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  • 1.
    Aijaz, Asim
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Ji, Yu-Xia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Montero, Jose
    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.
    Kubart, Tomas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Low-temperature synthesis of thermochromic vanadium dioxide thin films by reactive high power impulse magnetron sputtering2016In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 149, p. 137-144Article in journal (Refereed)
    Abstract [en]

    Thermochromic (TC) vanadium dioxide thin films provide means for controlling solar energy throughput and can be used for energy-saving applications such as smart windows. One of the factors limiting the deployment of VO2 films in TC devices is the growth temperature tau(s). At present, temperatures in excess of 450 degrees C are required, which clearly can be an impediment especially for temperature-sensitive substrates. Here we address the issue of high tau(s) by synthesizing VO2 thin films from highly ionized fluxes of depositing species generated in high power impulse magnetron sputtering (HiPIMS) discharges. The use of ions facilitates low-temperature film growth because the energy of the depositing species can be readily manipulated by substrate bias. For comparison, films were also synthesized by pulsed direct current magnetron sputtering. Structural and optical characterization of VO2 thin films on ITO-coated glass substrates confirms previous results that HiPIMS allows tau(s) to be reduced from 500 to 300 degrees C. Importantly, we demonstrated that HiPIMS permits the composition and TC response of the films to be tuned by altering the energy of the deposition flux via substrate bias. An optimum ion energy of 100 eV was identified, which points at a potential for further reduction of tau(s) thereby opening new possibilities for industrially-relevant applications of VO2-based TC thin films. Weak TC activity was observed even at tau(s) approximate to 200 degrees C in HiPIMS-produced films.

  • 2.
    Arvizu, Miguel A
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Triana, Carlos A
    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.
    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.
    Electrochromism in sputter-deposited W-Ti oxide films: Durability enhancement due to Ti2014In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 125, p. 184-189Article in journal (Refereed)
    Abstract [en]

    Thin films of W-Ti oxide were prepared by reactive DC magnetron sputtering and were characterized by Rutherford bathcattering spectrometry, X-ray diffraction, scanning electron microscopy and atomic force microscopy. The electrochromic properties were studied by cyclic voltammetry in an electrolyte of lithium perchlorate in propylene carbonate and by optical transmittance measurements. The addition of Ti significantly promoted the amorphous nature of the films and stabilized their electrochemical cycling performance and dynamic range for electrochromism. (C) 2014 Elsevier B.V. All rights reserved.

  • 3.
    Backholm, Jonas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Avendaño, Esteban
    Azens, Andris
    de M. Azevedo, Gustavo
    Coronel, Ernesto
    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.
    Iridium-based oxides: Recent advances in coloration mechanism, structural and morphological characterization2008In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 92, no 2, p. 91-96Article in journal (Refereed)
    Abstract [en]

    Films of iridium-tantalum oxide and iridium oxide have been prepared by sputtering and studied regarding their structure and electrochemical properties. X-ray diffraction and transmission electron microscopy showed an average grain size of 3-4 nm for both films. Point energy dispersive X-ray spectrometry showed an inhomogeneous distribution of iridium and tantalum indicating that the iridium-tantalum oxide may be a mixture of small IrO2 and Ta2O5 grains, which is consistent with the determined composition IrTa1.4O5.6. X-ray photoelectron spectroscopy gave valuable information on the stabilization process of the as-deposited films involving an uptake of oxygen, and on a coloration mechanism only including protons.

  • 4.
    Backholm, Jonas
    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.
    Optical properties of electrochromic iridium oxide and iridium-tantalum oxide thin films in different colouration states2008In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 92, no 11, p. 1388-1392Article in journal (Refereed)
    Abstract [en]

    Electrochromic iridium oxide (IrOx) and iridium-tantalum oxide (IrTaOx) thin films were prepared by sputtering. Complex refractive indices were determined for samples deposited on indium-tin oxide covered glass in different colouration states, and for as-deposited samples on sapphire and Corning glass. The refractive index was found to be practically constant for both IrOx (similar to 1.3) and IrTaOx (similar to 2). The extinction coefficient was found to vary between the coloured and bleached states with similar to 35% for IrOx and similar to 55% for IrTaOx at 660 nm. This is believed to be a result of the removal of intraband transitions within the Ir t(2g) band during bleaching.

  • 5.
    Barrios, David
    et al.
    Escuela Superior Ploytechnica de Chimborazo, Ecuador.
    Vergaz, Ricardo
    Universidad Carlos III de Madrid.
    Sanchez-Pena, Jose M
    Universidad Carlos III de Madrid.
    Garcia-Camara, Braulio
    Universidad Carlos III de Madrid.
    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.
    Simulation of the thickness dependence of the optical properties of suspended particle devices2015In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 143, p. 613-622Article in journal (Refereed)
    Abstract [en]

    Suspended particle devices (SPDs) constitute an electrically powered chromogenic technology, in which the active layer quickly are able to rapidly switches from a dark bluish-black dark color state to a clear greyish color appearance when an AC electric field is applied. Two-flux and four-flux models were used to derive refractive indices and extinction coefficients, as well as scattering and absorption coefficients, of the particle-containing active layer. These entities were used in model calculations to predict the direct, total and diffuse components of the transmittance andthe reflectance, together along with the color appearance and haze, as a function of the thickness of the active layer. An optimum thickness for the optical contrast of the SPD was determined in this way and was found to be in the range of 200 to 300 nm. The SPDdevices device exhibits a significant reflectance  haze particularly in reflection.

  • 6.
    Barrios, David
    et al.
    Universidad Carlos III de Madrid.
    Vergaz, Ricardo
    Universidad Carlos III de Madrid.
    Sanchez-Pena, Jose M.
    Universidad Carlos III de Madrid.
    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.
    Toward a quantitative model for suspended particle devices: Optical scattering and absorption coefficients2013In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 111, p. 115-122Article in journal (Refereed)
    Abstract [en]

    Suspended particle devices (SPDs) allow rapid voltage-controlled modulation of their optical transmittance and are of interest for solar-energy-related and other applications. We investigated the spectral total and diffuse transmittance of an SPD, including its angular dependence. The optical modulation was large for visible light but almost nil in the infrared, and the devices had noticeable haze. A theoretical two-flux model was formulated and provided a quantitative description of the absorption and scattering coefficients and thereby of the detailed optical performance. This analysis gives a benchmark for assessing improvements of the SPD technology as well as for comparing it with alternative technologies for optical modulation.

