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  • 1.
    Ellis, Hanna
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Kaufmann Eriksson, Susanna
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Feldt, Sandra
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Gabrielsson, Erik
    KTH, Organisk kemi.
    Lohse, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    Lindblad, Rebecka
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Sun, Licheng
    KTH, Organisk kemi.
    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.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Linker Unit Modification of Triphenylamine-based Organic Dyes for Efficient Cobalt Mediated Dye-Sensitized Solar Cells2013In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 117, no 41, p. 21029-21036Article in journal (Refereed)
    Abstract [en]

    Linker unit modification of donor-linker-acceptor-based organic dyes was investigated with respect to the spectral and physicochemical properties of the dyes. The spectral response for a series of triphenylamine (TPA)-based organic dyes, called LEG1-4, was shifted into the red wavelength region, and the extinction coefficient of the dyes was increased by introducing different substituted dithiophene units on the pi-conjugated linker. The photovoltaic performance of dye-sensitized solar cells (DSCs) incorporating the different dyes in combination with cobalt-based electrolytes was found to be dependent on dye binding. The binding morphology of the dyes on the TiO2 was studied using photoelectron spectroscopy, which demonstrated that the introduction of alkyl chains and different substituents on the dithiophene linker unit resulted in a larger tilt angle of the dyes with respect to the normal of the TiO2-surface, and thereby a lower surface coverage. The good photovoltaic performance for cobalt electrolyte-based DSCs found here and by other groups using TPA-based organic dyes with a cyclopentadithiophene linker unit substituted with alkyl chains was mainly attributed to the extended spectral response of the dye, whereas the larger tilt angle of the dye with respect to the TiO2-surface resulted in less efficient packing of the dye molecules and enhanced recombination between electrons in TiO2 and Co(III) species in the electrolyte.

  • 2.
    Eriksson K., Susanna
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Josefsson, Ida
    Ellis, Hanna
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Amat, Anna
    Pastore, Mariachiara
    Oscarsson, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Lindblad, Rebecka
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Eriksson, Anna I. K.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Johansson, Erik
    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.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Fantacci, Simona
    Odelius, Michael
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Geometrical and energetical structural changes in organic dyes for dye-sensitized solar cells probed with photoelectron spectroscopy and DFT2016In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 18, no 1, p. 252-260Article in journal (Other academic)
    Abstract [en]

    The effects of alkoxy chain length in triarylamine based donor acceptor organic dyes are investigated with respect to the electronic and molecular surface structures on the performance of solar cells and the electron lifetime. The dyes were investigated when adsorbed on TiO2 in a configuration that can be used for dye sensitized solar cells (DSCs). Specifically, the two dyes D35 and D45 were compared using photoelectron spectroscopy (PES) and density functional theory (DFT) calculations. The differences in solar cell characteristics when longer alkoxy chains are introduced in the dye donor unit are attributed to geometrical changes in dye packing while only minor differences were observed in the electronic structure. A higher dye load was observed for D45 on TiO2. However, D35 based solar cells result in higher photocurrent although the dye load is lower. This is explained by different geometrical structures of the dyes on the surface.

  • 3.
    Fredin, Kristofer
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Johansson, Erik M. J.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Hahlin, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Schölin, Rebecka
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Plogmaker, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Gabrielsson, Erik
    Sun, Licheng
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Solid state dye-sensitized solar cells prepared by infiltrating a molten hole conductor into a mesoporous film at a temperature below 150 degrees C2011In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 161, no 21-22, p. 2280-2283Article in journal (Refereed)
    Abstract [en]

    Infiltration of a molten hole conductor in a mesoporous film at an elevated temperature exhibits good wetting performance and the procedure is therefore suitable as part of the preparation method for solid state dye-sensitized solar cells. Herein, we present a system prepared by infiltrating 4-(diethylamino)benzaldehyde-1,1)-diphenyl-hydrazone in its molten form at a temperature below 150 degrees C. The system displays a maximum photon-to-current conversion efficiency of about 35%, a value corresponding to an increase of about 5 times in comparison with a previously published system prepared by infiltrating a molten hole-conductor at a temperature exceeding 250 degrees C. By means of comparing charge transport and recombination with the results measured for a liquid analogue, we conclude that whereas the transport rates are similar, recombination is significantly more rapid in the solid-state device.

  • 4.
    Johansson, Erik M. J.
    et al.
    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.
    Siegbahn, Hans
    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.
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Atomic and Electronic Structures of Interfaces in Dye-Sensitized, Nanostructured Solar Cells2014In: ChemPhysChem, ISSN 1439-4235, E-ISSN 1439-7641, Vol. 15, no 6, p. 1006-1017Article, review/survey (Refereed)
    Abstract [en]

    Key processes in nanostructured dye-sensitized solar cells occur at material interfaces containing, for example, oxides, dye molecules, and hole conductors. A detailed understanding of interfacial properties is therefore important for new developments and device optimization. The implementation of X-ray-based spectroscopic methods for atomic-level understanding of such properties is reviewed. Specifically, the use of the chemical and element sensitivity of photoelectron spectroscopy, hard X-ray photoelectron spectroscopy, and resonant photoelectron spectroscopy for investigating interfacial molecular and electronic properties are described; examples include energy matching, binding configurations, and molecular orbital composition. Finally, results from the complete oxide/dye/hole-conductor systems are shown and demonstrate how the assembly itself can affect the molecular and electronic structure of the materials.

