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  • 1.
    Arvizu, Miguel A
    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 W(1-x-y)Ti(x)lo(y)O(3) Thin Films Made by Sputter Deposition: Large Optical Modulation, Good Cycling Durability, and Approximate Color Neutrality2017In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 29, no 5, p. 2246-2253Article in journal (Refereed)
    Abstract [en]

    Tungsten oxide thin films are used in electrochromic devices such as variable-transmittance "smart windows" for energy efficient buildings with good indoor comfort. Two long-standing issues for WO3 thin films are their limited durability under electrochemical cycling and their blue color in transmission. Here, we show that both of these problems can be significantly alleviated by additions of titanium and molybdenum. We found that similar to 300 nm-thick films of sputter deposited W1-x-yTixMoyO3 are able to combine a midluminous transmittance modulation of 0.4 similar to 70% with good color neutrality and durability under extended electrochemical cycling. The Ti content should be similar to 10 at. % in order to achieve durability without impairing transmittance modulation significantly, and the Mo content preferably should be no larger than 6 at. % in order to maintain durability. Hence, our results give clear guidelines for making three-component mixed-oxide thin films that are suitable for electrochromic "smart windows".

  • 2.
    Atluri, Rambabu
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Garcia-Bennett, Alfonso
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Hedin, Niklas
    Hydrothermal Phase Transformation of Bicontinuous Cubic Mesoporous Material AMS-62008In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 20, no 12, p. 3857-3866Article in journal (Refereed)
    Abstract [en]

    The controlled synthesis of ordered anionic surfactant templated mesoporous silica with cubic Ia3 structure (AMS-6) is reported via prolonged periods of hydrothermal treatment (HT). The cubic Ia3 mesophase transforms to hexagonal p6mm after 8 days of HT at 100 °C. Surprisingly, the hexagonal phase is stable only for a limited period after which a reversal to the cubic Ia3 mesostructure is observed. Characterization methods such as powder X-ray diffraction (XRD), electron microscopy (SEM, TEM), N2-isotherms, magic-angle spinning (MAS) 29Si NMR spectroscopy, and thermogravimetric analysis (TGA) have been employed to follow structural and textural changes of the materials prepared. Data show that the resultant mesostructure and its textural properties are highly dependent on the period of HT with less unit-cell shrinkage on calcination after extensive HT. Furthermore, evidence of two different solid−solid phase mechanisms during HT is presented. The initial transition is consistent with a restructuring of the surfactant packing and a depletion of the organic moieties from the organo-silica wall as evident from 29Si NMR spectroscopy. The return to the bicontinuous cubic phase is driven by changes in charge matching at the organic−inorganic interface as a result of increases in the polymerization of the silica wall. The textural properties, and in particular the presence or absence of surface porosity, has been controlled through variations in hydrothermal treatment. These are associated with specific growth directions of cubic AMS-6 crystals. The synthetic method described allows us to easily prepare phase pure and intermediate mesostructured nanoparticles.

  • 3.
    Banerjee, Hrishit
    et al.
    SN Bose Natl Ctr Basic Sci, Dept Condensed Matter Phys & Mat Sci, JD Block,Sect 3, Kolkata 700106, India..
    Chakraborty, Sudip
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Saha-Dasgupta, Tanusri
    SN Bose Natl Ctr Basic Sci, Dept Condensed Matter Phys & Mat Sci, JD Block,Sect 3, Kolkata 700106, India..
    Cationic Effect on Pressure Driven Spin-State Transition and Cooperativity in Hybrid Perovskites2016In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 28, no 22, p. 8379-8384Article in journal (Refereed)
    Abstract [en]

    Hybrid or metal organic framework (MOP) perovskites of general composition, ABX(3), are known to show interesting properties that can lead to a variety of technological applications. Our first-principles study shows they are also potential candidates for exhibiting cooperative spin-state transitions upon application of external stimuli. We demonstrate this by considering two specific Fe-based MOF perovskites, namely dimethylammonium iron formate, [CH3NH2CH3][Fe(HCOO)(3)], and hydroxylammonium iron formate, [NH3OH][Fe(HCOO)(3)]. Both the compounds are found to undergo high-spin (S = 2) to low-spin (S = 0) transition at Fe(II) site upon application of moderate strength of hydrostatic pressure, along with large hysteresis. This spin-state transition is signaled by the changes in electronic, magnetic, and optical properties. We find both the transition pressure and the width of the hysteresis to be strongly dependent on the choice of A-site cation, dimethylammonium or hydroxylammonium, implying that tuning of spin-switching properties is achievable by chemical variation of the amine cation in the structure. Our findings open up novel functionalities in this family of materials of recent interest, which can have important usage in sensors and memory devices.

  • 4.
    Bilousov, Oleksandr V.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Ren, Yi
    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.
    Donzel-Gargand, Olivier
    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.
    Platzer-Björkman, Charlotte
    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.
    Hägglund, Carl
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Atomic Layer Deposition of Cubic and Orthorhombic Phase Tin Monosulfide2017In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 29, no 7, p. 2969-2978Article in journal (Refereed)
    Abstract [en]

    Tin monosulfide (SnS) is a promising light-absorbing material with weak environmental constraints for application in thin film solar cells. In this paper, we present low-temperature atomic layer deposition (ALD) of high-purity SnS of both cubic and orthorhombic phases. Using tin(II) 2,4-pentanedionate [Sn(acac)(2)] and hydrogen sulfide (H2S) as precursors, controlled growth of the two polymorphs is achieved. Quartz crystal microbalance measurements are used to establish saturated conditions and show that the SnS ALD is self-limiting over temperatures from at least 80 to 160 degrees C. In this temperature window, a stable mass gain of 19 ng cm(-2) cycle(-1) is observed. The SnS thin film crystal structure and morphology undergo significant changes depending on the conditions. High-resolution transmission electron microscopy and X-ray diffraction demonstrate that fully saturated growth requires a large H2S dose and results in the cubic phase. Smaller H2S doses and higher temperatures favor the orthorhombic phase. The optical properties of the two polymorphs differ significantly, as demonstrated by spectroscopic ellipsometry. The orthorhombic phase displays a wide (0.3-0.4 eV) Urbach tail in the near-infrared region, ascribed to its nanoscale structural disorder and/or to sulfur vacancy-induced gap states. In contrast, the cubic phase is smooth and void-free and shows a well-defined, direct forbidden-type bandgap of 1.64 eV.

  • 5.
    Blidberg, Andreas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Gustafsson, Torbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Tengstedt, Carl
    Scania CV AB, Södertälje, Sweden.
    Björefors, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Brant, William R.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Monitoring LixFeSO4F (x = 1, 0.5, 0) Phase Distributions in Operando To Determine Reaction Homogeneity in Porous Battery Electrodes2017In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 29, no 17, p. 7159-7169Article in journal (Refereed)
    Abstract [en]

    Increasing the energy and power density simultaneously remains a major challenge for improving electrochemical energy storage devices such as Li-ion batteries. Understanding the underlying processes in operating electrodes is decisive to improve their performance. Here, an extension of an in operando X-ray diffraction technique is presented, wherein monitoring the degree of coexistence between crystalline phases in multiphase systems is used to investigate reaction homogeneity in Li-ion batteries. Thereby, a less complicated experimental setup using commercially available laboratory equipment could be employed. By making use of the intrinsic structural properties of tavorite type LiFeSO4F, a promising cathode material for Li-ion batteries, new insights into its nonequilibrium behavior are gained. Differences in the reaction mechanism upon charge and discharge are shown; the influence of adequate electronic wiring for the cycling stability is demonstrated, and the effect of solid state transport on rate performance is highlighted. The methodology is an alternative and complementary approach to the expensive and demanding techniques commonly employed for time-resolved studies of structural changes in operating battery electrodes. The multiphase behavior of LiFeSO4F is commonly observed for other insertion type electrode materials, making the methodology transferable to other new energy storage materials. By expanding the possibilities for investigating complex processes in operating batteries to a larger community, faster progress in both electrode development and fundamental material research can be realized.

  • 6.
    Blidberg, Andreas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Häggström, Lennart
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Ericsson, Tore
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Tengstedt, Carl
    Gustafsson, Torbjorn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Björefors, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Structural and Electronic Changes in Li2FeP2O7 during Electrochemical Cycling2015In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 27, no 11, p. 3801-3804Article in journal (Refereed)
  • 7.
    Brant, William
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Mogensen, Ronnie
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Colbin, Simon
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Ojwang, Dickson O.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Schmid, Siegbert
    Univ Sydney, Sch Chem, Sydney, NSW 2006, Australia.
    Häggstrom, Lennart
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    Ericsson, Tore
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    Jaworski, Aleksander
    Stockholm Univ, Dept Mat & Environm Chem, SE-10691 Stockholm, Sweden.
    Pell, Andrew J.
    Stockholm Univ, Dept Mat & Environm Chem, SE-10691 Stockholm, Sweden.
    Younesi, Reza
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Selective Control of Composition in Prussian White for Enhanced Material Properties2019In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 31, no 18, p. 7203-7211Article in journal (Refereed)
    Abstract [en]

    Sodium-ion batteries based on Prussian blue analogues (PBAs) are ideal for large-scale energy storage applications due to the ability to meet the huge volumes and low costs required. For Na2-xFe[Fe(CN)(6)](1-y)center dot zH(2)O, realizing its commercial potential means fine control of the concentration of sodium, Fe(CN)(6) vacancies, and water content. To date, there is a huge variation in the literature of composition leading to variable electrochemical performance. In this work, we break down the synthesis of PBAs into three steps for controlling the sodium, vacancy, and water content via an inexpensive, scalable synthesis method. We produce rhombohedral Prussian white Na1.88(5)Fe[Fe-(CN)(6)]center dot 0.18(9)H2O with an initial capacity of 158 mAh/g retaining 90% capacity after 50 cycles. Subsequent characterization revealed that the increased polarization on the 3 V plateau is coincident with a phase transition and reduced utilization of the high-spin Fe(III)/Fe(II) redox couple. This reveals a clear target for subsequent improvements of the material to boost long-term cycling stability. These results will be of great interest for the myriad of applications of PBAs, such as catalysis, magnetism, electrochromics, and gas sorption.

