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  • 351.
    Wen, R.-T.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, C.-G.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Electrochromic performance of Ni oxide thin films intercalated with Li+ ions2014In: Journal of Physics, Conference Series, ISSN 1742-6588, E-ISSN 1742-6596, Vol. 559, no 1, article id 012006Article in journal (Refereed)
    Abstract [en]

    ABSTRACT: Porous Ni oxide thin films were deposited on unheated ITO/glass substrates by sputtering in argon–oxygen. The as-deposited thin films have a cubic NiO structure and still exhibit such a structure after 10,000 electrochemical cycles in 1 M LiClO 4 in propylene carbonate in the range between 2.0 and 4.1 V vs Li/Li + . Electrochromic performance showed a rapid drop of charge density over the first hundreds of cycles and subsequently a very slow decrease. The charge density was 87% of the initial one after 1,000 cycles and 82% after 10,000 cycles, indicating an extremely slow decay after 1,000 cycles. Optical modulation was also slightly decreased after 10,000 cycles, which is due to the drop of charge density.

    Full-text · Conference Paper · Sep 2014

  • 352.
    Wen, R.-T.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, C.-G.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Improved Electrochromic Durability of Nickel Oxide by Iridium Doping2014In: Abstracts European Materials Research Society (E-MRS) Spring Meeting: Abstract L VIII-1, 2014, Vol. L VIII-1Conference paper (Refereed)
  • 353.
    Wen, Rui-Tao
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Arvizu, Miguel A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Morales-Luna, Michael
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, Claes-Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Ion Trapping and Detrapping in Amorphous Tungsten Oxide Thin Films Observed by Real-Time Electro-Optical Monitoring2016In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 28, no 13, p. 4670-4676Article in journal (Refereed)
    Abstract [en]

    Several technologies for energy saving and storage rely on ion exchange between electrodes and electrolytes. In amorphous electrode materials, a detailed knowledge of Li-ion intercalation is hampered by limited information about the structure and transport properties of the materials. Amorphous tungsten oxide is the most studied electrochromic material and suffers from ion trapping-induced degradation of charge capacity and optical modulation span upon extensive electrochemical cycling. In this paper, we investigate trapping and detrapping processes in connection with performance degradation and specifically use real-time electro-optical monitoring to identify different trap energy ranges pertinent to the ion-intercalated system. Evidence of three kinds of traps that degrade electrochromic tungsten oxide during ion intercalation is presented: (i) shallow traps that erode the colored state, (ii) deep traps that lower the bleached-state transmittance, and (iii) irreversible traps. Importantly, Li-ion detrapping from shallow and deep traps takes place by different processes: continuous Li-ion extraction is possible from shallow traps, whereas a certain release time must be exceeded for detrapping from deep traps. Our notions for ion trapping and detrapping, presented here, may serve as a starting point for discussing ion intercalation in various amorphous materials of interest for energy-related applications.

  • 354.
    Wen, Ruitao
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Arvizu, Miguel A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, Claes-Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Electrochromics for energy efficient buildings: Towards long-term durability and materials rejuvenation2016In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 290, p. 135-139Article in journal (Refereed)
    Abstract [en]

    Electrochromic devices such as "smart windows" for energy efficient windows must be durable enough for many years of practical use. Typical devices employ films based on W oxide and Ni oxide, and this paper surveys recent progress on durability-related issues for these materials. In the case of W oxide, we discuss the beneficial effects of Ti addition, and we describe recent and unexpected progress concerning galvanostatic rejuvenation of aged W oxide films. For Ni oxide, we report how charge exchange declination during extended voltammetric cycling can be modeled in terms of a power law.

  • 355.
    Wen, Rui-Tao
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Arvizu, Miguel A
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, Claes-Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Progress in Electrochromics: Towards Long-Term Durability and Materials Rejuvenation for Oxide-Based Thin Films2015In: ECS Transactions, Electrochemical Society, 2015, Vol. 66 (31), p. 9-16Conference paper (Refereed)
    Abstract [en]

    Most electrochromic devices, such as “smart windows” for energy efficient glazings, must be durable enough for many years of service life. Typical constructions use films based on thin films of W oxide and Nioxide, and this paper summarizes progress on durability-related issues for these materials. For W oxide, we describe recent and unexpected progress on galvanostatic rejuvenation of aged W oxide films, and we also discuss the beneficial effects of Ti addition. For Ni oxide, we report how charge exchange declination during extended voltammetric cycling can be modeled in terms of a power law and also demonstrate how modest additions of Ir can dramatically extend the cycling durability.