  • 5.
    Johansson, Erik M. J.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Schölin, Rebecka
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Siegbahn, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Energy level alignment in TiO(2)/dipole-molecule/P3HT interfaces2011In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 515, no 1-3, p. 146-150Article in journal (Refereed)
    Abstract [en]

    Controlling the energy levels at the interface between an inorganic and an organic material is of importance to improve the properties in devices based on such hybrid interfaces, and can be obtained by the incorporation of dipole molecules between the materials. In this report interfaces containing TiO(2), a dipole molecule (benzoic acid or 4-nitrobenzoic acid) and a polymer, poly(3-hexylthiophene) (P3HT) were investigated using high kinetic energy photoelectron spectroscopy. We could successfully measure through all materials in the fully assembled systems, and thereby experimentally quantify the dipole induced change in the energy level alignment of the polymer and the TiO(2).

  • 6.
    Knut, Ronny
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Lindblad, Rebecka
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Gorgoi, Mihaela
    Rensmo, Hakan
    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.
    High energy photoelectron spectroscopy in basic and applied science: Bulk and interface electronic structure2013In: Journal of Electron Spectroscopy and Related Phenomena, ISSN 0368-2048, E-ISSN 1873-2526, Vol. 190, p. 278-288Article in journal (Refereed)
    Abstract [en]

    With the access of new high-performance electron spectrometers capable of analyzing electron energies up to the order of 10 keV, the interest for photoelectron spectroscopy has grown and many new applications of the technique in areas where electron spectroscopies were considered to have limited use have been demonstrated over the last few decades. The technique, often denoted hard X-ray photoelectron spectroscopy (HX-PES or HAXPES), to distinguish the experiment from X-ray photoelectron spectroscopy performed at lower energies, has resulted in an increasing interest in photoelectron spectroscopy in many areas. The much increased mean free path at higher kinetic energies, in combination with the elemental selectivity of the core level spectroscopies in general has led to this fact. It is thus now possible to investigate the electronic structure of materials with a substantially enhanced bulk sensitivity. In this review we provide examples from our own research using HAXPES which to date has been performed mainly at the HIKE facility at the KMC-1 beamline at HZB, Berlin. The review exemplifies the new opportunities using HAXPES to address both bulk and interface electronic properties in systems relevant for applications in magnetic storage, energy related research, but also in purely curiosity driven problems.

  • 7.
    Knut, Ronny
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Lindblad, Rebecka
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Gorgoi, Mihaela
    Rensmo, Hakan
    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.
    High energy photoelectron spectroscopy in basic and applied science: Bulk and interface electronic structure2013In: Journal of Electron Spectroscopy and Related Phenomena, Vol. 190, p. 278-288Article in journal (Refereed)
  • 8.
    Knut, Ronny
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Lindblad, Rebecka
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Grachev, Sergey
    Faou, Jean-Yvon
    Gorgoi, Mihaela
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Søndergård, Elin
    Karis, Olof
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Reactive ZnO/Ti/ZnO interfaces studied by hard x-ray photoelectron spectroscopy2014In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 115, no 4, p. 043714-043714-7Article in journal (Refereed)
    Abstract [en]

    The chemistry and intermixing at buried interfaces in sputter deposited ZnO/Ti/ZnO thin layers were studied by hard x-ray photoelectron spectroscopy. The long mean free path of the photoelectrons allowed for detailed studies of the oxidation state, band bending effects, and intrinsic doping of the buried interfaces. Oxidation of the Ti layer was observed when ZnO was deposited on top. When Ti is deposited onto ZnO, Zn Auger peaks acquire a metallic character indicating a strong reduction of ZnO at the interface. Annealing of the stack at 200 °C results in further reduction of ZnO and oxidation of Ti. Above 300 °C, oxygen transport from the bulk of the ZnO layer takes place, leading to re-oxidation of ZnO at the interface and further oxidation of Ti layer. Heating above 500 °C leads to an intermixing of the layers and the formation of a ZnxTiOy compound.

  • 9. Leijtens, Tomas
    et al.
    Stranks, Samuel D.
    Eperon, Giles E.
    Lindblad, Rebecka
    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.
    McPherson, Ian J.
    Rensmo, Hakan
    Ball, James M.
    Lee, Michael M.
    Snaith, Henry J.
    Electronic Properties of Meso-Superstructured and Planar Organometal Halide Perovskite Films: Charge Trapping, Photodoping, and Carrier Mobility2014In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 8, no 7, p. 7147-7155Article in journal (Refereed)
    Abstract [en]

    Solution-processed organometal trihalide perovskite solar cells are attracting increasing interest, leading to high performances over 15% in thin film architectures. Here, we probe the presence of sub gap states in both solid and mesosuperstructured perovskite films and determine that they strongly influence the photoconductivity response and splitting of the quasi-Fermi levels in films and solar cells. We find that while the planar perovskite films are superior to the mesosuperstructured films in terms of charge carrier mobility (in excess of 20 cm(2) V-1 s(-1)) and emissivity, the planar heterojunction solar cells are limited in photovoltage by the presence of sub gap states and low intrinsic doping densities.