  • 8.
    Bryngelsson, Hanna
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Eskhult, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Nyholm, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Herranen, Merja
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Alm, Oscar
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Edström, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Electrodeposited Sb and Sb/Sb2O3 nanoparticle coatings as anode materials for Li-ion batteries2007In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 19, no 5, p. 1170-1180Article in journal (Refereed)
    Abstract [en]

    Galvanostatically electrodeposited coatings of pure Sb or co-deposited Sb and Sb2O3 nanoparticles, prepared from antimony tartrate solutions, were studied as anode materials in Li-ion batteries. It is demonstrated that the co-deposition of 20-25% (w/w) Sb2O3 results from a local pH increase at the cathode (due to protonation of liberated tartrate) in poorly buffered solutions. This causes precipitation of Sb2O3 nanoparticles and inclusion of some of the particles in the deposit where they become coated with a protecting layer of Sb. Chronopotentiometric cycling of the deposits, which also were characterized using, e.g., SEM, TEM, and XRD, clearly showed that the Sb2O3-containing deposits were superior as anode materials. While the Sb/Sb2O3 coatings exhibited a specific capacity close to the Sb theoretical value of 660 mA·h·g -1 during more than 50 cycles, the capacity for the Sb coatings gradually decreased to about 250 mA·h·g-1. This indicates that the influence of the significant volume changes present upon the formation and oxidation of Li3Sb was much smaller for the Sb/Sb2O3 nanoparticle coatings. The improved performance can be explained by significant formation of Sb2O3 during the reoxidation, the presence of smaller Sb particles in the Sb/Sb2O3 coatings, and the formation of buffering nanoparticles of Li2O in a matrix of Sb during the first reduction cycle for the Sb/Sb2O3 deposits.

  • 9. Chen, Ruikui
    et al.
    Yang, Xichuan
    Tian, Haining
    Wang, Xiuna
    Hagfeldt, Anders
    Sun, Licheng.
    Effect of Tetrahydroquinoline Dyes Structure on the Performance of Organic Dye-Sensitized Solar Cells.2007In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 19, no 16, p. 4007-4015Article in journal (Refereed)
    Abstract [en]

    Eleven novel donor acceptor π-conjugated (D-π-A) org. dyes were engineered and synthesized as sensitizers for the application in dye-sensitized solar cells (DSSCs). The electron-donating moieties are substituted tetrahydroquinoline, and the electron-withdrawing parts are cyanoacrylic acid group or cyanovinylphosphonic acid group. Different lengths of thiophene-contg. conjugation moieties (thienyl, thienylvinyl, and dithieno[3,2-b;2',3'-d]thienyl) are introduced to the mols. and serve as electron spacers. Detailed study on the relation between the dye structure, photophys. and photoelectrochem. properties, and performance of DSSCs is described here. The bathochromic shift and increase of the molar absorptivity of the absorption spectrum are achieved by introduction of larger conjugation moiety. Even small structural changes of dyes result in significant changes in redox energies and adsorption manner of the dyes on TiO2 surface, affecting dramatically the performance of DSSCs based on these dyes. The higher performances are obtained by DSSCs based on the rigid dye mols., C2 series dyes (Figure 1), although these dyes have lower light absorption abilities relative to other dyes. A max. solar-to-elec. energy conversion efficiency (η) of 4.53% is achieved under simulated AM 1.5 irradn. (100 mW/cm2) with a DSSC based on C2-2 dye (Voc = 597 mV, Jsc = 12.00 mA/cm2, ff = 0.63). D. functional theory (DFT) calcns. were performed on the dyes, and electron distribution from the whole mols. to the anchoring moieties occurred during the HOMO-LUMO excitation. The cyanoacrylic acid groups or cyanovinylphosphonic acid group are essentially coplanar with respect to the thiophene units, reflecting the strong conjugation across the thiophene-anchoring groups. [on SciFinder(R)]

  • 10.
    Cheng, Ming
    et al.
    KTH Royal Inst Technol, Dept Chem, Organ Chem, SE-10044 Stockholm, Sweden..
    Chen, Cheng
    KTH Royal Inst Technol, Dept Chem, Appl Phys Chem, SE-10044 Stockholm, Sweden..
    Aitola, Kerttu
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Zhang, Fuguo
    Dalian Univ Technol DUT, DUT KTH Joint Educ & Res Ctr Mol Devices, Inst Artificial Photosynth, State Key Lab Fine Chem, Dalian 116024, Peoples R China..
    Hua, Yong
    KTH Royal Inst Technol, Dept Chem, Appl Phys Chem, SE-10044 Stockholm, Sweden..
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Kloo, Lars
    KTH Royal Inst Technol, Dept Chem, Appl Phys Chem, SE-10044 Stockholm, Sweden..
    Sun, Licheng
    KTH Royal Inst Technol, Dept Chem, Organ Chem, SE-10044 Stockholm, Sweden.;Dalian Univ Technol DUT, DUT KTH Joint Educ & Res Ctr Mol Devices, Inst Artificial Photosynth, State Key Lab Fine Chem, Dalian 116024, Peoples R China..
    Highly Efficient Integrated Perovskite Solar Cells Containing a Small Molecule-PC70BM Bulk Heterojunction Layer with an Extended Photovoltaic Response Up to 900 nm2016In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 28, no 23, p. 8631-8639Article in journal (Refereed)
    Abstract [en]

    We demonstrate a high efficiency perovskite solar cell (PSC) integrated with a bulk heterojunction layer, based on acceptor-donor-acceptor (A-D-A) type hole transport material (HTM) and PC70BM composite, yielding improved photoresponse. Two A-D-A-structured hole transporting materials termed M3 and M4 were designed and synthesized. Applied as HTMs in PSCs, power conversion efficiencies (PCEs) of 14.8% and 12.3% were obtained with M3 and M4, respectively. The HTMs M3 and M4 show competitive absorption, but do not contribute to photocurrent, resulting in low current density. This issue was solved by mixing the HTMs with PC70BM to form a bulk heterojunction (BHJ) layer and integrating this layer into the PSC as hole transport layer (HTL). Through careful interface optimization, the (FAPbI(3))(0.85)(MAPbBr(3))(0.15)/HTM:PC70BM integrated devices showed improved efficiencies of 16.2% and 15.0%, respectively. More importantly, the incident-photon-to-current conversion efficiency (IPCE) spectrum shows that the photoresponse is extended to 900 nm by integrating the M4:PC70BM based BHJ and (FAPbI(3))(0.85)(MAPbBr(3))(0.15) layers.

  • 11.
    Davydova, Alexandra
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Rudisch, Katharina
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Scragg, Jonathan J. S.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    The Single Phase Region in Cu2ZnSnS4 Thin Films from Theory and Combinatorial Experiments2018In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 30, no 14, p. 4624-4638Article in journal (Refereed)
    Abstract [en]

    Cu2ZnSnS4 (CZTS) is hoped to be a future, earth-abundant absorber material for thin film solar cells, but performance remains below the level needed for commercialization. In this work, the size of the single phase region of CZTS obtained from thin film synthesis methods is explored, to determine the scope available for defect engineering and thereby future improvements in solar cell performance. A chemical model for the single phase region is presented, based on equilibria between defect complexes in the CZTS phase and the other solid- and gas-phase components present during synthesis. The model predicts a variable single phase region size, depending on the partial pressures of SnS and S2. The model is verified by analysis of combinatorial thin-film CZTS samples prepared with different synthetic conditions and characterized by Raman and compositional mapping. We conclude that typical synthesis strategies for CZTS are not capable of accessing the full range of the CZTS single phase region since the required partial pressure of S2 is very large. The important implication is that our understanding of CZTS defect chemistry from experimental studies is incomplete and that scope exists for tuning the defect properties toward better solar cell performance.

  • 12.
    De Toro, José A.
    et al.
    Univ Castilla La Mancha, IRICA, E-13071 Ciudad Real, Spain.;Univ Castilla La Mancha, Dept Fis Aplicada, E-13071 Ciudad Real, Spain.
    Vasilakaki, Marianna
    NCSR Demokritos, Inst Nanosci & Nanotechnol, Athens 15310, Greece.
    Lee, Su Seong
    Inst Bioengn & Nanotechnol, 31 Biopolis Way, Singapore 138669, Singapore.
    Andersson, Mikael
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Normile, Peter S.
    Univ Castilla La Mancha, IRICA, E-13071 Ciudad Real, Spain.;Univ Castilla La Mancha, Dept Fis Aplicada, E-13071 Ciudad Real, Spain.
    Yaacoub, Nader
    Univ Maine, CNRS, UMR 6283, Inst Mol & Mat Mans, F-72085 Le Mans, France.
    Murray, Peyton
    Univ Calif Davis, Dept Phys, Davis, CA 95616 USA.
    Sanchez, Elena H.
    Univ Castilla La Mancha, IRICA, E-13071 Ciudad Real, Spain.;Univ Castilla La Mancha, Dept Fis Aplicada, E-13071 Ciudad Real, Spain.
    Muñiz, Pablo
    Univ Castilla La Mancha, IRICA, E-13071 Ciudad Real, Spain.;Univ Castilla La Mancha, Dept Fis Aplicada, E-13071 Ciudad Real, Spain.
    Peddis, Davide
    CNR, Ist Struttura Mat, I-00015 Monterotondo Scale, RM, Italy.
    Mathieu, Roland
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Liu, Kai
    Univ Calif Davis, Dept Phys, Davis, CA 95616 USA.
    Geshev, Julian
    Univ Fed Rio Grande do Sul, Inst Fis, BR-91501970 Porto Alegre, RS, Brazil.
    Trohidou, Kalliopi N.
    NCSR Demokritos, Inst Nanosci & Nanotechnol, Athens 15310, Greece.
    Nogués, Josep
    CSIC, Catalan Inst Nanosci & Nanotechnol ICN2, Campus UAB, Barcelona 08193, Spain.;Barcelona Inst Sci & Technol, Campus UAB, Barcelona 08193, Spain.;ICREA, Pg Lluis Co 23, Barcelona 08010, Spai.
    Remanence Plots as a Probe of Spin Disorder in Magnetic Nanoparticles2017In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 29, no 19, p. 8258-8268Article in journal (Refereed)
    Abstract [en]

    Remanence magnetization plots (e.g., Henkel or delta M plots) have been extensively used as a straightforward way to determine the presence and intensity of dipolar and exchange interactions in assemblies of magnetic nanoparticles or single domain grains. Their evaluation is particularly important in functional materials whose performance is strongly affected by the intensity of interparticle interactions, such as patterned recording media and nanostructured permanent magnets, as well as in applications such as hyperthermia and magnetic resonance imaging. Here, we demonstrate that delta M plots may be misleading when the nanoparticles do not have a homogeneous internal magnetic configuration. Substantial dips in the delta M plots of gamma-Fe2O3 nanoparticles isolated by thick SiO2 shells indicate the presence of demagnetizing interactions, usually identified as dipolar interactions. results, however, demonstrate that it is the inhomogeneous spin structure of the nanoparticles, as most clearly evidenced by Mossbauer measurements, that has a pronounced effect on the delta M plots, leading to features remarkably similar to those produced by dipolar interactions. X-ray diffraction results combined with magnetic characterization indicate that this inhomogeneity is due to the presence of surface structural (and spin) disorder. Monte Carlo simulations unambiguously corroborate the critical role of the internal magnetic structure in the delta M plots. Our findings constitute a cautionary tale on the widespread use of remanence plots to assess interparticle interactions as well as offer new perspectives in the use of Henkel and delta M plots to quantify the rather elusive inhomogeneous magnetization states in nanoparticles.