  • 356.
    Wen, Ruitao
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Arvizu, Miguel A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, Claes-Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Electrochromics for energy efficient buildings: Towards long-term durability and materials rejuvenation2015In: Surface and Coating Technology, ISSN 0257-8972, Vol. 278, p. 121-125Article in journal (Refereed)
    Abstract [en]

    Electrochromic devices such as “smart windows” for energy efficient windows must be durable enough for many years of practical use. Typical devices employ films based on W oxide and Ni oxide, and this paper surveys recent progress on durability-related issues for these materials. In the case of W oxide, we discuss the beneficial effects of Ti addition, and we describe recent and unexpected progress concerning galvanostatic rejuvenation of aged W oxide films. For Ni oxide, we report how charge exchange declination during extended voltammetric cycling can be modeled in terms of a power law.

  • 357.
    Wen, Rui-Tao
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, C.-G.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Corrigendum: Anodic Electrochromic Nickel Oxide Thin Films: Decay of Charge upon Extensive Electrochemical Cycling2016In: ChemElectroChem, no 3, p. 675-Article in journal (Refereed)
  • 358.
    Wen, Rui-Tao
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, Claes G.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Anodic Electrochromic Nickel Oxide Thin Films: Decay of Charge Density upon Extensive Electrochemical Cycling2016In: ChemElectroChem, E-ISSN 2196-0216, Vol. 3, no 2, p. 266-275Article in journal (Refereed)
    Abstract [en]

    Electrochromic (EC) Ni oxide thin films are a critical component in the smart windows. However, long-term decay of the EC performance in aprotic electrolytes is persistent and poorly understood, and it is difficult to assess lifetimes of EC devices. Here we report on charge density decline upon electrochemical cycling. The charge density decay was modeled with a power law or, alternatively, a stretched exponential; both models describe a rapid drop of charge density during the first hundreds of cycles and a subsequent slower decline. The decay is independent of film composition and applied potential range as long as the upper limit of the potential is 4.4V vs. Li/Li+. Our decay models are interpreted in terms of dispersive chemical reaction kinetics and point at ion diffusion as the rate-limiting step. Power-law exponents are consistent with diffusion. The results provide a framework for evaluating EC durability of Ni-oxide-based thin films and may be important for assessing the durability of EC devices.

  • 359.
    Wen, Rui-Tao
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, Claes G.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Anodic Electrochromism for Energy-Efficient Windows: Cation/Anion-Based Surface Processes and Effects of Crystal Facets in Nickel Oxide Thin Films2015In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 25, no 22, p. 3359-3370Article in journal (Refereed)
    Abstract [en]

    Anodic electrochromic (EC) oxides are of major interest as counter electrodes for smart window applications owing to their unique optical properties upon charge insertion and extraction. However, performance optimization of such oxides has been hampered by limited understanding of their EC mechanism, particularly in Li+-conducting electrolytes. This paper reports on NiOx films with 1.16 x 1.32, prepared by sputter deposition. These films are immersed in an electrolyte of lithium perchlorate in propylene carbonate, and EC properties are studied by cyclic voltammetry and in situ optical transmittance measurements. The electrochromism is significantly enhanced at large values of x. It has been found that charge exchange in Ni oxide is mainly due to surface processes and involves both cations and anions from the electrolyte, which is different from the case of cathodic EC materials such as WO3. Whereas previous studies of Ni oxide have focused on cation intercalation, the cation/anion-based mechanism presented here offers a new paradigm for designing and developing EC devices such as smart windows for energy efficient buildings.