  • 10.
    Lindblad, Rebecka
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Electronic Structures and Energy Level Alignment in Mesoscopic Solar Cells: A Hard and Soft X-ray Photoelectron Spectroscopy Study2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Photoelectron spectroscopy is an experimental method to study the electronic structure in matter. In this thesis, a combination of soft and hard X-ray based photoelectron spectroscopy has been used to obtain atomic level understanding of electronic structures and energy level alignments in mesoscopic solar cells. The thesis describes how the method can be varied between being surface and bulk sensitive and how to follow the structure linked to particular elements. The results were discussed with respect to the material function in mesoscopic solar cell configurations.

    The heart of a solar cell is the charge separation of photoexcited electrons and holes, and in a mesoscopic solar cell, this occurs at interfaces between different materials. Understanding the energy level alignment between the materials is important for developing the function of the device. In this work, it is shown that photoelectron spectroscopy can be used to experimentally follow the energy level alignment at interfaces such as TiO2/metal sulfide/polymer, as well as TiO2/perovskite.

    The electronic structures of two perovskite materials, CH3NH3PbI3 and CH3NH3PbBr3 were characterized by photoelectron spectroscopy and the results were discussed with support from quantum chemical calculations. The outermost levels consisted mainly of lead and halide orbitals and due to a relatively higher cross section for heavier elements, hard X-ray excitation was shown useful to study the position as well as the orbital character of the valence band edge.

    Modifications of the energy level positions can be followed by core level shifts. Such studies showed that a commonly used additive in mesoscopic solar cells, Li-TFSI, affected molecular hole conductors in the same way as a p-dopant. A more controlled doping can also be achieved by redox active dopants such as Co(+III) complexes and can be studied quantitatively with photoelectron spectroscopy methods.

    Hard X-rays allow studies of hidden interfaces, which were used to follow the oxidation of Ti in stacks of thin films for conducting glass. By the use of soft X-rays, the interface structure and bonding of dye molecules to mesoporous TiO2 or ZnO could be studied in detail. A combination of the two methods can be used to obtain a depth profiling of the sample. 

    List of papers
    1. Preventing Dye Aggregation on ZnO by Adding Water in the Dye-Sensitization Process
    Open this publication in new window or tab >>Preventing Dye Aggregation on ZnO by Adding Water in the Dye-Sensitization Process
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    2011 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 115, no 39, p. 19274-19279Article in journal (Refereed) Published
    Abstract [en]

    ZnO based dye-sensitized solar cells have been studied using N719 and Z-907 as sensitizing dyes, with and without including water to the dye solution. The solar cells have been characterized with photoelectric measurements and the interface between the dye and the ZnO surface has been studied using photoelectron spectroscopy. It was shown that water in the dye solution greatly reduces surface dye aggregation and thereby enhances the solar cell performance for N719. For Z-907 where no sign of dye aggregation could be found, the presence of water had minor effect on the surface structure and solar cell performance.

    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:uu:diva-160379 (URN)10.1021/jp206052t (DOI)000295245500046 ()
    Available from: 2011-10-24 Created: 2011-10-24 Last updated: 2017-12-08Bibliographically approved
    2. Influence of Water on the Electronic: and Molecular Surface Structures of Ru-Dyes at Nanostructured TiO2
    Open this publication in new window or tab >>Influence of Water on the Electronic: and Molecular Surface Structures of Ru-Dyes at Nanostructured TiO2
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    2011 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 115, no 24, p. 11996-12004Article in journal (Refereed) Published
    Abstract [en]

    The influence of water on the surface electronic and molecular properties of three Ru-dyes adsorbed at nanostructured TiO2 was investigated using photoelectron spectroscopy (PES). The dyes investigated were the Ru(dcbpy)(2)(NCS)(2) in its acid (N3) and in its 2-fold deprotonated form (N719) as well as a similar dye (Z-907) containing the hydrophobic ligand 4,4'-dinonyl-2,2'-bipyridine. Trends in surface structures depending on water exposure were followed for the three dyes. The results showed that the hydrophobic chains of the Z-907 dye effectively inhibit surface reorganization while large changes in surface electronic and molecular structure were observed for the N3 and N719 molecular layers. Specifically, large effects involving the thiocyanate ligands were detected, and the S2p and N Is core level spectra indicate that the changes involve mixing of only two dominating surface configurations. Moreover, the PES results also showed water-induced changes in the energy level matching between the dye and the TiO2, and water induced desorption of the TBA(+) counterion. Basic photoelectrochemical trends depending on water exposure to dye-sensitized solar cell systems were also verified.

    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:uu:diva-155932 (URN)10.1021/jp1076609 (DOI)000291709600016 ()
    Available from: 2011-07-04 Created: 2011-07-04 Last updated: 2017-12-11Bibliographically approved
    3. Energy level alignment in TiO2/metal sulfide/polymer interfaces for solar cell applications
    Open this publication in new window or tab >>Energy level alignment in TiO2/metal sulfide/polymer interfaces for solar cell applications
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    2014 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 16, no 32, p. 17099-17107Article in journal (Refereed) Published
    Abstract [en]

    Semiconductor sensitized solar cell interfaces have been studied with photoelectron spectroscopy to understand the interfacial electronic structures. In particular, the experimental energy level alignment has been determined for complete TiO2/metal sulfide/polymer interfaces. For the metal sulfides CdS, Sb2S3 and Bi2S3 deposited from single source metal xanthate precursors, it was shown that both driving forces for electron injection into TiO2 and hole transfer to the polymer decrease for narrower bandgaps. The energy level alignment results were used in the discussion of the function of solar cells with the same metal sulfides as light absorbers. For example Sb2S3 showed the most favourable energy level alignment with 0.3 eV driving force for electron injection and 0.4 eV driving force for hole transfer and also the most efficient solar cells due to high photocurrent generation. The energy level alignment of the TiO2/Bi2S3 interface on the other hand showed no driving force for electron injection to TiO2, and the performance of the corresponding solar cell was very low.