  • 13.
    Flores, Eibar
    et al.
    Paul Scherrer Inst, Electrochem Lab, Villigen, Switzerland.
    Vonrüti, Nathalie
    Univ Bern, Dept Chem & Biochem, Bern, Switzerland.
    Novák, Petr
    Paul Scherrer Inst, Electrochem Lab, Villigen, Switzerland.
    Aschauer, Ulrich
    Univ Bern, Dept Chem & Biochem, Bern, Switzerland.
    Berg, Erik Jämstorp
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry. Paul Scherrer Inst, Electrochem Lab, Villigen, Switzerland.
    Elucidation of LixNi0.8Co0.15Al0.05O2 Redox Chemistry by Operando Raman Spectroscopy2018In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 30, no 14, p. 4694-4703Article in journal (Refereed)
    Abstract [en]

    The local structure evolution of LixNi0.8Co0.15Al0.05O2 (NCA) is linked to its electrochemical response during cycling (and overcharge) by operando Raman spectroscopy with findings supported by complementary techniques, such as online electrochemical mass spectrometry (OEMS) and density functional theory (DFT) phonon calculations. The vibrational motion of lattice oxygens is observed to be highly dependent on the local LixMO2 lattice environment, e.g. M—O bonding strength/length and state of lithiation x. All vibrational modes generally harden upon delithiation due to M—O bond character (ionic → covalent) evolution (disregarding an early bond softening due to Li+ vacancy formation) and evidence the important influence of the local structural lattice configuration on the electrochemical response of NCA. Although the intensities of all Raman active bands generally increase upon delithiation, a major inflection point at x = 0.2 marks the onset of a partly irreversible fundamental transition within NCA that is most likely related to electron removal from MO bonding states and partial oxidation of oxygen sublattice, which is also indicated by the observed concomitant O2 release from the particle surface. Operando Raman spectroscopy with higher time resolution provides unique possibilities for detailed studies of how chemical parameters (Li+ vacancy formation, transition metal cation concentration, and lattice doping, etc.) may govern the onset and nature of processes (such as bond character evolution and stability) that define the performance of the LixMO2 class of oxides. The further insights thus gained can be exploited to guide the development of next-generation layered cathodes for Li-ion batteries operating stably at higher voltages and capacities.

  • 14.
    House, Robert A.
    et al.
    Univ Oxford, Dept Mat, Parks Rd, Oxford OX1 3PH, England.
    Maitra, Urmimala
    Univ Oxford, Dept Mat, Parks Rd, Oxford OX1 3PH, England;Justus Liebig Univ Giessen, Inst Phys Chem, Heinrich Buff Ring 17,Room B48, D-35392 Giessen, Germany.
    Jin, Liyu
    Univ Oxford, Dept Mat, Parks Rd, Oxford OX1 3PH, England.
    Lozano, Juan G.
    Univ Oxford, Dept Mat, Parks Rd, Oxford OX1 3PH, England.
    Somerville, James W.
    Univ Oxford, Dept Mat, Parks Rd, Oxford OX1 3PH, England.
    Rees, Nicholas H.
    Univ Oxford, Dept Chem, Mansfield Rd, Oxford OX1 3TA, England.
    Naylor, Andrew J.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Duda, Laurent
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Massel, Felix
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Chadwick, Alan V.
    Univ Kent, Sch Phys Sci, Canterbury CT2 7NH, Kent, England.
    Ramos, Silvia
    Univ Kent, Sch Phys Sci, Canterbury CT2 7NH, Kent, England.
    Pickup, David M.
    Univ Kent, Sch Phys Sci, Canterbury CT2 7NH, Kent, England.
    McNally, Daniel E.
    Paul Scherrer Inst, Swiss Light Source, Photon Sci Div, CH-5232 Villigen, Switzerland.
    Lu, Xingye
    Paul Scherrer Inst, Swiss Light Source, Photon Sci Div, CH-5232 Villigen, Switzerland.
    Schmitt, Thorsten
    Paul Scherrer Inst, Swiss Light Source, Photon Sci Div, CH-5232 Villigen, Switzerland.
    Roberts, Matthew R.
    Univ Oxford, Dept Mat, Parks Rd, Oxford OX1 3PH, England.
    Bruce, Peter G.
    Univ Oxford, Dept Mat, Parks Rd, Oxford OX1 3PH, England;Univ Oxford, Faraday Inst, Mansfield Rd, Oxford OX1 3TA, England;Univ Oxford, Dept Chem, Mansfield Rd, Oxford OX1 3TA, England.
    What Triggers Oxygen Loss in Oxygen Redox Cathode Materials?2019In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 31, no 9, p. 3293-3300Article in journal (Refereed)
    Abstract [en]

    It is possible to increase the charge capacity of transition metal (TM) oxide cathodes in alkali-ion batteries by invoking redox reactions on the oxygen. However, oxygen loss often occurs. To explore what affects oxygen loss in oxygen redox materials, we have compared two analogous Na-ion cathodes, P2-Na0.67Mg0.28Mn0.72O2 and P2-Na0.78Li0.25Mn0.75O2. On charging to 4.5 V, >0.4e(-) are removed from the oxide ions of these materials, but neither compound exhibits oxygen loss. Li is retained in P2-Na0.78Li0.25Mn0.25O2 but displaced from the TM to the alkali metal layers, showing that vacancies in the TM layers, which also occur in other oxygen redox compounds that exhibit oxygen loss such as Li[Li0.2Ni0.2Mn0.6]O-2, are not a trigger for oxygen loss. On charging at 5 V, P2-Na0.78Li0.25Mn0.75O2 exhibits oxygen loss, whereas P2-Na0.67Mg0.28Mn0.72O2 does not. Under these conditions, both Na+ and Li+ are removed from P2-Na0.78Li0.25Mn0.75O2, resulting in underbonded oxygen (fewer than 3 cations coordinating oxygen) and surface-localized O loss. In contrast, for P2-Na0.67Mg0.28Mn0.72O2, oxygen remains coordinated by at least 2 Mn4+ and 1 Mg2+ ions, stabilizing the oxygen and avoiding oxygen loss.

  • 15.
    Ivanov, Sergey A.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Mathieu, Roland
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Nordblad, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Tellgren, Roland
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Ritter, C.
    Politova, E.
    Kaleva, G.
    Mosunov, A.
    Stefanovich, S.
    Weil, M.
    Spin and Dipole Ordering in Ni2InSbO6 and Ni2ScSbO6 with Corundum-Related Structure2013In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 25, no 6, p. 935-945Article in journal (Refereed)
    Abstract [en]

    The complex metal oxides Ni2InSbO6 (NISO) and Ni2ScSbO6 (NSSO) have been prepared in the form of polycrystalline powders by a solid state reaction route. The crystal structure and magnetic properties of the compounds were investigated using a combination of X-ray and neutron powder diffraction, electron microscopy, calorimetric, and magnetic measurements. The compounds adopt a trigonal structure, space group R3, of the corundum related Ni3TeO6 (NTO) type. Only one of the octahedral Ni positions (Ni(2)) of the NTO structure was found to be occupied by In (Sc). NTO has noncentrosymmetric structure and is ferroelectric below 1000 K; dielectric and second harmonic measurements suggest that also NISO and NSSO are correspondingly ferroelectric. Magnetization measurements signified antiferromagnetic ordering below T-N = 60 K (NSSO) and 76 K (NISO). The magnetic structure is formed by two antiferromagnetically coupled incommensurate helices with the spiral axis along the b-axis and propagation vector k = [0, k(y),0] with k(y) = 0.036(1) (NSSO) and k(y) = 0.029(1) (NISO). The observed structural and magnetic properties of NISO and NSSO are discussed and compared with those of NTO.

  • 16.
    Johansson, Erik M. J.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics I.
    Karlsson, Patrik G.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics I.
    Hedlund, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics I.
    Ryan, Declan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics I.
    Siegbahn, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics I.
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics I.
    Photovoltaic and Interfacial Properties of Heterojunctions Containing Dye-sensitized Dense TiO2 and Triarylamine derivatives2007In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 19, no 8, p. 2071-2078Article in journal (Refereed)
    Abstract [en]

    A series of solid-state heterojunctions comprising a dense TiO2 film electrode as an electron conductor, a ruthenium polypyridine complex (Ru(dcbpy)2(NCS)2) as a light-absorbing dye, and different triarylamine derivatives as hole conductors were prepared, and their photovoltaic properties as well as the molecular and electronic interfacial structures were investigated. The photovoltaic properties were compared to systems containing the hole conductors dissolved in an organic solvent as well as to a system containing a liquid electrolyte containing the iodide/tri-iodide redox couple. Two of the solid-state heterojunctions showed conversion efficiencies close to those of the system containing the iodide/tri-iodide redox couple, while one system was clearly less efficient. To explain the differences in photovoltaic properties the electronic and molecular interfacial structures of the solid-state heterojunctions were investigated by photoelectron spectroscopy (PES). By valence level PES the electronic energy levels highest in energy for the dye and the hole conductors were mapped, and the differences in energy matching partly explain the trends in photovoltaic properties. Differences in the molecular surface structure of the heterojunctions were also observed from the N Is core level measurements. Specifically it was found that the smaller hole conductor, showing low photocurrent yield, is inserted into the dye layer.

  • 17.
    Källquist, Ida
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Naylor, Andrew J.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Baur, Christian
    Helmholtz Inst Ulm, Helmholtzstr 11, D-89081 Ulm, Germany.
    Chable, Johann
    Helmholtz Inst Ulm, Helmholtzstr 11, D-89081 Ulm, Germany.
    Kullgren, Jolla
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Fichtner, Maximilian
    Helmholtz Inst Ulm, Helmholtzstr 11, D-89081 Ulm, Germany;Karlsruhe Inst Technol, Inst Nanotechnol, Box 3640, D-76021 Karlsruhe, Germany.
    Edström, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Brandell, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Hahlin, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Degradation Mechanisms in Li2VO2F Li-Rich Disordered Rock-Salt Cathodes2019In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 31, no 16, p. 6084-6096Article in journal (Refereed)
    Abstract [en]

    The increased energy density in Li-ion batteries is particularly dependent on the cathode materials that so far have been limiting the overall battery performance. A new class of materials, Li-rich disordered rock salts, has recently been brought forward as promising candidates for next-generation cathodes because of their ability to reversibly cycle more than one Li-ion per transition metal. Several variants of these Li-rich cathode materials have been developed recently and show promising initial capacities, but challenges concerning capacity fade and voltage decay during cycling are yet to be overcome. Mechanisms behind the significant capacity fade of some materials must be understood to allow for the design of new materials in which detrimental reactions can be mitigated. In this study, the origin of the capacity fade in the Li-rich material Li2VO2F is investigated, and it is shown to begin with degradation of the particle surface that spreads inward with continued cycling.