  • 7.
    Bayrak Pehlivan, I.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Marsal, R.
    Pehlivan, E.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Runnerstrom, E. L.
    Milliron, D. J.
    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.
    Electrochromic Devices with Polymer Electrolytes Functionalized by SiO2 and In2O3:Sn Nanoparticles: Rapid Coloration/Bleaching Dynamics and Strong Near-Infrared Absorption2014In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 126, p. 241-247Article in journal (Refereed)
  • 8.
    Bayrak Pehlivan, Ilknur
    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.
    Marsal, Roser
    ChromoGenics AB, Uppsala.
    Georen, Peter
    ChromoGenics AB, Uppsala.
    Niklasson, Gunnar A
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    [PEI-SiO2]:[LiTFSI] nanocomposite polymer electrolytes: Ion conduction and optical properties2012In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 98, p. 465-471Article in journal (Refereed)
    Abstract [en]

    Ion conductivity and optical properties were investigated for polymer electrolytes based on poly (ethyleneimine) and lithium bis(trifluoromethylsulfonyl)imide and also containing up to 9 wt.% of 7-nm-diameter SiO2 nanoparticles. The [N]:[Li] molar ratio was kept constant at 50:1. Impedance measurements were performed in the frequency range 10(-2)-10(7) Hz and between the temperatures 20 and 70 degrees C with an applied ac voltage of 1 V. Spectrophotometric data of total and diffuse transmittance were taken between the wavelengths 300 and 2500 nm. The bulk impedance was fitted to a conductive Havriliak-Negami circuit model. The ion conductivity increased monotonically for increasing SiO2 contents: specifically its room temperature value went from 8.5 x 10(-7) S/cm without nanoparticles to 3.8 x 10(-5) S/cm for 8 wt.% of SiO2 while the diffuse transmittance remained at similar to 1% so that optical clarity prevailed.

  • 9.
    Berggren, Lars
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Ederth, Jesper
    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.
    Electrical Conductivity as a Function of Temperature in Amorphous Lithium Tungsten Oxide2004In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 84, no 1, p. 329-336Article in journal (Refereed)
    Abstract [en]

    Tungsten oxide is a widely used electrochromic material for smart windows. In order to study the charge carriers involved in the electrochromic process, it is important to characterize the electrical transport in tungsten oxide. Substoichiometric amorphous tungsten oxide films were prepared by DC-magnetron sputtering. The films were electrochemically intercalated with lithium. The Li/W intercalation ratios for the tungsten oxide films were in the range 0.15–0.53. Temperature dependent resistivity measurements were performed in the temperature range 77–300 K for samples at different lithium intercalation levels. It was found that the data are consistent with the variable range hopping model.

  • 10.
    Berggren, Lars
    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.
    Influence of sputtering conditions on the solar and luminous optical properties of amorphous LixWoy thin films2005In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 85, no 4, p. 573-586Article in journal (Refereed)
    Abstract [en]

    Thin films of amorphous tungsten oxide were deposited by sputtering onto glass substrates coated by conductive indium–tin oxide. The films were sputtered at different oxygen-to-argon flow ratios with different pressure and power. Elastic recoil detection analysis determined the density and the stoichiometry. X-ray diffraction measurements showed that the films were amorphous. The films were electrochemically intercalated with lithium ions. At several intercalation levels of each film, the optical reflectance and transmittance were measured in the wavelength range 0.3–2.5 μm. We study the effect of various sputtering conditions on the coloration efficiency of the films and on the luminous and solar optical properties. The O2/Ar ratio and the sputter pressure determine to a large extent the optical absorption. As-deposited sputtered tungsten oxide with sufficiently little oxygen exhibits an absorption peak similar to the case of lithium intercalation.

  • 11.
    Boström, Tobias
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Jensen, Jens
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Ion Physics.
    Valizadeh, Sima
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Westin, Gunnar
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Wäckelgård, Ewa
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    ERDA of Ni-Al2O3/SiO2 solar thermal selective absorbers2008In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 92, no 10, p. 1177-1182Article in journal (Refereed)
    Abstract [en]

    Thin film materials for the use in solar thermal absorbers have been investigated using time-of-flight energy elastic recoil detection analysis (ERDA). The ERDA measurements proved to be very efficient in detecting the elemental depth composition of a selective solar absorber. The three-layer absorber is composed of an 80% nickel-20% alumina film at the base, a 40% nickel-60% alumina layer in the middle and finally an AR film of silica or hybrid-silica film at the top. The difference between solution volume percent and actual volume percent could be investigated when studying individual nickel-alumina films with varying ratios coated on glass substrates. The result showed that there was a maximum difference of 3% between the calculated solution volume percent and the actual volume percentages in the solid films. The ERDA measurements also indicate that about 15% of the nickel found in the nickel-alumina composite films is bound in the form of NiO.

  • 12.
    Boström, Tobias
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Westin, Gunnar
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Wäckelgård, Ewa
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Optimization of a solution-chemically derived solar absorbing spectrally selective surface2007In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 91, no 1, p. 38-43Article in journal (Refereed)
    Abstract [en]

    A previously studied solution chemically derived two layer absorber has been improved by adding a third layer. Simulations done with a thin film program showed that the optimized three layer selective absorber should be composed of an 80% nickel-20% alumina film of 100 nm at the base, a 40% nickel-60% alumina film of 60 nm in the middle and finally a 100% silica film of 85 nm at the top. Experimental results confirmed the computer simulated three layer structure. Prepared absorber consisting of the theoretically found optimized layer structure achieved a solar absorptance, alpha(sol), of 0.97 and a thermal emittance, epsilon(therm), of 0.05.

  • 13.
    Brogren, Maria
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Helgesson, Anna
    Karlsson, Björn
    Nilsson, Johan
    Roos, Arne
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Optical properties, durability, and system aspects of a new aluminium-polymer-laminated steel reflector for solar concentrators2004In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 82, no 3, p. 387-412Article in journal (Refereed)
    Abstract [en]

    A newly developed aluminium-polymer-laminated steel reflector for use in solar concentrators was evaluated with respect to its optical properties, durability, and reflector performance in solar thermal and photovoltaic systems. The optical properties of the reflector material were investigated using spectrophotometer and scatterometry. The durability of the reflector was tested in a climatic test chamber as well as outdoors in Älvkarleby , Sweden. Before ageing, the solar weighted total and specular reflectance values were 82% and 77%, respectively, and the reflector scattered light isotropically. After 1 year's outdoor exposure, the total and specular solar reflectance had decreased by less than 1%. However, after in damp heat and simulated solar radiation, the optical properties had changed significantly: The light scattering was anisotropic and the total and specular solar reflectance values had decreased to 75% and 42%, respectively. The decrease was found to be due to degradation of the protective polyethylene terephthalate (PET) layer, caused by UV radiation and high temperature. The conclusions are that the degradation is climate dependent and that PET is not suitable as a protective coating under extreme conditions, such as those in the climatic test chamber. However, the results from outdoor testing indicate that the material withstands exposure in a normal Swedish climate.

  • 14. Bruder, Ingmar
    et al.
    Karlsson, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Eickenmeyer, Felix
    Hwang, Jaehyung
    Erk, Peter
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Weis, Jürgen
    Pschirer, Neil
    Efficient organic tandem cell combining a solid state dye-sensitized and a vacuum deposited bulk heterojunction solar cell2009In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 93, no 10, p. 1896-1899Article in journal (Refereed)
    Abstract [en]

    In this letter, we report on an efficient organic tandem solar cell combining a solid state dye-sensitized with a ZnPc/C60-based, vacuum deposited bulk heterojunction solar cell. Due to an effective serial connection of both subcells and to the complementary absorption of the dyes used, a power conversion efficiency of ηp=(6.0±0.1)% was achieved under simulated AM 1.5 illumination. The device parameters are , and FF=(54±1)%.

