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  • 251.
    Södergren, S
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Siegbahn, H
    Uppsala University.
    Rensmo, H
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Lindström, H
    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.
    Lindquist, S-E
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Lithium intercalation in nanoporous anatase TiO2 studied with XPS1997In: JOURNAL OF PHYSICAL CHEMISTRY B, ISSN 1089-5647, Vol. 101, no 16, p. 3087-3090Article in journal (Other academic)
    Abstract [en]

    Intercalation of lithium ions in nanoporous anatase TiO2 was studied with XPS using a novel electrochemical preparation technique. The electrolyte was 0.5 M LiClO4 in acetonitrile (not water-free). The electrochemical insertion of lithium ions creates red

  • 252. Tefashe, Ushula Mengesha
    et al.
    Nonomura, Kazuteru
    Vlachopouos, Nikolaos
    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.
    Wittstock, Gunther
    Effect of Cation on Dye Regeneration Kinetics of N719-Sensitized TiO2 Films in Acetonitrile-Based and Ionic-Liquid-Based Electrolytes Investigated by Scanning Electrochemical Microscopy2012In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 116, no 6, p. 4316-4323Article in journal (Refereed)
    Abstract [en]

    Scanning electrochemical microscopy (SECM) in the feedback mode has been used to investigate the kinetics of dye regeneration on cis-di(thiocyanato)-bis(2,2'-bipyridyl-4,4 ''-dicarboxylate) ruthenium(II)-sensitized TiO2 photoelectrochemical electrodes in contact with room temperature ionic liquids electrolytes. Acetonitrile based electrolytes were used for comparison. The data are analyzed with the help of a revised model for relating steady state approach curves in the SECM feedback mode to an effective rate constant for the dye regeneration process. This effective rate constant summarizes the effect of electron transfer kinetics, mass transport of the mediator inside the porous electrode, and recombination processes. We found a remarkable dependence of the dye regeneration on the nature and concentration of deliberately added cations.

  • 253.
    Teng, Chao
    et al.
    Dalian University of Technology, China.
    Yang, Xichuan
    Dalian University of Technology, China.
    Yang, Chao
    Dalian University of Technology, China.
    Li, Shifeng
    Dalian University of Technology, China.
    Cheng, Ming
    Dalian University of Technology, China.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Sun, Licheng
    Organic Chemistry KTH and Dalian University of Technology, China.
    Molecular Design of Anthracene-Bridged Metal-Free Organic Dyes for Efficient Dye-Sensitized Solar Cells2010In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 114, no 19, p. 9101-9110Article in journal (Refereed)
    Abstract [en]

    A series of metal-free organic dyes bridged by anthracene-containing π-conjugations were designed and synthesized as new chromophores for the application of dye-sensitized solar cells (DSCs). Detailed investigations on the relationship between the dye structures, photophysical properties, electrochemical properties, and performances of DSCs are described. With the introduction of the anthracene moiety, together with a triple bond for the fine-tuning of molecular planar configurations and to broaden absorption spectra, the short-circuit photocurrent densities (Jsc) and open-circuit photovoltages (Voc) of DSCs were improved to a large extent. The improvement of Jsc is attributed to much broader absorption spectra of the dyes with the anthracene moiety. Electrochemical impedance spectroscopy (EIS) analysis reveals that the introduction of the anthracene moiety suppresses the charge recombination arising from electrons in TiO2 films with I3 ions in the electrolyte, thus improving Voc considerably. On the basis of optimized molecular structures and DSC test conditions, the dye TC501 shows a prominent solar energy conversion efficiency (η) up to 7.03% (Jsc = 12.96 mA·cm−2, VOC = 720 mV, ff = 0.753) under simulated AM 1.5 irradiation (100 mW·cm−2).

