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  • 1. Abdi-Jalebi, Mojtaba
    et al.
    Andaji-Garmaroudi, Zahra
    Cacovich, Stefania
    Stavrakas, Camille
    Philippe, Bertrand
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Richter, Johannes M.
    Alsari, Mejd
    Booker, Edward P.
    Hutter, Eline M.
    Pearson, Andrew J.
    Lilliu, Samuele
    Savenije, Tom J.
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Divitini, Giorgio
    Ducati, Caterina
    Friend, Richard H.
    Stranks, Samuel D.
    Maximizing and stabilizing luminescence from halide perovskites with potassium passivation2018In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 555, p. 497-501Article in journal (Refereed)
    Abstract [en]

    Metal halide perovskites are of great interest for various high-performance optoelectronic applications. The ability to tune the perovskite bandgap continuously by modifying the chemical composition opens up applications for perovskites as coloured emitters, in building-integrated photovoltaics, and as components of tandem photovoltaics to increase the power conversion efficiency. Nevertheless, performance is limited by non-radiative losses, with luminescence yields in state-of-the-art perovskite solar cells still far from 100 per cent under standard solar illumination conditions. Furthermore, in mixed halide perovskite systems designed for continuous bandgap tunability2 (bandgaps of approximately 1.7 to 1.9 electronvolts), photoinduced ion segregation leads to bandgap instabilities. Here we demonstrate substantial mitigation of both non-radiative losses and photoinduced ion migration in perovskite films and interfaces by decorating the surfaces and grain boundaries with passivating potassium halide layers. We demonstrate external photoluminescence quantum yields of 66 per cent, which translate to internal yields that exceed 95 per cent. The high luminescence yields are achieved while maintaining high mobilities of more than 40 square centimetres per volt per second, providing the elusive combination of both high luminescence and excellent charge transport. When interfaced with electrodes in a solar cell device stack, the external luminescence yield—a quantity that must be maximized to obtain high efficiency—remains as high as 15 per cent, indicating very clean interfaces. We also demonstrate the inhibition of transient photoinduced ion-migration processes across a wide range of mixed halide perovskite bandgaps in materials that exhibit bandgap instabilities when unpassivated. We validate these results in fully operating solar cells. Our work represents an important advance in the construction of tunable metal halide perovskite films and interfaces that can approach the efficiency limits in tandem solar cells, coloured-light-emitting diodes and other optoelectronic applications.

  • 2.
    Abdi-Jalebi, Mojtaba
    et al.
    Univ Cambridge, Dept Phys, Cavendish Lab, JJ Thomson Ave, Cambridge, England.
    Pazoki, Meysam
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Philippe, Bertrand
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Dar, M. Ibrahim
    Ecole Polytech Fed Lausanne, Inst Chem Sci & Engn, Lab Photon & Interfaces, Lausanne, Switzerland.
    Alsari, Mejd
    Univ Cambridge, Dept Phys, Cavendish Lab, JJ Thomson Ave, Cambridge, England.
    Sadhanala, Aditya
    Univ Cambridge, Dept Phys, Cavendish Lab, JJ Thomson Ave, Cambridge, England.
    Diyitini, Giorgio
    Univ Cambridge, Dept Mat Sci & Met, Charles Babbage Rd, Cambridge, England.
    Imani, Roghayeh
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Lilliu, Samuele
    Univ Sheffield, Dept Phys & Astron, Sheffield, S Yorkshire, England; UAE Ctr Crystallog, Dubai, U Arab Emirates.
    Kullgren, Jolla
    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.
    Gratzel, Michael
    Ecole Polytech Fed Lausanne, Inst Chem Sci & Engn, Lab Photon & Interfaces, Lausanne, Switzerland.
    Friend, Richard H.
    Univ Cambridge, Dept Phys, Cavendish Lab, JJ Thomson Ave, Cambridge, England.
    Dedoping of Lead Halide Perovskites Incorporating Monovalent Cations2018In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 12, no 7, p. 7301-7311Article in journal (Refereed)
    Abstract [en]

    We report significant improvements in the optoelectronic properties of lead halide perovskites with the addition of monovalent ions with ionic radii close to Pb2+. We investigate the chemical distribution and electronic structure of solution processed CH3NH3PbI3 perovskite structures containing Na+, Cu+, and Ag+, which are lower valence metal ions than Pb2+ but have similar ionic radii. Synchrotron X-ray diffraction reveals a pronounced shift in the main perovskite peaks for the monovalent cation-based films, suggesting incorporation of these cations into the perovskite lattice as well as a preferential crystal growth in Ag+ containing perovskite structures. Furthermore, the synchrotron X-ray photoelectron measurements show a significant change in the valence band position for Cu- and Ag-doped films, although the perovskite bandgap remains the same, indicating a shift in the Fermi level position toward the middle of the bandgap. Such a shift infers that incorporation of these monovalent cations dedope the n-type perovskite films when formed without added cations. This dedoping effect leads to cleaner bandgaps as reflected by the lower energetic disorder in the monovalent cation-doped perovskite thin films as compared to pristine films. We also find that in contrast to Ag+ and Cu+, Na+ locates mainly at the grain boundaries and surfaces. Our theoretical calculations confirm the observed shifts in X-ray diffraction peaks and Fermi level as well as absence of intrabandgap states upon energetically favorable doping of perovskite lattice by the monovalent cations. We also model a significant change in the local structure, chemical bonding of metal-halide, and the electronic structure in the doped perovskites. In summary, our work highlights the local chemistry and influence of monovalent cation dopants on crystallization and the electronic structure in the doped perovskite thin films.

  • 3.
    Böhme, Solveig
    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.
    Edström, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Nyholm, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Photoelectron Spectroscopic Evidence for Overlapping Redox Reactions for SnO2 Electrodes in Lithium-Ion Batteries2017In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 121, no 9, p. 4924-4936Article in journal (Refereed)
    Abstract [en]

    In-house and synchrotron-based photoelectron spectroscopy (XPSand HAXPES) evidence is presented for an overlap between the conversion andalloying reaction during the cycling of SnO2 electrodes in lithium-ion batteries(LIBs). This overlap resulted in an incomplete initial reduction of the SnO2 as wellas the inability to regenerate the reduced SnO2 on the subsequent oxidative scan.The XPS and HAXPES results clearly show that the SnO2 conversion reactionoverlaps with the formation of the lithium tin alloy and that the conversion reactiongives rise to the formation of a passivating Sn layer on the SnO2 particles. The latterlayer renders the conversion reaction incomplete and enables lithium tin alloy toform on the surface of the particles still containing a core of SnO2. The results alsoshow that the reoxidation of the lithium tin alloy is incomplete when the formationof tin oxide starts. It is proposed that the rates of the electrochemical reactions andhence the capacity of SnO2-based electrodes are limited by the lithium masstransport rate through the formed layers of the reduction and oxidations products.In addition, it is shown that a solid electrolyte interphase (SEI) layer is continuously formed at potentials lower than about 1.2 VLi+/Li during the first scan and that a part of the SEI dissolves on the subsequent oxidative scan. While the SEI was found tocontain both organic and inorganic species, the former were mainly located at the SEI surface while the inorganic species werefound deeper within the SEI. The results also indicate that the SEI dissolution process predominantly involves the organic SEIcomponents.

  • 4.
    Cappel, Ute B.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics. KTH Royal Inst Technol, Div Appl Phys Chem, Dept Chem, Stockholm, Sweden.
    Liu, Peng
    KTH Royal Inst Technol, Div Appl Phys Chem, Dept Chem, SE-10044 Stockholm, Sweden.
    Johansson, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Philippe, Bertrand
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Giangrisostomi, Erika
    Helmholtz Zentrum Berlin GmbH, Inst Methods & Instrumentat Synchrotron Radiat Re, Albert Einstein Str 15, D-12489 Berlin, Germany.
    Ovsyannikov, Ruslan
    Helmholtz Zentrum Berlin GmbH, Inst Methods & Instrumentat Synchrotron Radiat Re, Albert Einstein Str 15, D-12489 Berlin, Germany.
    Lindblad, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Kloo, Lars
    KTH Royal Inst Technol, Div Appl Phys Chem, Dept Chem, SE-10044 Stockholm, Sweden.
    Gardner, James M.
    KTH Royal Inst Technol, Div Appl Phys Chem, Dept Chem, SE-10044 Stockholm, Sweden.
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Electronic Structure Characterization of Cross-Linked Sulfur Polymers2018In: ChemPhysChem, ISSN 1439-4235, E-ISSN 1439-7641, Vol. 19, no 9, p. 1041-1047Article in journal (Refereed)
    Abstract [en]

    Cross-linked polymers of elemental sulfur are of potential interest for electronic applications as they enable facile thin-film processing of an abundant and inexpensive starting material. Here, we characterize the electronic structure of a cross-linked sulfur/diisopropenyl benzene (DIB) polymer by a combination of soft and hard X-ray photoelectron spectroscopy (SOXPES and HAXPES). Two different approaches for enhancing the conductivity of the polymer are compared: the addition of selenium in the polymer synthesis and the addition of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) during film preparation. For the former, we observe the incorporation of Se into the polymer structure resulting in a changed valence-band structure. For the latter, a Fermi level shift in agreement with p-type doping of the polymer is observed and also the formation of a surface layer consisting mostly of TFSI anions.