    Place, publisher, year, edition, pages
    The Royal Society of Chemistry, 2014
    Keywords
    Photoelectron spectroscopy, semiconductor sensitised solar cells, metal xhanthate, Sb2S3
    National Category
    Atom and Molecular Physics and Optics
    Identifiers
    urn:nbn:se:uu:diva-221439 (URN)10.1039/C4CP01581A (DOI)000340353000025 ()
    Funder
    Swedish Research Council, 20124721EU, FP7, Seventh Framework Programme, 308997
    Available from: 2014-03-31 Created: 2014-03-31 Last updated: 2017-12-05Bibliographically approved
    4. Electronic Structure of TiO2/CH3NH3PbI3 Perovskite Solar Cell Interfaces
    Open this publication in new window or tab >>Electronic Structure of TiO2/CH3NH3PbI3 Perovskite Solar Cell Interfaces
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    2014 (English)In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 5, no 4, p. 648-653Article in journal (Refereed) Published
    Abstract [en]

    The electronic structure and chemical composition of efficient CH3NH3PbI3 perovskite solar cell materials deposited onto mesoporous TiO2 were studied using photoelectron spectroscopy with hard X-rays. With this technique, it is possible to directly measure the occupied energy levels of the perovskite as well as the TiO2 buried beneath and thereby determine the energy level matching of the interface. The measurements of the valence levels were in good agreement with simulated density of states, and the investigation gives information on the character of the valence levels. We also show that two different deposition techniques give results indicating similar electronic structures.

    National Category
    Atom and Molecular Physics and Optics
    Identifiers
    urn:nbn:se:uu:diva-220599 (URN)10.1021/jz402749f (DOI)000331860900002 ()
    Available from: 2014-03-17 Created: 2014-03-17 Last updated: 2017-12-05Bibliographically approved
    5. The electronic structure of CH3NH3PbX3 perovskites; the dependence on the halide moeity
    Open this publication in new window or tab >>The electronic structure of CH3NH3PbX3 perovskites; the dependence on the halide moeity
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    (English)Manuscript (preprint) (Other academic)
    National Category
    Atom and Molecular Physics and Optics
    Identifiers
    urn:nbn:se:uu:diva-221448 (URN)
    Available from: 2014-03-31 Created: 2014-03-31 Last updated: 2016-04-20
    6. Energy level alignment in TiO(2)/dipole-molecule/P3HT interfaces
    Open this publication in new window or tab >>Energy level alignment in TiO(2)/dipole-molecule/P3HT interfaces
    Show others...
    2011 (English)In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 515, no 1-3, p. 146-150Article in journal (Refereed) Published
    Abstract [en]

    Controlling the energy levels at the interface between an inorganic and an organic material is of importance to improve the properties in devices based on such hybrid interfaces, and can be obtained by the incorporation of dipole molecules between the materials. In this report interfaces containing TiO(2), a dipole molecule (benzoic acid or 4-nitrobenzoic acid) and a polymer, poly(3-hexylthiophene) (P3HT) were investigated using high kinetic energy photoelectron spectroscopy. We could successfully measure through all materials in the fully assembled systems, and thereby experimentally quantify the dipole induced change in the energy level alignment of the polymer and the TiO(2).

    National Category
    Physical Sciences Chemical Sciences
    Identifiers
    urn:nbn:se:uu:diva-162364 (URN)10.1016/j.cplett.2011.09.014 (DOI)000296551300027 ()
    Available from: 2011-11-30 Created: 2011-11-30 Last updated: 2017-12-08Bibliographically approved
    7. Energy Level Shifts in Spiro-OMeTAD Molecular Thin Films When Adding Li-TFSI
    Open this publication in new window or tab >>Energy Level Shifts in Spiro-OMeTAD Molecular Thin Films When Adding Li-TFSI
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    2012 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 116, no 50, p. 26300-26305Article in journal (Refereed) Published
    Abstract [en]

    Hard X-ray photoelectron spectroscopy (HAXPES) has been used to study the effects of adding Li-TFSI to hole conducting molecular thin films of 2,2',7,7'-tetrakis(N,N'-di-p-methoxyphenylamine)-9,9'-spirobifluorene (spiro-OMeTAD). The work shows that a procedure of mixing a Li-TFSI solution into a spiro-OMeTAD solution, and subsequent spin-coating this mixture into a solid thin film causes the Fermi level of the molecular film to move closer to the HOMO level. Hence, adding the Li-TFSI gives similar effects to spiro-OMeTAD as a p-dopant. Specific effects from doping on the valence levels were also characterized. Absorbance measurements also showed that the spiro-OMeTAD film was partially oxidized when Li-TFSI was added before spin-coating. By varying the photon energy in the photoelectron spectroscopy measurements, the probe depth varies between being surface sensitive (<1 nm) and bulk sensitive (inelastic mean free path >= 10 nm). This property was used to follow differences in the composition at different depth of the spiro-OMeTAD/Li-TFSI film. It could be concluded that there was a concentration gradient in the molecular film and that the concentration of Li-TFSI was dominating at the interface between the spiro-OMeTAD/Li-TFSI film and vacuum.