  • 254.
    Teng, Chao
    et al.
    Dalian University of Technology, China.
    Yang, Xichuan
    Dalian University of Technology, China.
    Yang, Chao
    Dalian University of Technology, China.
    Tian, Haining
    Dalian University of Technology, China.
    Li, Shifeng
    Dalian University of Technology, China.
    Wang, Xiuna
    Dalian University of Technology, China.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Sun, Licheng
    Center of Molecular Devices, Physical Chemistry, KTH.
    Influence of Triple Bonds as π-Spacer Units in Metal-Free Organic Dyes for Dye-SensitizedSolar Cells2010In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 114, no 25, p. 11305-11313Article in journal (Refereed)
    Abstract [en]

    Four metal-free organic sensitizers (TC101-TC104) with triple bonds in pi-spacers and five reference dyes (TC, TC105, TPC1, D5, and TH208) without triple bonds were applied in dye-sensitized solar cells to study the influence of triple bonds as pi-spacer units on their photoelectrochemical properties and dye-sensitized solar cells (DSCs) performance. Results show that the introduction of triple bond could red-shift the dye's absorption spectrum due to the enhancement of the pi-spacer. However, the spectrum red-shift is much less than that of the introduction of double bond because of more electronegativity of triple bond. The incident photon-to-current conversion efficiency reveals that the electron transfer yield (Phi(nu)(ET)) of DSCs becomes larger with the introduction of triple bond. Electrochemical impedance spectroscopy analysis reveals that the introduction of triple bond almost does not change the electron lifetimes in TiO2 films but decreases the effective diffusion lengths.

  • 255. Tian, Haining
    et al.
    Bora, Ilkay
    Jiang, Xiao
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Gabrielsson, Erik
    Karlsson, Karl Martin
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Sun, Licheng
    Modifying organic phenoxazine dyes for efficient dye-sensitized solar cells2011In: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 21, no 33, p. 12462-12472Article in journal (Refereed)
    Abstract [en]

    Four organic dyes bearing the phenoxazine chromophore have been synthesized and applied in dye-sensitized solar cells (DSCs). The effect of different dye structures on the performance of the DSCs was investigated systematically with photophysical, photovoltaic as well as photoelectrochemical methods. Due to the slow recombination process between injected electrons and electrolyte, the IB3 dye with two 2,4-dibutoxyphenyl units showed the best efficiency of 7.0% under 100 mW cm(-2) light illumination in the liquid state-DSCs. Moreover, the phenoxazine dyes-based solid state-DSCs were fabricated for the first time. With the IB4 dye, a higher efficiency of 3.2% has been achieved under the same light intensity.

  • 256. Tian, Haining
    et al.
    Gabrielsson, Erik
    Lohse, Peter William
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Vlachopoulos, Nikolaos
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Kloo, Lars
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Sun, Licheng
    Development of an organic redox couple and organic dyes for aqueous dye-sensitized solar cells2012In: Energy & Environmental Science, ISSN 1754-5692, E-ISSN 1754-5706, Vol. 5, no 12, p. 9752-9755Article in journal (Refereed)
    Abstract [en]

    A water-soluble organic redox couple (TT-/DTT) and new organic dyes (D45 and D51) have been developed for aqueous dye-sensitized solar cells (DSCs). An optimal efficiency of 3.5% was obtained using the D51 dye and an optimized electrolyte composition. The highest IPCE value obtained was 68% at 460 nm.

  • 257. Tian, Haining
    et al.
    Gabrielsson, Erik
    Yu, Ze
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Kloo, Lars
    Sun, Licheng
    A thiolate/disulfide ionic liquid electrolyte for organic dye-sensitized solar cells based on Pt-free counter electrodes2011In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 47, no 36, p. 10124-10126Article in journal (Refereed)
    Abstract [en]

    The ionic liquid, 1-ethyl-3-methylimidazolium tetracyanoborate, was employed to prepare a thiolate/disulfide ionic liquid electrolyte with low viscosity for organic dye-sensitized solar cells (DSCs). CoS was introduced and showed better photovoltaic performance in DSCs than the ubiquitous platinized FTO CE.