  • 5.
    Cappel, Ute B.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Svanström, Sebastian
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Lanzilotto, Valeria
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Johansson, Fredrik O. L.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Aitola, Kerttu
    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.
    Giangrisostomi, Erika
    Helmholtz Zentrum Berlin GmbH, Inst Methods & Instrumentat Synchrotron Radiat Re, Albert Einstein Str 15, D-12489 Berlin, Germany..
    Ovsyannikov, Ruslan
    Helmholtz Zentrum Berlin GmbH, Inst Methods & Instrumentat Synchrotron Radiat Re, Albert Einstein Str 15, D-12489 Berlin, Germany..
    Leitner, Torsten
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Foehlisch, Alexander
    Helmholtz Zentrum Berlin GmbH, Inst Methods & Instrumentat Synchrotron Radiat Re, Albert Einstein Str 15, D-12489 Berlin, Germany.;Univ Potsdam, Inst Phys & Astron, Karl Liebknecht Str 24-25, D-14476 Potsdam, Germany..
    Svensson, Svante
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Mårtensson, Nils
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics. Uppsala Berlin Joint Lab Next Generat Photoelectr, Albert Einstein Str 15, D-12489 Berlin, Germany..
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Lindblad, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Rensmo, Håkan
    Partially Reversible Photoinduced Chemical Changes in a Mixed-Ion Perovskite Material for Solar Cells2017In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 9, no 40, p. 34970-34978Article in journal (Refereed)
    Abstract [en]

    Metal halide perovskites have emerged as materials of high interest for solar energy-to-electricity conversion, and in particular, the use of mixed-ion structures has led to high power conversion efficiencies and improved stability. For this reason, it is important to develop means to obtain atomic level understanding of the photoinduced behavior of these materials including processes such as photoinduced phase separation and ion migration. In this paper, we implement a new methodology combining visible laser illumination of a mixed-ion perovskite ((FAP-bI(3))(0.85)(MAPbBr(3))(0.15)) with the element specificity and chemical sensitivity of core-level photoelectron spectroscopy. By carrying out measurements at a synchrotron beamline optimized for low X-ray fluxes, we are able to avoid sample changes due to X-ray illumination and are therefore able to monitor what sample changes are induced by visible illumination only. We find that laser illumination causes partially reversible chemistry in the surface region, including enrichment of bromide at the surface, which could be related to a phase separation into bromide- and iodide-rich phases. We also observe a partially reversible formation of metallic lead in the perovskite structure. These processes occur on the time scale of minutes during illumination. The presented methodology has a large potential for understanding light-induced chemistry in photoactive materials and could specifically be extended to systematically study the impact of morphology and composition on the photostability of metal halide perovskites.

  • 6.
    Chernysheva, Ekaterina
    et al.
    UMR 125 CNRS St Gobain Rech, SVI, 39 Quai Lucien Lefranc, F-93303 Aubervilliers, France;Sorbonne Univ, CNRS, Inst NanoSci Paris, UMR 7588, 4 Pl Jussieu, F-75005 Paris, France.
    Srour, Waked
    Sorbonne Univ, CNRS, Inst NanoSci Paris, UMR 7588, 4 Pl Jussieu, F-75005 Paris, France.
    Philippe, Bertrand
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Baris, Bulent
    Sorbonne Univ, CNRS, Ecole Super Phys & Chim Ind, Lab Phys & Etud Mat,UMR 8213, 10 Rue Vauquelin, F-75005 Paris, France.
    Chenot, Stephane
    Sorbonne Univ, CNRS, Inst NanoSci Paris, UMR 7588, 4 Pl Jussieu, F-75005 Paris, France.
    Felix Duarte, Roberto
    Helmholtz Zentrum Berlin Mat & Energie GmbH, D-12489 Berlin, Germany.
    Gorgoi, Mihaela
    Helmholtz Zentrum Berlin Mat & Energie GmbH, D-12489 Berlin, Germany.
    Cruguel, Herve
    Sorbonne Univ, CNRS, Inst NanoSci Paris, UMR 7588, 4 Pl Jussieu, F-75005 Paris, France.
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Montigaud, Herve
    UMR 125 CNRS St Gobain Rech, SVI, 39 Quai Lucien Lefranc, F-93303 Aubervilliers, France.
    Jupille, Jacques
    Sorbonne Univ, CNRS, Inst NanoSci Paris, UMR 7588, 4 Pl Jussieu, F-75005 Paris, France.
    Cabailh, Gregory
    Sorbonne Univ, CNRS, Inst NanoSci Paris, UMR 7588, 4 Pl Jussieu, F-75005 Paris, France.
    Grachev, Sergey
    UMR 125 CNRS St Gobain Rech, SVI, 39 Quai Lucien Lefranc, F-93303 Aubervilliers, France.
    Lazzari, Remi
    Sorbonne Univ, CNRS, Inst NanoSci Paris, UMR 7588, 4 Pl Jussieu, F-75005 Paris, France.
    Band alignment at Ag/ZnO(0001) interfaces: A combined soft and hard x-ray photoemission study2018In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 97, no 23, article id 235430Article in journal (Refereed)
    Abstract [en]

    Band alignment at the interface between evaporated silver films and Zn- or O-terminated polar orientations of ZnO is explored by combining soft and hard x-ray photoemissions on native and hydrogenated surfaces. Ultraviolet photoemission spectroscopy (UPS) is used to track variations of work function, band bending, ionization energy, and Schottky barrier during silver deposition. The absolute values of band bending and the bulk position of the Fermi level are determined on continuous silver films by hard x-ray photoemission spectroscopy (HAXPES) through a dedicated modeling of core levels. Hydrogenation leads to the formation of similar to 0.3 monolayer of donorlike hydroxyl groups on both ZnO-O and ZnO-Zn surfaces and to the release of metallic zinc on ZnO-Zn. However, no transition to an accumulation layer is observed. On bare surfaces, silver adsorption is cationic on ZnO(000 (1) over bar)-O [anionic on ZnO(0001)-Zn] at the earliest stages of growth as expected from polarity healing before adsorbing as a neutral species. UPS and HAXPES data appear quite consistent. The two surfaces undergo rather similar band bendings for all types of preparation. The downward band bending of V-bb,(ZnO-O) = -0.4 eV and V-bb,(ZnO-Zn) = -0.6 eV found for the bare surfaces is reinforced upon hydrogenation (V-bb,(ZnO-O+H) = -1.1 eV, V-bb,(ZnO-Zn+H) = -1.2 eV). At the interface with Ag, a unique value of band bending of -0.75 eV is observed. While exposure to atomic hydrogen modulates strongly the energetic positions of the surface levels, a similar Schottky barrier of 0.5-0.7 eV is found for thick silver films on the two surfaces.

  • 7.
    Daniel, Quentin
    et al.
    KTH Royal Inst Technol, Sch Chem Sci & Engn, Dept Chem, S-10044 Stockholm, Sweden..
    Anabre, Ram B.
    KTH Royal Inst Technol, Sch Chem Sci & Engn, Dept Chem, S-10044 Stockholm, Sweden..
    Zhang, Biaobiao
    KTH Royal Inst Technol, Sch Chem Sci & Engn, Dept Chem, S-10044 Stockholm, Sweden..
    Philippe, Bertrand
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Chen, Hong
    KTH Royal Inst Technol, Sch Chem Sci & Engn, Dept Chem, S-10044 Stockholm, Sweden..
    Li, Fusheng
    KTH Royal Inst Technol, Sch Chem Sci & Engn, Dept Chem, S-10044 Stockholm, Sweden..
    Fan, Ke
    KTH Royal Inst Technol, Sch Chem Sci & Engn, Dept Chem, S-10044 Stockholm, Sweden..
    Ahmadi, Sareh
    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.
    Sun, Licheng
    KTH Royal Inst Technol, Sch Chem Sci & Engn, Dept Chem, S-10044 Stockholm, Sweden.;Dalian Univ Technol, State Key Lab Fine Chem, DUT KTH Joint Educ & Res Ctr Mol Devices, Dalian 116024, Peoples R China..
    Re-Investigation of Cobalt Porphyrin for Electrochemical Water Oxidation on FTO Surface: Formation of CoOx as Active Species2017In: ACS Catalysis, ISSN 2155-5435, E-ISSN 2155-5435, Vol. 7, no 2, p. 1143-1149Article in journal (Refereed)
    Abstract [en]

    The use of cobalt porphyrin complexes as efficient and cost-effective molecular catalysts for water oxidation has been investigated previously. However, by combining a set of analytical techniques (electrochemistry, ultraviolet-visible spectroscopy (UV-vis), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and synchrotron-based photoelectron spectroscopy (SOXPES and HAXPES)), we have demonstrated that three different cobalt porphyrins, deposited on FTO glasses, decompose promptly into a thin film of CoOx on the surface of the electrode during water oxidation under certain conditions (borate buffer pH 9.2). It is presumed that the film is composed of CoO, only detectable by SOXPES, as conventional techniques are ineffective. This newly formed film has a high turnover frequency (TOF), while the high transparency of the CoOx-based electrode is very promising for future application in photoelectrochemical cells.

