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  • 51.
    Ellis, Hanna
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Schmidt, Ina
    Carl von Ossietzky Univ Oldenburg, Inst Chem, Ctr Interface Sci, Fac Math & Nat Sci, D-26111 Oldenburg, Germany..
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry. Ecole Polytech Fed Lausanne, Inst Chem Sci & Engn, Lab Photomol Sci, EPFL FSB ISIC LSPM, CH-1015 Lausanne, Switzerland.;King Abdulaziz Univ, Ctr Excellence Adv Mat Res, Jeddah 21589, Saudi Arabia..
    Wittstock, Gunther
    Carl von Ossietzky Univ Oldenburg, Inst Chem, Ctr Interface Sci, Fac Math & Nat Sci, D-26111 Oldenburg, Germany..
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry. Uppsala Univ, Dept Chem, Ctr Mol Devices, Phys Chem,Angstrom Lab, SE-75120 Uppsala, Sweden..
    Influence of Dye Architecture of Triphenylamine Based Organic Dyes on the Kinetics in Dye-Sensitized Solar Cells2015In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 119, no 38, p. 21775-21783Article in journal (Refereed)
    Abstract [en]

    The impact of the dye architecture on the kinetics in the dyesensitized solar cell (DSC) was investigated for two structurally similar organic dyes, adsorbed adsorbed to a mesoporous TiO2 film. Differences in the HOMO and LUMO levels of the triphenylamine dyes D35 and D45 were negligible, indicating that the changes in kinetics of the electron transfer processes in the solar cells can be attributed to structural differences of the organic dyes. The electron transfer kinetics of various processes was investigated by scanning electrochemical microscopy (SECM), transient absorption spectroscopy (TAS), and impedance spectroscopy (IS). SECM was used for the first time to determine the rate constants of the regeneration (reduction) of a photooiddized organic dye by a oneelectron cobalt mediator. Both TAS and IS measurements showed differences in recombination of electrons in TiO2, with oxidized D35 and D45. D45 with its shorter dimethoxyphenyl units yielded faster recombination and regeneration than D35, as measured by SECM and TAS. The results of this study show that small details in the dye structure significantly affect the kinetics of organic triphenylamine dye based dye-sensitized solar cells.

  • 52.
    Ellis, Hanna
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Vlachopoulos, Nick
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Häggman, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Perruchot, Christian
    Jouini, Mohamed
    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.
    PEDOT counter electrodes for dye-sensitized solar cells prepared by aqueous micellar electrodeposition2013In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 107, p. 45-51Article in journal (Refereed)
    Abstract [en]

    Electropolymerization of 3,4-ethylenedioxythiophene (EDOT) was performed in an aqueous micellar solution onto conducting glass and conducting flexible plastic substrates using a simple, scalable process. The background electrolyte in the process consisted merely of a micellar aqueous sodium dodecyl sulfate (SDS) solution. Electrodeposition of poly(3,4-ethylenedioxythiophene) (PEDOT) was conducted at constant current, resulting in homogeneous films, even on large sized conducting glass and plastic substrates (9 cm x 9 cm). The use of water as electrolyte, application on large substrates and applicability on flexible plastic substrates demonstrates the feasibility of this method for upscaling and use in industrial fabrication of DSCs. DSCs were assembled using three different PEDOT thicknesses on conducting glass as counter electrodes and a comparison was made with thermally platinized conducting glass counter electrodes. In cobalt tris(bipyridine)-based electrolyte, the catalytic performance of the PEDOT counter electrodes was significantly higher than that of platinized counter electrodes. DSCs with PEDOT counter electrodes gave higher efficiencies due to higher fill factors and a lower charge transfer resistance. The low charge transfer resistance and good catalytic performance of the PEDOT counter electrodes can be related to its mesoporous morphology resembling crumpled sheets of paper. 

  • 53.
    Eriksson, Anna
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Bergquist, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry.
    Edwards, Katarina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Malmström, David
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry.
    Agmo Hernández, Víctor
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Optimized Protocol for On-Target Phosphopeptide Enrichment Prior to Matrix-Assisted Laser Desorption-Ionization Mass Spectrometry Using Mesoporous Titanium Dioxide2010In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 82, no 11, p. 4577-4583Article in journal (Refereed)
    Abstract [en]

    A novel on-target phosphopeptide enrichment method is presented that allows specific enrichment and direct analysis by matrix assisted laser desorption-ionization mass spectrometry (MALDI-MS) of phosphorylated peptides. Spots consisting of a thin film of anatase titanium dioxide are sintered onto a conductive glass surface. Enrichment and analysis can be performed on the modified target with minimal sample handling. The protocol leads to an enrichment efficiency that is superior to what has been reported before for similar methods. The method was tested using beta-casein as a model phosphorylated protein as well as with a custom peptide mixed with its phosphorylated form. A very low detection limit, a significantly improved phosphoprofiling capability, and a simple experimental approach provide a powerful tool for the enrichment, detection, and analysis of phosphopeptides.

  • 54.
    Eriksson, Anna
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Bergquist, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry.
    Edwards, Katarina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Malmström, David
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry.
    Hernandez, Victor Agmo
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Mesoporous TiO2-Based Experimental Layout for On-Target Enrichment and Separation of Multi- and Monophosphorylated Peptides Prior to Analysis with Matrix-Assisted Laser Desorption-Ionization Mass Spectrometry2011In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 83, no 3, p. 761-766Article in journal (Refereed)
    Abstract [en]

    A simple method for on-target enrichment and subsequent separation and analysis of phosphorylated peptides is presented. The tryptic digest of a phosphorylated protein, in this case beta-casein, is loaded onto a spot on a thin stripe made of mesoporous TiO2 sintered onto a conductive glass surface. After washing with a salicylic buffer in order to remove the nonphosphorylated peptides, the stripe is placed in an elution chamber containing a phosphate solution. In a way analogous to thin layer chromatography (TLC), the phosphate solution acts as an eluent, clearly separating multi- and monophosphorylated peptides. By performing matrix-assisted laser desorption-ionization mass spectrometry (MALDI-MS) along the stripe, the detection of all phosphorylated peptides present in the digest is facilitated, as they are isolated from each other. The method was also tested on commercial drinking milk, achieving successful separation between multi- and monophosphorylated peptides, as well as a detection limit in the femtomole range. As the enrichment, separation, and analysis take place in the same substrate, sample handling and risk of contamination and sample loss is minimized. The results obtained suggest that the method, once optimized, may successfully provide a complete phosphoproteome.

  • 55.
    Eriksson, Anna
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Edwards, Katarina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Agmo Hernández, Víctor
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Physicochemical Characterization of Phosphopeptide/Titanium Dioxide Interactions Employing the Quartz Crystal Microbalance Technique2013In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 117, no 7, p. 2019-2025Article in journal (Refereed)
    Abstract [en]

    The rapidly growing field of phosphoproteomics has led to a strong demand for procedures enabling fast and reliable isolation and enrichment of phosphorylated proteins and peptides. During the past decade, several novel phosphopeptide enrichment methods based on the affinity of phosphoryl groups for titanium dioxide (TiO2) have been developed and tested. The ultimate goal of obtaining comprehensive phosphoproteomes has, however, been found difficult to achieve and the obtained results often vary, dependent on the enrichment method and protocol used. In the present study, the physical chemistry of the phosphopeptide binding to TiO2 is investigated by means of measurements using a quartz crystal microbalance with dissipation monitoring (QCM-D). Special emphasis is put on the effect of the degree of phosphorylation of the phosphopeptide, the impact of the primary amino acid structure, and the role of electrostatic interactions. The results show that, in general, adsorption of phosphopeptides follows the Langmuir model and that the affinity for the TiO2 surface increases in a nonlinear fashion with increasing degree of phosphorylation. An exception was detected, however, where positive cooperativity between the peptides existed and the Langmuir model no longer applied. The source behind the cooperativity could be traced back to the primary amino acid structure and, more specifically, the presence of positively charged amino acids in positions that enable electrostatic interaction with phosphoryl groups on neighboring peptides. Regardless of the net peptide charge, the TiO2–phosphopeptide interaction was for all phosphopeptides investigated found to be mainly of electrostatic origin. This study highlights and explains some of the most common problems with the TiO2-based enrichment methods used today.