  • 18.
    Lanzilotto, Valeria
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics. Univ Florence, Dept Chem Ugo Schiff, I-50019 Sesto Fiorentino, Italy.;Univ Florence, INSTM Res Unit, I-50019 Sesto Fiorentino, Italy..
    Malavolti, Luigi
    Univ Florence, Dept Chem Ugo Schiff, I-50019 Sesto Fiorentino, Italy.;Univ Florence, INSTM Res Unit, I-50019 Sesto Fiorentino, Italy.;Max Planck Inst Struct & Dynam Matter, D-22761 Hamburg, Germany..
    Ninova, Silviya
    Univ Florence, Dept Chem Ugo Schiff, I-50019 Sesto Fiorentino, Italy.;Univ Florence, INSTM Res Unit, I-50019 Sesto Fiorentino, Italy.;Univ Bern, Dept Chem & Biochem, Freiestr 3, CH-3012 Bern, Switzerland..
    Cimatti, Irene
    Univ Florence, Dept Chem Ugo Schiff, I-50019 Sesto Fiorentino, Italy.;Univ Florence, INSTM Res Unit, I-50019 Sesto Fiorentino, Italy..
    Poggini, Lorenzo
    Univ Florence, Dept Chem Ugo Schiff, I-50019 Sesto Fiorentino, Italy.;Univ Florence, INSTM Res Unit, I-50019 Sesto Fiorentino, Italy.;Inst Chim Matiere Condensee Bordeaux, Grp Mol & Mat Commutables, 87 Ave Docteur Schweitzer, F-33608 Pessac, France..
    Cortigiani, Brunetto
    Univ Florence, Dept Chem Ugo Schiff, I-50019 Sesto Fiorentino, Italy.;Univ Florence, INSTM Res Unit, I-50019 Sesto Fiorentino, Italy..
    Mannini, Matteo
    Univ Florence, Dept Chem Ugo Schiff, I-50019 Sesto Fiorentino, Italy.;Univ Florence, INSTM Res Unit, I-50019 Sesto Fiorentino, Italy..
    Totti, Federico
    Univ Florence, Dept Chem Ugo Schiff, I-50019 Sesto Fiorentino, Italy.;Univ Florence, INSTM Res Unit, I-50019 Sesto Fiorentino, Italy..
    Gornia, Andrea
    Univ Modena & Reggio Emilia, Dept Chem & Geol Sci, I-41125 Modena, Italy.;Univ Modena & Reggio Emilia, INSTM Res Unit, I-41125 Modena, Italy..
    Sessoli, Roberta
    Univ Florence, Dept Chem Ugo Schiff, I-50019 Sesto Fiorentino, Italy.;Univ Florence, INSTM Res Unit, I-50019 Sesto Fiorentino, Italy..
    The Challenge of Thermal Deposition of Coordination Compounds: Insight into the Case of an Fe-4 Single Molecule Magnet2016In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 28, no 21, p. 7693-7702Article in journal (Refereed)
    Abstract [en]

    Realization of well-controlled hybrid interfaces between solid surfaces and functional complex molecules can be hampered by the presence of contaminants originated by the fragmentation of fragile architectures based on the coordinative bond. Here, we present a morphological and spectroscopic analysis of submonolayer films obtained by sublimation of the [Fe-4(L)(2)(dpm)(6)] (Fe-4) single molecule magnet on different substrates. Though intact tetranuclear molecules can be transferred to surfaces, smaller molecular species are often codeposited. By comparison of substrates characterized by different reactivities, such as Au(111), Cu(100), and Cu2N, and employing a protocol of indirect exposure of the substrate, we infer that the observed fragments do not originate from the reaction of Fe-4 molecules with the surface but rather are produced during Fe-4 sublimation, which releases Fe(dpm)(3) as a very volatile compound. Fe(dpm)(3) undergoes substrate-dependent on-surface decomposition to final products that have been identified by combined STM, UPS, XPS, and DFT studies.

  • 19.
    Lee, Kathleen
    et al.
    Univ Calif Davis, Dept Chem, One Shields Ave, Davis, CA 95616 USA..
    Kamali, Saeed
    Univ Tennessee, Inst Space, Mech Aerosp & Biomed Engn Dept, Tullahoma, TN 37388 USA..
    Ericsson, Tore
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Bellard, Maverick
    Univ Calif Davis, Dept Chem, One Shields Ave, Davis, CA 95616 USA..
    Kovnir, Kirill
    Univ Calif Davis, Dept Chem, One Shields Ave, Davis, CA 95616 USA..
    GeAs: Highly Anisotropic van der Waals Thermoelectric Material2016In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 28, no 8, p. 2776-2785Article in journal (Refereed)
    Abstract [en]

    GeAs and Sn-doped GeAs were synthesized from elements. Both crystallize in a layered crystal structure in the C2/m space group (No. 12) in the GaTe structure type. The crystal structure consists of As-terminated layers separated by van der Waals gaps. Sn-119 Mossbauer spectroscopy reveals that in the doped compound, Sn atoms are situated in a symmetric and homogeneous environment, most probably in the form of Sn-2 dumbbells. The anisotropic crystal structure of GeAs leads to highly anisotropic transport properties. High electrical and thermal conductivities were determined along the crystallographic layers. For the perpendicular direction across the layers, a sharp drop of more than an order of magnitude was observed for the transport properties of the GeAs single crystal. As a result, an order of magnitude difference in the figure of merit, ZT, was achieved: High-temperature thermoelectric characterization of the Sn-doped compound reveals a remarkable ZT with a maximum of 0.35 at 660 K.

  • 20.
    Ma, Yue
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Asfaw, Habtom Desta
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Edström, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    A General Method to Fabricate Free-Standing Electrodes: Sulfonate Directed Synthesis and their Li+ Storage Properties2015In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 27, no 11, p. 3957-3965Article in journal (Refereed)
    Abstract [en]

    For materials based on a spatially varied conversion reaction, Li+ storage properties largely hinge on the rational design of the concurrent electronic and ionic pathways in the electrode. We herein present a scalable approach for integrating size-tunable Fe3O4 nanocrystals with hierarchical porous carbon foam by employing sulfonated high internal phase emulsion polymers (polyHIPE) as the carbon source and substrate. To verify the feasibility of our configuration design, the electrodes of such a type were directly evaluated in pouch cells without using an auxiliary binder or a metallic current collector: The best performing composite electrode, with optimized oxide size range, exhibits a good capacity retention of 89.7% of the first charge capacity after 100 cycles and high rate durability up to 4 A g–1. Furthermore, this synthetic approach was also applied to develop carbon/FeS free-standing anodes using the sulfonate groups as the sulfur source, demonstrating its generic applicability to the fabrication of other free-standing electrodes with enhanced Li+ storage properties.

  • 21.
    Ma, Yue
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Tai, Cheuk-Wai
    Stockholm Univ, Dept Mat & Environm Chem, Arrhenius Lab, SE-10691 Stockholm, Sweden..
    Younesi, Reza
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Gustafsson, Torbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Lee, Jim Yang
    Natl Univ Singapore, Dept Biomol & Chem Engn, Singapore 119260, Singapore..
    Edström, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Iron Doping in Spinel NiMn2O4: Stabilization of the Mesoporous Cubic Phase and Kinetics Activation toward Highly Reversible Li+ Storage2015In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 27, no 22, p. 7698-7709Article in journal (Refereed)
    Abstract [en]

    Quaternary oxide structures with a three-dimensional macro/mesoporous network are synthesized via a facile nanocasting method followed by a calcination process. Structural engineering integrates multiscale pores by using a hydrophilic membrane with tunable-porosity as the sacrificial template. Through tailoring the metal precursor ratio, the tetragonal sites of spinel oxide are preferentially occupied by iron, resulting in a stabilized mesoporous cubic phase. Crystal field theory together with compositional characterizations from energy-dispersive spectrometry (EDS), X-ray photoelectron spectroscopy (XPS), Mossbauer, and electron energy loss spectroscopy (EELS) direct our detailed analysis of the cation distribution in the spinel structures. Galvanostatic tests based on the best performing electrode exhibits a robust cycle life stable for 1200 cycles at a high current density of 1500 mA g(-1). This good Li+ storage performance could be attributed to the mutually beneficial synergy of the optimal level of iron doping which improves the electrical conductivity and structural robustness, as well as the presence of extended, hierarchical macro/mesoporous network. Finally, we demonstrate three feasible surface modification strategies for the oxide anodes toward better reversibility of Li+ storage.

  • 22.
    Mindemark, Jonas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry. Umea Univ, Dept Phys, Organ Photon & Elect Grp, SE-90187 Umea, Sweden..
    Tang, Shi
    Umea Univ, Dept Phys, Organ Photon & Elect Grp, SE-90187 Umea, Sweden..
    Wang, Jia
    Umea Univ, Dept Phys, Organ Photon & Elect Grp, SE-90187 Umea, Sweden..
    Kaihovirta, Nikolai
    Umea Univ, Dept Phys, Organ Photon & Elect Grp, SE-90187 Umea, Sweden..
    Brandell, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Edman, Ludvig
    Umea Univ, Dept Phys, Organ Photon & Elect Grp, SE-90187 Umea, Sweden..
    High-Performance Light-Emitting Electrochemical Cells by Electrolyte Design2016In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 28, no 8, p. 2618-2623Article in journal (Refereed)
    Abstract [en]

    Polymer light-emitting electrochemical cells (LECs) are inherently dependent on a suitable electrolyte for proper function. Here, we design and synthesize a series of alkyl carbonate-capped star-branched oligoether-based electrolytes with large electrochemical stability windows, facile ion release, and high compatibility with common light-emitting materials. LECs based on such designed electrolytes feature fast turn-on, a long operational lifetime of 1400 h at >100 cd m(-2) and a record-high power conversion efficiency of 18.1 lm W-1, when equipped with an external outcoupling film.

  • 23.
    Muscas, Giuseppe
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Singh, G.
    Glomm, W. R.
    Mathieu, Roland
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Kumar Puri, Anil
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Concas, G.
    Agostinelli, E.
    Peddis, D.
    Tuning the Size and Shape of Oxide Nanoparticles by Controlling Oxygen Content in the Reaction Environment: Morphological Analysis by Aspect Maps2015In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 27, no 6, p. 1982-1990Article in journal (Refereed)
    Abstract [en]

    The thermal decomposition of acetylacetonate precursors is one of the most employed syntheses to prepare high quality colloidal magnetic nanopartides. In this paper, an advanced version of this synthetic approach was developed to prepare cobalt ferrite nanopartides, introducing for the first time a rigorous control on one commonly neglected reaction parameter, that is, the residual oxygen content in the reaction environment. A new concept derived from the statistical analysis of S(T)EM images, i.e., the so-called aspects maps, was introduced: this tool has allowed us to clearly identify the optimal value of pressure to produce particles with an average size,similar to 19 nm and with a very narrow size distribution (polydispersity 0.4 nm(-1)). The magnetic properties of this sample were also analyzed, and a strong improvement of the magnetization reversal mechanism, which is a critical issue for several technological applications, was observed.