  • 8.
    Doubaji, Siham
    et al.
    Univ Cadi Ayyad, FST Marrakesh, LCME, Marrakech 40000, Morocco..
    Philippe, Bertrand
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Saadoune, Ismael
    Univ Cadi Ayyad, FST Marrakesh, LCME, Marrakech 40000, Morocco.;Univ Mohammed VI Polytech, Ctr Adv Mat, Ben Guerir, Morocco..
    Gorgoi, Mihaela
    Helmholtz Zentrum Berlin Mat & Energie, D-12489 Berlin, Germany..
    Gustafsson, Torbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Solhy, Abderrahim
    Univ Mohammed VI Polytech, Ctr Adv Mat, Ben Guerir, Morocco..
    Valvo, Mario
    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.
    Passivation Layer and Cathodic Redox Reactions in Sodium-Ion Batteries Probed by HAXPES2016In: ChemSusChem, ISSN 1864-5631, E-ISSN 1864-564X, Vol. 9, no 1, p. 97-108Article in journal (Refereed)
    Abstract [en]

    The cathode material P2-NaxCo2/3Mn2/9Ni1/9O2, which could be used in Na-ion batteries, was investigated through synchrotron-based hard X-ray photoelectron spectroscopy (HAXPES). Nondestructive analysis was made through the electrode/electrolyte interface of the first electrochemical cycle to ensure access to information not only on the active material, but also on the passivation layer formed at the electrode surface and referred to as the solid permeable interface (SPI). This investigation clearly shows the role of the SPI and the complexity of the redox reactions. Cobalt, nickel, and manganese are all electrochemically active upon cycling between 4.5 and 2.0V; all are in the 4+ state at the end of charging. Reduction to Co3+, Ni3+, and Mn3+ occurs upon discharging and, at low potential, there is partial reversible reduction to Co2+ and Ni2+. A thin layer of Na2CO3 and NaF covers the pristine electrode and reversible dissolution/reformation of these compounds is observed during the first cycle. The salt degradation products in the SPI show a dependence on potential. Phosphates mainly form at the end of the charging cycle (4.5V), whereas fluorophosphates are produced at the end of discharging (2.0V).

  • 9.
    Edström, Kristina
    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, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Younesi, Reza
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Sodium batteries and their interfaces2017Conference paper (Other academic)
  • 10.
    Fan, Ke
    et al.
    KTH Royal Inst Technol, Dept Chem, Organ Chem, S-10044 Stockholm, Sweden.;Wuhan Univ Technol, State Key Lab Adv Technol Mat Synth & Proc, Wuhan 430070, Peoples R China..
    Chen, Hong
    KTH Royal Inst Technol, Dept Chem, Organ Chem, S-10044 Stockholm, Sweden..
    Ji, Yongfei
    KTH Royal Inst Technol, Sch Biotechnol, Div Theoret Chem & Biol, SE-10691 Stockholm, Sweden..
    Huang, Hui
    KTH Royal Inst Technol, Dept Chem Surface & Corros Sci, SE-10044 Stockholm, Sweden..
    Claesson, Per Martin
    KTH Royal Inst Technol, Dept Chem Surface & Corros Sci, SE-10044 Stockholm, Sweden..
    Daniel, Quentin
    KTH Royal Inst Technol, Dept Chem, Organ Chem, S-10044 Stockholm, Sweden..
    Philippe, Bertrand
    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.
    Li, Fusheng
    KTH Royal Inst Technol, Dept Chem, Organ Chem, S-10044 Stockholm, Sweden..
    Luo, Yi
    KTH Royal Inst Technol, Sch Biotechnol, Div Theoret Chem & Biol, SE-10691 Stockholm, Sweden..
    Sun, Licheng
    KTH Royal Inst Technol, Dept Chem, Organ Chem, S-10044 Stockholm, Sweden.;Dalian Univ Technol, DUT KTH Joint Educ & Res Ctr Mol Devices, State Key Lab Fine Chem, Dalian 116024, Peoples R China..
    Nickel-vanadium monolayer double hydroxide for efficient electrochemical water oxidation2016In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 7, article id 11981Article in journal (Refereed)
    Abstract [en]

    Highly active and low-cost electrocatalysts for water oxidation are required due to the demands on sustainable solar fuels; however, developing highly efficient catalysts to meet industrial requirements remains a challenge. Herein, we report a monolayer of nickel-vanadium-layered double hydroxide that shows a current density of 27 mA cm(-2) (57 mA cm(-2) after ohmic-drop correction) at an overpotential of 350 mV for water oxidation. Such performance is comparable to those of the best-performing nickel-iron-layered double hydroxides for water oxidation in alkaline media. Mechanistic studies indicate that the nickel-vanadium-layered double hydroxides can provide high intrinsic catalytic activity, mainly due to enhanced conductivity, facile electron transfer and abundant active sites. This work may expand the scope of cost-effective electrocatalysts for water splitting.

  • 11.
    Jacobsson, Jesper
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Svanström, Sebastian
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Andrei, Virgil
    Univ Cambridge, Dept Chem, Lensfield Rd, Cambridge CB2 1EW, England.
    Rivett, Jasmine P. H.
    Univ Cambridge, Dept Phys, Cavendish Lab, JJ Thomson Ave, Cambridge CB3 0HE, England.
    Kornienko, Nikolay
    Univ Cambridge, Dept Chem, Lensfield Rd, Cambridge CB2 1EW, England.
    Philippe, Bertrand
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Cappel, Ute B.
    KTH Royal Inst Technol, Dept Chem, Tekn Ringen 30, S-10044 Stockholm, Sweden.
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Deschler, Felix
    Univ Cambridge, Dept Phys, Cavendish Lab, JJ Thomson Ave, Cambridge CB3 0HE, England.
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Extending the Compositional Space of Mixed Lead Halide Perovskites by Cs, Rb, K, and Na Doping2018In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 122, no 25, p. 13548-13557Article in journal (Refereed)
    Abstract [en]

    A trend in high performing lead halide perovskite solar cell devices has been increasing compositional complexity by successively introducing more elements, dopants, and additives into the structure; and some of the latest top efficiencies have been achieved with a quadruple cation mixed halide perovskite Cs(x)FA(y)MA(z)Rb(1-x-y-z)PbBr(q)I(3-9). This paper continues this trend by exploring doping of mixed lead halide perovskites, FA(0.83)MA(0.17)PbBr(0.51)I(2.49), with an extended set of alkali cations, i.e., Cs+, Rb+, K+, and Na+, as well as combinations of them. The doped perovskites were investigated with X-ray diffraction, energy-dispersive X-ray spectroscopy, scanning electron microscopy, hard X-ray photoelectron spectroscopy, UV-vis, steady state fluorescence, and ultrafast transient absorption spectroscopy. Solar cell devices were made as well. Cs+ can replace the organic cations in the perovskite structure, but Rb+, K+, and Na+ do not appear to do that. Despite this, samples doped with K and Na have substantially longer fluorescence lifetimes, which potentially could be beneficial for device performance.

  • 12.
    Jacobsson, T. Jesper
    et al.
    Univ Cambridge, Dept Chem, Lensfield Rd, Cambridge CB2 1EW, England; Ecole Polytech Fed Lausanne, Lab Photomol Sci, Inst Chem Sci & Engn, CH-1015 Lausanne, Switzerland.
    Correa-Baena, Juan-Pablo
    Ecole Polytech Fed Lausanne, Lab Photomol Sci, Inst Chem Sci & Engn, CH-1015 Lausanne, Switzerland.
    Anaraki, Elham Halvani
    Ecole Polytech Fed Lausanne, Lab Photomol Sci, Inst Chem Sci & Engn, CH-1015 Lausanne, Switzerland;Isfahan Univ Technol, Dept Mat Engn, Esfahan 8415683111, Iran.
    Philippe, Bertrand
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Stranks, Samuel D.
    MIT, Elect Res Lab, 77 Massachusetts Ave, Cambridge, MA 02139 USA;] Cavendish Lab, JJ Thomson Ave, Cambridge CB3 0HE, England.
    Bouduban, Marine E. F.
    Ecole Polytech Fed Lausanne, Photochem Dynam Grp, Inst Chem Sci & Engn, CH-1015 Lausanne, Switzerland.
    Tress, Wolfgang
    Ecole Polytech Fed Lausanne, Lab Photon & Interfaces, Inst Chem Sci & Engn, CH-1015 Lausanne, Switzerland.
    Schenk, Kurt
    Ecole Polytech Fed Lausanne, CH-1015 Lausanne, Switzerland.
    Teuscher, Joël
    Ecole Polytech Fed Lausanne, Photochem Dynam Grp, Inst Chem Sci & Engn, CH-1015 Lausanne, Switzerland.
    Moser, Jacques
    Ecole Polytech Fed Lausanne, Photochem Dynam Grp, Inst Chem Sci & Engn, CH-1015 Lausanne, Switzerland.
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry. Ecole Polytech Fed Lausanne, Lab Photomol Sci, Inst Chem Sci & Engn, CH-1015 Lausanne, Switzerland.
    Unreacted PbI2 as a Double-Edged Sword for Enhancing the Performance of Perovskite Solar Cells2016In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 138, no 32, p. 10331-10343Article in journal (Refereed)
    Abstract [en]