  • 15. Dam, B.
    et al.
    Granqvist, C.-G.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Pemble, M.
    Rougier, A.
    Chromogenic Materials and Devices2015In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 143, p. 591-640Article in journal (Refereed)
  • 16. Dam, B
    et al.
    Granqvist, CG
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Pemble, M
    Rougier, A
    Preface2015In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 143, p. 591-Article in journal (Refereed)
  • 17. Fabregat-Santiago, Francisco
    et al.
    Bisquert, Juan
    Garcia-Belmonte, Germa
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry I.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry I.
    Influence of electrolyte in transport and recombination in dye-sensitized solar cells studied by impedance spectroscopy2005In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 87, no 1-4, p. 117-131Article in journal (Refereed)
    Abstract [en]

    The main features of the characteristic impedance spectra of dye-sensitized solar cells are described in a wide range of potential conditions: from open to short circuit. An equivalent circuit model has been proposed to describe the parameters of electron transport, recombination, accumulation and other interfacial effects separately. These parameters were determined in the presence of three different electrolytes, both in the dark and under illumination. Shift in the conduction band edge due to the electrolyte composition was monitored in terms of the changes in transport resistance and charge accumulation in TiO2. The interpretation of the current-potential curve characteristics, fill factor, open-circuit photopotential and efficiency in the different conditions, was correlated with this shift and the features of the recombination resistance.

  • 18.
    Frisk, Christopher
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Ericson, Tove
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Li, Shu-Yi
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Szaniawski, Piotr
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Olsson, Jörgen
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Platzer-Björkman, Charlotte
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Combining strong interface recombination with bandgap narrowing and short diffusion length in Cu2ZnSnS4 device modeling2016In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 144, p. 364-370Article in journal (Refereed)
    Abstract [en]

    In this work we establish a device model in SCAPS, incorporating bandgap narrowing, short minority carrier diffusion length and interface recombination. The model is based on a reference device with standard structure; sputtered Mo on soda lime glass, a reactively sputtered and annealed Cu2ZnSnS4 (CZTS) absorber layer, chemical bath deposited CdS and sputtered i-ZnO buffer layers, and front contact formed with sputtered ZnO:Al and an evaporated Ni/Al/Ni grid. The efficiency of the reference device is 6.7%. Model parameter values of the absorber layer are based on the analysis of temperature dependent current–voltage (JVT) measurements, capacitance–voltage (CV) and drive-level capacitance profiling (DLCP) measurements, performed on the reference device, and on the comparison of simulated and measured quantum efficiency (QE) and current–voltage (JV) performance. Additional parameters are taken from literature. The key elements, electron–hole pair generation and recombination in the absorber layer, are the main focus in this study. Reported values of the absorption coefficient of CZTS vary around one order of magnitude when comparing data from reflectance–transmission (RT) measurements with ellipsometry measurements, and calculations. Therefore, a modified semi-empirical absorption coefficient, extracted from RT and QE measurements, with the depletion width from CV and DLCP, is presented and used in this study. The dominating recombination path is evaluated with JVT   analysis and the zero Kelvin activation energy (EA,0) is extracted from both temperature dependent open circuit voltage (VOC) and from modified Arrhenius plots. In each case,is found to be substantially smaller than the bandgap energy, even when considering bandgap narrowing due to disorder, which is an indication that the deficit observed in our CZTS device dominated by interface recombination. Finally, a complete device model is established, with JV   and QE simulations in good agreement with corresponding measurements, where the interface has the biggest impact on the Voc deficit, but with clear contribution from bulk recombination, with minority carrier diffusion length 250 nm, and from bandgap narrowing, giving a lower than nominal bandgap energy of 1.35 eV.

  • 19.
    Granqvist, C.-G.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Oxide Electrochromics: An Introduktion to Devices and Materials2012In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 99, p. 1-13Article in journal (Refereed)
  • 20.
    Granqvist, Claes G.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Azens, A
    Heszler, P
    Kish, L B
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Nanomaterials for benign indoor environments: Electrochromics for “smart windows”, sensors for air quality, and photo-catalysts for air cleaning2007In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 91, no 4, p. 355-365Article in journal (Refereed)
    Abstract [en]

    Nanomaterials can be used in a number of technologies in order to accomplish benign indoor environments. This paper takes a unified view on this problem from a solar-energy-based perspective and specifically considers electrochromics for achieving good day-lighting jointly with energy efficiency, sensors aimed at air quality assessment, and photocatalysis for air cleaning. Recent results, mainly from the authors’ laboratories, are reported for all of these areas.

  • 21.
    Granqvist, Claes Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Oxide Electrochromics: Why, How, and Whither2008In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 92, no 2, p. 203-208Article in journal (Refereed)
    Abstract [en]

    Electrochromic oxides form the basis of "smart windows" which are able to provide energy efficiency and indoor comfort simultaneously. This paper attempts to give an introduction to "smart windows" technology, which finally seems to be ready for large-scale applications. The "whys" and "hows" are discussed from the viewpoints of materials, device technology, low-cost manufacturing aspects, and applications to buildings as well as niche products. Furthermore, there are some speculations as to the "whithers" of oxide electrochromics for applications to buildings of the future.

  • 22.
    Granqvist, Claes Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Transparent Conductors as Solar Energy Materials: A Panoramic Review2007In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 91, no 17, p. 1529-1598Article, review/survey (Refereed)
    Abstract [en]

    Transparent conductors(TCs) have a multitude of applications for solar energy utilization and for energy savings, especially in buildings. The largest of these applications, in terms of area, make use of the fact that the TCs have low infrared emittance and hence can be used to improve the thermal properties of modern fenestration. Depending on whether the TCs are reflecting or not in the near infrared pertinent to solar irradiation, the TCs can serve in "solar control" or "low-emittance" windows. Other applications rely on the electrical conductivity of the TCs, which make them useful as current collectors in solar cells and for inserting and extracting electrical charge in electrochromic "smart windows" capable of combining energy efficiency and indoor comfort in buildings. This Review takes a "panoramic" view on TCs and discusses their properties from the perspective of the radiative properties in our ambience. This approach leads naturally to considerations of spectral selectivity, angular selectivity, and temporal variability of TCs, as covered in three subsequent sections. The spectrally selective materials are thin films based on metals (normally gold or titanium nitride) or wide band gap semiconductors with heavy doping (normally based on indium, tin, or zinc). Their applications to energy-efficient windows are covered in detail, experimentally as well as theoretically, and briefer discussions are given applications to solar cells and solar collectors. Photocatalytic properties and super-hydrophilicity are touched upon. Angular selective TCs, for which the angular properties are caused by inclined columnar nanostructures, are then covered. A discussion of TC-like materials with thermochromic and electrochromic properties follows in the final part. Detailed treatments are given for thermochromic materials based on vanadium dioxide and for electrochromic multi-layer structures (incorporating TCs as essential components). The reference list is extensive and aims at giving an easy entrance to the many varied aspects of TCs.