  • 258. Tian, Haining
    et al.
    Jiang, Xiao
    Yu, Ze
    Kloo, Lars
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry.
    Sun, Licheng
    Efficient Organic-Dye-Sensitized Solar Cells Based on an Iodine-Free Electrolyte2010In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 49, no 40, p. 7328-7331Article in journal (Refereed)
  • 259.
    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.

  • 260.
    Tian, Haining
    et al.
    KTH, Royal Institue of Technology.
    Soto, Andrea
    Xu, Bo
    Sun, Licheng
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Fabregat-Santiago, Francisco
    Mora-Sero, Ivan
    Kang, Yong Soo
    Bisquert, Juan
    Barea, Eva M.
    Effect of the Chromophores Structures on the Performance of Solid-State Dye Sensitized Solar Cells2014In: Nano, ISSN 1793-2920, Vol. 9, no 5, p. 1440005-Article in journal (Refereed)
    Abstract [en]

    The er effect of metal-free chromophores on dye-sensitized solar cell performance is investigated. Solid state dye-sensitized solar cells (ssDSCs) using dirfferent molecular sensitizers based on tri-phenylamine (TPA) with thiophene linkers and different alkyl chain in the donor unit have been characterized using impedance spectroscopy (IS). We show that different molecular structures play a fundamental role on solar cell performance, by the effect produced on TiO2 conduction band position and in the recombination rate. Dye structure and its electronic properties are the main factors that control the recombination, the capacitance and the efficiency of the cells. A clear trend between the performance of the cell and the optimization level of the blocking effect of the dye structure has been identified in the solid state solar cells with Spiro-OMeTAD hole conductor.

  • 261. Tian, Haining
    et al.
    Yu, Ze
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Kloo, Lars
    Sun, Licheng
    Organic Redox Couples and Organic Counter Electrode for Efficient Organic Dye-Sensitized Solar Cells2011In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 133, no 24, p. 9413-9422Article in journal (Refereed)
    Abstract [en]

    A series of organic thiolate/disulfide redox couples have been synthesized and have been studied systematically in dye-sensitized solar cells (DSCs) on the basis of an organic dye (TH305). Photophysical, photoelectrochemical, and photovoltaic measurements were performed in order to get insights into the effects of different redox couples on the performance of DSCs. The polymeric, organic poly(3,4-ethylenedioxythiophene) (PEDOT) material has also been introduced as counter electrode in this kind of noniodine-containing DSCs showing a promising conversion efficiency of 6.0% under AM 1.5G, 100 mW.cm(-2) light illumination. Detailed studies using electrochemical impedance spectroscopy and linear-sweep voltammetry reveal that the reduction of disulfide species is more efficient on the PEDOT counter electrode surface than on the commonly used platinized conducting glass electrode. Both pure and solvated ionic-liquid electrolytes based on a thiolate anion have been studied in the DSCs. The pure and solvated ionic-liquid-based electrolytes containing an organic redox couple render efficiencies of 3.4% and 1.2% under 10 mW.cm(-2) light illumination, respectively.

  • 262.
    Unger, Eva L.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Edvinsson, Tomas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Roy-Mayhew, Joseph D.
    Rensmo, Håkan
    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 Chemistry - Ångström, Physical Chemistry.
    Johansson, Erik M. J.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Excitation Energy Dependent Charge Separation at Hole-Transporting Dye/TiO2 Hetero Interface2012In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 116, no 40, p. 21148-21156Article in journal (Refereed)
    Abstract [en]