  • 24. Neuschitzer, Markus
    et al.
    Sanchez, Yudania
    Olar, Tetiana
    Thersleff, Thomas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Lopez-Marino, Simon
    Oliva, Florian
    Espindola-Rodriguez, Moises
    Xie, Haibing
    Placidi, Marcel
    Izquierdo-Roca, Victor
    Lauermann, Iver
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Perez-Rodriguez, Alejandro
    Saucedo, Edgardo
    Complex Surface Chemistry of Kesterites: Cu/Zn Reordering after Low Temperature Postdeposition Annealing and Its Role in High Performance Devices2015In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 27, no 15, p. 5279-5287Article in journal (Refereed)
    Abstract [en]

    A detailed study explaining the beneficial effects of low temperature postdeposition annealing combined with selective surface etchings for Cu2ZnSnSe4 (CZTSe) based solar cells is presented. After performing a selective oxidizing surface etching to remove ZnSe secondary phases typically formed during the synthesis processes an additional 200 degrees C annealing step is necessary to increase device performance from below 3% power conversion efficiency up to 8.3% for the best case. This significant increase in efficiency can be explained by changes in the surface chemistry which results in strong improvement of the CdS/CZTSe heterojunction commonly used in this kind of absorber/buffer/window heterojunction solar cells. XPS measurements reveal that the 200 degrees C annealing promotes a Cu depletion and Zn enrichment of the etched CZTSe absorber surface relative to the CZTSe bulk. Raman measurements confirm a change in Cu/Zn ordering and an increase in defect density. Furthermore, TEM microstructural investigations indicate a change of grain boundaries composition by a reduction of their Cu content after the 200 degrees C annealing treatment. Additionally, insights in the CdS/CZTSe interface are gained showing a significant amount of Cu in the CdS buffer layer which further helps the formation of a Cu-depleted surface and seems to play an important role in the formation of the pn-heterojunction.

  • 25.
    Nordlinder, Sara
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Augustsson, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Schmitt, Thorsten
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics II.
    Guo, Jinghua
    Duda, Laurent-C.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Nordgren, Joseph
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics II.
    Gustafsson, Torbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Edström, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Redox Behavior of Vanadium Oxide Nanotubes As Studied by X-ray Photoelectron Spectroscopy and Soft X-ray Absorption Spectroscopy2003In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 15, no 16, p. 3227-3232Article in journal (Refereed)
  • 26.
    Oltean, Viorica Alina
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Philippe, Bertrand
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Renault, Steven
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Duarte, Roberto Felix
    Helmholtz Zentrum Berlin Mat & Energie GmbH, Renewable Energy, D-14109 Berlin, Germany..
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Brandell, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Investigating the Interfacial Chemistry of Organic Electrodes in Li- and Na-Ion Batteries2016In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 28, no 23, p. 8742-8751Article in journal (Refereed)
    Abstract [en]

    Organic compounds are increasingly being investigated as electrode materials for Li- or Na-ion batteries. Even though their gravimetric capacity can challenge that of their inorganic counterparts, a number of problems need further attention, not least their chemical and electrochemical stability toward the electrolyte systems. There has been speculation that several of these issues have their origin in the formation of a less stable solid electrolyte interphase (SEI) layer and its evolution during battery cycling. We here present the very first thorough characterization of the organic electrode material SEI layer using hard X-ray photoelectron spectroscopy (HAXPES), for both Li- and Na-based electrodes. Dilithium and disodium benzenediacrylates have been used for battery construction and investigated electrochemically followed by HAXPES measurements electrolyte and after cycling. The Na-based electrodes react spontaneously with the electrolyte, and the SEI layer is dominated by inorganic species with continuous salt degradation during cycling. The Li-based electrodes display an SEI layer with primarily organic species from solvent degradation products appearing only after cycling and increasing in amount with the number of electrochemical cycles.

  • 27.
    Park, Byung-wook
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Philippe, Bertrand
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Gustafsson, Torbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Sveinbjörnsson, Kári
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Johansson, Erik M. J.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Enhanced Crystallinity in Organic-Inorganic Lead Halide Perovskites on Mesoporous TiO2 via Disorder-Order Phase Transition2014In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 26, no 15, p. 4466-4471Article in journal (Refereed)
    Abstract [en]

    Organic-inorganic halide perovskite (OIHP) compounds are very interesting materials for device application in, for example, solar cells, electro-optics, and electronic circuits. In this report, we investigated OIHPs reported as CH3NH3PbI3-xClx (MAPbI(3-x)Cl(x)) and CH3NH3PbI3 (MAPbI(3)) prepared from solution on mesoporous TiO2/glass substrates. A long-term conversion from disordered to more crystalline OIHPs was observed for both types of samples from XRD patterns over 5 weeks. The conversion rate to more crystalline OIHPs could be increased by increasing the temperature of the sample. SEM analyses of the two types of OIHPs show remarkably different surface microstructures. The X-ray diffractograms suggest that both samples are dominated by the similar crystal structure, although the preferential orientation for the crystal structure is different. Moreover, the results suggest that the material reported as MAPbI(3-x)Cl(x) is a combination of MAPbI(3) and MAPbCl(3). The crystal structure and exact nature of the material is important for the understanding and optimization of devices, and the possibility for enhanced crystallinity of the OIHPs shown in this report will therefore be important for further improvement and understanding of the devices.

  • 28. Peddis, D.
    et al.
    Cannas, C.
    Musinu, A.
    Ardu, A.
    Orrù, F.
    Fiorani, D.
    Laureti, S.
    Rinaldi, D.
    Muscas, Giuseppe
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Concas, G.
    Piccaluga, G.
    Beyond the Effect of Particle Size: Influence of CoFe2O4 Nanoparticle Arrangements on Magnetic Properties2013In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 25, no 10, p. 2005-2013Article in journal (Refereed)
  • 29.
    Philippe, Bertrand
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Dedryvere, Remi
    Université de Pau, France.
    Allouche, Joachim
    Lindgren, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Gorgoi, Mihaela
    Helmholtz Zentrum Berlin Germany.
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Gonbeau, Danielle
    Université de Pau, France.
    Edström, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Nanosilicon Electrodes for Lithium-Ion Batteries: Interfacial Mechanisms Studied by Hard and Soft X-ray Photoelectron Spectroscopy2012In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 24, no 6, p. 1107-1115Article in journal (Refereed)
    Abstract [en]

    Largely based on its very high rechargeable capacity, silicon appears as an ideal candidate for the next generation of negative electrodes for Li-ion batteries. However, a crucial problem with silicon is the large volume expansion undergone upon alloying with lithium, which results in stability problems. Means to avoid such problems are largely linked to the understanding of the interfacial chemistry during charging/discharging. This is especially of great importance when using nanometric silicon particles. In this work, the interfacial mechanisms (reaction of surface oxide, Li-Si alloying process, and passivation layer formation) accompanying lithium insertion/extraction into Si/C/CMC composite electrodes have been scrutinized by Xray photoelectron spectroscopy (XPS). A thorough nondestructive depth-resolved analysis was carried out by using both soft X-rays (100-800 eV) and hard X-rays (2000-7000 eV) from two different synchrotron facilities compared with in-house XPS (1487 eV). The unique combination utilizing hard and soft X-ray photoelectron spectroscopy accompanied with variation of the analysis depth allowed us to access interfacial phase transitions at the surface of silicon particles as well as the composition and thickness of the SEI (electrode/electrolyte interface layer).

  • 30.
    Philippe, Bertrand
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Dedryvère, Rémi
    Université de Pau, France.
    Gorgoi, Mihaela
    Helmholtz Zentrum Berlin.
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Gonbeau, Danielle
    Université de Pau France.
    Edström, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Role of the LiPF6 Salt for the Long-Term Stability of Silicon Electrodes in Li-Ion Batteries: A Photoelectron Spectroscopy Study2013In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 25, no 3, p. 394-404Article in journal (Refereed)
    Abstract [en]

    Silicon presents a very high theoretical capacity (3578 mAh/g) and appears as a promising candidate for the next generation of negativeelectrodes for Li-ion batteries. An important issue for the implementation ofsilicon is the understanding of the interfacial chemistry taking place duringcharge/discharge since it partly explains the capacity fading usually observedupon cycling. In this work, the mechanism for the evolution of the interfacialchemistry (reaction of surface oxide, Li−Si alloying process, and passivationlayer formation) upon long-term cycling has been investigated byphotoelectron spectroscopy (XPS or PES). A nondestructive depth resolved analysis was carried out by using both soft Xrays(100−800 eV) and hard X-rays (2000−7000 eV) from two different synchrotron facilities. The results are compared withthose obtained with an in-house spectrometer (1486.6 eV). The important role played by the LiPF6 salt on the stability of thesilicon electrode during cycling has been demonstrated in this study. A partially fluorinated species is formed upon cycling at theoutermost surface of the silicon nanoparticles as a result of the reaction of the materials toward the electrolyte. We have shownthat a similar species is also formed by simple contact between the electrolyte and the pristine electrode. The reactivity betweenthe electrode and the electrolyte is investigated in this work. Finally, we also report in this work the evolution of the compositionand covering of the SEI upon cycling as well as proof of the protective role of the SEI when the cell is at rest.

  • 31.
    Philippe, Bertrand
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Park, Byung-Wook
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Lindblad, Rebecka
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Oscarsson, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Ahmadi, Sareh
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Johansson, Erik M. J.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Chemical and Electronic Structure Characterization of Lead Halide Perovskites and Stability Behavior under Different Exposures-A Photoelectron Spectroscopy Investigation2015In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 27, no 5, p. 1720-1731Article in journal (Refereed)
    Abstract [en]

    The past few years, two perovskite materials have attracted much attention in the solar cell community: CH3NH3PbI3 and CH3NH3PbI3xClx. While these materials are usually characterized using their structure (via X-ray diffraction (XRD)) and performance within solar cell communities, not so much attention has been devoted to their surface chemical composition and, specifically, the surface composition. Photoelectron spectroscopy (PES) can easily fulfill this task, and, in addition to chemical information, PES provides an overall picture of the electronic structure of the perovskite and its relation to mesoporous TiO2 when studied with hard X-rays. In this work, CH3NH3PbI3 and CH3NH3PbI3xClx have been compared with each other and also to CH3NH3PbI3, and it appears that, despite very different morphologies and kinetics of formation, the two former materials present a very similar electronic structure and chemical composition (i.e., no chlorine is observed in the final CH3NH3PbI3xClx materials). Nevertheless, chlorine is very important during the preparation, because it affects the formation of crystalline CH3NH3PbI3. We have also exposed the classical CH3NH3PbI3 to various environments, such as water, temperature, and long-time storage in air and argon, and followed changes of the surface composition with PES. The main result of the different exposures is that the perovskite is decomposed into PbI2, but an important point is that this degradation seems to occur already at 100 degrees C and is not only related to large humidity. Indeed, even in an inert atmosphere such as argon, a slow degradation to PbI2 is observed. The results obtained are crucial for a better understanding of this material and will help to improve not only the post-conditioning of the cells but also their synthesis.