  • 23.
    Granqvist, Claes-Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Preparation of thin films and nanostructured coatings for clean tech applications: A primer2012In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 99, p. 166-175Article in journal (Refereed)
    Abstract [en]

    Thin films and nanostructured coatings are of great and increasing importance for clean tech, including applications to solar energy and energy efficiency. This tutorial review discusses why this is so and surveys the major preparation technologies and their characteristics. Particular attention is given to techniques requiring vacuum or plasmas-with foci on evaporation and sputtering-but a wide range of other techniques is surveyed as well. Large-scale deposition is discussed in some detail, and perspectives are given on possible future developments.

  • 24.
    Granqvist, Claes-Göran
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Lansåker, Pia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Mlyuka, Nuru
    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.
    Avendano, Esteban
    Progress in Chromogenics: New Results for Electrochromic and Thermochromic Materials and Devices2009In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 93, no 12, p. 2032-2039Article in journal (Refereed)
    Abstract [en]

    Chromogenic device technology can be used to vary the throughput of   visible light and solar energy for windows in buildings as well as for   other see-through applications. The technologies can make use of a   range of "chromic" materials - such as electrochromic, thermochromic,   photochromic, etc - either by themselves or in combinations. The first   part of this paper points at the great energy savings that can be   achieved by use of chromogenic technologies applied in the built   environment, and that these savings can be accomplished jointly with   improved indoor comfort for the users of the building. Some recent data   are presented on a foil-type electrochromic device incorporating   tungsten oxide and nickel oxide. In particular, we consider the   possibilities of controlling the near-infrared transmittance an   optimize this property for specific climates. To that end we discuss   Au-based transparent conductors for electrochromics as well as   high-transmittance thermochromic multilayer films incorporating VO2 and TiO2.

  • 25.
    Granqvist, Claes-Göran
    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.
    Solar energy materials for thermal applications: A primer2018In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 180, p. 213-226Article in journal (Refereed)
    Abstract [en]

    Solar energy materials have properties that are tailored to the characteristics of the electromagnetic radiation in our natural surroundings, specifically its spectral distribution, angle of incidence and intensity. This tailoring can be made with regard to solar irradiation, thermal emission, atmospheric absorption, visible light, photosynthetic efficiency and more. Solar energy materials can be of many kinds, e.g., metallic, semiconducting, dielectric, glassy, polymeric, gaseous, etc. In particular, thin surface coatings of solar energy materials may exhibit the desired properties in their own right or may yield such properties when backed by an appropriate substrate. This article surveys a number of topics related to thermal applications such as solar thermal converters, transparent thermal insulators, devices for radiative cooling by exposure to the clear sky, and windows and glass facades with static or dynamic properties. The purpose of the present paper is to provide a bird's eye view over a wide class of materials of rising importance rather than giving detailed accounts of highly specialized topics.

  • 26.
    Green, Sara
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Backholm, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Georen, P
    Granqvist, Claes-Göran
    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.
    Electrochromism in Nickel Oxide and Tungsten Oxide Thin Films: Ion Intercalation from Different Electrolytes2009In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 93, no 12, p. 2050-2055Article in journal (Refereed)
    Abstract [en]

    Electrochromic (EC) NiOz and WOy thin films were prepared by sputtering   and were used in a feasibility study aimed at investigating mixtures of   these two oxides. The object was to identify a suitable electrolyte,   compatible with both NiOz and WOy. To that end we carried out cyclic   voltammetry (CV) in potassium hydroxide (KOH), propionic acid, and   lithium perchlorate in propylene carbonate (Li-PC). WOy could be   coloured in propionic acid and Li-PC, while NiOz could be coloured only   in KOH. Both films showed best stability in Li-PC, which hence is well   suited for further studies of mixed NiOz and WOy.

  • 27.
    Green, Sara
    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
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Structure and optical properties of electrochromic tungsten-containing nickel oxide films2014In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 126, p. 248-259Article in journal (Refereed)
    Abstract [en]

    Electrochromic NixW1-x oxide thin films with 0.5 < x < 1, were deposited by co-sputtering from one Ni and one W metal target. The different compositions were structurally characterized by X-ray diffraction, X-ray photoelectron spectroscopy and Rutherford backscattering spectroscopy. The optical and electrochemical properties were investigated by spectrophotometry and cyclic voltammetry in LiClO4 dissolved in propylene carbonate. It was found that the samples turned amorphous upon W addition and that the NixW1-x oxides probably consisted of hydrated Ni oxides and NiWO4. The charge insertion/extraction and optical modulation was unfortunately very modest. Moreover, an aging effect, resulting in a strong bleaching process of the samples was observed. Nevertheless, it was found that, for electrochromic applications, the advantage of W addition was that the transparency at the bleached state was enhanced for all compositions and for wavelengths of 400 nm up to NIR.

  • 28.
    Green, Sara V
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Pehlivan, Esat
    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.
    Electrochromism in sputter deposited nickel-containing tungsten oxide films2012In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 99, p. 339-344Article in journal (Refereed)
    Abstract [en]

    Thin films of NixW1-x oxide were prepared by reactive DC magnetron co-sputtering and were investigated by optical and electrochemical measurements. Electrochromism was found only for 0<x<0.3 but not for 0.3<x<0.6, though films with x~0.4 could still sustain reversible charge insertion. The coloration efficiency was largest for 0.10<x<0.15. The charge capacity of the NixW1-x oxide films decreased upon increasing the value of x as a consequence of a decreasing ion diffusion coefficient leading to slower kinetics.

  • 29.
    Guo, Junji
    et al.
    Beihang Univ, Sch Phys & Nucl Energy Engn, Electrochrom Ctr, Beijing 100191, Peoples R China..
    Wang, Mei
    Beihang Univ, Sch Phys & Nucl Energy Engn, Electrochrom Ctr, Beijing 100191, Peoples R China..
    Zhang, Zhi-Bin
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Dong, Guobo
    Beihang Univ, Sch Phys & Nucl Energy Engn, Electrochrom Ctr, Beijing 100191, Peoples R China..
    Liu, Famin
    Beihang Univ, Sch Phys & Nucl Energy Engn, Electrochrom Ctr, Beijing 100191, Peoples R China..
    Wang, Hao
    Beijing Univ Technol, Coll Mat Sci & Engn, Beijing 100124, Peoples R China..
    Yu, Hang
    Beihang Univ, Sch Phys & Nucl Energy Engn, Electrochrom Ctr, Beijing 100191, Peoples R China..
    Xiao, Yu
    Beihang Univ, Sch Phys & Nucl Energy Engn, Electrochrom Ctr, Beijing 100191, Peoples R China..
    Liu, Jiang
    Jiangsu Fanhua Glass Co Ltd, Nantong, Jiangsu, Peoples R China..
    Diao, Xungang
    Beihang Univ, Sch Phys & Nucl Energy Engn, Electrochrom Ctr, Beijing 100191, Peoples R China..
    Vacancy dependent electrochromic behaviors of NiOx anodes: As a single layer and in devices2018In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 178, p. 193-199Article in journal (Refereed)
    Abstract [en]