    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:uu:diva-220596 (URN)10.1021/jp306433g (DOI)
    Available from: 2014-03-17 Created: 2014-03-17 Last updated: 2017-12-05Bibliographically approved
    8. Controlling energy level positions in hole conducting molecular films by additives
    Open this publication in new window or tab >>Controlling energy level positions in hole conducting molecular films by additives
    Show others...
    2018 (English)In: Journal of Electron Spectroscopy and Related Phenomena, ISSN 0368-2048, E-ISSN 1873-2526, Vol. 224, p. 100-106Article in journal (Refereed) Published
    Abstract [en]

    Hard X-ray photoelectron spectroscopy (HAXPES) has been used to study the bulk electronic structure of thin molecular films of the organic compounds 2,2',7,7'-tetrakis (N,N'-di-p-methoxyphenyl-amine)-9,9'-spiro-bifluorene (spiro-OMeTAD), 4-(diethylamino)-benzaldehyde-1,1-diphenyl-hydrazone (DEH) and poly(3-hexylthiophene) (P3HT). Molecular layers of these compounds are hole conducting, a property that for example has been used in different solar cell configurations. The function of such a device benefits from the inclusion of additives such as Li-TFSI, or dopants such as Co-complexes, into the molecular layer. Here we report on effects of adding Li-TFSI to DEH and P3HT as observed by photoelectron spectroscopy and we compare with results on the spiro-OMeTAD hole conductor. It can be concluded that the Li-salt causes a shift of the Fermi level in DEH and P3HT towards the HOMO resulting in a p-doping of the molecular material. Similar shifts of the Fermi level could also be observed when adding different Co(+III) complexes to the Spiro-OMeTAD hole conductor, indicating means for more controlled doping.

    Place, publisher, year, edition, pages
    Elsevier, 2018
    Keywords
    HAXPES, Mesoscopic solar cells, Spiro-OMeTAD, P3HT
    National Category
    Atom and Molecular Physics and Optics Physical Chemistry
    Identifiers
    urn:nbn:se:uu:diva-221447 (URN)10.1016/j.elspec.2017.03.009 (DOI)000428825400016 ()
    Funder
    Swedish Research Council, 2012-4721EU, FP7, Seventh Framework Programme, 226716Carl Tryggers foundation Swedish Foundation for Strategic Research Swedish Energy AgencyGöran Gustafsson Foundation for promotion of scientific research at Uppala University and Royal Institute of Technology
    Available from: 2014-03-31 Created: 2014-03-31 Last updated: 2018-06-04Bibliographically approved
    9. Reactive ZnO/Ti/ZnO interfaces studied by hard x-ray photoelectron spectroscopy
    Open this publication in new window or tab >>Reactive ZnO/Ti/ZnO interfaces studied by hard x-ray photoelectron spectroscopy
    Show others...
    2014 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 115, no 4, p. 043714-043714-7Article in journal (Refereed) Published
    Abstract [en]

    The chemistry and intermixing at buried interfaces in sputter deposited ZnO/Ti/ZnO thin layers were studied by hard x-ray photoelectron spectroscopy. The long mean free path of the photoelectrons allowed for detailed studies of the oxidation state, band bending effects, and intrinsic doping of the buried interfaces. Oxidation of the Ti layer was observed when ZnO was deposited on top. When Ti is deposited onto ZnO, Zn Auger peaks acquire a metallic character indicating a strong reduction of ZnO at the interface. Annealing of the stack at 200 °C results in further reduction of ZnO and oxidation of Ti. Above 300 °C, oxygen transport from the bulk of the ZnO layer takes place, leading to re-oxidation of ZnO at the interface and further oxidation of Ti layer. Heating above 500 °C leads to an intermixing of the layers and the formation of a ZnxTiOy compound.

    National Category
    Atom and Molecular Physics and Optics
    Identifiers
    urn:nbn:se:uu:diva-220603 (URN)10.1063/1.4854636 (DOI)000331210800061 ()
    Available from: 2014-03-17 Created: 2014-03-17 Last updated: 2017-12-05Bibliographically approved
  • 11.
    Lindblad, Rebecka
    et al.
    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.
    Park, Byung-wook
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Oscarsson, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Gorgoi, Mihaela
    Siegbahn, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Odelius, Michael
    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.
    Electronic Structure of TiO2/CH3NH3PbI3 Perovskite Solar Cell Interfaces2014In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 5, no 4, p. 648-653Article in journal (Refereed)
    Abstract [en]

    The electronic structure and chemical composition of efficient CH3NH3PbI3 perovskite solar cell materials deposited onto mesoporous TiO2 were studied using photoelectron spectroscopy with hard X-rays. With this technique, it is possible to directly measure the occupied energy levels of the perovskite as well as the TiO2 buried beneath and thereby determine the energy level matching of the interface. The measurements of the valence levels were in good agreement with simulated density of states, and the investigation gives information on the character of the valence levels. We also show that two different deposition techniques give results indicating similar electronic structures.

