as electrodes for solar cells or light-emitting diodes, as channels for organic electrochemical transistors, and as p-type legs for organic thermoelectric generators. Although many studies have been dedicated to PEDOT-based materials, there has been a lack of a unified model to describe their optical properties across different spectral ranges. In addition, the interesting optical properties of PEDOT-based materials, benefiting from its semi-metallic character, have only been rarely studied and utilized, and could potentially enable new applications.

Plasmonics is a research field focusing on interactions between light and metals, such as the noble metals (gold and silver). It has enabled various opportunities in fundamental photonics as well as practical applications, varying from biosensors to colour displays. This thesis explores highly conducting polymers as alternatives to noble metals and as a new type of active plasmonic materials. Despite high degrees of microstructural disorder, conducting polymers can possess electrical conductivity approaching that of poor metals, with particularly high conductivity for PEDOT deposited via vapour phase polymerization (VPP). In this thesis, we systematically studied the optical and structural properties of VPP PEDOT thin films and their nanostructures for plasmonics and other optical applications. 

We employed ultra-wide spectral range ellipsometry to characterize thin VPP PEDOT films and proposed an anisotropic Drude-Lorentz model to describe their optical conductivity, covering the ultraviolet, visible, infrared, and terahertz ranges. Based on this model, PEDOT doped with tosylate (PEDOT:Tos) presented negative real permittivity in the near infrared range. While this indicated optical metallic character, the material also showed comparably large imaginary permittivity and associated losses. To better understand the VPP process, we carefully examined films with a collection of microstructural and spectroscopic characterization methods and found a vertical layer stratification in these polymer films. We unveiled the cause as related to unbalanced transport of polymerization precursors. By selection of suitable counterions, e.g., trifluoromethane sulfonate (OTf), and optimization of reaction conditions, we were able to obtain PEDOT films with electrical conductivity exceeding 5000 S/cm. In the near infrared range from 1 to 5 µm, these PEDOT:OTf films provided a well-defined plasmonic regime, characterized by negative real permittivity and lower magnitude imaginary component. Using a colloidal lithography-based approach, we managed to fabricate nanodisks of PEDOT:OTf and showed that they exhibited clear plasmonic absorption features. The experimental results matched theoretical calculations and numerical simulations. Benefiting from their mixed ionic-electronic conducting characters, such organic plasmonic materials possess redox-tunable properties that make them promising as tuneable optical nanoantennas for spatiotemporally dynamic systems. Finally, we presented a low-cost and efficient method to create structural colour surfaces and images based on UV-treated PEDOT films on metallic mirrors. The concept generates beautiful and vivid colours through-out the visible range utilizing a synergistic effect of simultaneously modulating polymer absorption and film thickness. The simplicity of the device structure, facile fabrication process, and tunability make this proof-of-concept device a potential candidate for future low-cost backlight-free displays and labels.

Place, publisher, year, edition, pages
Linköping University Electronic Press, 2021. p. 114
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 2107
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:liu:diva-173352 (URN)10.3384/diss.diva-173352 (DOI)9789179297459 (ISBN)
Public defence
2021-03-22, K3, Kåkenhus, Campus Norrköping, Norrköping, 10:00 (English)
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Available from: 2021-02-19 Created: 2021-02-17 Last updated: 2023-12-28Bibliographically approved

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Chen, ShangzhiRossi, StefanoKuhne, PhilippStanishev, ValleryEngquist, IsakBerggren, MagnusDarakchieva, VanyaEdberg, JesperJonsson, Magnus

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Chen, ShangzhiRossi, StefanoKuhne, PhilippStanishev, ValleryEngquist, IsakBerggren, MagnusDarakchieva, VanyaEdberg, JesperJonsson, Magnus
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Materials Chemistry

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