    Lead halide perovskites have over the past few years attracted considerable interest as photo absorbers in PV applications with record efficiencies now reaching 22%. It has recently been found that not only the composition but also the precise stoichiometry is important for the device performance. Recent reports have, for example, demonstrated small amount of PbI2 in the perovskite films to be beneficial for the overall performance of both the standard perovskite, CH3NH3PbI3, as well as for the mixed perovskites (CH3NH3)(x)-(CH(NH2)(2))((1x))PbBryI(3y). In this work a broad range of characterization techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), photo electron spectroscopy (PES), transient absorption spectroscopy (TAS), UVvis, electroluminescence (EL), photoluminescence (PL), and confocal PL mapping have been used to further understand the importance of remnant PbI2 in perovskite solar cells. Our best devices were over 18% efficient, and had in line with previous results a small amount of excess PbI2. For the PbI2-deficient samples, the photocurrent dropped, which could be attributed to accumulation of organic species at the grain boundaries, low charge carrier mobility, and decreased electron injection into the TiO2. The PbI2-deficient compositions did, however, also have advantages. The record V-oc was as high as 1.20 V and was found in PbI2-deficient samples. This was correlated with high crystal quality, longer charge carrier lifetimes, and high PL yields and was rationalized as a consequence of the dynamics of the perovskite formation. We further found the ion migration to be obstructed in the PbI2-deficient samples, which decreased the JV hysteresis and increased the photostability. PbI2-deficient synthesis conditions can thus be used to deposit perovskites with excellent crystal quality but with the downside of grain boundaries enriched in organic species, which act as a barrier toward current transport. Exploring ways to tune the synthesis conditions to give the high crystal quality obtained under PbI2-poor condition while maintaining the favorable grain boundary characteristics obtained under PbI2-rich conditions would thus be a strategy toward more efficiency devices.

  • 13.
    Jain, Sagar M.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry. Swansea Univ Bay Campus, Coll Engn, SPECIFIC, Fabian Way, Swansea SA1 8EN, W Glam, Wales.
    Phuyal, Dibya
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Davies, Matthew L.
    Swansea Univ Bay Campus, Coll Engn, SPECIFIC, Fabian Way, Swansea SA1 8EN, W Glam, Wales.
    Li, Meng
    Swansea Univ Bay Campus, Coll Engn, SPECIFIC, Fabian Way, Swansea SA1 8EN, W Glam, Wales;Soochow Univ, Inst Funct Nano & Soft Mat, Suzhou 215000, Peoples R China.
    Philippe, Bertrand
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    De Castro, Catherine
    Swansea Univ Bay Campus, Coll Engn, SPECIFIC, Fabian Way, Swansea SA1 8EN, W Glam, Wales.
    Qiu, Zhen
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Kim, Jinhyun
    Imperial Coll London, Dept Chem, Exhibit Rd, London SW7 2AZ, England;Imperial Coll London, Ctr Plast Elect, Exhibit Rd, London SW7 2AZ, England.
    Watson, Trystan
    Swansea Univ Bay Campus, Coll Engn, SPECIFIC, Fabian Way, Swansea SA1 8EN, W Glam, Wales.
    Tsoi, Wing Chung
    Swansea Univ Bay Campus, Coll Engn, SPECIFIC, Fabian Way, Swansea SA1 8EN, W Glam, Wales.
    Karis, Olof
    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.
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Edvinsson, Tomas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Durrant, James R.
    Swansea Univ Bay Campus, Coll Engn, SPECIFIC, Fabian Way, Swansea SA1 8EN, W Glam, Wales;Imperial Coll London, Dept Chem, Exhibit Rd, London SW7 2AZ, England;Imperial Coll London, Ctr Plast Elect, Exhibit Rd, London SW7 2AZ, England.
    An effective approach of vapour assisted morphological tailoring for reducing metal defect sites in lead-free, (CH3NH3)(3)Bi2I9 bismuth-based perovskite solar cells for improved performance and long-term stability2018In: Nano Energy, ISSN 2211-2855, E-ISSN 2211-3282, Vol. 49, p. 614-624Article in journal (Refereed)
    Abstract [en]

    We present a controlled, stepwise formation of methylammonium bismuth iodide (CH3NH3)(3)Bi2I9 perovskite films prepared via the vapour assisted solution process (VASP) by exposing BiI3 films to CH3NH3I (MAI) vapours for different reaction times, (CH3NH3)(3)Bi2I9 semiconductor films with tunable optoelectronic properties are obtained. Solar cells prepared on mesoporous TiO2 substrates yielded hysteresis-free efficiencies upto 3.17% with good reproducibility. The good performance is attributed mainly to the homogeneous surface coverage, improved stoichiometry, reduced metallic content in the bulk, and desired optoelectronic properties of the absorbing material. In addition, solar cells prepared using pure BiI3 films without MAI exposure achieved a power conversion efficiency of 0.34%. The non-encapsulated (CH3NH3)(3)Bi2I9 devices were found to be stable for as long as 60 days with only 0.1% drop in efficiency. This controlled formation of (CH3NH3)(3)Bi2I9 perovskite films highlights the benefit of the VASP technique to optimize material stoichiometry, morphology, solar cell performance, and long-term durability.

  • 14.
    Jain, Sagar Motilal
    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.
    Johansson, Erik M. J.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Park, Byung-Wook
    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.
    Edvinsson, Tomas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Vapor phase conversion of PbI2 to CH3NH3PbI3: spectroscopic evidence for formation of an intermediate phase2016In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 4, no 7, p. 2630-2642Article in journal (Refereed)
    Abstract [en]

    The formation of CH3NH3PbI3 (MAPbI(3)) from its precursors is probably the most significant step in the control of the quality of this semiconductor perovskite material, which is highly promising for photovoltaic applications. Here we investigated the transformation of spin coated PbI2 films to MAPbI(3) using a reaction with MAI in vapor phase, referred to as vapor assisted solution process (VASP). The presence of a mesoporous TiO2 scaffold on the substrate was found to speed up reaction and led to complete conversion of PbI2, while reaction on glass substrates was slower, with some PbI2 remaining even after prolonged reaction time. Based on data from UV-visible spectroscopy, Raman spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy, the formation of an X-ray amorphous intermediate phase is proposed, which is identified by an increasing absorption from 650 to 500 nm in the absorption spectrum. This feature disappears upon long reaction times for films on planar substrates, but persists for films on mesoporous TiO2. Poor solar cell performance of planar VASP prepared devices was ascribed to PbI2 remaining in the film, forming a barrier between the perovskite layer and the compact TiO2/FTO contact. Good performance, with efficiencies up to 13.3%, was obtained for VASP prepared devices on mesoporous TiO2.

  • 15.
    Jalebi, Mojtaba Abdi
    et al.
    Univ Cambridge, Dept Phys, Cavendish Lab, Cambridge CB3 0HE, England.
    Andaji-Garmaroudi, Pzahra
    Univ Cambridge, Dept Phys, Cavendish Lab, Cambridge CB3 0HE, England.
    Pearson, Andrew J.
    Univ Cambridge, Dept Phys, Cavendish Lab, Cambridge CB3 0HE, England.
    Divitini, Giorgio
    Univ Cambridge, Dept Mat Sci & Met, Cambridge CB3 0FS, England.
    Cacovich, Stefania
    Univ Cambridge, Dept Mat Sci & Met, Cambridge CB3 0FS, England;Inst Photovolta IledeFrance IPVF 30, Route Dept 128, F-91120 Palaiseau, France.
    Philippe, Bertrand
    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.
    Ducati, Caterina
    Univ Cambridge, Dept Mat Sci & Met, Cambridge CB3 0FS, England.
    Friend, Richard H.
    Univ Cambridge, Dept Phys, Cavendish Lab, Cambridge CB3 0HE, England.
    Stranks, Samuel D.
    Univ Cambridge, Dept Phys, Cavendish Lab, Cambridge CB3 0HE, England.
    Potassium- and Rubidium-Passivated Alloyed Perovskite Films: Optoelectronic Properties and Moisture Stability2018In: ACS ENERGY LETTERS, ISSN 2380-8195, Vol. 3, no 11, p. 2671-2678Article in journal (Refereed)
    Abstract [en]

    Halide perovskites passivated with potassium or rubidium show superior photovoltaic device performance compared to unpassivated samples. However, it is unclear which passivation route is more effective for film stability. Here, we directly compare the optoelectronic properties and stability of thin films when passivating triple-cation perovskite films with potassium or rubidium species. The optoelectronic and chemical studies reveal that the alloyed perovskites are tolerant toward higher loadings of potassium than rubidium. Whereas potassium complexes with bromide from the perovskite precursor solution to form thin surface passivation layers, rubidium additives favor the formation of phase-segregated micron-sized rubidium halide crystals. This tolerance to higher loadings of potassium allows us to achieve superior passivation. We also find that exposure to a humid atmosphere drives phase luminescent properties with potassium segregation and grain coalescence for all compositions, with the rubidium-passivated sample showing the highest sensitivity to nonperovskite phase formation. Our work highlights the benefits but also the limitations of these passivation approaches in maximizing both optoelectronic properties and the stability of perovskite films.