  • 360.
    Wen, Rui-Tao
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, Claes Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar A
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Cyclic voltammetry on sputter-deposited films of electrochromic Ni oxide: Power-law decay of the charge density exchange2014In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 105, no 16, p. 163502-Article in journal (Refereed)
    Abstract [en]

    Ni-oxide-based thin films were produced by reactive direct-current magnetron sputtering and were characterized by X-ray diffraction and Rutherford backscattering spectroscopy. Intercalation of Li+ ions was accomplished by cyclic voltammetry (CV) in an electrolyte of LiClO4 in propylene carbonate, and electrochromism was documented by spectrophotometry. The charge density exchange, and hence the optical modulation span, decayed gradually upon repeated cycling. This phenomenon was accurately described by an empirical power law, which was valid for at least 10(4) cycles when the applied voltage was limited to 4.1V vs Li/Li+. Our results allow lifetime assessments for one of the essential components in an electrochromic device such as a "smart window" for energy-efficient buildings.

  • 361.
    Wen, Rui-Tao
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, Claes
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Eliminating degradation and uncovering ion-trapping dynamics in electrochromic WO3 thin films2015In: Nature Materials, ISSN 1476-1122, E-ISSN 1476-4660, Vol. 14, p. 996-1001Article in journal (Refereed)
    Abstract [en]

    There is keen interest in the use of amorphous WO3 thin films as cathodic electrodes in transmittance-modulating electrochromic devices1–4. However, these films suer from ion-trapping-induced degradation of optical modulation and reversibility on extended LiC-ion exchange. Here,we demonstrate that ion-trapping-induced degradation, which is commonly believed to be irreversible, can be successfully eliminatedby constant-current-driven de-trapping; that is, WO3 films can be rejuvenated and regain their initial highly reversible electrochromic performance. Pronounced ion trapping occurs when x exceeds 0.65 in LixWO3 during ion insertion. We find two main kinds of Li+-ion-trapping site (intermediate and deep) in WO3, where the intermediate ones are most prevalent. Li+ ions can be completely removed from intermediate traps but are irreversibly bound in deep traps. Our results provide a general framework for developing and designing superior electrochromic materials and devices.

  • 362.
    Wen, Rui-Tao
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics. MIT, Ctr Mat Proc, Cambridge, MA 02139 USA..
    Malmgren, Sara
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Granqvist, Claes G.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Degradation Dynamics for Electrochromic WO3 Films under Extended Charge Insertion and Extraction: Unveiling Physicochemical Mechanisms2017In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 9, no 14, p. 12872-12877Article in journal (Refereed)
    Abstract [en]

    Degradation of electrochromic thin films under extended charge insertion and extraction is a technically important phenomenon for which no in-depth understanding is currently on hand. Here, we report on an explorative study of sputter-deposited WO3 films in a Li-ion-conducting electrolyte by use of cyclic voltammetry, in situ optical transmittance, and impedance spectroscopy. A cycling-dependent decrease of the charge capacity could be accurately modeled by a power-law function, and impedance spectroscopy gave evidence for anomalous diffusion as well as a higher charge transfer resistance during deintercalation than during intercalation. Thus, a consistent conceptual picture emerged for the degradation dynamics; it includes the growth of an interfacial barrier layer and also embraces anomalous diffusion coupled with dispersive power-law chemical kinetics.

  • 363.
    Wen, Rui-Tao
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, Claes G.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Electrochromic iridium oxide films: Compatibility with propionic acid, potassium hydroxide, and lithium perchlorate in propylene carbonate2014In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 120, no Part A, p. 151-156Article in journal (Refereed)
    Abstract [en]

    Porous thin films of It oxide were prepared by reactive dc magnetron sputtering onto unheated substrates. The crystallite size was similar to 5 nm, and a small amount of unoxidized Ir was present. The electrochromic performance was studied by optical transmittance measurements and cyclic voltammetry applied to films in aqueous and non-aqueous electrolytes, specifically being 1 M propionic acid, 1 M potassium hydroxide (KOH), and 1 M lithium perchlorate in propylene carbonate (Li-PC). Cyclic voltammetry measurements indicated that the films had a fractal surface structure. Good electrochromism, with mid-luminous transmittance modulation between similar to 55 and similar to 90% in similar to 100-nm-thick films, was documented in all of the electrolytes.