  • 32.
    Philippe, Bertrand
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Saliba, Michael
    Laboratory of Photonics and Interfaces, Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne, CH-1015-Lausanne, Switzerland.
    Correa-Baena, Juan-Pablo
    Laboratory for Photomolecular Science, Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne, Switzerland; Massachusetts Institute of Technology, Cambridge, Massachusetts..
    Cappel, Ute B.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Turren-Cruz, Silver-Hamill
    Laboratory for Photomolecular Science, Institute of Chemical Sciences and Engineering, École Polytechnique, Lausanne, Switzerland; Benemérita Universidad Autónoma de Puebla, México.
    Grätzel, Michael
    Laboratory for Photomolecular Science, Institute of Chemical Sciences and Engineering, École Polytechnique, Lausanne, Switzerland.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry. Laboratory for Photomolecular Science, Institute of Chemical Sciences and Engineering, École Polytechnique, Lausanne, Switzerland.
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Chemical Distribution of Multiple Cation (Rb+, Cs+, MA+, and FA+) Perovskite Materials by Photoelectron Spectroscopy2017In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 29, no 8, p. 3589-3596Article in journal (Refereed)
    Abstract [en]

    Lead-based mixed perovskite materials have emerged in the last couple of years as promising photovoltaic materials. Recently, it was shown that improved material stability can be achieved by incorporating small amounts of inorganic cations (Cs+  and Rb+ ), partially replacing the more common organic cations (e.g., methylammonium, MA, and formamidinium, FA). Especially, a mixed cation composition containing Rb+ , Cs+ , MA+ , and FA+  was recently shown to have benefi cial optoelectronic properties and was stable at elevated temperature. This work focuses on the composition of this material using synchrotron-based photoelectron spectroscopy. Diff erent probing depths were considered by changing the photon energy of the X-ray source providing insights on the chemical composition and the chemical distribution near the surface of the samples. Perovskite materials containing two, three, or four monovalent cations were analyzed and compared.

    The presence of Cs and Rb was observed both at the sample surface and toward the bulk, and we found that in the presence of three or four cations, less unreacted PbI2  remains in the sample. Interestingly, Rb and Cs appear to act jointly resulting in a different cation depth profile compared to that of the triple counterparts. Our findings provide significant understanding of the intricate depth-dependent chemical composition in perovskite materials using the common practice of cation mixing.

  • 33.
    Philippe, Bertrand
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Valvo, Mario
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Lindgren, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Edström, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Investigation of the Electrode/Electrolyte Interface of Fe2O3 Composite Electrodes: Li vs Na Batteries2014In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 26, no 17, p. 5028-5041Article in journal (Refereed)
    Abstract [en]

     We have investigated the properties of the electrode/electrolyte interfaces of composite electrodes based on nanostructured iron oxide cycled in Li- and Na-half cells containing analogous electrolytes (i.e., LiClO4  or NaClO4  in ethylene carbonate:diethyl carbonate (EC:DEC)). A meticulous nondestructive step-by-step analysis of the first discharge/charge cycle has been conducted via soft X-ray photoelectron spectroscopy using synchrotron radiation. In

    this way, diff erent depths were probed by varying the photon energy (hν ) for both electrochemical systems. The results of this thorough study clearly highlight the diff erences and the similarities of their respective solid electrolyte interface (SEI) layers in terms of formation, composition, structure, or thickness, as well as their conversion mechanisms. We specifi cally point out that the SEI coverage is more pronounced, and a homogeneous

    distribution rich in inorganic species exists in the case of Na, compared to the organic/inorganic layered structure observed for the Li system. The SEI formation gradually occurs during the fi rst discharge in both Li- and Na-half cells. For Na, a predeposit layer is formed directly by simple contact of the electrode with the electrolyte. Despite using similar electrolytes, the nature of the cation (Li+  or Na+ ) has signifi cant impact on the overall composition/structure of the resulting SEI.

  • 34.
    Phuyal, Dibya
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Safdari, Majid
    KTH Royal Institute of Technology.
    Pazoki, Meysam
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Liu, Peng
    KTH Royal Institute of Technology.
    Philippe, Bertrand
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Kvashnina, Kristina O.
    ESRF.
    Karis, Olof
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Butorin, Sergei
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Edvinsson, Tomas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Kloo, Lars
    KTH Royal Institute of Technology.
    Gardner, James
    KTH Royal Institute of Technology.
    Electronic Structure of Two-Dimensional Lead(II) Iodide Perovskites: An Experimental and Theoretical Study2018In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 30, no 15, p. 4959-4967Article in journal (Refereed)
    Abstract [en]

    Layered two-dimensional (2D) hybrid organic-inorganic perovskites (HOP) are promising materials for light-harvesting applications because of their chemical stability, wide flexibility in composition and dimensionality, and increases in photovoltaic power conversion efficiencies. Three 2D lead iodide perovskites were studied through various X-ray spectroscopic techniques to derive detailed electronic structures and band energetics profiles at a titania interface. Core-level and valence band photoelectron spectra of HOP were analyzed to resolve the electronic structure changes due to the reduced dimensionality of inorganic layers. The results show orbital narrowing when comparing the HOP, the layered precursor PbI2, and the conventional 3D (CH3NH3)PbI3 such that different localizations of band edge states and narrow band states are unambiguously due to the decrease in dimensionality of the layered HOPs. Support from density functional theory calculations provide further details on the interaction and band gap variations of the electronic structure. We observed an interlayer distance dependent dispersion in the near band edge electronic states. The results show how tuning the interlayer distance between the inorganic layers affects the electronic properties and provides important design principles for control of the interlayer charge transport properties, such as the change in effective charge masses as a function of the organic cation length. The results of these findings can be used to tune layered materials for optimal functionality and new applications.

  • 35.
    Pious, Johnpaul K.
    et al.
    CSIR Natl Inst Interdisciplinary Sci & Technol NI, Photosci & Photon Sect, Thiruvananthapuram 695019, Kerala, India;Acad Sci & Innovat Res AcSIR, Ghaziabad 201002, India.
    Katre, Ankita
    Savitribai Phule Pune Univ, Ctr Modelling & Simulat, Pune 411007, Maharashtra, India.
    Muthu, Chinnadurai
    CSIR Natl Inst Interdisciplinary Sci & Technol NI, Photosci & Photon Sect, Thiruvananthapuram 695019, Kerala, India;Acad Sci & Innovat Res AcSIR, Ghaziabad 201002, India.
    Chakraborty, Sudip
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Krishna, Swathi
    CSIR Natl Inst Interdisciplinary Sci & Technol NI, Photosci & Photon Sect, Thiruvananthapuram 695019, Kerala, India.
    Nair, Vijayakumar C.
    CSIR Natl Inst Interdisciplinary Sci & Technol NI, Photosci & Photon Sect, Thiruvananthapuram 695019, Kerala, India;Acad Sci & Innovat Res AcSIR, Ghaziabad 201002, India.
    Zero-Dimensional Lead-Free Hybrid Perovskite-like Material with a Quantum-Well Structure2019In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 31, no 6, p. 1941-1945Article in journal (Refereed)
    Abstract [en]

    Low-dimensional perovskites are an emerging class of materials with high stability and excellent optoelectronic properties. Herein, we introduce a novel, lead-free, zero-dimensional perovskite-like material, (1,3-propanediammonium)(2)Bi2I10 center dot 2H(2)O, for optoelectronic applications. This material exhibited good moisture and thermal stability under ambient conditions. Single-crystal X-ray diffraction analysis revealed a quantum-well structure having the inorganic Bi2I104- clusters periodically arranged in the crystallographic "c" axis separated by a distance of 5.36 angstrom, sandwiched by independent layers of organic cations. The density functional theory calculations showed that the oxygen in water molecules has a significant contribution to the band edges of the material. The photodetector device fabricated using this material showed an efficient charge separation at low voltage (1 V) due to the good electronic conduction between the Bi2I104- dimer units.

  • 36.
    Ren, Yi
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Ross, Nils
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Larsen, Jes K.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Rudisch, Katharina
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Scragg, Jonathan J.
    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.
    Evolution of Cu2ZnSnS4 during Non-Equilibrium Annealing with Quasi-in Situ Monitoring of Sulfur Partial Pressure2017In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 29, no 8, p. 3713-3722Article in journal (Refereed)
    Abstract [en]

    Chalcogen-based materials like Cu2ZnSnS4 (CZTS) have attracted extensive attention for applications such as photovoltaics and water splitting. However, an inability to monitor the sulfur partial pressure (P-S2) during the non equilibrium annealing process at high temperatures complicates the synthesis of CZTS with controlled optoelectronic properties. Here we demonstrate that P-S2 can be monitored by investigating the Sn-S phase transformation. We showed that P-S2 drops considerably over the annealing time, causing gradual alterations in CZTS: (i) a change in defect type and (ii) evolution of ZnS and SnxSy phases. With additional ordering treatment, we observed that the low room-temperature photoluminescence energy usually seen in CZTS can result from insufficient P-S2 during annealing. It is proven that remarkable V-oc beyond 700 mV for solar cells with nonoptimal CdS buffer can be repeatedly achieved when CZTS is prepared under a sufficiently high P-S2. An ordering treatment before CdS deposition can further improve V-oc to 783 mV.

  • 37. Ren, Yi
    et al.
    Ross, Nils
    Larsen, Jes.K.
    Rudisch, Katharina
    J.S.Scragg, Jonthan
    Platzer-Björkman, Charlotte
    Evolution of Cu2ZnSnS4 in non-equilibrium thermal processing with Quasi-in-situ Monitoring of Sulfur Partial Pressure2017In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002Article in journal (Refereed)
  • 38.
    Renman, Viktor
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Hu, Shichao
    Stockholm Univ, Dept Mat & Environm Chem, SE-10691 Stockholm, Sweden..
    Eriksson, Rickard
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Maibach, Julia
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Johnsson, Mats
    Stockholm Univ, Dept Mat & Environm Chem, SE-10691 Stockholm, Sweden..
    Gómez, Cesar Pay
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Edström, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Ni3Sb4O6F6 and Its Electrochemical Behavior toward Lithium-A Combination of Conversion and Alloying Reactions2016In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 28, no 18, p. 6520-6527Article in journal (Refereed)
    Abstract [en]

    A group of oxohalides, where Ni3Sb4O6F6 is one example, has been investigated with respect to its electrochemical reactions toward Li+/Li. In situ and ex situ XRD measurements reveal that the original structure collapses and the material becomes amorphous upon insertion of Li at low potentials versus Li+/Li. With continued cycling, a nanocrystalline phase of NiSb, which reacts reversibly with Li, appears and steadily grows more stable. Electrochemical experiments (i.e., chronopotentiometry and cyclic voltammetry) show that multiple reactions of both conversion- and alloying-type are active in the system. High storage capacities are achieved initially but with rapid fading as a consequence of a limited reversibility of the Ni2+/Ni redox process, as shown by X-ray absorption spectroscopy of the first discharge/charge cycle. Stable cycling can be achieved by optimizing the cutoff potentials (i.e., excluding poorly reversible reactions at high and low voltages, respectively), yielding long-term cycling with a practical gravimetric capacity of similar to 200 mAh g(-1).