    Interfacial charge separation in hybrid solar cells depends on both the energetic alignment and electronic coupling between the inorganic and organic semiconducting materials at the hetero interface. In the present work, bilayer solar cells comprising the small molecular semiconducting dye TDCV-TPA (tris-(thienylene-vinylene)-triphenylamine) and dense titanium dioxide (TiO2) films were investigated. The internal quantum efficiency and degree of photoluminescence quenching were found to be excitation energy dependent. The molecular interaction and interfacial energy level alignment was investigated using a combination of UV-vis and photoelectron spectroscopy (PES). Stationary and time-dependent density functional theory calculations were used to assign and distinguish between different experimentally determined molecular energy levels (PES) and electronic transitions (UV-vis). Photoelectron spectroscopy results suggest surface induced interactions of TDCV-TPA with TiO2 involving the peripheral CN-groups of the molecule which would imply a favorable electronic coupling for photoinduced interfacial charge transfer. In an energy level diagram distinguishing between the different electronic transitions in the molecule, the differences in the thermodynamic driving force for electron injection from the excited states were found small. Therefore, it is suggested that the observed higher internal quantum efficiency at shorter wavelength can be rationalized by a more favorable driving force for the regeneration of holes created at the hetero interface at higher excitation energy.

  • 263.
    Unger, Eva L.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Morandeira, Ana
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Chemical Physics.
    Persson, Mats
    Zietz, Burkhard
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Chemical Physics.
    Ripaud, Emilie
    Leriche, Philippe
    Roncali, Jean
    Hagfeldt, Anders
    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.
    Contribution from a hole-conducting dye to the photocurrent in solid-state dye-sensitized solar cells2011In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 13, no 45, p. 20172-20177Article in journal (Refereed)
    Abstract [en]

    The hole transporting medium in solid-state dye-sensitized solar cells can be utilized to harvest sunlight. Herein we demonstrate that a triphenylamine-based dye, used as hole-transporting medium, contributes to the photocurrent in a squaraine-sensitized solid-state dye-sensitized solar cell. Steady-state photoluminescence measurements have been used to distinguish between electron transfer and energy transfer processes leading to energy conversion upon light absorption in the hole-transporting dye.

  • 264.
    Unger, Eva L.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Spadavecchia, Francesca
    Nonomura, Kazuteru
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Palmgren, Pal
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Cappelletti, Giuseppe
    Hagfeldtt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Johansson, Erik M. J.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Effect of the Preparation Procedure on the Morphology of Thin TiO2 Films and Their Device Performance in Small-Molecule Bilayer Hybrid Solar Cells2012In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 4, no 11, p. 5997-6004Article in journal (Refereed)
    Abstract [en]

    Flat titanium dioxide films, to be used as the acceptor layer in bilayer hybrid solar cell devices, were prepared by spray-pyrolysis and by spin-casting. Both preparation methods resulted in anatase titania films with similar optical and electronic properties but considerably different film morphologies. Spray pyrolysis resulted in dense TiO2 films grown onto and affected by the surface roughness of the underlying conducting glass substrates. The spin-casting preparation procedure resulted in nanoporous titania films. Hybrid solar cell devices with varying layer thickness of the small-molecule semiconducting dye TDCV-TPA were investigated. Devices built with spray-pyrolyzed titania substrates yielded conversion efficiencies up to 0.47%. Spin-cast titania substrates exhibited short circuits for thin dye layer thickness. For thicker dye layers the performance of these devices was up to 0.6% due to the higher interfacial area for charge separation of these nanoporous TiO2 substrates.

  • 265.
    Unger, Eva
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Ripaud, Emilie
    University of Angers.
    Leriche, Philippe
    University of Angers.
    Cravino, Antonio
    University of Angers.
    Roncali, Jean
    University of Angers.
    Johansson, Erik M. J.
    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.
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Bilayer hybrid solar cells based on triphenylamine-thienylenevinylene dye and TiO22010In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 114, no 26, p. 11659-11664Article in journal (Refereed)
    Abstract [en]

    Photoinduced energy conversion from multilayers of organic dye on dense TiO2 films was investigated in bilayer hybrid solar cells. Dye layers of varying thicknesses were prepared by spin-casting the star-shaped dye [tris(dicyano-vinyl-2-thienyl)phenyl]amine (1) from solutions onto dense TiO2 on conducting glass substrates. A spin-cast layer of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and graphite powder was used for contacting the devices. Excitons generated in the dye multilayer contribute to the power conversion efficiency, reaching a maximum of ca. 0.3% at a dye layer thickness of ca. 8 nm for the devices described herein. For dye layers exceeding 5 nm, the cell performance becomes limited by the exciton diffusion length LED and the hole mobility in the organic layer. Using dye multilayers is a viable way to increase light harvesting in solid-state dye-sensitized solar cells.