  • 364.
    Wen, Rui-Tao
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, Claes G.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Eliminating Electrochromic Degradation in Amorphous TiO2 through Li-Ion Detrapping2016In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 8, no 9, p. 5777-5782Article in journal (Refereed)
    Abstract [en]

    The quest for superior and low-cost electroehromic (EC) thin films, for applications in smart windows, remains strong because of their large importance for energy-efficient buildings. Although the development of new EC materials for improved devices is important, diminishing or reversing degradation is another key issue, and electrical rejuvenation of degraded EC materials can offer new opportunities. Here we demonstrate that cathodically coloring EC thin films of TiO2, which normally suffer from ion-trapping-induced degradation of charge capacity and optical modulation upon extensive electrochemical cycling, can recover their initial EC performance by a rejuvenation procedure involving Li+ ion detrapping. Thus, the initial performance can be regained, and refreshed TiO2 films exhibit the same degradation features as as-deposited films upon prolonged electrochemical cycling. The rejuvenation was carried out by using either galvanostatic or potentiostatic treatments. Our study may open avenues to explore the recovery not only of EC materials and devices based on those but also for other ion-exchange-based devices.

  • 365.
    Wen, Rui-Tao
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, Claes G.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Sustainable rejuvenation of electrochromic WO3 films2015In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 7, no 51, p. 28100-28104Article, review/survey (Refereed)
    Abstract [en]

    Devices relying on ion transport normally suffer from a decline of their long-term performance due to irreversible ion accumulation in the host material, and this effect may severely curtail the operational lifetime of the device. In this work, we demonstrate that degraded electrochromic WO3 films can sustainably regain their initial performance through galvanostatic de-trapping of Li+ ions. The rejuvenated films displayed degradation features similar to those of the as-prepared films, thus indicating that the de-trapping process is effectively reversible so that long-term performance degradation can be successfully avoided. De-trapping did not occur in the absence of an electric current.

  • 366.
    Wen, Rui-Tao
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, Claes-Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Anodic Electrochromic Nickel Oxide: The Role of Film Composition and Working Potential2014In: European Materials Research Society (E-MRS) Spring Meeting, Lille, France, 26-30 May: Symposium L: Chromogenic Materials and Devices, 2014Conference paper (Refereed)
  • 367.
    Wen, Rui-Tao
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, Claes-Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Electrochromic durability of iridium-doped nickel oxide thin films.2014In: 5th International Symposium on Transparent Conductive Materials, 12-17 October 2014, Chania, Crete, Greece, 2014Conference paper (Refereed)
  • 368.
    Wen, Rui-Tao
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, Claes-Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Electrochromic Iridium-Containing Nickel Oxide Films with Excellent Electrochemical Cycling Performance2016In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 163, no 2, p. E7-E13Article in journal (Refereed)
    Abstract [en]

    Electrochromic Ni oxide thin films attract much interest because of their large potential for applications as optically active layers in energy-saving and comfort enhancing smart windows in buildings. However Ni oxide, typically being the anodic counter electrode in a W-oxide-based device, may suffer severe charge capacity degradation upon extended electrochemical cycling. It is therefore important to identify improved Ni-oxide-based thin films for electrochromics. Here we describe a new class of such films wherein an addition of a small amount of Ir to Ni oxide is found to provide strongly improved electrochemical cycling durability. Best properties were achieved with Ir/(Ir + Ni) = 7.6%, and such films displayed charge capacity and optical modulation that, remarkably, were still increasing after 10,000 cycles.

  • 369.
    Wen, Rui-Tao
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, Claes-Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Electrochromic nickel oxide films and their compatibility with potassium hydroxide and lithium perchlorate in propylene carbonate: Optical, electrochemical and stress-related properties2014In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 565, p. 128-135Article in journal (Refereed)
    Abstract [en]

    Porous nickel oxide films were deposited onto unheated indium tin oxide coated glass substrates by reactive dc magnetron sputtering. These films had a cubic NiO structure. Electrochromic properties were evaluated in 1 M potassium hydroxide (KOH) and in 1 M lithium perchlorate in propylene carbonate (Li-PC). Large optical modulation was obtained for similar to 500-nm-thick films both in KOH and in Li-PC (similar to 70% and similar to 50% at 550 nm, respectively). In KOH, tensile and compressive stresses, due to the expansion and contraction of the lattice, were found for films in their bleached and colored state, respectively. In Li-PC, compressive stress was seen both in colored and bleached films. Durability tests with voltage sweeps between -0.5 and 0.65 V vs Ag/AgCl in KOH showed good durability for 10,000 cycles, whereas voltage sweeps between 2.0 and 4.7 V vs Li/Li+ in Li-PC yielded significant degradation after 1000 cycles.