  • 39.
    Santra, Pralay K.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics. Stanford Univ, Dept Chem Engn, Stanford, CA 94305 USA..
    Palmstrom, Axel F.
    Stanford Univ, Dept Chem Engn, Stanford, CA 94305 USA..
    Tassone, Christopher J.
    SLAC Natl Accelerator Lab, Stanford Synchrotron Radiat Lightsource, Menlo Pk, CA 94025 USA..
    Bent, Stacey F.
    Stanford Univ, Dept Chem Engn, Stanford, CA 94305 USA..
    Molecular Ligands Control Superlattice Structure and Crystallite Orientation in Colloidal Quantum Dot Solids2016In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 28, no 19, p. 7072-7081Article in journal (Refereed)
    Abstract [en]

    Colloidal quantum dot solids represent a new materials platform that has garnered interest for a variety of electronic, optoelectronic, and photovoltaic applications. In such solids, individual quantum dots must be coupled with each other to facilitate charge transport through the solid. Past improvements on charge transport of colloidal quantum dot solids have been achieved primarily through the control of the interparticle spacing. However, the role of morphological ordering of the crystalline facets of individual quantum dots on the charge transport of the quantum dot solid is unknown. Here, we show for the first time that small passivating ligand molecules around the quantum dots can control the arrangement of different facets of quantum dots within the quantum dot solid. The insights from this study provide important directions for future enhancement in orientation of quantum dots in colloidal quantum dot solids.

  • 40.
    Scragg, Jonathan J.
    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.
    Kubart, Tomas
    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.
    Platzer-Björkman, Charlotte
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Chemical Insights into the Instability of Cu(2)ZnSnS(4) Films during Annealing2011In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 23, no 20, p. 4625-4633Article in journal (Refereed)
    Abstract [en]

    Cu(2)ZnSnS(4) (CZTS) shows great potential for cheap, efficient photovoltaic devices. However, one problem during synthesis of CZTS films is the loss of Sn as a result of decomposition and evaporation of SnS. This paper uses kinetic models to show that the mechanism of the decomposition reaction probably occurs in at least two stages; first, a loss of sulfur which causes dissociation of the structure into binary sulfides, and only then the evaporation of SnS. Knowledge of the reaction mechanism helps to identify the driving force for decomposition as arising from the relative instability of Sn(IV) in CZTS against reduction; this theory is backed up by thermodynamic data. The volatility of SnS further exaggerates the decomposition by rendering it irreversible. This insight, alongside experimental data, allows prediction of the annealing conditions required to stabilize CZTS surfaces. A fundamental incompatibility of CZTS with high-temperature, vacuum-based processing is exposed, distinguishing it from related indium-containing compounds. This offers an explanation as to why the most efficient CZTS devices to-date all arise from "two-stage" fabrication processes involving low temperature deposition followed by annealing at high pressure, and provides key information for designing successful annealing strategies.

  • 41.
    Scragg, Jonathan J.
    et al.
    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.
    Wätjen, Timo
    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.
    Linnarsson, Margareta K.
    Platzer-Björkman, Charlotte
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Effects of Back Contact Instability on Cu2ZnSnS4 Devices and Processes2013In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 25, no 15, p. 3162-3171Article in journal (Refereed)
    Abstract [en]

    Cu2ZnSnS4 (CZTS) is a promising material for thin film solar cells based on sustainable resources. This paper explores some consequences of the chemical instability between CZTS and the standard Mo “back contact” layer used in the solar cell. Chemical passivation of the back contact interface using titanium nitride (TiN) diffusion barriers, combined with variations in the CZTS annealing process, enables us to isolate the effects of back contact chemistry on the electrical properties of the CZTS layer that result from the synthesis, as determined by measurements on completed solar cells. It is found that instability in the back contact is responsible for large current losses in the finished solar cell, which can be distinguished from other losses that arise from instabilities in the surface of the CZTS layer during annealing. The TiN-passivated back contact is an effective barrier to sulfur atoms and therefore prevents reactions between CZTS and Mo. However, it also results in a high series resistance and thus a reduced fill factor in the solar cell. The need for high chalcogen pressure during CZTS annealing can be linked to suppression of the back contact reactions and could potentially be avoided if better inert back contacts were to be developed.

  • 42.
    Seymour, Ieuan D.
    et al.
    Univ Cambridge, Dept Chem, Cambridge CB2 1EW, England..
    Chakraborty, Sudip
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Middlemiss, Derek S.
    Univ Warwick, Dept Chem, Coventry CV4 7AL, W Midlands, England..
    Wales, David J.
    Univ Cambridge, Dept Chem, Cambridge CB2 1EW, England..
    Grey, Clare P.
    Univ Cambridge, Dept Chem, Cambridge CB2 1EW, England..
    Mapping Structural Changes in Electrode Materials: Application of the Hybrid Eigenvector-Following Density Functional Theory (DFT) Method to Layered Li0.5MnO22015In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 27, no 16, p. 5550-5561Article in journal (Refereed)
    Abstract [en]

    The migration mechanism associated with the initial layered-to-spinel transformation of partially delithiated layered LiMnO2 was studied using hybrid eigenvector-following coupled with density functional theory. The initial part of the transformation mechanism of Li0.5MnO2 involves the migration of Li into both octahedral and tetrahedral local minima within the layered structure. The next stage of the transformation process involves the migration of Mn and was found to occur through several local minima, including an intermediate square pyramidal MnO5 configuration and an independent Mn3+ to Mn2+ charge-transfer process. The migration pathways were found to be significantly affected by the size of the supercell used and the inclusion of a Hubbard U parameter in the DFT functional. The transition state searching methodology described should be useful for studying the structural rearrangements that can occur in electrode materials during battery cycling, and more generally, ionic and electronic transport phenomena in a wide range of energy materials.

  • 43.
    Shi, Liyang
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Polymer Chemistry.
    Carstensen, Hauke
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Hölzl, Katja
    Institute of Materials Science and Technology, Technische Universität Wien.
    Lunzer, Markus
    Institute of Materials Science and Technology, Technische Universität Wien.
    Li, Hao
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Otolaryngology and Head and Neck Surgery.
    Hilborn, Jöns
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Polymer Chemistry.
    Ovsianikov, Aleksandr
    Institute of Materials Science and Technology, Technische Universität Wien.
    Ossipov, Dmitri A.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Polymer Chemistry.
    Dynamic Coordination Chemistry Enables Free Directional Printing of Biopolymer Hydrogel2017In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 29, p. 5816-5823Article in journal (Refereed)
    Abstract [en]

    Three-dimensional (3D) printing is a promising technology to develop customized biomaterials in regenerative medicine. However, for the majority of printable biomaterials (bioinks) there is always a compromise between excellent printability of fluids and good mechanical properties of solids. 3D printing of soft materials based on the transition from a fluid to gel state is challenging because of the difficulties to control such transition as well as to maintain uniform conditions three-dimensionally. To solve these challenges, a facile chemical strategy for the development of a novel hydrogel bioink with shear-thinning and self-healing properties based on dynamic metal-ligand coordination bonds is presented. The non-covalent cross-linking allows easy extrusion of the bioink from a reservoir without changing of its bulk mechanical properties. The soft hydrogel can avoid deformation and collapse using omnidirectional embedding of the printable hydrogel into a support gel bath sharing the same cross-linking chemistry. After combination with photo-initiated covalent cross-linking, it enables manufacturing of hydrogel structures with complex shapes and precise location of chemically attached ligands. Living cells can be entrapped in the new printable hydrogel and survive the following in situ photocross-linking. The presented printable hydrogel mate-rial expands the existing tool-box of bioinks for generation of in vitro 3D tissue-like structures and direct in vivo 3D printing.

  • 44. Shi, Yantao
    et al.
    Zhu, Chao
    Wang, Lin
    Zhao, Chunyu
    Li, Wei
    Fung, Kwok Kwong
    Ma, Tingli
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Wang, Ning
    Ultrarapid Sonochemical Synthesis of ZnO Hierarchical Structures: From Fundamental Research to High Efficiencies up to 6.42% for Quasi-Solid Dye-Sensitized Solar Cells2013In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 25, no 6, p. 1000-1012Article in journal (Refereed)
    Abstract [en]

    Zinc oxide (ZnO) hierarchical structures (HSs) have recently demonstrated notable photochemical and photovoltaic performances attributed to their nano/micro combined architectures. In this study, ZnO HSs were synthesized at room temperature using ultrarapid sonochemistry. This novel approach can effectively overcome deficiencies in the synthesis via traditional direct precipitation by promoting nucleation and accelerating diffusion. Only 15 min was needed to complete the formation of highly crystallized and uniformed HSs consisting of interconnected monocrystalline nanosheets using sonochemistry. The formation of HSs through in situ observations was interpreted using a new mechanism based on oriented attachment and reconstruction. In the nonequilibrium synthesis system, thicker, porous, and coarse crystallized ZnO sheets were first constructed via oriented attachment of small-sized nanocrystals. After reconstruction, untrathin, integrated, and monocrystalline nanosheets were obtained. According to the two-dimensional nanosheets to three-dimensional HSs, the formation was much more sophisticated because repeated and parallel heterogeneous oriented attachments with reconstructions dominated the final morphologies of the HSs. The relationships between synthetic conditions and HSs structures were established. Based on the photoanodes in dye-sensitized solar cells (DSCs), the performances of these differently structured HSs were tested. HSs with densely assembled nanosheets exhibited better performances in photoelectric conversions. Systematic investigations were also carried out by selecting two representative HSs to demonstrate the critical factors governing the optical and electrical properties of photoanodes. Finally, under AM 1.5 and 100mW cm(-2) light irradiation, high photoelectric conversion efficiencies of up to 6.42% were achieved. These results established a new record for quasi-solid ZnO-based DSCs.

  • 45.
    Slawinski, Wojciech A.
    et al.
    STFC Rutherford Appleton Lab, ISIS Facil, Didcot OX11 0QX, Oxon, England;Chalmers Univ Technol, Dept Chem & Chem Engn, SE-41296 Gothenburg, Sweden;Univ Warsaw, Fac Chem, Pasteura 1, PL-02093 Warsaw, Poland.
    Playford, Helen Y.
    STFC Rutherford Appleton Lab, ISIS Facil, Didcot OX11 0QX, Oxon, England.
    Hull, Stephen
    STFC Rutherford Appleton Lab, ISIS Facil, Didcot OX11 0QX, Oxon, England.
    Norberg, Stefan T.
    Chalmers Univ Technol, Dept Chem & Chem Engn, SE-41296 Gothenburg, Sweden;AstraZeneca, Pharmaceut Technol & Dev, Pepparedsleden 1, S-43183 Molndal, Sweden.
    Eriksson, Sten G.
    Chalmers Univ Technol, Dept Chem & Chem Engn, SE-41296 Gothenburg, Sweden.
    Gustafsson, Torbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Edström, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Brant, William R.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Neutron Pair Distribution Function Study of FePO4 and LiFePO42019In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 31, no 14, p. 5024-5034Article in journal (Refereed)
    Abstract [en]

    Neutron powder diffraction studies of the compounds FePO4 and LiFePO4 are reported. Rietveld refinement of the diffraction data provides averaged structures for both materials that are in good agreement with the published structures. In addition, detailed investigations of the short-range ion-ion correlations within each compound have been performed using the reverse Monte Carlo (RMC) modeling of the total scattering (Bragg plus diffuse) data. Although the short-range structural information for LiFePO4 is consistent with the long-range (averaged) picture, a small, but statistically significant, proportion of the anions is displaced away from their ideal sites within the RMC configurations of FePO4. These anion displacements are discussed in terms of a small concentration of Li+/Fe2+ occupying the empty octahedral sites, probably arising from incomplete delithiation of the LiFePO4 and/or antisite (Li+-Fe2+) defects introduced during the delithiation process.