    Electrochromic(EC), nonstoichiometric NiOx thin films were made by reactive magnetron sputtering at low oxygen flow ratio(i.e., P = O-2/Ar + O-2 < 10%). The results of optical spectral, x-ray diffraction spectrum, and x-ray photoelectron spectroscopy analyses indicate that the samples are oxygen(nickel)-deficient as P <= %4(>=%6), resulting in sub(over)-stoichiometry films. Spectroelectrochemical measurements show that the EC effect of NiOx in nonaqueous PC - LiClO4 electrolyte is direct correlation with the nickel vacancy concentration in films, while that in the aqueous KOH solution is nearly uninfluenced upon the change in stoichiometry as P >= %4. The films deposited at P = 6% exhibit higher coloration efficiency of - 25.3 cm(2)C(-1), larger ionic diffusion coefficient of - 2.84 x 10(-14) m(2)s(-1), and broader EC modulation span of 24% in PC - LiClO4 than the other ones. Based upon these values, EC devices featuring a WO3/PMMA - PC - LiClO4/NiOx structure and excellent performances were fabricated. We demonstrated that the nickel anodization should be responsible for the initial "activation" phenomena, which decreases(increases) the number of oxygen(nickel) vacancies. Moreover, the cause of degradation resulting from Li+-ion trapping in the IS layer was also clarified. This work provides a general framework for studying and designing superior EC devices, experimentally as well as theoretically.

  • 30.
    Gómez, M.M.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Beermann, N.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Lu, J.
    Olsson, E.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Niklasson, G A
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Granqvist, Claes-Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Dye-sensitized sputtered titanium oxide films for photovoltaic applications: influence of the O2/Ar gas flow ratio during the deposition2003In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 76, no 1, p. 37-56Article in journal (Refereed)
    Abstract [en]

    Titanium oxide films were prepared by reactive DC magnetron sputtering onto SnO2:F coated glass substrates. The O-2/Ar gas flow ratio was kept at a constant value Gamma during the deposition, and a series of films were deposited with 0.050 < Gamma < 0.072. Structural studies were performed by X-ray diffraction and transmission electron microscopy; the structure displayed penniform features with a clear dependence on F. Charge transport in the films was evaluated by use of time-resolved photocurrents; a diffusion model was fitted to the experimental data and two different transport mechanisms were proposed depending on the film stoichiometry. Dye sensitization in cis-dithiocyanato-bis(2,2'-bipyridyl-4,4'-dicarboxylate) ruthenium (II) was performed to evaluate incident photon-to-current conversion efficiency and solar cell properties of the films. These parameters showed a clear dependence on Gamma. Optical measurements gave evidence for the presence of polaron absorption for the film deposited at Gamma = 0.050.

  • 31.
    Hagfeldt, Anders
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Didriksson, B
    Lindström, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Södergren, Sven
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Lindquist, Sten-Eric
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Verification of High Efficiencies for the Grätzel Cell: A 7% Efficient Solar Cell Based on Dye-Sensitized Colloidal TiO2 Films.1994In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 31, no 481Article in journal (Other (popular science, discussion, etc.))
  • 32. Hatwaambo, Sylvester
    et al.
    Hakansson, Hakan
    Roos, Arne
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Karlsson, Bjorn
    Mitigating the non-uniform illumination in low concentrating CPCs using structured reflectors2009In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 93, no 11, p. 2020-2024Article in journal (Refereed)
    Abstract [en]

    One problem in concentrating photovoltaic systems without active cooling is the formation of hot spots on the solar module cells. These hotspots are a result of uneven concentration of radiation within the solar module cells. The overall effect of concentrated heating is the reduction in the fill-factor of the solar module cell and the subsequent decrease in the overall efficiency of the system. In this paper, we investigate one alternative of improving the performance of a low concentrating photovoltaic system using semi-diffuse rolled reflective elements. Our results indicate that rolling marks on the reflector aligned parallel to the plane of the solar module cell improve the performance of the photovoltaic system. (C) 2009 Elsevier B.V. All rights reserved.

  • 33.
    Heise, S. J.
    et al.
    Carl von Ossietzky Univ Oldenburg, Inst Phys, Dept Energy & Semicond Res, Lab Chalcogenide Photovolta, D-26111 Oldenburg, Germany..
    Gerliz, V.
    Carl von Ossietzky Univ Oldenburg, Inst Phys, Dept Energy & Semicond Res, Lab Chalcogenide Photovolta, D-26111 Oldenburg, Germany..
    Hammer, M. S.
    Carl von Ossietzky Univ Oldenburg, Inst Phys, Dept Energy & Semicond Res, Lab Chalcogenide Photovolta, D-26111 Oldenburg, Germany..
    Ohland, J.
    Carl von Ossietzky Univ Oldenburg, Inst Phys, Dept Energy & Semicond Res, Lab Chalcogenide Photovolta, D-26111 Oldenburg, Germany..
    Keller, Jan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Hammer-Riedel, I.
    Carl von Ossietzky Univ Oldenburg, Inst Phys, Dept Energy & Semicond Res, Lab Chalcogenide Photovolta, D-26111 Oldenburg, Germany..
    Light-induced changes in the minority carrier diffusion length of Cu(In,Ga) Se-2 absorber material2017In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 163, p. 270-276Article in journal (Refereed)
    Abstract [en]

    In this study strong evidence for an illumination-induced change in minority charge carrier diffusion length is given for Cu(In,Ga)Se-2 solar cells. After annealing under illumination (light soaking) the cells show the metastable increase in open circuit voltage, but also a metastable reduction in current collection efficiency (which can be reversed by annealing in the dark). Partly, this can be attributed to an increase in doping density causing a reduced space charge region width as verified by capacitance-voltage profiling. Nevertheless, by using time-resolved photoluminescence and electron-beam-induced current measurements we found that the changes in doping density and space charge region width are not sufficient to describe the modification in current collection efficiency. Additionally there seems to be a reduction in minority carrier diffusion length and lifetime after white light soaking. This can be explained by a metastable change of electronic defects as found in temperature-dependent admittance spectroscopy. Device simulations confirm the impact of the found defects on the photocurrent

  • 34.
    Hultqvist, Adam
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Platzer-Björkman, Charlotte
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Coronel, Ernesto
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Edoff, Marika
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Experimental investigation of Cu(In1-x,Ga-x)Se-2/Zn(O1-z,S-z) solar cell performance2011In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 95, no 2, p. 497-503Article in journal (Refereed)
    Abstract [en]

    In this study we investigate the performance of Cu(In1-x,Ga-x)Se-2/Zn(O1-z,S-z) solar cells by changing the gallium content of the absorber layer in steps from CuInSe2 to CuGaSe2 and at each step vary the sulfur content of the Zn(O,S) buffer layer. By incorporating more or less sulfur into the Zn(O,S) buffer layer it is possible to change its morphology and band gap energy. Surprisingly, the best solar cells with Zn(O,S) buffer layers in this study are found for close to or the same Zn(O,S) buffer layer composition for all absorber Ga compositions. In comparison to their CdS references the best solar cells with Zn(O,S) buffer layers have slightly lower open circuit voltage, V-oc, lower fill factor, FF, and higher short circuit current density, J(sc), which result in comparable or slightly lower conversion efficiencies. The exception to this trend is the CuGaSe2 solar cells, where the best devices with Zn(O,S) have substantially lowered efficiency compared with the CdS reference, because of lower V-oc, FF and J(sc). X-ray photon spectroscopy and X-ray diffraction measurements show that the best Zn(O,S) buffer layers have similar properties independent of the Ga content. In addition, energy dispersive spectroscopy scans in a transmission electron microscope show evidence of lateral variations in the Zn(O,S) buffer layer composition at the absorber/buffer layer interface. Finally, a hypothesis based on the results of the buffer layer analysis is suggested in order to explain the solar cell parameters.