  • 266.
    Vayssieres, L
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Beermann, N
    Lindquist, SE
    Hagfeldt, Anders
    Controlled aqueous chemical growth of oriented three-dimensional crystalline nanorod arrays: Application to iron(III) oxides2001In: CHEMISTRY OF MATERIALS, ISSN 0897-4756, Vol. 13, no 2, p. 233-235 Language: EnglishArticle in journal (Refereed)
  • 267.
    Vayssieres, L
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Hagfeldt, Anders
    Lindquist, SE
    Purpose-built metal oxide nanomaterials. The emergence of a new generation of smart materials2000In: PURE AND APPLIED CHEMISTRY, ISSN 0033-4545, Vol. 72, no 1-2, p. 47-52 Language: EnglishArticle in journal (Refereed)
    Abstract [en]

    A new concept has been developed in order to achieve a new generation of smart materials, namely purpose-built materials, modeled and designed to match the physical and structural requirements of their applications. A model based on the thermodynamic moni

  • 268.
    Vayssieres, L
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Keis, K
    Lindquist, SE
    Hagfeldt, Anders
    Purpose-built anisotropic metal oxide material: 3D highly oriented microrod array of ZnO2001In: JOURNAL OF PHYSICAL CHEMISTRY B, ISSN 1089-5647, Vol. 105, no 17, p. 3350-3352 Language: EnglishArticle in journal (Refereed)
    Abstract [en]

    We are reporting here on the inexpensive fabrication of large three-dimensional and highly oriented porous microrod array of n-type ZnO semiconductor with a unique designed architecture consisting of well-defined, length-tailored, monodisperse, perpendicu

  • 269.
    Vayssieres, Lionel
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Keis, Karin
    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.
    Lindquist, Sten-Eric
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Three-dimensional array of highly oriented crystalline ZnO microtubes2001In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 13, no 12, p. 4395-4398Article in journal (Refereed)
    Abstract [en]

    The ability to generate homogeneous particulate thin films of highly orientedand highly porous microparticles of a post transition metal oxide onto polycrystalline and single-crystalline substrates, at low cost, by a template-free, aqueous low-temperature coating process is demonstrated by the fabrication of a large three-dimensional array ofperpendicularly oriented hexagonal microtubes of crystalline zincite ZnO from an aqueous solution of zinc nitrate and methenamine.

  • 270. Vlachopoulos, Nick
    et al.
    Nissfolk, Jarl
    Moeller, Martin
    Briancon, Alain
    Corr, David
    Grave, Christian
    Leyland, Nigel
    Mesmer, Ralf
    Pichot, Francois
    Ryan, Michael
    Boschloo, Gerrit
    KTH, Dept. of Chemistry.
    Hagfeldt, Anders
    KTH, Dept. of Chemistry.
    Electrochemical aspects of display technology based on nanostructured titanium dioxide with attached viologen chromophores2008In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, ISSN 0013-4686, Vol. 53, no 11, p. 4065-4071Article in journal (Refereed)
    Abstract [en]