  • 56.
    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.

  • 57. Eriksson, Susanna K.
    et al.
    Hahlin, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Axnanda, Stephanus
    Univ Calif Berkeley, Lawrence Berkeley Natl Lab, Adv Light Source, One Synchrotron Rd, Berkeley, CA 94720 USA..
    Crumlin, Ethan
    Univ Calif Berkeley, Lawrence Berkeley Natl Lab, Adv Light Source, One Synchrotron Rd, Berkeley, CA 94720 USA..
    Wilks, Regan
    Helmholtz Zentrum Berlin Mat & Energie GmbH, Renewable Energy, Hahn Meitner Pl 1, D-14109 Berlin, Germany.;Helmholtz Zentrum Berlin Mat & Energie GmbH, Energy Mat In Situ Lab EMIL, Albert Einstein Str 15, D-12489 Berlin, Germany..
    Odelius, Michael
    Stockholm Univ, AlbaNova Univ Ctr, Dept Phys, S-10691 Stockholm, Sweden..
    Eriksson, Anna I. K.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Liu, Zhi
    Univ Calif Berkeley, Lawrence Berkeley Natl Lab, Adv Light Source, One Synchrotron Rd, Berkeley, CA 94720 USA..
    Ahlund, John
    VG Scienta AB, Box 15120, S-75015 Uppsala, Sweden..
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Starr, David E.
    Helmholtz Zentrum Berlin Mat & Energie GmbH, Inst Solar Fuels, Hahn Meitner Pl 1, D-14109 Berlin, Germany..
    Baer, Marcus
    Helmholtz Zentrum Berlin Mat & Energie GmbH, Renewable Energy, Hahn Meitner Pl 1, D-14109 Berlin, Germany.;Helmholtz Zentrum Berlin Mat & Energie GmbH, Energy Mat In Situ Lab EMIL, Albert Einstein Str 15, D-12489 Berlin, Germany.;Brandenburg Tech Univ Cottbus Senftenberg, Inst Chem & Phys, Pl Deutsch Einheit 1, D-03046 Cottbus, Germany..
    Rensmo, Håkan
    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.
    In-Situ Probing of H2O Effects on a Ru-Complex Adsorbed on TiO2 Using Ambient Pressure Photoelectron Spectroscopy2016In: Topics in catalysis, ISSN 1022-5528, E-ISSN 1572-9028, Vol. 59, no 5-7, p. 583-590Article in journal (Refereed)
    Abstract [en]

    Dye-sensitized interfaces in photocatalytic and solar cells systems are significantly affected by the choice of electrolyte solvent. In the present work, the interface between the hydrophobic Ru-complex Z907, a commonly used dye in molecular solar cells, and TiO2 was investigated with ambient pressure photoelectron spectroscopy (AP-PES) to study the effect of water atmosphere on the chemical and electronic structure of the dye/TiO2 interface. Both laboratory-based Al K alpha as well as synchrotron-based ambient pressure measurements using hard X-ray (AP-HAXPES) were used. AP-HAXPES data were collected at pressures of up to 25 mbar (i.e., the vapor pressure of water at room temperature) showing the presence of an adsorbed water overlayer on the sample surface. Adopting a quantitative AP-HAXPES analysis methodology indicates a stable stoichiometry in the presence of the water atmosphere. However, solvation effects due to the presence of water were observed both in the valence band region and for the S 1s core level and the results were compared with DFT calculations of the dye-water complex.

  • 58.
    Eriksson, Susanna K
    et al.
    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, Molecular and Condensed Matter Physics.
    Kahk, Juhan Matthias
    Villar-Garcia, Ignacio J
    Webb, Matthew J
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Physical Organic Chemistry.
    Grennberg, Helena
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Physical Organic Chemistry.
    Yakimova, Rositza
    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.
    Hagfeldt, Anders
    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.
    Edwards, Mårten O M
    Karlsson, Patrik G
    Backlund, Klas
    Ahlund, John
    Payne, David J
    A versatile photoelectron spectrometer for pressures up to 30 mbar2014In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 85, no 7, p. 075119-Article in journal (Refereed)
    Abstract [en]

    High-pressure photoelectron spectroscopy is a rapidly developing technique with applications in a wide range of fields ranging from fundamental surface science and catalysis to energy materials, environmental science, and biology. At present the majority of the high-pressure photoelectron spectrometers are situated at synchrotron end stations, but recently a small number of laboratory-based setups have also emerged. In this paper we discuss the design and performance of a new laboratory based high pressure photoelectron spectrometer equipped with an Al Kα X-ray anode and a hemispherical electron energy analyzer combined with a differentially pumped electrostatic lens. The instrument is demonstrated to be capable of measuring core level spectra at pressures up to 30 mbar. Moreover, valence band spectra of a silver sample as well as a carbon-coated surface (graphene) recorded under a 2 mbar nitrogen atmosphere are presented, demonstrating the versatility of this laboratory-based spectrometer.

  • 59.
    Eriksson, Susanna K.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Josefsson, Ida
    Ottosson, Niklas
    Ohrwall, Gunnar
    Bjorneholm, Olle
    Siegbahn, Hans
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Odelius, Michael
    Rensmo, Hakan
    Solvent Dependence of the Electronic Structure of I- and I-3(-)2014In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 118, no 11, p. 3164-3174Article in journal (Refereed)
    Abstract [en]

    We present synchrotron-based I4d photoelectron spectroscopy experiments of solutions from LiI and LiI3 in water, ethanol, and acetonitrile. The experimentally determined solvent-induced binding energy shifts (SIBES) for the monatomic I- anion are compared to predictions from simple Born theory, PCM calculations, as well as multiconfigurational quantum chemical spectral calculations from geometries obtained through molecular dynamics of solvated clusters. We show that the SIBES for I- explicitly depend on the details of the hydrogen bonding configurations of the solvent to the I- and that static continuum models such as the Born model cannot capture the trends in the SIBES observed both in experiments and in higher-level calculations. To extend the discussion to more complex polyatomic anions, we also performed experiments on I-3(-) and I-/I-3(-) mixtures in different solvents and the results are analyzed in the perspective of SIBES. The experimental SIBES values indicate that the solvation effects even for such similar anions as I- and I-3(-) can be rather different in nature.