  • 35. Igalson, Malgorzata
    et al.
    Zabierowski, Pawel
    Przado, Daniel
    Urbaniak, Aleksander
    Edoff, Marika
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Shafarman, N
    Understanding defect-related issues limiting efficiency of CIGS solar cells2009In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 93, no 8, p. 1290-1295Article in journal (Refereed)
    Abstract [en]

    Many electrical characteristics of Cu(In,Ga)Se-2-based solar cells, including current-voltage characteristics, are affected by specific properties of negative-U defects in the absorber. We present these characteristics and discuss them in the framework of a V-Se-V-Cu defect model proposed by Lany and Zunger. We show how these defects influence photocarrier transport and the dominant recombination mechanism, and hence also the photovoltaic parameters of the cells. Numerical simulations validating our approach will also be presented. (C) 2009 Elsevier B.V. All rights reserved.

  • 36.
    Jacobsson, T. Jesper
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Fjällstrom, Viktor
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Edoff, Marika
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Edvinsson, Tomas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    A theoretical analysis of optical absorption limits and performance of tandem devices and series interconnected architectures for solar hydrogen production2015In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 138, p. 86-95Article in journal (Refereed)
    Abstract [en]

    Photo-driven catalytic (PDC) water splitting, using either photoelectrochemical cells (PEC-cells), PV-electrolyzers, or some hybrid system in-between, has attracted a lot of attention. In single-cell device architectures for solar hydrogen production, based on single band gap photoabsorbers, there is a fundamental efficiency problem originating from the energy distribution of the solar spectrum and the thermodynamic and kinetic requirements for splitting water. The minimum band gap for a single-junction device in order to withhold unbiased overall water splitting is considered to be at least 2.0 eV. This is far from the 1.35 eV which is the optimal band gap of a semiconductor for maximum power conversion of light in the solar spectrum. This discrepancy has been termed as the solar spectrum mismatch problem (the SSM-problem). The standard solution to this problem is to construct tandem devices, whereas an alternative is to interconnect several one band gap cells in series, side by side. Both approaches enable the use of low energy photons in the solar spectrum while still providing a sufficiently high photopotential for driving the full reaction, without seriously compromising with the area efficiency. In this paper, the tandem and serial architectures for handling the SSM-problem are analyzed and compared. The analysis is focused towards differences in the limits of optical absorption, the optimal number of optical. absorbers, and their corresponding band gaps. Taking losses due to charge carrier separation and catalysis into account, the maximum STH-efficiency for a series interconnected solar splitting device was found to be 24.6%, compared to 32.0% for an optimum tandem device at 1 Sun (air mass 1.5, 1000 W m(-2)). This can be compared with the maximum efficiency of 18.0% for an ideal single band gap photoabsorber in single junction device. The analysis shows that the maximum STH efficiency limits for series interconnected architectures for unassisted solar water splitting are not particularly far behind the more commonly studied tandem devices. They could then be an interesting alternative given the simplicity and versatility of series interconnected device architectures. The analysis also compares how tandem devices and series interconnected devices can differ in terms of charge carrier separation, charge carrier transport, catalysis, overall efficiency, device architecture, and expected cost.

  • 37.
    Jacobsson, T. Jesper
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Fjällstrom, Viktor
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Edoff, Marika
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Edvinsson, Tomas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    CIGS based devices for solar hydrogen production spanning from PEC-cells to PV-electrolyzers: a comparison of efficiency, stability and device topology2015In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 134, p. 185-93Article in journal (Refereed)
  • 38.
    Ji, Yu-Xia
    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.
    Boman, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Thermochromic VO2 films by thermal oxidation of vanadium in SO22016In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 144, p. 713-716Article in journal (Refereed)
    Abstract [en]

    Thermochromic films of VO2 were prepared by a two-step procedure: Sputtering was first used to deposit metallic vanadium, and such layers were subsequently oxidized in SO2 at a temperature in the 600-650 degrees C range. X-ray diffraction, Raman spectroscopy, measurements of temperature-dependent electrical resistance, and spectrophotometric transmittance data at different temperatures were employed to demonstrate that the films consisted of polycrystalline VO2 with good thermochromism, especially when oxidized at the highest temperature. Oxidation in SO2 is able to produce VO2 without the stringent process control that can be an obstacle for making VO2 by oxidation in O-2.

  • 39.
    Jonsson, Andreas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Roos, Arne
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    The effect on transparency and light scattering of dip coated antireflection coatings on window glass and plasticsIn: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398Article in journal (Refereed)
    Abstract [en]

    High visible transmittance values are interesting for windows in general and for the bleached state of smart windows in particular. For smart windows it is always possible to darken them and therefore the transparency of the bleached state can never become too high. One way of achieving a higher transmittance could be the use of antireflective coatings on the surfaces of the smart window. In this project the use of dip coating for putting antireflective coatings on window surfaces has been studied. The effect on transmittance and surface light scattering has been investigated and the results show that antireflective coatings on windows can have a positive impact on both.

  • 40.
    Jonsson, Andreas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Roos, Arne
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Jonson, Emma K.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    The effect on transparency and light scattering of dip coated antireflection coatings on window glass and electrochromic foil2010In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 94, no 6, p. 992-997Article in journal (Refereed)
    Abstract [en]

    Modern windows tend to include an increasing number of functional coatings and in order to keep the light transmittance at an acceptably high level antireflection coatings are likely to be used in future high performance windows. For switchable coatings this may be necessary in order to make them sufficiently light in the bleached state. In this paper we have investigated how haze levels of a selection of coatings on glass and plastics, including electrochromic PET foil, are influenced by the additional antireflection coatings. The results indicate a possible increase in light scattering levels for the antireflection coatings on PET foil and a reduction of haze for tin oxide coated glass.