  • 16.
    Johansson, Malin B
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics. 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, Chemistry, Department of Chemistry - Ångström, Structural Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Banerjee, Amitava
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Phuyal, Dibya
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Chakraborty, Sudip
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Cameau, Mathis
    Zhu, Huimin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Physics. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Boschloo, Gerrit
    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.
    Johansson, Erik M. J.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Cesium bismuth iodide, CsxBiyIz, solar cell compounds from systematic molar ratio variationManuscript (preprint) (Other academic)
  • 17.
    Lindblad, Rebecka
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Jena, Naresh K
    Philippe, Bertrand
    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.
    Bi, Dongqin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Lindblad, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Mandal, Suman
    Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore, India.
    Pal, Banabir
    Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore, India.
    Sarma, Dipankar Das
    Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore, India.
    Karis, Olof
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Siegbahn, Hans
    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.
    Odelius, Michael
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Electronic Structure of CH3NH3PbX3 Perovskites: Dependence on the Halide Moiety2015In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 119, no 4, p. 1818-1825Article in journal (Refereed)
    Abstract [en]

    A combination of measurements using photoelectron spectroscopy and calculations using density functional theory (DFT) was applied to compare the detailed electronic structure of the organolead halide perovskites CH3NH3PbI3 and CH3NH3PbBr3. These perovskite materials are used to absorb light in mesoscopic and planar heterojunction solar cells. The Pb 4f core level is investigated to get insight into the chemistry of the two materials. Valence level measurments are also included showing a shift of the valence band edges where there is a higher binding energy of the edge for the CH3NH3PbBr3 perovskite. These changes are supported by the theoretical calculations which indicate that the differences in electronic structure are mainly caused by the nature of the halide ion rather than structural differences. The combination of photoelectron spectroscopy measurements and electronic structure calculations is essential to disentangle how the valence band edge in organolead halide perovskites is governed by the intrinsic difference in energy levels of the halide ions from the influence of chemical bonding.

  • 18.
    Mussa, Abdilbari Shifa
    et al.
    KTH Royal Inst Technol, Appl Electrochem, SE-10044 Stockholm, Sweden.
    Liivat, Anti
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Marzano, Fernanda
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry. Scania CV AB, SE-15187 Sodertalje, Sweden.
    Klett, Matilda
    KTH Royal Inst Technol, Appl Electrochem, SE-10044 Stockholm, Sweden;Scania CV AB, SE-15187 Sodertalje, Sweden.
    Philippe, Bertrand
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Tengstedt, Carl
    Scania CV AB, SE-15187 Sodertalje, Sweden.
    Lindbergh, Goran
    KTH Royal Inst Technol, Appl Electrochem, SE-10044 Stockholm, Sweden.
    Edström, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Lindstrom, Rakel Wreland
    KTH Royal Inst Technol, Appl Electrochem, SE-10044 Stockholm, Sweden.
    Svens, Pontus
    KTH Royal Inst Technol, Appl Electrochem, SE-10044 Stockholm, Sweden;Scania CV AB, SE-15187 Sodertalje, Sweden.
    Fast-charging effects on ageing for energy-optimized automotive LiNi1/3Mn1/3Co1/3O2/graphite prismatic lithium-ion cells2019In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 422, p. 175-184Article in journal (Refereed)
    Abstract [en]

    The reactions in energy-optimized 25 Ah prismatic NMC/graphite lithium-ion cell, as a function of fast charging (1C-4C), are more complex than earlier described. There are no clear charging rate dependent trends but rather different mechanisms dominating at the different charging rates. Ageing processes are faster at 3 and 4C charging. Cycling with 3C-charging results in accelerated lithium plating but the 4C-charging results in extensive gas evolution that contribute significantly to the large cell impedance rise. Graphite exfoliation and accelerated lithium inventory loss point to the graphite electrode as the source of the gas evolution. The results are based on careful post-mortem analyses of electrodes using: scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and electrochemical impedance spectroscopy (EIS). SEM results show particle cracking independent of the charging rate used for the cycling. XPS and EIS generally indicate thicker surface film and larger impedance, respectively, towards the edge of the jellyrolls. For the intended application of a battery electric inner-city bus using this type of cell, charging rates of 3C and above are not feasible, considering battery lifetime. However, charging rates of 2C and below are too slow from the point of view of practical charging time.

  • 19.
    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.

  • 20.
    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.
    Jain, Sagar M.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Zhang, Xiaoliang
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Edvinsson, Tomas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics. Uppsala Univ, Dept Chem, Angstrom Lab, Inorgan Chem, SE-75120 Uppsala, Sweden..
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Zietz, Burkhard
    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. Uppsala Univ, Dept Chem, Angstrom Lab, Phys Chem, SE-75120 Uppsala, Sweden..
    Chemical engineering of methylammonium lead iodide/bromide perovskites: tuning of opto-electronic properties and photovoltaic performance2015In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 3, no 43, p. 21760-21771Article in journal (Refereed)
    Abstract [en]

    Hybrid (organic-inorganic) lead trihalide perovskites have attracted much attention in recent years due to their exceptionally promising potential for application in solar cells. Here a controlled one-step method is presented where PbCl2 is combined with three equivalents methylammonium halide (MAX, with X = land/or Br) in polar solvents to form MAPb(I-xBr(x))(3) perovskite films upon annealing in air at 145 degrees C. The procedure allows for a linear increment of the semiconductor bandgap from 1.60 eV to 2.33 eV by increasing the Br content. A transition from a tetragonal to a cubic structure is found when the Br fraction is larger than 0.3. X-ray photoelectron spectroscopy investigations shows that the increase of Br content is accompanied by a shift of the valence band edge to lower energy. Simultaneously, the conduction band moves to higher energy, but this shift is less pronounced. Time-resolved single-photon counting experiments of the perovskite materials on mesoporous TiO2 show faster decay kinetics for Br containing perovskites, indicative of improved electron injection into TiO2. Interestingly, kinetics of MAPb(12.7)Br(0.30)Cl(y) on TiO2 scaffold became faster after prolonged excitation during the measurement. In solar cell devices, MAPb(12.7)Br(0.30)), yielded best performance, giving more than 14% power conversion efficiency when used in combination with an n-type contact consisting of fluorine-doped tinoxide glass coated with dense TiO2 and a mesoporous Al2O3 scaffold, and a p-type contact, spiro-MeOTAD/Ag.

  • 21.
    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.
    Zhang, Xiaoliang
    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.
    Boschloo, Gerrit
    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.
    Bismuth Based Hybrid Perovskites A(3)Bi(2)I(9) (A: Methylammonium or Cesium) for Solar Cell Application2015In: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 27, no 43, p. 6806-6813Article in journal (Refereed)
    Abstract [en]

    Low-toxic bismuth-based perovskites are prepared for the possible replacement of lead perovskite in solar cells. The perovskites have a hexagonal crystalline phase and light absorption in the visible region. A power conversion efficiency of over 1% is obtained for a solar cell with Cs3Bi2I9 perovskite, and it is concluded that bismuth perovskites have very promising properties for further development in solar cells.

  • 22.
    Pati, Palas Baran
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Zhang, Lei
    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.
    Fernández-Terán, Ricardo
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Ahmadi, Sareh
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Tian, Lei
    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.
    Hammarström, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Tian, Haining
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Insights into the Mechanism of a Covalently Linked Organic Dye-Cobaloxime Catalyst System for Dye-Sensitized Solar Fuel Devices2017In: ChemSusChem, ISSN 1864-5631, E-ISSN 1864-564X, Vol. 10, no 11, p. 2480-2495Article in journal (Refereed)
    Abstract [en]

    A covalently-linked organic dye-cobaloxime catalyst system is developed by facile click reaction for mechanistic studies and application in a dye sensitized solar fuel device based on mesoporous NiO. This system has been systematically investigated by photophysical measurements, density functional theory, time resolved fluorescence, transient absorption spectroscopy as well as photoelectron spectroscopy. The results show that irradiation of the dye-catalyst on NiO leads to ultrafast hole injection into NiO from the excited dye, followed by a fast electron transfer to reduce the catalyst unit. Moreover, they suggest that the dye undergoes structural changes in the excited state and that excitation energy transfer occurs between neighboring molecules. The photoelectrochemical experiments also show the hydrogen production by this system-based NiO photocathode. The axial chloride ligands of the catalyst are released during photocatalysis to create the active sites for proton reduction. A working mechanism of the dye-catalyst on photocathode is eventually proposed on the basis of this study.