  • 12.
    Lindblad, Rebecka
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Cappel, Ute
    O'Mahony, Flannan
    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.
    Haque, Saif A.
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Energy level alignment in TiO2/metal sulfide/polymer interfaces for solar cell applications2014In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 16, no 32, p. 17099-17107Article in journal (Refereed)
    Abstract [en]

    Semiconductor sensitized solar cell interfaces have been studied with photoelectron spectroscopy to understand the interfacial electronic structures. In particular, the experimental energy level alignment has been determined for complete TiO2/metal sulfide/polymer interfaces. For the metal sulfides CdS, Sb2S3 and Bi2S3 deposited from single source metal xanthate precursors, it was shown that both driving forces for electron injection into TiO2 and hole transfer to the polymer decrease for narrower bandgaps. The energy level alignment results were used in the discussion of the function of solar cells with the same metal sulfides as light absorbers. For example Sb2S3 showed the most favourable energy level alignment with 0.3 eV driving force for electron injection and 0.4 eV driving force for hole transfer and also the most efficient solar cells due to high photocurrent generation. The energy level alignment of the TiO2/Bi2S3 interface on the other hand showed no driving force for electron injection to TiO2, and the performance of the corresponding solar cell was very low.

  • 13.
    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.

  • 14.
    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.
    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.
    Odelius, Michael
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    The electronic structure of CH3NH3PbX3 perovskites; the dependence on the halide moeityManuscript (preprint) (Other academic)
  • 15.
    Lindblad, Rebecka
    et al.
    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.
    Fredin, Kristofer
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Eriksson, Susanna K.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    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.
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Controlling energy level positions in hole conducting molecular films by additives2018In: Journal of Electron Spectroscopy and Related Phenomena, ISSN 0368-2048, E-ISSN 1873-2526, Vol. 224, p. 100-106Article in journal (Refereed)
    Abstract [en]

    Hard X-ray photoelectron spectroscopy (HAXPES) has been used to study the bulk electronic structure of thin molecular films of the organic compounds 2,2',7,7'-tetrakis (N,N'-di-p-methoxyphenyl-amine)-9,9'-spiro-bifluorene (spiro-OMeTAD), 4-(diethylamino)-benzaldehyde-1,1-diphenyl-hydrazone (DEH) and poly(3-hexylthiophene) (P3HT). Molecular layers of these compounds are hole conducting, a property that for example has been used in different solar cell configurations. The function of such a device benefits from the inclusion of additives such as Li-TFSI, or dopants such as Co-complexes, into the molecular layer. Here we report on effects of adding Li-TFSI to DEH and P3HT as observed by photoelectron spectroscopy and we compare with results on the spiro-OMeTAD hole conductor. It can be concluded that the Li-salt causes a shift of the Fermi level in DEH and P3HT towards the HOMO resulting in a p-doping of the molecular material. Similar shifts of the Fermi level could also be observed when adding different Co(+III) complexes to the Spiro-OMeTAD hole conductor, indicating means for more controlled doping.

  • 16.
    Malmgren, Sara
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Ciosek, Katarzyna
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Lindblad, Rebecka
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Plogmaker, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Kühn, Julius
    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.
    Edström, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Hahlin, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Consequences of Air Exposure on the Lithiated Graphite SEI2013In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 105, p. 83-91Article in journal (Refereed)
    Abstract [en]

    In the present work, consequences of air exposure on the surface composition of one of the most reactive lithium-ion battery components, the lithiated graphite, was investigated using 280–835 eV soft X-ray photoelectron spectroscopy (SOXPES) as well as 1486.7 eV X-ray photoelectron spectroscopy (XPS) (∼2 and ∼10 nm probing depth, respectively). Different depth regions of the solid electrolyte interphase (SEI) of graphite cycled vs. LiFePO4 were thereby examined. Furthermore, the air sensitivity of samples subject to four different combinations of pre-treatments (washed/unwashed and exposed to air before or after vacuum treatment) was explored. The samples showed important changes after exposure to air, which were found to be largely dependent on sample pre-treatment. Changes after exposure of unwashed samples exposed before vacuum treatment were attributed to reactions involving volatile species. On washed, air exposed samples, as well as unwashed samples exposed after vacuum treatment, effects attributed to lithium hydroxide formation in the innermost SEI were observed and suggested to be associated with partial delithiation of the surface region of the lithiated graphite electrode. Moreover, effects that can be attributed to LiPF6 decomposition were observed. However, these effects were less pronounced than those attributed to reactions involving solvent species and the lithiated graphite.

  • 17.
    Malmgren, Sara
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Ciosek, Katarzyna
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Lindblad, Rebecka
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Plogmaker, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Kühn, Julius
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    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.
    Hahlin, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Consequences of air exposure on the lithiated graphite SEI2013In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 105, p. 83-91Article in journal (Refereed)
    Abstract [en]

    In the present work, consequences of air exposure on the surface composition of one of the most reactive lithium-ion battery components, the lithiated graphite, was investigated using 280-835 eV soft X-ray photoelectron spectroscopy (SOXPES) as well as 1486.7 eV X-ray photoelectron spectroscopy (XPS) (similar to 2 and similar to 10 nm probing depth, respectively). Different depth regions of the solid electrolyte interphase (SEI) of graphite cycled vs. LiFePO4 were thereby examined. Furthermore, the air sensitivity of samples subject to four different combinations of pre-treatments (washed/unwashed and exposed to air before or after vacuum treatment) was explored. The samples showed important changes after exposure to air, which were found to be largely dependent on sample pre-treatment. Changes after exposure of unwashed samples exposed before vacuum treatment were attributed to reactions involving volatile species. On washed, air exposed samples, as well as unwashed samples exposed after vacuum treatment, effects attributed to lithium hydroxide formation in the innermost SEI were observed and suggested to be associated with partial delithiation of the surface region of the lithiated graphite electrode. Moreover, effects that can be attributed to LiPF6 decomposition were observed. However, these effects were less pronounced than those attributed to reactions involving solvent species and the lithiated graphite. 