  • 60. Fabregat-Santiago, Francisco
    et al.
    Bisquert, Juan
    Garcia-Belmonte, Germa
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry I.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry I.
    Influence of electrolyte in transport and recombination in dye-sensitized solar cells studied by impedance spectroscopy2005In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 87, no 1-4, p. 117-131Article in journal (Refereed)
    Abstract [en]

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

  • 61. Fan, Jiandong
    et al.
    Fabrega, Cristian
    Zamani, Reza R.
    Hao, Yan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Parra, Andres
    Andreu, Teresa
    Arbiol, Jordi
    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.
    Ramon Morante, Joan
    Cabot, Andreu
    Enhanced Photovoltaic Performance of Nanowire Dye-Sensitized Solar Cells Based on Coaxial TiO2@TiO Heterostructures with a Cobalt(II/III) Redox Electrolyte2013In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 5, no 20, p. 9872-9877Article in journal (Refereed)
    Abstract [en]

    The growth of a TiO shell at the surface of TiO2 nanowires (NWs) allowed us to improve the power conversion efficiency of NW-based dye-sensitized solar cells (DSCs) by a factor 2.5. TiO2@TiO core-shell NWs were obtained by a two-step process: First, rutile-phase TiO2 NWs were hydrothermally grown. Second, a hongquiite-phase TiO shell was electrochemically deposited at the surface of the TiO2 NWs. Bare TiO2 and heterojunction TiO2@TiO NW-based DSCs were obtained using a cobalt(II/III) redox electrolyte and LEG4 as the dye. With this electrolyte/dye combination, DSCs with outstanding V-oc values above 900 mV were systematically obtained. While TiO2@TiO NW-based DSCs had slightly lower V-oc values than bare TiO2 NW-based DSCs, they provided 3-fold higher photocurrents, overall reaching 2.5-fold higher power conversion efficiencies. The higher photocurrents were associated with the larger surface roughness and an enhanced charge-carrier separation/transfer at the NW/dye interface.

  • 62. Fan, Jiandong
    et al.
    Hao, Yan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Cabot, Andreu
    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.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Cobalt(II/III) Redox Electrolyte in ZnO Nanowire-Based Dye-Sensitized Solar Cells2013In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 5, no 6, p. 1902-1906Article in journal (Refereed)
    Abstract [en]

    In this work, we explore the use of cobalt complex redox shuttles in dye sensitized solar cells (DSCs) based on ZnO nanowires (NWs). Arrays of vertically aligned ZnO NWs produced by a low-cost hydrothermal method are used to fabricate DSCs with [Co(bpy)(3)](2+/3+) as electrolyte. A direct comparison of the performance of [Co(bpy)(3)](2+/3+)-based ZnO DSC with I-/I-3(-)-based ones demonstrates the higher suitability of the cobalt complex, both in terms of a larger open circuit voltage (V-OC) and a higher photocurrent. The [Co(bpy)(3)](2+/3+) electrolyte results in V-OC enhancements above 200 mV. This V-OC increase is associated to the better match between the cobalt complex redox potential and the oxidation potential of the dye. The incident photon-to-current efficiency (IPCE) enhancement is attributed to a less competitive visible light absorption of the cobalt redox couple. Thus the present study opens new opportunities to improve energy conversion efficiency in ZnO-based DSCs.

  • 63. Fan, Jiandong
    et al.
    Hao, Yan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Munuera, Carmen
    Garcia-Hernandez, Mar
    Gueell, Frank
    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.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Cabot, Andreu
    Influence of the Annealing Atmosphere on the Performance of ZnO Nanowire Dye-Sensitized Solar Cells2013In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 117, no 32, p. 16349-16356Article in journal (Refereed)
    Abstract [en]

    Postsynthesis thermal treatments are key to promote crystallinity and reduce the defect density in solution-processed nanomaterials. In particular, the annealing atmosphere strongly influences the functional properties of ZnO nanowires (NWs) and specifically their performance as photoanodes in dye-sensitized solar cells (DSCs). We prepared vertically aligned ZnO NWs by a low-cost, high-yield, and up-scalable hydrothermal method and studied the effect of the postannealing atmosphere on their optoelectronic properties and on their performance as electrodes in DSCs. When annealing ZnO NWs under argon, instead of air, significantly higher photoluminescence (PL) UV emission and relatively lower defects-related visible PL emission were obtained. At the same time, Ar-annealing rendered ZnO NWs with higher electrical conductivities, as observed from single NW measurements using conductive-atomic force microscopy. Furthermore, DSCs based on ZnO NWs annealed in argon were characterized by 50% higher photocurrents than those obtained from air-annealed ZnO. As a result 30% efficiency increases were systematically obtained when using argon as the annealing atmosphere. These results are discussed within the framework of a multiple trapping model for transport and charge transfer, taking into account differences in the defect concentration introduced during the annealing.

  • 64.
    Feldt, Sandra
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Lohse, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    Kessler, Florian
    Mohammed, Nazeeruddin
    Institute of chemical science and engineering, Ecole Polytechnique Fédérale de Lausanne.
    Grätzel, Michael
    Institute of chemical science and engineering, Ecole Polytechnique Fédérale de Lausanne.
    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.
    Regeneration and Recombination kinetics in Cobalt Polypyridine based Dye-Sensitized Solar Cells, explained using Marcus theory2013In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 15, no 19, p. 7087-7097Article in journal (Refereed)
    Abstract [en]

    Regeneration and recombination kinetics was investigated for dye-sensitized solar cells (DSCs) using a series of different cobalt polypyridine redox couples, ranging in redox potential in between 0.34 and 1.20 V vs. NHE. Marcus theory was applied to explain the rate of electron transfer. The regeneration kinetics for a number of different dyes (L0, D35, Y123, Z907) by most of the cobalt redox shuttles investigated occurred in the Marcus normal region. The calculated reorganization energies for the regeneration reaction ranged between 0.59 and 0.69 eV for the different organic and organometallic dyes investigated. Under the experimental conditions employed, the regeneration efficiency decreased when cobalt complexes with a driving force for regeneration of 0.4 eV and less were employed. The regeneration efficiency was found to depend on the structure of the dye and the concentration of the redox couples. [Co(bpy-pz)2]2+, which has a driving force for regeneration of 0.25 eV for the triphenylamine based organic dye, D35, was found to regenerate 84 % of the dye molecules, when a high concentration of the cobalt complex was used. Recombination kinetics between electrons in TiO2 and cobalt (III) species in the electrolyte was also studied using steady state dark current measurements. This reaction occurred in the Marcus inverted region for most of the cobalt complexes, and recombination losses are thus not expected to be problematic for D35-sensitized DSCs employing cobalt complexes with high redox potentials. Recombination mediated by surface states was, however, found to significantly influence the result for the cobalt complexes with most positive redox potentials. The calculated system reorganization energies using Marcus theory from the regeneration kinetics and steady state current measurements were very similar, indicating that they are mostly determined by the cobalt mediator.

  • 65.
    Feldt, Sandra M.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Cappel, Ute B.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Johansson, Erik M. J.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Characterization of surface passivation by poly(methylsiloxane) for dye-sensitized solar cells employing the ferrocene redox couple.2010In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 114, no 23, p. 10551-10558Article in journal (Refereed)
    Abstract [en]

    One-electron outer-sphere redox couples, such as ferrocene/ferrocenium, are an interesting alternative to the iodide/triiodide redox couple that is normally employed in dye-sensitized solar cells (DSCs) because they should reduce the driving force needed to regenerate the dye. Unfortunately, one-electron redox couples also show enhanced recombination with photoinjected electrons, and methods to inhibit this recombination are needed for functioning DSCs. In this study, dye-sensitized titanium dioxide surfaces were passivated by a trichloromethylsilane reaction in order to decrease the fast recombination rates when using the ferrocene redox couple. The formation and binding of poly(methylsiloxane) on the dye-sensitized TiO2 surface was verified with infrared spectroscopy and photoelectron spectroscopy. Photoelectrochemical characterization of the silanization method showed that the treatment decreased the recombination rate of photoinjected electrons with ferrocenium and thereby improved the efficiency of the DSC. Transient absorption spectroscopy revealed, however, that the poly(methylsiloxane) coatings slowed down the regeneration of the oxidized dye by the ferrocene and prevented the regeneration of some of the dye molecules.