  • 370.
    Wen, Rui-Tao
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, Claes-Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Improved Electrochromic Durability of Nickel Oxide by Iridium Doping2014In: European Materials Research Society (E-MRS) Spring Meeting, Lille, France, 26-30 May: Symposium L: Chromogenic Materials and Devices, 2014Conference paper (Refereed)
  • 371.
    Wen, Rui-Tao
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, Claes-Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Strongly Improved Electrochemical Cycling Durability by Adding Iridium to Electrochromic Nickel Oxide Films2015In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 7, no 18, p. 9319-9322Article in journal (Refereed)
    Abstract [en]

    Anodically colored nickel oxide (NiO) thin films :are of much interest as counter electrodes in tungsten oxide based electrochromic devices such as "smart windows" for energy-efficient buildings. However, NiO films are prone to Suffering severe charge density degradation upon prolonged electrochemical cycling, which can lead to insufficient device lifetime. Therefore, a means to improve the durability of NiO-based films is an important challenge at present. Here we report that the incorporation of a modest amount of iridium into NiO films [Ir/(Ir + Ni) = 7.6 atom %] leads to remarkable durability, exceeding 10000 cycles in a lithium-conducting, electrolyte, along with significantly improved optical modulation during extended cycling. Structure characterization showed that the face-centered-cubic-type NiO structure remained after iridium addition. Moreover, the crystallinity of these films was enhanced upon electrochemical cycling.

  • 372.
    Wen, Rui-Tao
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, Claes-Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Electrochromic performance of Ni oxide thin filmsintercalated with Li+ ions2014In: Journal of Physics, Conference Series, ISSN 1742-6588, E-ISSN 1742-6596, Vol. 559, p. 012006-Article in journal (Refereed)
    Abstract [en]

    Porous Ni oxide thin films were deposited on unheated ITO/glass substrates by sputtering in argon-oxygen. The as-deposited thin films have a cubic NiO structure and still exhibit such a structure after 10,000 electrochemical cycles in 1 M LiClO4 in propylene carbonate in the range between 2.0 and 4.1 V vs Li/Li+. Electrochromic performance showed a rapid drop of charge density over the first hundreds of cycles and subsequently a very slow decrease. The charge density was 87% of the initial one after 1,000 cycles and 82% after 10,000 cycles, indicating an extremely slow decay after 1,000 cycles. Optical modulation was also slightly decreased after 10,000 cycles, which is due to the drop of charge density.

  • 373.
    Yu-Xia, Ji
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Shu-Yi, Li
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Gunnar A., Niklasson
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Claes-Göran, Granqvist
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Effect of Al oxide top coatings on the durability of thermochromic VO2thin films2014Conference paper (Other academic)
  • 374.
    Århammar, Cecilia
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Pietzsch, Annette
    MAX-lab, Lunds universitet, Lund.
    Bock, Nicolas
    Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM, USA.
    Holmström, Erik
    Instituto di Fisica, Universidad Austral de Chile, Valdivia, Chile.
    Araujo, Carlos Moyses
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Gråsjö, Johan
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Zhao, Shuxi
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Green, Sara
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Peery, T
    Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM, USA.
    Hennies, Franz
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Amerioun, Shahrad
    Sandvik Tooling, R and D, Stockholm.
    Foehlisch, Alexander
    Insitute for Methods and Instrumentation in Synchrotron Radiation Research G-12, Helmhotz-Zentrum Berlin für Materialien und Energie, Berlin, Tyskland.
    Schlappa, Justine
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Schmitt, Thorsten
    Swiss Light Source, Paul Scherrer Institut, Villigen, Schweiz.
    Strocov, Vladimir N
    Swiss Light Source, Paul Scherrer Institut, Villigen, Schweiz.
    Niklasson, Gunnar A
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Wallace, Duane C
    Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM, USA.
    Rubensson, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Johansson, Börje
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Unveiling the complex electronic structure of amorphous metal oxides2011In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 108, no 16, p. 6355-6360Article in journal (Refereed)
    Abstract [en]