  • 46.
    Sobkowiak, Adam
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Roberts, Matthew R.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Häggström, Lennart
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Ericsson, Tore
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Andersson, Anna M.
    ABB.
    Edström, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Gustafsson, Torbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Björefors, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Identification of an Intermediate Phase, Li1/2FeSO4F, Formed during Electrochemical Cycling of Tavorite LiFeSO4F2014In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 26, no 15, p. 4620-4628Article in journal (Refereed)
    Abstract [en]

    Many compounds adopting the tavorite-type crystal structure have attracted considerable attention as cathode materials for lithium ion batteries due to the favorable structural characteristics, facilitating promising electrochemical performance. Recent reports have highlighted the complex mechanism of lithium insertion/extraction in some of these compounds, such as the stabilization of intermediate phases in the LiFeSO4OH and LiVPO4F systems. In the case of tavorite LiFeSO4F, reported density functional theory (DFT) calculations have suggested the possibility of a similar behavior, but thus far, no experimental verification of such a process has, to the best of our knowledge, been successfully demonstrated. In this work, we investigate the structural evolution of LiFeSO4F upon extraction/insertion of lithium ions from/into the host framework. By thorough ex situ characterizations of chemically and electrochemically prepared LixFeSO4F-samples (0 ≤ x ≤ 1), we demonstrate the stabilization of an intermediate phase, Li1/2FeSO4F, for which one possible structural model is proposed. However, results indicating charge ordering on the iron-sites, suggesting the formation of a super structure with a larger unit cell, are also highlighted. Moreover, the degree of formation of Li1/2FeSO4F is shown to be highly dependent on the rate of lithium extraction as a result of an exceptionally small potential separation (similar to 15 mV during charging) of the two subsequently occurring biphasic processes, LiFeSO4F/Li1/2FeSO4F and Li1/2FeSO4F/FeSO4F. Finally, the intermediate phase is shown to be formed both on charge and discharge during battery cycling, even though an apparent asymmetrical electrochemical trace suggests the contrary.

  • 47.
    Sobkowiak, Adam
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Roberts, Matthew R.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Younesi, Reza
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Ericsson, Tore
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Haggstrom, Lennart
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    Tai, Cheuk-Wai
    Stockholm University.
    Andersson, Anna M.
    ABB.
    Edström, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Gustafsson, Torbjorn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Björefors, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Understanding and Controlling the Surface Chemistry of LiFeSO4F for an Enhanced Cathode Functionality2013In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 25, no 15, p. 3020-3029Article in journal (Refereed)
    Abstract [en]

    The tavorite polymorph of LiFeSO4F has recently attracted a lot of interest as a cathode material for lithium ion batteries stimulated by its competitive specific capacity, high potential for the Fe2+/Fe3+ redox couple, and low-temperature synthesis. However, the synthesis routes explored to date have resulted in notably varied electrochemical performance. This inconsistency is difficult to understand given the excellent purity, crystallinity, and similar morphologies achieved via all known methods. In this work, we examine the role of the interfacial chemistry on the electrochemical functionality of LiFeSO4F. We demonstrate that particularly poor electrochemical performance may be obtained for pristine materials synthesized in tetraethylene glycol (TEG), which represents one of the most economically viable production methods. By careful surface characterization, we show that this restricted performance can be largely attributed to residual traces of TEG remaining on the surface of pristine materials, inhibiting the electrochemical reactions. Moreover, we show that optimized cycling performance of LiFeSO4F can be achieved by removing the unwanted residues and applying a conducting polymer coating, which increases the electronic contact area between the electrode components and creates a highly percolating network for efficient electron transport throughout the composite material. This coating is produced using a simple and scalable method designed to intrinsically favor the functionality of the final product.

  • 48.
    Sotiriou, Georgios A.
    et al.
    ETH, Particle Technol Lab, Inst Proc Engn, Dept Mech & Proc Engn, CH-8092 Zurich, Switzerland..
    Hirt, Ann M.
    ETH, Inst Geophys, Dept Earth Sci, CH-8092 Zurich, Switzerland..
    Lozach, Pierre-Yves
    ETH, Inst Biochem, Dept Biol, CH-8092 Zurich, Switzerland..
    Teleki, Alexandra
    ETH, Particle Technol Lab, Inst Proc Engn, Dept Mech & Proc Engn, CH-8092 Zurich, Switzerland..
    Krumeich, Frank
    ETH, Particle Technol Lab, Inst Proc Engn, Dept Mech & Proc Engn, CH-8092 Zurich, Switzerland..
    Pratsinis, Sotiris E.
    ETH, Particle Technol Lab, Inst Proc Engn, Dept Mech & Proc Engn, CH-8092 Zurich, Switzerland..
    Hybrid, Silica-Coated, Janus-Like Plasmonic-Magnetic Nanoparticles2011In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 23, no 7, p. 1985-1992Article in journal (Refereed)
    Abstract [en]

    Hybrid plasmonic-magnetic nanoparticles possess properties that are attractive in bioimaging, targeted drug delivery, in vivo diagnosis, and therapy. The stability and toxicity, however, of such nanoparticles challenge their safe use today. Here, biocompatible, SiO(2)-coated, Janus-like Ag/Fe(2)O(3) nanoparticles are prepared by one-step, scalable flame aerosol technology. A nanothin SiO(2) shell around these multifunctional nanoparticles leaves intact their morphology and magnetic and plasmonic properties but minimizes the release of toxic Ag(+) ions from the nanosilver surface and its direct contact with live cells. Furthermore, this silica shell hinders flocculation and allows for easy dispersion of such nanoparticles in aqueous and biological buffer (PBS) solutions without any extra fiinctionalization step. As a result, these hybrid particles exhibited no cytotoxicity during bioimaging and remained stable in suspension with no signs of agglomeration and sedimentation or settling. Their performance as biomarkers was explored by selectively binding them with live tagged Raji and HeLa cells enabling their detection under dark-field illumination. Therefore, these SiO(2)-coated Ag/Fe(2)O(3) nanoparticles do not exhibit the limiting physical properties of each individual component but retain their desired functionalities facilitating thus, the safe use of such hybrid nanoparticles in bioapplications.

  • 49.
    Sotiriou, Georgios A.
    et al.
    ETH, Dept Mech & Proc Engn, Particle Technol Lab, CH-8092 Zurich, Switzerland..
    Visbal-Onufrak, Michelle A.
    Univ Puerto Rico, Dept Elect & Comp Engn, Mayaguez, PR USA..
    Teleki, Alexandra
    ETH, Dept Mech & Proc Engn, Particle Technol Lab, CH-8092 Zurich, Switzerland..
    Juan, Eduardo J.
    Univ Puerto Rico, Dept Elect & Comp Engn, Mayaguez, PR USA..
    Hirt, Ann M.
    ETH, Dept Earth Sci, Inst Geophys, CH-8092 Zurich, Switzerland..
    Pratsinis, Sotiris E.
    ETH, Dept Mech & Proc Engn, Particle Technol Lab, CH-8092 Zurich, Switzerland..
    Rinaldi, Carlos
    Univ Puerto Rico, Dept Chem Engn, Mayaguez, PR USA.;Univ Florida, J Crayton Pruitt Family Dept Biomed Engn, Gainesville, FL 32611 USA.;Univ Florida, Dept Chem Engn, Gainesville, FL 32611 USA..
    Thermal Energy Dissipation by SiO2-Coated Plasmonic-Superpararnagnetic Nanoparticles in Alternating Magnetic Fields2013In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 25, no 22, p. 4603-4612Article in journal (Refereed)
    Abstract [en]

    Multifunctional nanoparticles show great potential in the biomedical field and may help the diagnosis and therapy of diseases. Superparamagnetic nanoparticles are especially attractive because of their ability to dissipate thermal energy in an alternating magnetic field. Furthermore, plasmonic nanoparticles can be effectively used in non- or minimally invasive therapy of tumors exploiting their plasmonic photothermal effect. Here, hybrid plasmonicmagnetic Ag/Fe2O3 nanoparticles are made by flame aerosol technology. These nanoparticles can be in situ encapsulated with an amorphous nanothin SiO2 film to facilitate their dispersion and block any toxicity from Ag/Fe2O3. Detailed physicochemical characterization, including electron microscopy, electron dispersive X-ray spectroscopy, and X-ray diffraction, is performed. Furthermore, their magnetic properties are characterized in detail by monitoring their hysteresis, first-order-reversal-curves, and isothermal remanent magnetization. Finally, the effect of SiO2 and Agcontent on the specific absorption rate (SAR) of the hybrid Ag/Fe2O3 nanoparticles is investigated. The obtained understanding will help the rational design and engineering of multifunctional hybrid nanoprobes targeting specific biomedical applications.

  • 50. Steenackers, Marin
    et al.
    Sharp, Ian D.
    Larsson, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Hutter, Naima A.
    Stutzmann, Martin
    Jordan, Rainer
    Structured Polymer Brushes on Silicon Carbide2010In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 22, no 1, p. 272-278Article in journal (Refereed)
    Abstract [en]

    A straightforward method is presented for the preparation of homogeneous as well as structured polymer brushes on SiC substrates. The self-initiated photografting and photopolymerization (SIPGP) of styrene and N,N-dimethylaminoethyl methacrylate (MAEMA) allows the preparation of polymer brush layers directly and selectively onto C—OH terminated (000) 6H-SiC surfaces in a single step reaction. In contrast, the analogous reaction on Si—OH terminated (0001) 6H-SiC does not occur. The reactivity contrast between Si—OH and C—OH terminated crystal faces for SIPGP was studied using the density functional theory method which showed a higher SiO—H bond dissociation energy for hydrogen abstraction on the Si-polar relative to the C-polar crystal face. Furthermore, structured polymer brushes on the submicrometer scale could be prepared by the carbon templating (CT) technique on Si—OH terminated (0001) 6H-SiC surfaces. First, an ultrathin template layer was formed by electron beam induced carbon deposition (EBCD) on SiC by means of a focused electron beam. Amplification of the template by SIPGP resulted in polymer brush structures with controlled three-dimensional shapes. The effect of the applied electron dose as well as the initial lateral structure size on the brush layer morphology was investigated.

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