  • 66.
    Feldt, Sandra M.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Gibson, Elizabeth A.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Gabrielsson, Erik
    KTH, Organisk kemi.
    Sun, Licheng
    KTH, Organisk kemi.
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Design of organic dyes and cobalt polypyridine redox mediators for high-efficiency dye-sensitized solar cells2010In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 132, no 46, p. 16714-16724Article in journal (Refereed)
    Abstract [en]

    Dye-sensitized solar cells (DSCs) with cobalt-based mediators with efficiencies surpassing the record for DSCs with iodide-free electrolytes were developed by selecting a suitable combination of a cobalt polypyridine complex and an organic sensitizer. The effect of the steric properties of two triphenylamine-based organic sensitizers and a series of cobalt polypyridine redox mediators on the overall device performance in DSCs as well as on transport and recombination processes in these devices was compared. The recombination and mass-transport limitations that, previously, have been found to limit the performance of these mediators were avoided by matching the properties of the dye and the cobalt redox mediator. Organic dyes with higher extinction coefficients than the standard ruthenium sensitizers were employed in DSCs in combination with outer-sphere redox mediators, enabling thinner TiO2 films to be used. Recombination was reduced further by introducing insulating butoxyl chains on the dye rather than on the cobalt redox mediator, enabling redox couples with higher diffusion coefficients and more suitable redox potential to be used, simultaneously improving the photocurrent and photovoltage of the device. Optimization of DSCs sensitized with a triphenylamine-based organic dye in combination with tris(2,2'-bipyridyl)cobalt(II/III) yielded solar cells with overall conversion efficiencies of 6.7% and open-circuit potentials of more than 0.9 V under 1000 W m(-2) AM1.5 G illumination. Excellent performance was also found under low light intensity indoor conditions.

  • 67.
    Feldt, Sandra M.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Gibson, Elizabeth A.
    Wang, Gang
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Fabregat, Guillermo
    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.
    Carbon counter electrodes efficient catalysts for the reduction of Co(III) in cobalt mediated dye-sensitized solar cells2014In: Polyhedron, ISSN 0277-5387, E-ISSN 1873-3719, Vol. 82, p. 154-157Article in journal (Refereed)
    Abstract [en]

    The solar energy conversion efficiency of cobalt-based dye-sensitized solar cells using carbon materials as the catalyst was found similar or better than that of platinum. 

  • 68.
    Feldt, Sandra M.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Wang, Gang
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Effects of Driving Forces for Recombination and Regeneration on the Photovoltaic Performance of Dye-Sensitized Solar Cells using Cobalt Polypyridine Redox Couples2011In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 115, no 43, p. 21500-21507Article in journal (Refereed)
    Abstract [en]

    Dye-sensitized solar cells (DSCs) with open-circuit potentials above 1 V were obtained by employing the triphenylamine based organic dye D35 in combination with cobalt phenanthroline redox couples. A series of cobalt bipyridine and cobalt phenanthroline complexes with different redox potentials were investigated to examine the dependence of the driving force for recombination and dye regeneration on the photovoltaic performance. The photovoltage of the devices was found to increase and the photocurrent to decrease with increasing redox potential of the complexes. The halftime for regeneration of the oxidized dye by cobalt trisbipyrine was about 20 mu s, similar to that found for the iodide/triiodide redox couple, whereas regeneration kinetics became slower for cobalt complexes with less driving force for regeneration. A driving force for dye regeneration of 390 mV for cobalt(II/III) tris(5-chloro-1,10-phenanthroline) was found sufficient to regenerate more than 80% of the D35 dye molecules, resulting in a conversion of incident photons to electric current of above 80%. The photocurrent of the D35 sensitized DSCs using cobalt phenanthroline complexes decreased, however, with increasing Nernst potential of the redox couples, due to the increased recombination and the decreased regeneration rate constants.

  • 69.
    Figgemeier, Egbert
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Aranyos, Viviane
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Constable, E. C.
    Handel, R. W.
    Housecroft, C. E.
    Risinger, Christian
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Mukhtar, Emad
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Modification of electron transfer properties in photoelectrochemical solar cells by substituting {Ru(terpy)(2)}(2+) dyes with thiophene2004In: Inorganic Chemistry Communications, ISSN 1387-7003, E-ISSN 1879-0259, Vol. 7, no 1, p. 117-121Article in journal (Refereed)
    Abstract [en]

    A comparison of the properties of the 2-thienyl-substituted carboxyphenyl {RuII(terpy)2} dyes with their non-substituted analogues has enabled us to gain insight into the electronic properties that are prerequisite for efficient electron injection into the TiO2 conduction band in photoelectrochemical solar cells. Introducing the thienyl group has a profound effect upon the efficiency of photoinduced electron injection. This effect can be explained by a significant shift in the LUMO position from the terpy ligand anchored on the TiO2 surface towards the 2-thienyl substituted ligand, which is shown by means of electrochemistry and semiempirical calculations.

  • 70.
    Figgemeier, Egbert
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical Chemistry. Department of Physical and Analytical Chemistry, Physical Chemistry I.
    Hagfeldt, Anders
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical Chemistry. Department of Physical and Analytical Chemistry, Physical Chemistry I.
    Are dye-sensitized nano-structured solar cells stable? An overview of device testing and component analyses2004In: International Journal of Photoenergy, Vol. 6, no 3, p. 127-140Article in journal (Refereed)
  • 71.
    Fredin, Kristofer
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical Chemistry. Department of Physical and Analytical Chemistry, Physical Chemistry I.
    Nissfolk, Jarl
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical Chemistry. Department of Physical and Analytical Chemistry, Physical Chemistry I.
    Hagfeldt, Anders
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical Chemistry. Department of Physical and Analytical Chemistry, Physical Chemistry I.
    Brownian dynamics simulations of electrons and ions in mesoporous films2005In: Solar Energy Materials & Solar Cells, Vol. 86, no 2, p. 283-297Article in journal (Refereed)
  • 72.
    Fredin, Kristofer
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical Chemistry. Department of Physical and Analytical Chemistry, Physical Chemistry I.
    Nissfolk, Jarl
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical Chemistry. Department of Physical and Analytical Chemistry, Physical Chemistry I.
    Hagfeldt, Anders
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical Chemistry. Department of Physical and Analytical Chemistry, Physical Chemistry I.
    Brownian dynamics simulations of electrons and ions in mesoporous films2004In: Solar Energy Materials & Solar Cells, Vol. 86, no 2, p. 283-297Article in journal (Refereed)
  • 73.
    Freitag, Marina
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Daniel, Quentin
    KTH Royal Inst Technol, Sch Chem Sci & Engn, Dept Chem, S-10044 Stockholm, Sweden..
    Pazoki, Meysam
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Sveinbjörnsson, Kári
    Zhang, Jinbao
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Sun, Licheng
    KTH Royal Inst Technol, Sch Chem Sci & Engn, Dept 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..
    Hagfeldt, Anders
    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.
    High-efficiency dye-sensitized solar cells with molecular copper phenanthroline as solid hole conductor2015In: Energy & Environmental Science, ISSN 1754-5692, E-ISSN 1754-5706, Vol. 8, no 9, p. 2634-2637Article in journal (Refereed)
    Abstract [en]

    Copper phenanthroline complexes in the solid phase can act as efficient molecular hole transporting material (HTM) for hybrid solar cells. We prepared solid-state dye-sensitized solar cells with the organic dye LEG4 and bis(2,9-dimethyl-1,10-phenanthroline)copper(I/II) (Cu(dmp)(2)) and achieved power conversion efficiencies of more than 8% under 1000 W m(-2) AM1.5G illumination, with open-circuit potentials of more than 1.0 V. The successful application of a copper-complex based HTM paves the way for low-cost and efficient hybrid solar cells, as well as for other opto-electronic devices.