  • 18. O'Mahony, Flannan T. F.
    et al.
    Cappel, Ute B.
    Tokmoldin, Nurlan
    Lutz, Thierry
    Lindblad, Rebecka
    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.
    Haque, Saif A.
    Low-Temperature Solution Processing of Mesoporous Metal-Sulfide Semiconductors as Light-Harvesting Photoanodes2013In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 52, no 46, p. 12047-12051Article in journal (Refereed)
  • 19.
    Oscarsson, Johan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Eriksson K., Susanna
    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.
    Johansson, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Eriksson, Anna I. K.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    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.
    Interface Structure Effects upon Co-Adsorption of Black Dye and D35 on TiO2Manuscript (preprint) (Other academic)
  • 20.
    Oscarsson, Johan
    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.
    Johansson, Erik M. J.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Eriksson, Susanna K.
    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.
    Eriksson, Anna I. K.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Zia, Azhar
    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.
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Coadsorption of Dye Molecules at TiO2 Surfaces: A Photoelectron Spectroscopy Study2016In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 120, no 23, p. 12484-12494Article in journal (Refereed)
    Abstract [en]

    The effects of coadsorbing the amphiphilic ruthenium-based dye Z907 (cis-bis(isothiocyanato)(2,20-bipyridy1-4,40-dicarboxylato)(4,40-dinony1-20-bipyridy1)-ruthenium(II)) with the coadsorbent DPA (n-decylphosphonic acid) and with the organic dye D35 ((E)-3-(5-(4-(bis(2',4'-dibutoxybiphenyl-4-yl)amino)phenyl)thiophen-2-yl)-2-cyanoacrylic acid) on mesoporous TiO2 were investigated using photoelectron spectroscopy (PES). Z907 is expected to adsorb to the TiO2 surface via the carboxylic acid groups. However, Z907 also shows signs of interacting with the TiO2 via the sulfur of the thiocyanate groups, and this interaction is affected by both the addition of DPA and D35. DPA, when added, exchanges with Z907 at the TiO2 surface, and each Z907 is replaced by six DPA molecules, but it does not affect the energy level alignment between Z907 and TiO2 substantially. Adding D35 to Z907 induces changes in the adsorption configuration of Z907 by the means of suppressing the interaction of the thiocyanate ligands and the TiO2 surface. The HOMO level of Z907 is shifted by the addition of D35. Coadsorbing Z907 with D35 thus gives changes at a molecular level, meaning that this is an example of collaborative sensitization.

  • 21.
    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.

  • 22.
    Scholin, Rebecka
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Karlsson, Martin H.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Eriksson, Susanna K.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    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.
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Energy Level Shifts in Spiro-OMeTAD Molecular Thin Films When Adding Li-TFSI2012In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 116, no 50, p. 26300-26305Article in journal (Refereed)
    Abstract [en]

    Hard X-ray photoelectron spectroscopy (HAXPES) has been used to study the effects of adding Li-TFSI to hole conducting molecular thin films of 2,2',7,7'-tetrakis(N,N'-di-p-methoxyphenylamine)-9,9'-spirobifluorene (spiro-OMeTAD). The work shows that a procedure of mixing a Li-TFSI solution into a spiro-OMeTAD solution, and subsequent spin-coating this mixture into a solid thin film causes the Fermi level of the molecular film to move closer to the HOMO level. Hence, adding the Li-TFSI gives similar effects to spiro-OMeTAD as a p-dopant. Specific effects from doping on the valence levels were also characterized. Absorbance measurements also showed that the spiro-OMeTAD film was partially oxidized when Li-TFSI was added before spin-coating. By varying the photon energy in the photoelectron spectroscopy measurements, the probe depth varies between being surface sensitive (<1 nm) and bulk sensitive (inelastic mean free path >= 10 nm). This property was used to follow differences in the composition at different depth of the spiro-OMeTAD/Li-TFSI film. It could be concluded that there was a concentration gradient in the molecular film and that the concentration of Li-TFSI was dominating at the interface between the spiro-OMeTAD/Li-TFSI film and vacuum.

  • 23.
    Schölin, Rebecka
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Quintana, Maria
    Johansson, Erik M. J.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Hahlin, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Marinado, Tannia
    Hagfeldt, Anders
    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, Surface and Interface Science.
    Preventing Dye Aggregation on ZnO by Adding Water in the Dye-Sensitization Process2011In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 115, no 39, p. 19274-19279Article in journal (Refereed)
    Abstract [en]

    ZnO based dye-sensitized solar cells have been studied using N719 and Z-907 as sensitizing dyes, with and without including water to the dye solution. The solar cells have been characterized with photoelectric measurements and the interface between the dye and the ZnO surface has been studied using photoelectron spectroscopy. It was shown that water in the dye solution greatly reduces surface dye aggregation and thereby enhances the solar cell performance for N719. For Z-907 where no sign of dye aggregation could be found, the presence of water had minor effect on the surface structure and solar cell performance.