  • 41.
    Jonsson, Jacob
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Materials Science.
    Karlsson, Linus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Materials Science.
    Nostell, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Materials Science.
    Niklasson, Gunnar
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Materials Science.
    Smith, Geoffrey
    Angle-dependent light scattering in materials with controlled diffuse solar optical properties2004In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 84, no 1-4, p. 427-439Article in journal (Refereed)
    Abstract [en]

    Light scattering plays a prominent role in a wide range of energy-efficient materials and solar applications. Some examples are materials for daylighting, diffusely reflecting sunscreens, foils for radiative cooling and nanocrystalline solar cells. Measurements of the angular profile of light scattering are very useful for obtaining a detailed characterization of the light scattering mechanisms. We review recent theoretical results on the forward and backward light scattering profiles. Forward scattering is of major importance for novel pigmented polymeric daylighting materials. Measurements of scattering profiles are in good agreement with Mie theory. Backscattering profiles from highly diffusely reflecting paints containing titanium oxide-based pigments have also been measured. It seems that scattering from the paint surface dominates at low pigment volume fractions. Results for paints with high pigment volume fractions are interpreted in terms of coherent backscattering effects from the pigment particles.

  • 42. Katumba, G.
    et al.
    Olumekor, L.
    Forbes, A.
    Makiwa, G.
    Mwakikunga, B.
    Lu, J.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Wäckelgård, Eva
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Optical, thermal and structural characteristics of carbon nanoparticles embedded in ZnO and NiO as selective solar absorbers2008In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 92, no 10, p. 1285-1292Article in journal (Refereed)
    Abstract [en]

    Selective solar absorber coatings of carbon embedded in ZnO and NiO matrices on aluminium substrates have been fabricated by a sol-gel technique. Spectrophotometry was used to determine the solar absorptance and the thermal emittance of the composite coatings. The surface morphology of the samples was studied by scanning electron microscopy (SEM). Cross-sectional high-resolution transmission electron microscopy (X-HRTEM) was used to study the fine structure of the samples. Chemical composition analysis was done by energy dispersive spectroscopy (EDS) and electron energy loss spectroscopy (EELS). The crystal structure of ZnO and NiO samples was also investigated with an X-ray diffraction (XRD) technique. Samples were subjected to an accelerated ageing test for 95 h, with condensation at relative humidity of 95% and at a climate chamber temperature of 45 degrees C. The thermal emittances of the samples were 6% for the ZnO and 4% for the NiO matrix materials. The solar absorptances were 71% and 84% for ZnO and NiO samples, respectively. The SEM revealed a smooth featureless surface for both C-ZnO and C-NiO samples. Some C-NiO samples showed dentritic features. X-HRTEM, EDS and EELS studies revealed a nanometric grain size for both types of samples. The C-ZnO and C-NiO coatings contained amorphous carbon embedded in nanocrystalline ZnO and NiO matrices, respectively. Selected area electron diffraction (SAED) showed that a small amount of Ni grains of 30 nm diameter also existed in the NiO matrix. The accelerated ageing tests produced performance criterion (PC) values of 0.15 and 0.054 at 95 h for the C-ZnO and C-NiO samples, respectively. Based on these results, C-NiO samples proved to have better solar selectivity behaviour than the C-ZnO counterparts.

  • 43.
    Keis, Karin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Magnusson, Eva
    Lindström, Henrik
    Lindquist, Sten-Eric
    Hagfeldt, Anders
    A 5% efficient photoelectrochemical solar cell based on nanostructured ZnO electrodes2002In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 73, p. 51-58Article in journal (Refereed)
  • 44.
    Keller, Jan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Aijaz, Asim
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Gustavsson, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Kubart, Tomas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Stolt, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics. Solibro Res AB, Vallvagen 5, S-75151 Uppsala, Sweden..
    Edoff, Marika
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Törndahl, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Direct comparison of atomic layer deposition and sputtering of In2O3:H used as transparent conductive oxide layer in CuIn1-xGaxSe2 thin film solar cells2016In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 157, p. 757-764Article in journal (Refereed)
    Abstract [en]

    In this study thin films of hydrogenated In2O3 (IOH) were fabricated by physical vapor deposition (PVD) with and without a post-annealing step, and by atomic layer deposition (ALD). The electro-optical properties on glass as well as the performance as a transparent conductive oxide (TCO) layer in CuIn1-xGaxSe2 (CIGSe)-based solar cells are compared and related to a ZnO:Al (AZO) baseline TCO. Corresponding TCO film thicknesses were adjusted to a resulting sheet resistance of about R-sh = 20 Omega/sq for all samples. Structural investigations were conducted by X-ray diffraction (XRD) and transmission electron microscopy (TEM), while Hall and optical absorption measurements were performed to analyze the electrical and optical quality of the window layers. It is shown that the fully crystallized IOH layers processed by ALD and PVD show similar microstructural and electro-optical properties, which are superior to the AZO baseline. The finalized solar cells were characterized by current-voltage and reflectance-corrected quantum efficiency measurements. While there is no significant gain in short circuit current density (J(sc)) for as-deposited PVD In2O3 layers, the application of crystalline In2O3 TCOs leads to an improvement of more than 2 mA/cm(2) due to an increase in "optical" band gap energy and less free charge carrier absorption (FCA). The open circuit voltage (V-oc) of the best cells is 10-15 mV higher as compared to the AZO reference, independent of the crystallinity and process of the In2O3 films. The results indicate that the gain in V-oc is due to inherent material properties of the IOH films and does not originate from less sputter damage or an affected i-ZnO/TCO interface. Device simulations show that the higher electron affinity chi of the IOH can explain an increased V-oc if the Fermi level (E-F) is pinned at the CIGSe/CdS interface and why it might not be possible to see the gain when alternative buffer layers are applied.

  • 45.
    Keller, Jan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Gustavsson, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Stolt, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Edoff, Marika
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Törndahl, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    On the beneficial effect of Al2O3 front contact passivation in Cu(In,Ga)Se2 solar cells2017In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 159, p. 189-196Article in journal (Refereed)
    Abstract [en]

    This study reports on the beneficial effect of an absorber surface passivation by Al2O3 on the performance of Cu(In, Ga)Se-2 (CIGSe) solar cells. Here the Al2O3 layer is deposited by atomic layer deposition (ALD) subsequently to a CdS buffer layer. It is shown that a very thin film of about 1 nm efficiently reduces the interface recombination rate if the buffer layer is too thin to not fully cover the CIGSe absorber. An Al2O3 thickness of 1 nm is sufficiently low to allow current transport via tunneling. Increasing the thickness to > 1 nm leads to a detrimental blocking behavior due to an exponentially decreasing tunnel current. Losses in open circuit voltage (V-oc) and fill factor (FF) when reducing the buffer layer thickness are significantly mitigated by implementing an optimized Al2O3 layer. It is further shown, that the heat treatment during the ALD step results in an increase in short circuit current density (J(sc)) of about 2 mA/cm(2). This observation is attributed to a widening of the space charge region in the CIGSe layer that in turn improves the collection probability of electrons. For not fully covering CdS layers the decrease in interface defect density by the passivation contributes as well, leading to a gain of about 5 mA/cm2 for cells without a buffer. Finally, the leakage current of the solar cell devices could be reduced when applying the Al2O3 layer on insufficiently covering CdS films, which proves the capability of mitigating the effect of shunts or bad diodes.