  • 74.
    Freitag, Marina
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry. Uppsala Univ, Dept Chem, Angstrom Lab, Box 523, SE-75120 Uppsala, Sweden.;Ecole Polytech Fed Lausanne, Inst Chem Sci & Engn, Lab Photomol Sci, CH-1015 Lausanne, Switzerland..
    Giordano, Fabrizio
    Ecole Polytech Fed Lausanne, Inst Chem Sci & Engn, Lab Photon & Interfaces, CH-1015 Lausanne, Switzerland..
    Yang, Wenxing
    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.
    Hao, Yan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Zietz, Burkhard
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Graetzel, Michael
    Ecole Polytech Fed Lausanne, Inst Chem Sci & Engn, Lab Photon & Interfaces, CH-1015 Lausanne, Switzerland..
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry. Ecole Polytech Fed Lausanne, Inst Chem Sci & Engn, Lab Photomol Sci, CH-1015 Lausanne, Switzerland..
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Copper Phenanthroline as a Fast and High-Performance Redox Mediator for Dye-Sensitized Solar Cells2016In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 120, no 18, p. 9595-9603Article in journal (Refereed)
    Abstract [en]

    The most commonly used redox mediators in dye-sensitized solar cells (DSCs), iodide/triiodide and cobalt trisbipyridine ([Co(bpy)(3)](2+/3+)), were successfully replaced by bis (2,9-dimethy1-1,10-phenanthroline) copp er (I/H) ([Cu(dmp)(2)](1+/2+)). The use of the copper complex based electrolyte led to an exceptionally high photovoltaic performance of 8.3% for LEG4-sensitized TiO2 solar cells, with a remarkably high open-circuit potential of above 1.0 V at 1000 W m(-2) under AM1.5G conditions. The copper complex based redox electrolyte has higher diffusion coefficients and is considerably faster in dye regeneration than comparable cobalt trisbipyridine based electrolytes. A driving force for dye regeneration of only 0.2 eV is sufficient to obtain unit yield, pointing to new possibilities for improvement in DSC efficiencies. The interaction of the excited dye with components of the electrolyte was monitored using steady-state emission measurements and time-correlated single-photon counting (TC-SPC). Our results indicate bimolecular reductive quenching of the excited LEG4 dye by the [Cu(dmp)(2)](2+) complex through a dynamic mechanism. Excited-state dye molecules can readily undergo bimolecular electron transfer with a suitable donor molecule. In DSCs this process can occur when the excited dye is unable to inject electrons into the TiO2. With a high electrolyte concentration the excited dye can be intercepted with an electron from the electrolyte resulting in the reduced state of the dye. Quenching of the reduced dye by the electrolyte competes with electron injection and results in a lower photocurrent. Quenching of excited LEG4 by complexes of [Cu(dmp)(2)](+), [Co(bpy)(3)](2+), and [Co(bpy)(3)](3+) followed a static mechanism, due ground-state dye-quencher binding. Inhibition of unwanted quenching processes by structural modifications may open ways to further increase the overall efficiency.

  • 75. Gabrielsson, Erik
    et al.
    Ellis, Hanna
    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.
    Tian, Haining
    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.
    Sun, Licheng
    Convergent/Divergent Synthesis of a Linker-Varied Series of Dyes for Dye-Sensitized Solar Cells Based on the D35 Donor2013In: Advanced Energy Materials, ISSN 1614-6840, Vol. 3, no 12, p. 1647-1656Article in journal (Refereed)
    Abstract [en]

    A series of four new dyes, based on the D35 type donor moiety with varied linker units, is synthesized using a facile convergent/divergent method, enabled by an improved synthesis of the D35 donor. The dyes are evaluated in dye sensitized solar cells with Co(II/III)(bpy)3-based electrolytes. By extending the linker fragment, higher photocurrents and solar energy conversion efficiencies are achieved. It is also found that the linker unit plays a crucial role in maintaining a high open-circuit photovoltage. Based on the photovoltaic performance it is concluded that the hexylthiophene unit is the most suitable for this purpose, as it allows further enhancement of the already high open-circuit voltage of D35 to 0.92 V. The best dye in this series reaches an efficiency of 6.8%.

  • 76. Gabrielsson, Erik
    et al.
    Tian, Haining
    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.
    Gao, Jiajia
    Chen, Hong
    Li, Fusheng
    Oscarsson, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Sun, Junliang
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Kloo, Lars
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Sun, Licheng
    Dipicolinic acid: a strong anchoring group with tunable redox and spectral behavior for stable dye-sensitized solar cells2015In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 51, no 18, p. 3858-3861Article in journal (Refereed)
    Abstract [en]

    Dipicolinic acidwas investigated as a new anchoring group for DSSCs. A pilot dye (PD2) bearing this new anchoring group was found to adsorb significantly stronger to TiO2 than its cyanoacrylic acid analogue. The electrolyte composition was found to have a strong effect on the photoelectrochemical properties of the adsorbed dye in the device, allowing the dye LUMO energy to be tuned by 0.5 eV. Using a pyridine-free electrolyte, panchromatic absorption of the dye on TiO2 extending to 900 nm has been achieved. Solar cells using PD2 and a Co(bpy)(3) based electrolyte showed unique stability under simulated sunlight and elevated temperatures.

  • 77.
    Gamstedt, Helene
    et al.
    KTH.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Kloo, Lars
    KTH.
    Photoelectrochemical studies of ionic liquid-containing solar cells sensitized with different polypyridyl-ruthenium complexes2009In: Polyhedron, ISSN 0277-5387, E-ISSN 1873-3719, Vol. 28, no 4, p. 757-762Article in journal (Refereed)
    Abstract [en]

    The efficiency of dye-sensitized nanocryst. solar cells contg. ionic liqs., composed of org. sulfonium or imidazolium iodides, or a std. org.-liq.-based electrolyte was studied, while using sensitizers based on different polypyridyl-ruthenium complexes. The dyes N-719, [cis-Ru(II)(H2dcbpy)2(NCS)2(TBA)2] and Z-907, [cis-Ru(II)(H2dcbpy)(dnbpy)(NCS)2, Z-907 having a more hydrophobic character, as well as a bidentate beta -diketonato complex, [(dcbpy)2Ru(acetylacetonate)]Cl-, was studied. Solar cells sensitized with the dye N-719 were more efficient than the Z-907 cells, for all electrolytes studied. Adding a co-adsorbent, the amphiphilic hexadecylmalonic acid (HDMA), to Z-907 solar cells contg. an org.-liq. electrolyte resulted in increased overall light-to-electricity conversion efficiencies, from 3.7% to 4.0%, (100 W m-2, AM 1.5). Possibly, this is caused by an insulating hydrophobic barrier formed to suppress unwanted electron losses. By applying TiO2 (P25) nanoparticles, assumed to support electron transfer reactions, to the org.-liq. electrolyte, the conversion efficiency was increased from 4.1% to 4.6% (100 W m-2, AM 1.5). In 1000 W m-2 illumination, the highest overall short-circuit c.d., 9.3 mA cm-2, was achieved with the N-719 sensitized cells, with the TiO2 nanocomposite-contg. org.-liq.-based electrolyte. For solar cells sensitized with N-719, Z-907 or the beta -diketonato complex, and contg. imidazolium or sulfonium iodide ionic liqs., no improvements of the overall conversion efficiency could be noticed at addn. of HDMA to the dye or nanoparticles to the electrolyte.