  • 23.
    Philippe, Bertrand
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Insights in Li-ion Battery Interfaces through Photoelectron Spectroscopy Depth Profiling2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Compounds forming alloys with lithium, such as silicon or tin, are promising negative electrode materials for the next generation of Li-ion batteries due to their higher theoretical capacity compared to the current commercial electrode materials.

    An important issue is to better understand the phenomena occurring at the electrode/electrolyte interfaces of these new materials. The stability of the passivation layer (SEI) is crucial for good battery performance and its nature, formation and evolution have to be investigated. It is important to follow upon cycling alloying/dealloying processes, the evolution of surface oxides with battery cycling and the change in surface chemistry when storing electrodes in the electrolyte.

    The aim of this thesis is to improve the knowledge of these surface reactions through a non-destructive depth-resolved PES (Photoelectron spectroscopy) analysis of the surface of new negative electrodes. A unique combination utilizing hard and soft-ray photoelectron spectroscopy allows by variation of the photon energy an analysis from the extreme surface (soft X-ray) to the bulk (hard X-ray) of the particles. This experimental approach was used to access the interfacial phase transitions at the surface of silicon or tin particles as well as the composition and thickness/covering of the SEI.

    Interfacial mechanisms occurring upon the first electrochemical cycle of Si-based electrodes cycled with the classical salt LiPF6 were investigated.

    The mechanisms of Li insertion (LixSi formation) have been illustrated as well as the formation of a new irreversible compound, Li4SiO4, at the outermost surface of the particles. Upon long cycling, the formation of SiOxFy was shown at the extreme surface of the particles by reaction of SiO2 with HF contributing to battery capacity fading.

    The LiFSI salt, more stable than LiPF6, improved the electrochemical performances. This behaviour is correlated to the absence of SiOxFy upon long-term cycling. Some degradation of LiFSI was shown by PES and supported by calculations.

    Finally, interfacial reactions occurring upon the first cycle of an intermetallic compound MnSn2 were studied. Compared to Si based electrodes, the SEI chemical composition is similar but the alloying process and the role played by the surface metal oxide are different.

    List of papers
    1. Nanosilicon Electrodes for Lithium-Ion Batteries: Interfacial Mechanisms Studied by Hard and Soft X-ray Photoelectron Spectroscopy
    Open this publication in new window or tab >>Nanosilicon Electrodes for Lithium-Ion Batteries: Interfacial Mechanisms Studied by Hard and Soft X-ray Photoelectron Spectroscopy
    Show others...
    2012 (English)In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 24, no 6, p. 1107-1115Article in journal (Refereed) Published
    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).

    Keywords
    lithium-ion batteries, silicon, alloy, SEI, XPS, PES, synchrotron
    National Category
    Inorganic Chemistry
    Research subject
    Chemistry with specialization in Inorganic Chemistry
    Identifiers
    urn:nbn:se:uu:diva-173341 (URN)10.1021/cm2034195 (DOI)000301947000020 ()
    Funder
    StandUp
    Available from: 2012-04-24 Created: 2012-04-23 Last updated: 2017-12-30
    2. Role of the LiPF6 Salt for the Long-Term Stability of Silicon Electrodes in Li-Ion Batteries: A Photoelectron Spectroscopy Study
    Open this publication in new window or tab >>Role of the LiPF6 Salt for the Long-Term Stability of Silicon Electrodes in Li-Ion Batteries: A Photoelectron Spectroscopy Study
    Show others...
    2013 (English)In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 25, no 3, p. 394-404Article in journal (Refereed) Published
    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.

    Place, publisher, year, edition, pages
    American Chemical Society (ACS), 2013
    Keywords
    lithium-ion batteries, silicon, alloy, SEI, XPS, PES, synchrotron
    National Category
    Inorganic Chemistry
    Research subject
    Chemistry with specialization in Inorganic Chemistry
    Identifiers
    urn:nbn:se:uu:diva-196593 (URN)10.1021/cm303399v (DOI)000315018500016 ()
    Funder
    StandUpEU, European Research Council, ALiSTORE
    Available from: 2013-03-11 Created: 2013-03-11 Last updated: 2017-12-30
    3. Improved performances of nanosilicon electrodes using the salt LiFSI: A photoelectron spectroscopy study
    Open this publication in new window or tab >>Improved performances of nanosilicon electrodes using the salt LiFSI: A photoelectron spectroscopy study
    Show others...
    2013 (English)In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 135, no 26, p. 9829-9842Article in journal (Refereed) Published
    Abstract [en]

    Silicon is a very good candidate for the next generation of negative electrodes for Li-ion batteries, due to its high rechargeable capacity. An important issue for the implementation of silicon is the control of the chemical reactivity at the electrode/electrolyte interface upon cycling, especially when using nanometric silicon particles. In this work we observed improved performances of Li//Si cells by using the new salt lithium bis(fluorosulfonyl)imide (LiFSI) with respect to LiPF6. The interfacial chemistry upon long-term cycling was investigated by photoelectron spectroscopy (XPS or PES). A 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 and in-house XPS (1486.6 eV). We show that LiFSI allows avoiding the fluorination process of the silicon particles surface upon long-term cycling, which is observed with the common salt LiPF6. As a result the composition in surface silicon phases is modified, and the favorable interactions between the binder and the active material surface are preserved. Moreover a reduction mechanism of the salt LiFSI at the surface of the electrode could be evidenced, and the reactivity of the salt toward reduction was investigated using ab initio calculations. The reduction products deposited at the surface of the electrode act as a passivation layer which prevents further reduction of the salt and preserves the electrochemical performances of the battery.

    Place, publisher, year, edition, pages
    American Chemical Society (ACS), 2013
    National Category
    Physical Chemistry
    Identifiers
    urn:nbn:se:uu:diva-198221 (URN)10.1021/ja403082s (DOI)000321541800045 ()
    Funder
    StandUp
    Available from: 2013-04-10 Created: 2013-04-10 Last updated: 2017-12-30
    4. MnSn2 electrodes for Li-ion batteries: Mechanisms at the nano scale and electrode/electrolyte interface
    Open this publication in new window or tab >>MnSn2 electrodes for Li-ion batteries: Mechanisms at the nano scale and electrode/electrolyte interface
    Show others...
    2014 (English)In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 123, p. 72-83Article in journal (Refereed) Published
    Abstract [en]

    We have investigated the reaction mechanisms occurring upon the first discharge/charge cycle of a MnSn2//Li electrochemical cell, by using bulk- and surface-sensitive characterization techniques (Xray Diffraction, Sn-119 Mossbauer spectroscopy, magnetic measurements, X-ray photoelectron and Auger spectroscopies). Compared to other tin-transition metal alloys, MnSn2 displays an original behaviour. Lithium insertion into MnSn2 particles results in a nanocomposite consisting of Li7Sn2 phase, and of Mn nanoparticles which are immediately oxidized at their surface. Lithium extraction from this nanocomposite leads to the formation of magnetic MnSn2 particles and to our knowledge it is the first time such a mechanism is observed in tin-based intermetallic electrode materials due to electrochemical reaction with Li. The solid electrolyte interphase (SEI) is formed at the beginning of the first discharge and its thickness slightly increases upon further lithium insertion. A partial re-dissolution process occurs upon lithium extraction from the material, while its chemical composition is very stable over the whole cycle.

    Place, publisher, year, edition, pages
    elsevier: , 2014
    Keywords
    Lithium-ion batteries, MnSn2, Tin, Intermetallics, Mössbauer, XPS, Magnetism
    National Category
    Materials Chemistry
    Identifiers
    urn:nbn:se:uu:diva-198264 (URN)10.1016/j.electacta.2014.01.010 (DOI)000334898800010 ()
    Available from: 2013-04-11 Created: 2013-04-11 Last updated: 2017-12-30
    5. Electrochemical performances and mechanisms of MnSn2 as anode material for Li-ion batteries
    Open this publication in new window or tab >>Electrochemical performances and mechanisms of MnSn2 as anode material for Li-ion batteries
    Show others...
    2013 (English)In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 244, p. 246-251Article in journal (Refereed) Published
    Abstract [en]

    A synthesis method consisting of a mechanical ball milling activation process followed by a sinteringheating treatment is proposed to obtain MnSn2 as anode material for Li-ion batteries. This two-stepapproach strongly reduces the amount of bSn impurities and provides a better material morphology.This improves the electrochemical performances, even at high C-rate, as shown from the comparisonbetween electrode materials obtained with and without this preliminary activation process. The electrochemicalreactions have been followed at the atomic scale by in situ 119Sn Mössbauer spectroscopy.The first discharge is a restructuring step that transforms the pristine material into Mn/Li7Sn2 nanocompositewhich should be considered as the real starting material for cycling. The delithiation of thisnanocomposite is characterized by two plateaus of potential attributed to the de-alloying of Li7Sn2 followedby the back reaction of Mn with poorly lithiated LixSn alloys, respectively. The composition and thestability of the solid electrolyte interphase were characterized by X-ray photoelectron spectroscopy.