    Progress in recent years in the field of electrochromic displays based on viologen modified high-surface area TiO2 electrodes (Vio(2+)/TiO2) has moved the technology towards commercialisation. Viologen molecules (Vio(2+)), derivatised with phosphonic acid attachment groups can be chemisorbed on nanostructured TiO2 layers of thickness 2-10 mu m. Characterisation by cyclic voltammetry, spectroelectrochemistry and impedance spectroscopy demonstrates that colourless Vio(2+)/TiO2 is reversibly reduced to the strongly coloured cation radical species Vio(+center dot)/TiO2. This system can constitute the working electrode of an electrochromic display with a capacitive doped SnO2 electrode as counter electrode, the latter coated by an electrochemically inert white fight-reflecting layer. Such a device is stable upon repeated colouration-bleaching cycles with a bleached-to-coloured state contrast ratio exceeding 5. Multicolour displays can be achieved by patterning different electrochromophores onto different areas of one working electrode. (C) 2007 Elsevier Ltd. All rights reserved.

  • 271.
    Waita, S. M.
    et al.
    Department of Physics, University of Nairobi.
    Aduda, B. O.
    Department of Physics, University of Nairobi.
    Mwabora, J. M.
    Department of Physics, University of Nairobi.
    Granqvist, Claes-Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Lindquist, Sten-Eric
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Hagfeldt, Anders
    KTH, Fysikalisk kemi, Physical Chemistry.
    Boschloo, Gerrit K.
    KTH, Fysikalisk kemi, Physical Chemistry.
    Electron Transport and Recombination in Dye Sensitized Solar Cells Fabricated from Obliquely Sputter Deposited and Thermally Annealed TiO2 Films2007In: Journal of Electroanalytical Chemistry, ISSN 0022-0728, E-ISSN 1873-2569, Vol. 605, no 2, p. 151-156Article in journal (Refereed)
    Abstract [en]

    Dye sensitized solar cells based on annealed titanium dioxide films prepared by oblique reactive DC magnetron sputtering have been investigated in detail. Electron transport and recombination were studied using intensity-modulated photocurrent and photovoltage spectroscopy. Electron transport time as well as lifetime were found to increase upon lowering of the light intensity and to increase upon increasing the thickness of the TiO2 film. The properties are very similar to those observed for solar cells based on colloidal TiO2 films despite the morphologies being very different. In all cases, films are composed of a porous assembly of TiO2 nanocrystals. Grain boundaries with associated trap and/or energy barriers may explain the observed transport properties.

  • 272. Wang, Heli
    et al.
    Lindgren, Torbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    He, Jianjun
    Hagfeldt, Anders
    Lindquist, Sten-Eric
    Photoelectrochemistry of Nanostructured WO3 Thin Film Electrodes for Water Oxidation: Mechanism of Electron Transport2000In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 104, p. 5686-5696Article in journal (Refereed)
  • 273.
    Wang, HL
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    He, JJ
    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.
    Lindström, H
    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.
    Lindquist, S-E
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Electrochemical investigation of traps in a nanostructured TiO2 film2001In: JOURNAL OF PHYSICAL CHEMISTRY B, ISSN 1089-5647, Vol. 105, no 13, p. 2529-2533 Language: EnglishArticle in journal (Refereed)
    Abstract [en]

    Electron traps at the nanostructured TiO2 (anatase)/aqueous electrolyte interface have been studied by means of electrochemical methods. The transient current decays at different potentials positive of the flat band potential clearly illustrate the trap-f

  • 274.
    Wang, HL
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Lindgren, T
    He, JJ
    Hagfeldt, Anders
    Lindquist, SE
    Photolelectrochemistry of nanostructured WO3 thin film electrodes for water oxidation: Mechanism of electron transport2000In: JOURNAL OF PHYSICAL CHEMISTRY B, ISSN 1089-5647, Vol. 104, no 24, p. 5686-5696 Language: EnglishArticle in journal (Refereed)
    Abstract [en]

    Nanostructured WO3 thin films were prepared, and photooxidation of water at such films was studied in a pH 4.68 solution. The cathodic current at potentials below -100 mV versus a saturated Ag/AgCl electrode was related to the reversible intercalation of