  • 78.
    Ghamgosar, Pedram
    et al.
    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.
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Dye adsorption on TiO2 electrodes studied using modulated photocurrent measurements2014In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 560, p. 10-13Article in journal (Refereed)
  • 79. Gibson, Elizabeth A.
    et al.
    Awais, Muhammad
    Dini, Danilo
    Dowling, Denis P.
    Pryce, Mary T.
    Vos, Johannes G.
    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.
    Dye sensitised solar cells with nickel oxide photocathodes prepared via scalable microwave sintering2013In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 15, no 7, p. 2411-2420Article in journal (Refereed)
    Abstract [en]

    Photoactive NiO electrodes for cathodic dye-sensitised solar cells (p-DSCs) have been prepared with thicknesses ranging between 0.4 and 3.0 mu m by spray-depositing pre-formed NiO nanoparticles on fluorine-doped tin oxide (FTO) coated glass substrates. The larger thicknesses were obtained in sequential sintering steps using a conventional furnace (CS) and a newly developed rapid discharge sintering (RDS) method. The latter procedure is employed for the first time for the preparation of p-DSCs. In particular, RDS represents a scalable procedure that is based on microwave-assisted plasma formation that allows the production in series of mesoporous NiO electrodes with large surface areas for p-type cell photocathodes. RDS possesses the unique feature of transmitting heat from the bulk of the system towards its outer interfaces with controlled confinement of the heating zone. The use of RDS results in a drastic reduction of processing times with respect to other deposition methods that involve heating/calcination steps with associated reduced costs in terms of energy. P1-dye sensitized NiO electrodes obtained via the RDS procedure have been tested in DSC devices and their performances have been analysed and compared with those of cathodic DSCs derived from CS-deposited samples. The largest conversion efficiencies (0.12%) and incident photon-to-current conversion efficiencies, IPCEs (50%), were obtained with sintered NiO electrodes having thicknesses of similar to 1.5-2.0 mu m. In all the devices, the photogenerated holes in NiO live significantly longer (tau(h) similar to 1 s) than have previously been reported for P1-sensitized NiO photocathodes. In addition, P1-sensitised sintered electrodes give rise to relatively high photovoltages (up to 135 mV) when the triiodide-iodide redox couple is used.

  • 80.
    Gibson, Elizabeth A.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Le Pleux, Loic
    Fortage, Jerome
    Pellegrin, Yann
    Blart, Errol
    Odobel, Fabrice
    Hagfeldt, Anders
    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.
    Role of the Triiodide/Iodide Redox Couple in Dye Regeneration in p-Type Dye-Sensitized Solar Cells2012In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 28, no 15, p. 6485-6493Article in journal (Refereed)
    Abstract [en]

    A series of perylene dyes with different optical and electronic properties have been used as photosensitizers in NiO-based p-type dye-sensitized solar cells. A key target is to develop dyes that absorb light in the red to near-infrared region of the solar spectrum in order to match photoanodes optically in tandem devices; however, the photocurrent produced was found to decrease dramatically as the absorption maxima of the dye used was varied from 517 to 565 nm and varied strongly with the electrolyte solvent (acetonitrile, propionitrile, or propylene carbonate). To determine the limitations of the energy properties of the dye molecules and to provide guidelines for future sensitizer design, we have determined the redox potentials of the duodide radical intermediate involved in the charge-transfer reactions in different solvents using photomodulated voltammetry. E degrees(I-3(-)/I-2(center dot-)) (V vs Fe(Cp)(2)(+/0)) = -0.64 for propylene carbonate, -0.82 for acetonitrile, and -0.87 for propionitrile. Inefficient regeneration of the sensitizer appears to be the efficiency-limiting step in the device, and the values presented here will be used to design more efficient dyes, with more cathodic reduction potentials, for photocathodes in tandem dye-sensitized solar cells.

  • 81.
    Gibson, Elizabeth A.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Smeigh, Amanda L.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Le Pleux, Loic
    Fortage, Jerome
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Blart, Errol
    Pellegrin, Yann
    Odobel, Fabrice
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Hammarström, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Chemical Physics.
    A p-Type NiO-Based Dye-Sensitized Solar Cell with an Open-Circuit Voltage of 0.35 V2009In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 48, no 24, p. 4402-4405Article in journal (Refereed)
    Abstract [en]

    In tandem: Employing a molecular dyad and a cobalt-based electrolyte gives a threefold-increase in open-circuit voltage (VOC) for a p-type NiO device (VOC=0.35 V), and a fourfold better energy conversion efficiency. Incorporating these improvements in a TiO2/NiO tandem dye-sensitized solar cell (TDSC), results in a TDSC with a VOC=0.91 V

  • 82.
    Gibson, Elizabeth A.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry.
    Smeigh, Amanda L.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Le Pleux, Loic
    Hammarström, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Chemical Physics.
    Odobel, Fabrice
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Cobalt Polypyridyl-Based Electrolytes for p-Type Dye-Sensitized Solar Cells2011In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 115, no 19, p. 9772-9779Article in journal (Refereed)
    Abstract [en]

    A series of polypyridyl cobalt complexes with different substituents was applied as redox mediators in p-type dye-sensitized solar cells (p-DSCs), consisting of mesoporous NiO sensitized with a perylenemonoimide naphthalenediimide (PMI-NDI) dyad. The photocurrent and photovoltages of the devices were found to depend on the steric bulk of the redox species rather than their electrochemical potential. Bulky substituents were found to slow the detrimental charge recombination reactions between holes in the NiO semiconductor and the reduced form of the redox couple. The open-circuit potential (V-OC) of each of the devices was superior to the equivalent PMI-NDIsensitized p-DSCs containing the triiodide/iodide redox couple.

  • 83.
    Gomez, M
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry. SOLID STATE PHYSICS.
    Magnusson, E
    Olsson, E
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Lindquist, Sten-Eric
    Granqvist, CG
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science.
    Nanocrystalline Ti-oxide-based solar cells made by sputter deposition and dye sensitization: Efficiency versus film thickness2000In: SOLAR ENERGY MATERIALS AND SOLAR CELLS, ISSN 0927-0248, Vol. 62, no 3, p. 259-263Article in journal (Refereed)
    Abstract [en]

    Nanocrystalline TiO2-based films with a special penniform microstructure were prepared by reactive DC magnetron sputtering followed by dye sensitization. The films were integrated in a solar cell configuration and were able to yield a higher photocurrent

  • 84.
    Gomez, M
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science.
    Rodriguez, J
    Tingry, S
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Lindquist, Sten-Eric
    Granqvist, CG
    Photoelectrochemical effect in dye sensitized, sputter deposited Ti oxide films: The role of thickness-dependent roughness and porosity1999In: SOLAR ENERGY MATERIALS AND SOLAR CELLS, ISSN 0927-0248, Vol. 59, no 3, p. 277-287Article in journal (Refereed)
    Abstract [en]

    Ti oxide films were made by reactive DC magnetron sputtering onto electrically conducting glass substrates. The films were dye sensitized with an Ru complex, thereby yielding nanocrystalline solar cells. We investigated the microstructure of the films

  • 85. Gomez, M.M.
    et al.
    Jun, Lu
    Olsson, E
    Granqvist, Clas-Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Spectrally Selective Coatings2001In: in EuroSun 2000: Visions for the New Millennium,, 2001Conference paper (Other academic)
  • 86.
    Gomez, MM
    et al.
    SOLID STATE PHYSICS. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science.
    Lu, J
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Olsson, E
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Granqvist, CG
    High efficiency dye-sensitized nanocrystalline solar cells based on sputter deposited Ti oxide films2000In: SOLAR ENERGY MATERIALS AND SOLAR CELLS, ISSN 0927-0248, Vol. 64, no 4, p. 385-392Article in journal (Refereed)
    Abstract [en]

    Nanocrystalline solar cells were made by incorporation of cis-dithiocyanato-bis(2,2'-bipyridyl-4,4'-dicarboxylate) ruthenium (II) into sputter deposited titanium oxide films. After a pyridine treatment, it was possible to achieve a photoelectric conversio