  • 46.
    Laaksonen, Katri
    et al.
    Aalto University.
    Li, Shu-Yi
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Puisto, S. R.
    MatOx Oy.
    Rostedt, N. K. J.
    MatOx Oy.
    Ala-Nissila, T.
    Aalto University.
    Granqvist, Claes-Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Nieminen, R. M.
    Aalto University.
    Niklasson, Gunnar A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Nanoparticles of TiO2 and VO2 in dielectric media: Conditions for low optical scattering, and comparison between effective medium and four-flux theories2014In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 130, no SI, p. 132-137Article in journal (Refereed)
    Abstract [en]

    Spectral transmittance and reflectance in the 300 to 2500 nm solar-optical wavelength range were calculated for nanoparticles of titanium dioxide and vanadium dioxide with radii between 5 and 100 nm embedded in transparent dielectric media. Both of the materials are of large importance in green nanotechnologies: thus TiO2 is a photocatalyst that can be applied as a porous film or a nanoparticle composite on indoor or outdoor surfaces for environmental remediation, and VO2 is a thermochromic material with applications to energy-efficient fenestration. The optical properties, including scattering, of the nanoparticle composites were computed from the Maxwell–Garnett effective-medium theory as well as from a four-flux radiative transfer model. Predictions from these theories approach one another in the limit of small particles and in the absence of optical interference. Effects of light scattering can be modeled only by the four-flux theory, though. We found that nanoparticle radii should be less than ~20 nm in order to avoid pronounced light scattering.

  • 47.
    Lansåker, Pia C.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Petersson, P.
    Uppsala University, Disciplinary Domain of Science and Technology, För teknisk-naturvetenskapliga fakulteten gemensamma enheter, Tandem Laboratory.
    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.
    Thin sputter deposited gold films on In2O3:Sn, SnO2:In, TiO2 and glass: Optical, electrical and structural effects2013In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 117, no SI, p. 462-470Article in journal (Refereed)
    Abstract [en]

    Thin gold films are promising transparent conductors with many actual and potential uses in "green" technologies, transparent electronics, etc. These applications require different substrate materials, and hence it is important to understand the role of the substrate on Au thin film growth. Such effects have been studied in this work wherein Au films ranging from island structures, via large scale coalescence into meandering metal networks, to thin homogenous layers were deposited by DC magnetron sputtering onto glass substrates and In2O3:Sn (ITO), SnO2:In and TiO2 base layers backed by glass. Optical, electrical and structural properties were recorded for films deposited onto unheated substrates. We found distinct and characteristic differences in Au growth on the various backings. Thus ITO and SnO2:In base layers yielded gold films with island features remaining to larger thicknesses than for deposition directly onto glass, and the sheet resistance was lower for gold deposition onto SnO2:In and ITO only when the gold films were less than similar to 5 nm in thickness. Our results highlight the complexity of substrates' influence on thin film formation. 

  • 48.
    Larsson, Anna-Lena
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Solis, Jose
    Instituto Peruano de Energía Nuclear.
    Niklasson, Gunnar A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Infrared absorption in Li-intercalated tungsten oxide2007In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 91, no 13, p. 1248-1252Article in journal (Refereed)
    Abstract [en]

    Thin films of amorphous and polycrystalline tungsten oxide were produced by reactive dc magnetron sputtering and nanocrystalline films were deposited by advanced gas evaporation. The films were submitted to electrochemical intercalation of Li ions before infrared reflectance measurements were carried out. For crystalline films, the reflectance in the wavelength region 10–30 μm increases upon intercalation, indicating an increasing free-electron contribution. On the other hand, all the films display an increased absorption at wavelengths less than 10 μm when intercalated. The thermal emittance could be varied from about 0.5 to 0.7–0.75 by intercalation in films with thicknesses in excess of 1 μm. Both absorption and interference contribute to the emittance contrast.

  • 49.
    Larsson, Fredrik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Donzel-Gargand, Olivier
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Keller, Jan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Edoff, Marika
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Törndahl, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Atomic layer deposition of Zn(O,S) buffer layers for Cu(In,Ga)Se-2 solar cells with KF post-deposition treatment2018In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 183, p. 8-15Article in journal (Refereed)
    Abstract [en]

    We investigate the possibility to combine Zn(O,S) buffer layers grown by atomic layer deposition (ALD) with KF post-deposition treated Cu(In,Ga)Se-2 (CIGS-KF) in solar cells. It is shown that the beneficial effect on open-circuit voltage from the post-deposition treatment is essentially independent of buffer layer material. However, a wet chemical surface treatment is required prior to ALD in order to achieve competitive fill factor values. A water rinse is sufficient to create an absorber surface similar to the one formed during a conventional CdS chemical bath deposition process. However, it is observed that CIGS-KF/Zn(O,S) devices made with water-rinsed absorbers systematically result in lower fill factor values than for the corresponding CIGS-KF/CdS references. This effect can be mitigated by decreasing the H2S:H2O precursor ratio during ALD initiation, indicating that the fill factor limitation is linked to the initial Zn(O,S) growth on the modified CIGS-KF surface. The best CIGS-KF/Zn (O,S) devices were fabricated by etching away the KF-modified surface layer prior to ALD, followed by a low temperature anneal. The thermal treatment step is needed to increase the open-circuit voltage close to the value of the CdS devices. The results presented in this contribution indicate that the main beneficial effects from KFPDT in our devices are neither associated with the CdS CBD process nor due to the formation of a K-In-Serich phase on the CIGS surface.

  • 50.
    Lasri, Karima
    et al.
    Univ Cadi Ayyad, FST Marrakech, LCME, Ave A Khattabi,BP 549, Marrakech 40000, Morocco..
    Brandell, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Saadoune, Ismael
    Univ Cadi Ayyad, FST Marrakech, LCME, Ave A Khattabi,BP 549, Marrakech 40000, Morocco.;Univ Mohammed VI Polytech, Ctr Adv Mat, Lot 660 Hay Moulay Rachid, Ben Guerir, Morocco..
    Larzek, Mohamed
    Univ Mohammed VI Polytech, Ctr Adv Mat, Lot 660 Hay Moulay Rachid, Ben Guerir, Morocco..
    Edström, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Electrochemical characterizations of Co0.5TiOPO4 as anode material for lithium-ion batteries2016In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 148, p. 44-51Article in journal (Refereed)
    Abstract [en]

    Titanium oxyphosphate M0.5TiOPO4 (M=Ni, Cu, Fe) represent a promising candidate as an anode material for the lithium-ion batteries thanks to their good energetic performance and structural stability. In this work, we report on the high capacity of Co0.5TiOPO4/C electrode material. In particular, at C rate, the discharge capacity of more than 210 mA h/g was maintained for 80 charge/discharge cycles. Furthermore, Co0.5TiOPO4/C composite exhibits excellent rate-capability with excellent coulombic efficiency. The outstanding electrochemical performance of Co0.5TiOPO4/C anode material might be attributed to its well crystallinity, controlled morphology due to the sol-gel preparation method, and the particles surface carbon-coating.

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