  • 24.
    Sundberg, Jill
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Lindblad, Rebecka
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Gorgoi, Mihaela
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Lindblad, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Understanding the effects of sputter damage in W–S thin films by HAXPES2014In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 305, p. 203-213Article in journal (Refereed)
    Abstract [en]

    WS2 is an excellent solid lubricant in dry conditions, and can be applied as thin films. The analysis of WS2 and WS2-based films by x-ray photoelectron spectroscopy (XPS) can be challenging, due to contaminationand oxidized material on the surface. The investigations have traditionally therefore included sputter etching by ion bombardment, which however leads to changes of the remaining material. In this study, hard x-ray photoelectron spectroscopy (HAXPES) has been used to study W–S films deposited bymagnetron sputtering. High-resolution reference measurements for crystalline WS2 and metallic W are also presented. The W–S films were analyzed before and after sputter cleaning by Ar+ ion bombardment, using photon energies of 3 and 6 keV. The as-deposited films were found to consist mainly of a WSx phase,similar to WS2 but with a broader range of chemical states. It is shown that ion bombardment of the surface not only removes the outermost oxidized material, but also leads to preferential sputtering of sulfur and the formation of metallic tungsten. The results are of strong interest for the analysis of WS2-based materials, as they demonstrate that spectra from sputter-cleaned films include effects of sputter damage,and may not be representative of the original sample.

  • 25.
    Tian, Haining
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Oscarsson, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Gabrielsson, Erik
    KTH, Stockholm.
    Eriksson, Susanna K.
    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.
    Xu, Bo
    Hao, Yan
    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.
    Johansson, Erik M. J.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Gardner, James M.
    Hagfeldt, Anders
    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.
    Sun, Licheng
    KTH, Stockholm.
    Enhancement of p-Type Dye-Sensitized Solar Cell Performance by Supramolecular Assembly of Electron Donor and Acceptor2014In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 4, p. 4282-Article in journal (Refereed)
    Abstract [en]

    Supramolecular interactions based on porphyrin and fullerene derivatives were successfully adopted to improve the photovoltaic performance of p-type dye-sensitized solar cells (DSCs). Photoelectron spectroscopy (PES) measurements suggest a change in binding configuration of ZnTCPP after co-sensitization with C60PPy, which could be ascribed to supramolecular interaction between ZnTCPP and C60PPy. The performance of the ZnTCPP/C60PPy-based p-type DSC has been increased by a factor of 4 in comparison with the DSC with the ZnTCPP alone. At 560 nm, the IPCE value of DSCs based on ZnTCPP/C60PPy was a factor of 10 greater than that generated by ZnTCPP-based DSCs. The influence of different electrolytes on charge extraction and electron lifetime was investigated and showed that the enhanced V-oc from the Co2+/(3+)(dtbp)(3)-based device is due to the positive E-F shift of NiO.

  • 26.
    Yang, Lei
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry. Xian Univ Architecture & Technol, Sch Environm & Municipal Engn, Xian 710055, Shaanxi, Peoples R China.
    Schölin, Rebecka
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Gabrielsson, Erik
    Royal Inst Technol, Sch Chem Sci & Engn, Organ Chem, S-11428 Stockholm, Sweden.
    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.
    Sun, Licheng
    Xian Univ Architecture & Technol, Sch Environm & Municipal Engn, Xian 710055, Shaanxi, Peoples R China.
    Hagfeldt, Anders
    Swiss Fed Inst Technol, Dept Chem & Chem Engn, Lab Photomol Sci, Stn 6, CH-1015 Lausanne, Switzerland.
    Edvinsson, Tomas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Johansson, Erik M. J.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Experimental and Theoretical Investigation of the Function of 4-tert-Butyl Pyridine for Interface Energy Level Adjustment in Efficient Solid-State Dye-Sensitized Solar Cells2018In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 10, no 14, p. 11572-11579Article in journal (Refereed)
    Abstract [en]

    4-tert-Butylpyridine (t-BP) is commonly used in solid state dye-sensitized solar cells (ssDSSCs) to increase the photovoltaic performance. In this report, the mechanism how t-BP functions as a favorable additive is investigated comprehensively. ssDSSCs were prepared with different concentrations of t-BP, and a clear increase in efficiency was observed up to a maximum concentration and for higher concentrations the efficiency thereafter decreases. The energy level alignment in the complete devices was measured using hard X-ray photoelectron spectroscopy (HAXPES). The results show that the energy levels of titanium dioxide are shifted further away from the energy levels of spiro-OMeTAD as the t-BP concentration is increased. This explains the higher photovoltage obtained in the devices with higher t-BP concentration. In addition, the electron lifetime was measured for the devices and the electron lifetime was increased when adding t-BP, which can be explained by the recombination blocking effect at the surface of TiO2. The results from the HAXPES measurements agree with those obtained from density functional theory calculations and give an understanding of the mechanism for the improvement, which is an important step for the future development of solar cells including t-BP.

1 - 26 of 26
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