  • 87.
    Gomez, MM
    et al.
    SOLID STATE PHYSICS. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science.
    Lu, J
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Solis, JL
    Olsson, E
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Granqvist, CG
    Dye-sensitized nanocrystalline titanium-oxide-based solar cells prepared by sputtering: Influence of the substrate temperature during deposition2000In: JOURNAL OF PHYSICAL CHEMISTRY B, ISSN 1089-5647, Vol. 104, no 36, p. 8712-8718Article in journal (Refereed)
    Abstract [en]

    Nanocrystalline titanium oxide films were prepared by DC magnetron sputtering onto SnO2:F-coated glass substrates kept at temperatures in the 50 < tau(s) < 300 degrees C range. Dye sensitization in cis-dithiocyanato-bis(2,2'-bipyridyl-4,4'-dicarboxylate)

  • 88.
    Granqvist, Clas-Göran
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Gomez, M.M.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Hoel, A
    Joerger, R
    Kish, L. B.
    Klaus-Joerger, T
    Lantto, V
    Lu, J
    Olsson, E
    Rodriguez, J
    Saukko, S
    Solis, J. L.
    New Nanoparticle-based Materials and Devices Produced by Advanced Gas Evaporation, Reactive Sputtering and Microorganisms2001In: Proceedings of the International Symposium on Nanoparticles: Aerosols and Materials, 2001Conference paper (Refereed)
  • 89.
    Greijer Agrell, Helena
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Conductivity studies of nanostructured TiO2 films permeated with electrolyte2004In: Journal of Physical Chemistry B, Vol. 108, no 33, p. 12388-12396Article in journal (Refereed)
    Abstract [en]

    Charge transport in nanostructured TiO2 films permeated with an electrolyte was studied, using temperature-dependent conductivity and electron accumulation measurements. Two regions for charge transport were distinguished from the relationship between conductivity and electron concentration. In the first region (1−20 electrons per TiO2 particle), the effective electron mobility is dependent on the electron concentration and values between 7 × 10-4 and 78 × 10-4 cm2 V-1 s-1 were determined. The activation energy of the mobility was 0.3 eV. The charge transport can be described with a trapping/detrapping model that involves localized band-gap states. In the second region (> 20 electrons per TiO2 particle), the effective electron mobility is independent of electron concentration and values of 150 × 10-4 cm2 V-1 s-1 are calculated. The activation energy of mobility is in the range of 0−0.15 eV, depending on the electrolyte. Transport of electrons in the conduction band seems to be the most applicable model.

  • 90.
    Greijer Agrell, Helena
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical Chemistry. Department of Physical and Analytical Chemistry, Physical Chemistry I.
    Boschloo, Gerrit
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical Chemistry. Department of Physical and Analytical Chemistry, Physical Chemistry I.
    Hagfeldt, Anders
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical Chemistry. Department of Physical and Analytical Chemistry, Physical Chemistry I.
    Conductivity Studies of Nanostructured TiO2 Films Permeated with Electrolyte2004In: Journal of Physical Chemistry B, Vol. 108, no 33, p. 12388-12396Article in journal (Refereed)
  • 91.
    Greijer Agrell, Helena
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical Chemistry. Department of Physical and Analytical Chemistry, Physical Chemistry I. Department of Materials Chemistry, Structural Chemistry.
    Jan, Lindgren
    Department of Physical and Analytical Chemistry, Physical Chemistry I. Department of Materials Chemistry, Structural Chemistry. strukturkemi.
    Hagfeldt, Anders
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical Chemistry. Department of Physical and Analytical Chemistry, Physical Chemistry I. Department of Materials Chemistry, Structural Chemistry.
    Coordinative interactions in a dye-sensitized solar cell2004In: Journal of Photochemistry and Photobiology A: Chemistry, no 164, p. 23-27Article in journal (Refereed)
    Abstract [en]

    Resonance Raman scattering studies of a complete dye-sensitized solar cell (DSC) including iodine and lithium iodide in the electrolyte indicate that triiodide (I3-) exchange the SCN- ligand of the dye bis(tetrabutylammonium) cis-bis(thiocyanato)bis(2,2'-bipyridine-4-carboxylic acid, 4'-carboxylate)ruthenium(II). The choice of cation in the iodide salt influenced the ligand stability of the dye. It was proposed that an ion pair Li+...I3- formation occurred which by a reduced electrostatic repulsion between I3- and SCN- facilitated the exchange of these anions at Ru(II) of the dye. The additive 1-methylbenzimidazole (MBI) suppressed the SCN /Ij ligand exchange by forming a complex with Li+. The concentrations of Li+ and MBI have to be carefully balanced due to the SCN ligand exchange with the use of characterization methods with which complete devices can be studied is necessary.

  • 92.
    Greijer Agrell, Helena
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Lindgren, Jan
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Coordinative interactions in a dye-sensitized solar cell2004In: Journal of Photochemistry and Photobiology A: Chemistry, Vol. 164, no 1-3, p. 23-27Article in journal (Refereed)
    Abstract [en]

    Resonance Raman scattering studies of a complete dye-sensitized solar cell (DSC) including iodine and lithium iodide in the electrolyte indicate that triiodide (I3) exchange the SCN ligand of the dye bis(tetrabutylammonium) cis-bis(thiocyanato)bis(2,2′-bipyridine-4-carboxylic acid, 4′-carboxylate)ruthenium(II). The choice of cation in the iodide salt influenced the ligand stability of the dye. It was proposed that an ion pair Li+I3 formation occurred which by a reduced electrostatic repulsion between I3 and SCN facilitated the exchange of these anions at Ru(II) of the dye. The additive 1-methylbenzimidazole (MBI) suppressed the SCN/I3 ligand exchange by forming a complex with Li+. The concentrations of Li+ and MBI have to be carefully balanced due to the SCN ligand exchange with MBI in deficiency of Li+. In order to observe and understand the prevailing coordinative interactions between the components in a DSC, the use of characterization methods with which complete devices can be studied is necessary.

  • 93.
    Greijer Agrell, Helena
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Lindgren, Jan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Degradation mechanisms in a dye-sensitized solar cell studied by UV-VIS and IR spectroscopy2003In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 75, no 2, p. 169-180Article in journal (Refereed)
    Abstract [en]

    By deliberately causing degradation of components in a dye-sensitized solar cell we have studied failure mechanisms of such cells. The dye, bis(tetrabutylammonium) cis–bis(thiocyanato)bis(2,2-bipyridine-4-carboxylic acid, 4-carboxylate)ruthenium(II), adsorbed to a nanostructured TiO2 film was studied with UV–VIS and IR spectroscopy after being exposed to visual and ultra-violet radiation, increased temperature, air, electrolyte, and water in the electrolyte. The thiocyanate ion ligand is lost in air, at temperatures equal to and above 135 °C, in electrolyte and possibly upon UV irradiation. The loss of the SCN ligand in air was accelerated under visual illumination. From working electrodes immersed in the electrolyte or in degraded complete solar cells it was observed that the absorption peak from the thiocyanate ion ligand at around 2100 cm−1 had broadened, blue-shifted and decreased. One failure mechanism is thus that the thiocyanate ion ligand is lost from the dye together with the electrolyte. Together with water in the electrolyte (5 v%) the SCN ligand is exchanged with H2O and/or OH. The ligand exchange between SCN and H2O/OH was accelerated under visual illumination.