    Place, publisher, year, edition, pages
    Elsevier, 2013
    National Category
    Inorganic Chemistry
    Identifiers
    urn:nbn:se:uu:diva-197842 (URN)10.1016/j.jpowsour.2013.01.110 (DOI)
    Conference
    16th International Meeting on Lithium Batteries (IMLB)
    Available from: 2013-04-04 Created: 2013-04-04 Last updated: 2017-12-06Bibliographically approved
  • 24.
    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).

  • 25.
    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.
    Improved performances of nanosilicon electrodes using the salt LiFSI: A photoelectron spectroscopy study2013In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 135, no 26, p. 9829-9842Article in journal (Refereed)
    Abstract [en]

    Silicon is a very good candidate for the next generation of negative electrodes for Li-ion batteries, due to its high rechargeable capacity. An important issue for the implementation of silicon is the control of the chemical reactivity at the electrode/electrolyte interface upon cycling, especially when using nanometric silicon particles. In this work we observed improved performances of Li//Si cells by using the new salt lithium bis(fluorosulfonyl)imide (LiFSI) with respect to LiPF6. The interfacial chemistry upon long-term cycling was investigated by photoelectron spectroscopy (XPS or PES). A 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 and in-house XPS (1486.6 eV). We show that LiFSI allows avoiding the fluorination process of the silicon particles surface upon long-term cycling, which is observed with the common salt LiPF6. As a result the composition in surface silicon phases is modified, and the favorable interactions between the binder and the active material surface are preserved. Moreover a reduction mechanism of the salt LiFSI at the surface of the electrode could be evidenced, and the reactivity of the salt toward reduction was investigated using ab initio calculations. The reduction products deposited at the surface of the electrode act as a passivation layer which prevents further reduction of the salt and preserves the electrochemical performances of the battery.

  • 26.
    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.

  • 27.
    Philippe, Bertrand
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Hahlin, Maria
    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.
    Gustafsson, Torbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry. Uppsala Univ, Dept Chem, Angstrom Lab, SE-75121 Uppsala, Sweden..
    Siegbahn, Hans
    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.
    Photoelectron Spectroscopy for Lithium Battery Interface Studies2016In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 163, no 2, p. A178-A191Article in journal (Refereed)
    Abstract [en]

    Photoelectron spectroscopy (PES) has become an important tool for investigating Li-ion battery materials, in particular for analyzing interfacial structures and reactions. Since the methodology was introduced in the battery research area, PES has undergone a dramatic development regarding photon sources, sample handling and electron energy analyzers. This includes the possibility to use synchrotron radiation with increased intensity and the possibility to vary the photon energy. The aim of the present paper is to describe how PES can be used to investigate battery interfaces and specifically highlight how synchrotron based PES has been implemented to address different questions useful for the development of the Li-ion batteries. We also present some recent developments of the techniques, which have the potential to further push the limits for the use of photoelectron spectroscopy in battery research.

  • 28.
    Philippe, Bertrand
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Jacobsson, T. Jesper
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry. École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland.
    Correa-Baena, Juan-Pablo
    École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland; Massachusetts Institute of Technology, Cambridge, USA .
    Jena, Naresh K.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Banerjee, Amitava
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Chakraborty, Sudip
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Cappel, Ute B.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Hagfeldt, Anders
    École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland.
    Odelius, Michael
    Stockholm University, Stockholm, Sweden.
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Valence Level Character in a Mixed Perovskite Material and Determination of the Valence Band Maximum from Photoelectron Spectroscopy: Variation with Photon Energy2017In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 121, no 48, p. 26655-26666Article in journal (Refereed)
    Abstract [en]

    A better understanding of the electronic structure of perovskite materials used in photovoltaic devices is essential for their development and optimization. In this investigation, synchrotron based photoelectron spectroscopy (PES) was used to experimentally delineate the character and energy position of the valence band structures of a mixed perovskite. The valence band was measured using PES with photon energies ranging from UPS (21.2 eV) to hard X-rays (up to 4,000 eV) and by taking the variation of the photoionization cross-sections into account, we could experimentally determine the inorganic and organic contributions. The experiments were compared to theoretical calculations to further distinguish the role of the different anions in the electronic structure. The investigation also includes a thorough study of the valence band maximum (VBM) and its position in relation to the Fermi level, which is crucial for the design and optimization of complete solar cells and their functional properties.

  • 29.
    Philippe, Bertrand
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Mahmoud, Abdelfattah
    Ledeuil, Jean-Bernard
    Chamas, Mohamad
    Edström, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Dedryvère, Rémi
    Gonbeau, Danielle
    Université de Pau, France.
    Lippens, Pierre-Emmanuel
    MnSn2 electrodes for Li-ion batteries: Mechanisms at the nano scale and electrode/electrolyte interface2014In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 123, p. 72-83Article in journal (Refereed)
    Abstract [en]

    We have investigated the reaction mechanisms occurring upon the first discharge/charge cycle of a MnSn2//Li electrochemical cell, by using bulk- and surface-sensitive characterization techniques (Xray Diffraction, Sn-119 Mossbauer spectroscopy, magnetic measurements, X-ray photoelectron and Auger spectroscopies). Compared to other tin-transition metal alloys, MnSn2 displays an original behaviour. Lithium insertion into MnSn2 particles results in a nanocomposite consisting of Li7Sn2 phase, and of Mn nanoparticles which are immediately oxidized at their surface. Lithium extraction from this nanocomposite leads to the formation of magnetic MnSn2 particles and to our knowledge it is the first time such a mechanism is observed in tin-based intermetallic electrode materials due to electrochemical reaction with Li. The solid electrolyte interphase (SEI) is formed at the beginning of the first discharge and its thickness slightly increases upon further lithium insertion. A partial re-dissolution process occurs upon lithium extraction from the material, while its chemical composition is very stable over the whole cycle.

  • 30.
    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.

  • 31.
    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.

  • 32.
    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.

  • 33.
    Phuyal, Dibya
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Jain, Sagar Motilal
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry. Swansea Univ, Coll Engn, SPECIFIC, Bay Campus,Fabian Way, Swansea SA1 8EN, W Glam, Wales.
    Philippe, Bertrand
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Johansson, Malin B
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Pazoki, Meysam
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Kullgren, Jolla
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Kvashnina, Kristina O.
    ESRF, Rossendorf Beamline, CS40220, F-38043 Grenoble 9, France;HZDR, Inst Resource Ecol, POB 510119, D-01314 Dresden, Germany.
    Klintenberg, Mattias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Johansson, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Butorin, Sergei
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Karis, Olof
    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.
    The electronic structure and band interface of cesium bismuth iodide on a titania heterostructure using hard X-ray spectroscopy2018In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 6, no 20, p. 9498-9505Article in journal (Refereed)
    Abstract [en]

    Bismuth halide compounds as a non-toxic alternative are increasingly investigated because of their potential in optoelectronic devices and their rich structural chemistry. Hard X-ray spectroscopy was applied to the ternary bismuth halide Cs3Bi2I9 and its related precursors BiI3 and CsI to understand its electronic structure at an atomic level. We specifically investigated the core levels and valence band using X-ray photoemission spectroscopy (PES), high-resolution X-ray absorption (HERFD-XAS), and resonant inelastic X-ray scattering (RIXS) to get insight into the chemistry and the band edge properties of the two bismuth compounds. Using these element specific X-ray techniques, our experimental electronic structures show that the primary differences between the two bismuth samples are the position of the iodine states in the valence and conduction bands and the degree of hybridization with bismuth lone pair (6s(2)) states. The crystal structure of the two layered quasi-perovskite compounds plays a minor role in modifying the overall electronic structure, with variations in bismuth lone pair states and iodine band edge states. Density Functional Theory (DFT) calculations are used to compare with experimental data. The results demonstrate the effectiveness of hard X-ray spectroscopies to identify element specific bulk electronic structures and their use in optoelectronic devices.