    Amorphous materials represent a large and important emerging area of material's science. Amorphous oxides are key technological oxides in applications such as a gate dielectric in Complementary metal-oxide semiconductor devices and in Silicon-Oxide-Nitride-Oxide-Silicon and TANOS (TaN-Al2O3-Si3N4-SiO2-Silicon) flash memories. These technologies are required for the high packing density of today's integrated circuits. Therefore the investigation of defect states in these structures is crucial. In this work we present X-ray synchrotron measurements, with an energy resolution which is about 5-10 times higher than is attainable with standard spectrometers, of amorphous alumina. We demonstrate that our experimental results are in agreement with calculated spectra of amorphous alumina which we have generated by stochastic quenching. This first principles method, which we have recently developed, is found to be superior to molecular dynamics in simulating the rapid gas to solid transition that takes place as this material is deposited for thin film applications. We detect and analyze in detail states in the band gap that originate from oxygen pairs. Similar states were previously found in amorphous alumina by other spectroscopic methods and were assigned to oxygen vacancies claimed to act mutually as electron and hole traps. The oxygen pairs which we probe in this work act as hole traps only and will influence the information retention in electronic devices. In amorphous silica oxygen pairs have already been found, thus they may be a feature which is characteristic also of other amorphous metal oxides.

  • 375.
    Österlund, Lars
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Lebrun, Delphine
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Kaplakis, Vassilios
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Niklasson, Gunnar
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Sahoo, P. K.
    Anand, S.
    Precise tuning of the photonic band gap using multilayered inverse opals2014In: 12th Russia/CIS/Baltic/Japan Symposium on Ferroelectricity and 9th International conference on Functional Materials and Nanotechnologies – RCBJSF–2014-FM&NT / [ed] A. Sarakovskis, Ulma, Riga , 2014Conference paper (Refereed)
    Abstract [en]

    Inverse opals are photonic band gap (PBG) structures with a periodic arrangement of voids with low refractive index (air) in a high-refractive index dielectric media with sub-wavelength periodicity. In analogy with electronic band gaps in solid state semiconductors these structures form forbidden energy ranges for light, irrespective of the photon’s momentum. Recently, inverse opal structures have been studied for photocatalysis applications. Here the idea is to match the edge of the PBG with the electronic band gap of a semiconductor to allow for efficient light absorption. Here we present a novel approach to tune the position and shape of the PBG by purposefully deposit multilayers of oxides with controlled thicknesses on the inside walls of the inverse opals. This avoids the technical problems of changing the periodicity and materials of the opals. The fabrication involves a three-step process: It consists of self-assembly by convective evaporation of polystyrene beads into close-packed fcc structures; atomic layer deposition (ALD) of metal oxides (Al2O3) to fill the voids between the beads; and subsequent Ar ion etching and calcination to crystallize and develop the inverse opal structure. ALD is then repeated to make multi-layer structures of TiO2 with controlled thickness. The inverse opal structures were characterized by optical spectroscopy, X-ray spectroscopy, electron microscopy, and profilometry. Theoretical modeling was performed to describe the optical properties. The results are analyzed and compared with band structure calculations made by the plane-wave expansion method together with finite-difference time-domain simulations of the transmission spectra (Fig. 1). Our method is versatile and can be used to fabricate reactive nanoparticles with different chemical composition on the inside walls; as well as plasmonic nanoparticles embedded in the layers to efficiently absorb slow light.