  • 94.
    Greijer, H
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
    Lindgren, Jan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry. strukturkemi. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
    Hagfeldt, Anders
    Resonance Raman scattering of a dye-sensitized solar cell: Mechanism of thiocyanato ligand exchange2001In: JOURNAL OF PHYSICAL CHEMISTRY B, ISSN 1089-5647, Vol. 105, no 27, p. 6314-6320Article in journal (Refereed)
    Abstract [en]

    A method has been developed to study the mechanisms of the thiocyanato ligand exchange reactions between the redox couple I-/I-3(-) and the ruthenium complex bis(tetrabutylammonium) cis-bis(thiocyanato)bis(2,2 ' -bipyridine-4-carboxylic acid, 4 ' -carboxy

  • 95.
    Greijer, Helena
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Karlson, Lennart
    Lindquist, Sten-Eric
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Environmental aspects of electricity generation from a nanocrystalline dye-sensitized solar cell system2001In: Renewable Energy, Vol. 23, p. 27-39Article in journal (Refereed)
    Abstract [en]

    A Life Cycle Assessment, LCA, of a nanocrystalline dye sensitized solar cell (ncDSC) system has been performed, according to the ISO14040 standard. In brief, LCA is a tool to analyse the total environmental impact of a product or system from cradle to grave. Six different weighing methods were used to rank and select the significant environmental aspects to study further. The most significant environmental aspects according to the weighing methods are emission of sulphur dioxide and carbon dioxide. Carbon dioxide emission was selected as the environmental indicator depending on the growing attention on the global warming effect. In an environmental comparison of electricity generation from a ncDSC system and a natural gas/combined cycle power plant, the gas power plant would result in 450 g CO2/kWh and the ncDSC system in between 19–47 g CO2/kWh. The latter can be compared with 42 g CO2/kWh, according to van Brummelen et al. “Life Cycle Assessment of Roof Integrated Solar Cell Systems, (Report: Department of Science, Technology and Society, Utrecht University, The Netherlands, 1994)” for another thin film solar cell system made of amorphous silicon. The most significant activity/component contributing to environmental impact over the life cycle of the ncDSC system is the process energy for producing the solar cell module. Secondly comes the components; glass substrate, frame and junction box. The main improvement from an environmental point of view of the current technology would be an increase in the conversion efficiency from solar radiation to electricity generation and still use low energy demanding production technologies. Also the amount of material in the solar cell system should be minimised and designed to maximise recycling.

  • 96.
    Greijer, Helena
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Lindgren, Jan
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Resonance Raman scattering of a dye-sensitized solar cell: Mechanism of thiocyanato ligand exchange2001In: Journal of Physical Chemistry B, Vol. 105, p. 6314-6320Article in journal (Refereed)
    Abstract [en]

    A method has been developed to study the mechanisms of the thiocyanato ligand exchange reactions between the redox couple I-/ I3- and the ruthenium complex bis(tetrabutylammonium) cis-bis(thiocyanato)bis(2,2‘-bipyridine-4-carboxylic acid, 4‘-carboxylate)ruthenium(II), in a sealed dye-sensitized solar cell using resonance Raman scattering. Raman lines from the solar cell were assigned to vibrations from the different constituents. In a cell with only lithium iodide added to the solvent, the formation of triiodide was observed at 114 and 226 cm-1. The amount of thiocyanato group coordinated to the dye, estimated from the CN stretching observed at 2105 cm-1, decreased with the increased amount of iodine added or triiodide formed in the electrolyte. It was shown that the thiocyanato ligands formed a complex with iodine, I2SCN-, indicated by a weak Raman line at 165 cm-1. From UV−vis measurement, the dye after the SCN- loss is proposed to be a cis-bis(iodo)bis(2,2‘-bipyridine-4-carboxylic acid, 4‘-carboxylate)ruthenium(II) complex. It is suggested that the electrolyte additive 4-tert-butylpyridine suppresses the loss of the thiocyanato group from the dye.

  • 97. Guo, Wei
    et al.
    Shen, Yihua
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Ma, Tingli
    Influence of nitrogen dopants on N-doped TiO2 electrodes and their applications in dye-sensitized solar cells2011In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 56, no 12, p. 4611-4617Article in journal (Refereed)
    Abstract [en]

    Three different types of nanocrystalline, N-doped TiO2 electrodes were synthesized using several nitrogen dopants through wet methods. The obtained nanocrystalline, N-doped TiO2 electrodes possessed different crystallite sizes, surface areas, and N-doping amounts. Characterizations were performed to reveal the nitrogen-doping processes for the wet methods using ammonia, urea, and triethylamine as the nitrogen dopants. Additionally, a high conversion efficiency of 8.32% was achieved by the dye-sensitized solar cells, based on the N-doped TiO2 electrodes. For instance, in comparison with the commercial P25 (5.76%) and pure anatase TiO2 electrodes (7.14%), significant improvements (44% and 17%, respectively) in the efficiencies were obtained. The findings also indicated that the ammonia nitrogen dopant was more efficient than other two nitrogen dopants. The electron transports, electron lifetimes, and charge recombination in the dye-sensitized N-doped TiO2 solar cells also differed from those in the pure TiO2-based dye-sensitized solar cells (DSCs). Specifically, an enhanced photocurrent of ca. 36% in N-doped DSCs resulted from the synergistic effects of the high dye uptake and the efficient electron transport. Moreover, the relationship between charge and voltage revealed that less charge was needed to get a high open-circuit voltage in the N-doping films.

  • 98. Guo, Wei
    et al.
    Wu, Liqiong
    Chen, Zhuo
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Ma, Tingli
    Highly efficient dye-sensitized solar cells based on nitrogen-doped titania with excellent stability2011In: Journal of Photochemistry and Photobiology A: Chemistry, ISSN 1010-6030, E-ISSN 1873-2666, Vol. 219, no 2-3, p. 180-187Article in journal (Refereed)
    Abstract [en]

    A series of nitrogen-doped and undoped TiO2 nanocrystals was prepared by several simple methods. Needle-like N-doped TiO2 nanocrystals and nanoparticles were obtained from commercial TiO2 powders. Several dye-sensitized solar cells (DSCs) were fabricated based on N-doped and undoped TiO2 electrodes. The N-doped DSCs achieved a high conversion efficiency of 10.1% and 4.8% using an organic electrolyte and an ionic liquid electrolyte, respectively. Systemic investigations were carried out on the properties of N-doped and undoped TiO2 powders, films, and DSCs. The electron transport time and electron lifetime were investigated by intensity-modulated photocurrent and photovoltage spectroscopy (IMPS/IMVS). Moreover, the electron injection of N-doped DSCs was studied by surface photovoltage spectroscopy (SPS). The synergetic effect of higher dye uptake, faster electron transport and higher photovoltage contributes to a higher conversion efficiency of N-doped DSCs. The stability test also demonstrated that the photodegradation of the DSCs was not accelerated and the DSC system was stabilized by the introduction of nitrogen into the TiO2 photoelectrode. These results indicate that the N-doped TiO2 nanocrystals prepared by our approach from commercial TiO2 are ideal semiconductor materials for DSCs.

  • 99.
    Gómez, M M
    et al.
    SOLID STATE PHYSICS ANALYTICAL MATERIAL PHYSICS. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science.
    Lu, Jun
    Olsson, E
    Granqvist, C G
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    High Light-to TiO2 Energy Conversion Efficiency for Nanocrystalline, TiO2 Films Made by Sputter Depostion2001In: EuroSun 2000, 2001Conference paper (Other academic)
  • 100.
    Gómez, M
    et al.
    SOLID STATE PHYSICS. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science.
    Rodriguez, J
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Lindquist, Sten-Eric
    Granqvist, C.G.
    Incident Photon-to-current Efficiency of Porous Polycrystalline Ti Oxide Films Prepared by Sputtering1998In: Proc. Eurosun, Slovenia, 1998Conference paper (Other academic)
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