  • 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.
    Safdari, Majid
    et al.
    KTH Royal Inst Technol, Dept Chem, Appl Phys Chem, SE-10044 Stockholm, Sweden..
    Phuyal, Dibya
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Philippe, Bertrand
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Svensson, Per H.
    KTH Royal Inst Technol, Dept Chem, Appl Phys Chem, SE-10044 Stockholm, Sweden.;SP Proc Dev, Sodertalje, Sweden..
    Butorin, Sergei
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Kvashnina, Kristina O.
    ESRF European Synchrotron, CS40220, F-38043 Grenoble 9, France.;Helmholtz Zentrum Dresden Rossendorf, Inst Resource Ecol, D-01314 Dresden, Germany..
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Kloo, Lars
    KTH Royal Inst Technol, Dept Chem, Appl Phys Chem, SE-10044 Stockholm, Sweden..
    Gardner, James M.
    KTH Royal Inst Technol, Dept Chem, Appl Phys Chem, SE-10044 Stockholm, Sweden..
    Impact of synthetic routes on the structural and physical properties of butyl-1,4-diammonium lead iodide semiconductors2017In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 5, no 23, p. 11730-11738Article in journal (Refereed)
    Abstract [en]

    We report the significant role of synthetic routes and the importance of solvents in the synthesis of organic-inorganic lead iodide materials. Through one route, the intercalation of dimethylformamide in the crystal structure was observed leading to a one-dimensional (1D) [NH3(CH2)(4)NH3]Pb2I6 structure of the product. This product was compared with the two-dimensional (2D) [NH3(CH2)(4)NH3]PbI4 recovered from aqueous solvent based synthesis with the same precursors. UV-visible absorption spectroscopy showed a red-shift of 0.1 eV for the band gap of the 1D network in relation to the 2D system. This shift primarily originates from a shift in the valence band edge as determined from photoelectron-and X-ray spectroscopy results. These findings also suggest the iodide 5p orbital as the principal component in the density of states in the valence band edge. Single crystal data show a change in the local coordination around iodide, while in both materials, lead atoms are surrounded by iodide atoms in octahedral units. The conductivity of the one-dimensional material ([NH3(CH2)(4)NH3]Pb2I6) was 50% of the two-d(i)mensional material ([NH3(CH2)(4)NH3]PbI4). The fabricated solar cells reflect these changes in the chemical and electronic structure of both materials, although the total light conversion efficiencies of solar cells based on both products were similar.

  • 36.
    Valvo, Mario
    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.
    Lindgren, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Check-Wai, Tai
    Arrhenius Laboratory, Department of Materials and Environmental Chemistry, Stockholm.
    Edström, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Insight into the processes controlling the electrochemical reactions of nanostructured iron oxide electrodes in Li- and Na-half cells2016In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 194, p. 74-83Article in journal (Refereed)
    Abstract [en]

    The kinetics and the processes governing the electrochemical reactions of various types of iron oxide nanostructures (i.e., nanopowders, nanowires and thin-films) have been studied via cyclic voltammetry in parallel with Li- and Na-half cells containing analogous electrolytes (Li+/Na+, ClO4 in EC:DEC). The particular features arising from each electrode architecture are discussed and compared to shed light on the associated behaviour of the reacting nanostructured active materials. The influence of their characteristic structure, texture and electrical wiring on the overall conversion reaction upon their respective lithiation and sodiation has been analyzed carefully. The limiting factors existing for this reaction upon uptake of Li+ and Na+ ions are highlighted and the related issues in both systems are addressed. The results of this investigation clearly prove that the conversion of iron oxide into metallic Fe and Na2O is severely impeded compared to its analogous process upon lithiation, independently of the type of nanostructure involved in such reaction. The diffusion mechanisms of the different ions (i.e., Li+vs. Na+) through the phases formed upon conversion, as well as the influence of various interfaces on the resulting reaction, appear to pose further constraints on an efficient use of these compounds.

  • 37.
    Wang, Lei
    et al.
    KTH Royal Institute of Technology, Department of Chemistry.
    Fan, Ke
    KTH Royal Institute of Technology, Department of Chemistry.
    Chen, Hong
    KTH Royal Institute of Technology, Department of Chemistry.
    Daniel, Quentin
    KTH Royal Institute of Technology, Department of Chemistry.
    Philippe, Bertrand
    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.
    Sun, Licheng
    KTH Royal Institute of Technology, Department of Chemistry; Dalian University of Technology (DUT), DUT-KTH Joint Education and Research Center on Molecular Devices, State Key Laboratory of Fine Chemicals.
    Towards efficient and robust anodes for water splitting: Immobilization of Ru catalysts on carbon electrode and hematite by in situ polymerization2017In: Catalysis Today, ISSN 0920-5861, E-ISSN 1873-4308, Vol. 290, p. 73-77Article in journal (Refereed)
    Abstract [en]

    Ru-bda based molecular water oxidation catalysts 1 and 2 (H2bda = 2,2′–bipyridine–6,6′–dicarboxylic acid) containing a thiophene group are attached to the surfaces of electrodes by the method of electropolymerization. The Ru-bda molecular catalyst functionalized graphite carbon electrode can catalyze water oxidation efficiently under a overpotential of ca 500 mV to obtain current density of 5 mA cm−2; and the similarly functionalized photoelectrode based on α-Fe2O3 (hematite) film can work as an photoanode for light driven water splitting.

  • 38. Wang, Lei
    et al.
    Fan, Ke
    Daniel, Quentin
    Duan, Lele
    Li, Fusheng
    Philippe, Bertrand
    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.
    Chen, Hong
    Sun, Junliang
    Sun, Licheng
    Electrochemical driven water oxidation by molecular catalysts in situ polymerized on the surface of graphite carbon electrode2015In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 51, no 37, p. 7883-7886Article in journal (Refereed)
    Abstract [en]

    A simple strategy to immobilize highly efficient ruthenium based molecular water-oxidation catalysts on the basal-plane pyrolytic graphite electrode (BPG) by polymerization has been demonstrated. The electrode 1@BPG has obtained a high initial turnover frequency (TOF) of 10.47 s(-1) at similar to 700 mV overpotential, and a high turnover number (TON) up to 31600 in 1 h electrolysis.

  • 39.
    Xu, Chao
    et al.
    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.
    Philippe, Bertrand
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Gorgoi, Mihaela
    Helmholtz Zentrum Berlin Germany.
    Björefors, Fredrik
    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.
    Gustafsson, Torbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Improved Performance of the Silicon Anode for Li-Ion Batteries: Understanding the Surface Modification Mechanism of Fluoroethylene Carbonate as an Effective Electrolyte Additive2015In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 27, no 7, p. 2591-2599Article in journal (Refereed)
    Abstract [en]

    Silicon as a negative electrode material for lithium-ion batteries has attracted tremendous attention due to its high theoretical capacity, and fluoroethylene carbonate (FEC) was used as an electrolyte additive, which significantly improved the cyclability of silicon-based electrodes in this study. The decomposition of the FEC additive was investigated by synchrotron-based X-ray photoelectron spectroscopy (PES) giving a chemical composition depth-profile. The reduction products of FEC were found to mainly consist of LiF and -CHF-OCO2-type compounds. Moreover, FEC influenced the lithium hexafluorophosphate (LiPF6) decomposition reaction and may have suppressed further salt degradation. The solid electrolyte interphase (SEI) formed from the decomposition of ethylene carbonate (EC) and diethyl carbonate (DEC), without the FEC additive present, covered surface voids and lead to an increase in polarization. However, in the presence of FEC, which degrades at a higher reduction potential than EC and DEC, instantaneously a conformal SEI was formed on the silicon electrode. This stable SEI layer sufficiently limited the emergence of large cracks and preserved the original surface morphology as well as suppressed the additional SEI formation from the other solvent. This study highlights the vital importance of how the chemical composition and morphology of the SEI influence battery performance.

  • 40. Zhang, Biaobiao
    et al.
    Chen, Hong
    Daniel, Quentin
    Philippe, Bertrand
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Yu, Fengshou
    Valvo, Mario
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Li, Yuanyuan
    Ambre, Ram B.
    Zhang, Peili
    Li, Fei
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Sun, Licheng
    Defective and “c-Disordered” Hortensia-like Layered MnOx as an Efficient Electrocatalyst for Water Oxidation at Neutral pH2017In: ACS Catalysis, ISSN 2155-5435, E-ISSN 2155-5435, Vol. 7, no 9, p. 6311-6322Article in journal (Refereed)
    Abstract [en]

    The development of a highly active manganese-based water oxidation catalyst in the design of an ideal artificial photosynthetic device operating under neutral pH conditions remains a great challenge, due to the instability of pivotal Mn3+ intermediates. We report here defective and “c-disordered” layered manganese oxides (MnOx-300) formed on a fluorine-doped tin oxide electrode by constant anodic potential deposition and subsequent annealing, with a catalytic onset (0.25 mA/cm2) at an overpotential (η) of 280 mV and a benchmark catalytic current density of 1.0 mA/cm2 at an overpotential (η) of 330 mV under neutral pH (1 M potassium phosphate). Steady current density above 8.2 mA/cm2 was obtained during the electrolysis at 1.4 V versus the normal hydrogen electrode for 20 h. Insightful studies showed that the main contributing factors for the observed high activity of MnOx-300 are (i) a defective and randomly stacked layered structure, (ii) an increased degree of Jahn–Teller distorted Mn3+ in the MnO6 octahedral sheets, (iii) effective stabilization of Mn3+, (iv) a high surface area, and (v) improved electrical conductivity. These results demonstrate that manganese oxides as structural and functional models of an oxygen-evolving complex (OEC) in photosystem II are promising catalysts for water oxidation in addition to Ni/Co-based oxides/hydroxides.

1 - 40 of 40
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