  • 376.
    Österlund, Lars
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Mattsson, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Brischetto, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Johansson Byberg, Joel
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Stefanov, Bozhidar I
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Ji, Yu -Xia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Spectral Selective Solar Light Enhanced Photocatalysis: TiO2/TiAlN Bilayer Films2018In: Topics in catalysis, ISSN 1022-5528, E-ISSN 1572-9028, Vol. 61, no 15-17, p. 1607-1614Article in journal (Refereed)
    Abstract [en]

    We demonstrate that spectral selective photocatalytic multilayer films can be tailored such that they can harness the full solar spectrum for enhanced photocatalytic gas-phase oxidation of acetaldehyde. Thin films of anatase TiO2 were deposited on a thin solar absorber TiAlN film to fabricate bilayer TiO2/TiAlN films by dc magnetron sputtering on aluminium substrates. The structural and optical properties of the films were characterized by X-ray diffraction and Raman spectroscopy. The reaction rate and quantum yield for acetaldehyde removal was measured and an almost tenfold enhancement of the quantum yield was observed for the TiO2/TiAlN films compared with the single TiO2 film, on par with enhancements achieved with new heterojunction photocatalysts. The results were interpreted by a temperature-induced change of the reaction kinetics. Absorption of simulated solar light illumination resulted in a temperature increase of the TIAlN film that was estimated to be at most 126 K. We show that a concomitant temperature increase of the top layer TiO2 by 100 K shifts the water gas surface equilibrium from multilayer to submonolayer coverage. We propose that this is the main reason for the observed enhancement of the photocatalytic activity, whereby gas phase molecules may come in direct contact with free surface sites instead of having to diffuse through a thin water film. The implications of the results for judicious control of temperature and relative humidity for efficient gas-phase photocatalysis and exploitation of selective solar absorbing films are discussed.

  • 377.
    Österlund, Lars
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Mattsson, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Ji, Yu -Xia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, Claes Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Novel multi-functional self-cleaning, air cleaning and thermochromic films for the built environment2018In: FMNT Functional Materials and Nanotechnologies: Book of Abstracts, 2018, p. 63-, article id INV-10Conference paper (Refereed)
    Abstract [en]

    Spectrally selective photocatalytic multilayer films that exhibit dramatically enhanced photochemical reactivity upon solar light activation were fabricated. It is shown that synergistically enhanced physciochemcial properties can be achieved the surpass those of the constituting single-layer films. We present two case studies: TiO2/VO2 and TiO2/TiAlN bilayer films made by reactive dc magnetron sputtering. The TiO2/VO2 bilayer exhibits enhanced near-infrared light absorption, which thereby heats the TiO2 film by more than 15 degrees, resulting in an almost 2-fold increase of the reaction rate for photo-degradation of stearic acid layers. In addition, the TiO2/VO2 bilayer stack exhibited anti-reflective properties, and enhanced solar modulation (∼ 9%) compared to VO2, and ∼ 20% increased solar absorptance compared to TiO2. In the second example, bilayer TiO2/TiAlN films yielded an almost 10-fold enhancement of the quantum yield for acetaldehyde removal (on par with state-of-the-art, heterojunction photocatalysts), and an associated temperature rise larger than 120 degrees. Both findings can be understood by thermal activation to the increase the surface reaction kinetics, where water desorption from the oxide plays and important role. We generalize the results, and discuss their implications for green building technology and possible scenarios for their implementation.

    References

    1. Yu-Xia Ji, Andreas Mattsson, Gunnar A. Niklasson, Claes-Göran Granqvist, Lars Österlund TiO2/VO2 bilayer coatings for glazing: Synergetically enhanced photocatalytic, thermochromic, and luminous properties, submitted to Advanced Functional Materials 2018.

    2. Lars Österlund, Andreas Mattsson, Joel Martin, Spectrally selective heat absorptive bilayer photocatalyst with enhanced reactivity: TiO2/TiAlN, Topics in Catalysis, in press.

  • 378.
    Österlund, Lars
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Topalian, Z.
    Niklasson, Gunnar
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, C.-G.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Characterization of Oleophobic and Photocatalytic TiO2 Thin Films Prepared by Surface Functionalization with Reactive Sulfur Dioxide Gas2011In: Abstracts 2nd European Symp. Photocatalysis (JEP 2011), 2011Conference paper (Refereed)
5678 351 - 378 of 378
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