  • 275. Wang, Peng
    et al.
    Zakeeruddin, Shaik M.
    Moser, Jacques E.
    Humphry-Baker, Robin
    Comte, Pascal
    Aranyos, Viviane
    Hagfeldt, Anders
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical Chemistry. Department of Physical and Analytical Chemistry, Physical Chemistry I.
    Nazeeruddin, Mohammad K.
    Grätzel, Michael
    Stable new sensitizer with improved light harvesting for nanocrystalline dye-sensitized solar cells2004In: Advanced Materials (Weinheim, Germany), Vol. 16, no 20, p. 1806-1811Article in journal (Refereed)
  • 276. Wang, Yudi
    et al.
    Wu, Mingxing
    Lin, Xiao
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Ma, Tingli
    Optimization of the Performance of Dye-Sensitized Solar Cells Based on Pt-Like TiC Counter Electrodes2012In: European Journal of Inorganic Chemistry, ISSN 1434-1948, E-ISSN 1099-1948, no 22, p. 3557-3561Article in journal (Refereed)
    Abstract [en]

    Titanium carbide (TiC) has been used as a counter electrode (CE) catalyst in place of Pt for triiodide reduction in dye-sensitized solar cells (DSCs). Its catalytic activity can be comparable to that of Pt. The effect of the thickness of the TiC layer on the performance of the DSCs was investigated by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and Tafel polarization measurements. We found that as the film thickness increased, the fill factor and short-circuit current density increased, which led to improved power-conversion efficiency. When the TiC film was thicker than 20 mu m, however, no significant continuous improvement in the catalytic activity was observed. A high power-conversion efficiency of 6.46?% was obtained for the DSC by using a TiC CE at the optimized film thickness, a value similar to that obtained with a Pt CE.

  • 277. Wang, Yudi
    et al.
    Wu, Mingxing
    Lin, Xiao
    Shi, Zhicong
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Ma, Tingli
    Several highly efficient catalysts for Pt-free and FTO-free counter electrodes of dye-sensitized solar cells2012In: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 22, no 9, p. 4009-4014Article in journal (Refereed)
    Abstract [en]

    Three nanomaterials, namely, titanium carbide (TiC), tungsten oxide (WO2), and vanadium nitride (VN), are introduced into dye-sensitized solar cells (DSCs) as counter electrode (CE) catalysts to replace the expensive Pt CE. Three kinds of substrates of bare glass (BG), Ti foil, and polyimide (PI) film are applied as F-doped tin oxide (FTO)-free substrates for rigid and flexible DSCs; thus realizing FTO-free and Pt-free CEs simultaneously in the DSC system. A carbon layer is used as an electron collector to replace the expensive FTO conductive layer in the insulative BG and PI film. Cyclic voltammetry, electrochemical impedance spectroscopy, and Tafel polarization curves are performed to compare the catalytic activities of these CEs for the reduction of triiodide to iodide. The results demonstrate that the DSCs that use TiC, WO2, and VN as CEs on Ti foil have better photovoltaic performance than those that use CEs on traditional FTO glass. Moreover, the TiC, WO2, and VN on the BG substrates show excellent catalytic activities that can match the performance of the CEs on FTO glasses.

  • 278.
    Westermark, K
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics II. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Tingry, S
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics II. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Persson, P
    Rensmo, Håkan
    Lunell, S
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Quantum Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics II. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics II. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Siegbahn, H
    Triarylamine on nanocrystalline TiO2 studied in its reduced and oxidized state by photoelectron spectroscopy2001In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 105, no 30, p. 7182-7187Article in journal (Refereed)
    Abstract [en]

    The electronic and molecular structures of an electrochemically reduced and oxidized triarylamine layer (((3-ethyl(p-N,N-dimethylamino)phenyl)amino)propyl-1-phosphonic acid) adsorbed on a nanocrystalline TiO2 film have been investigated. Photoelectron spe

  • 279.
    Westermark, Karin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Henningsson, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Södergren, Sven
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Siegbahn, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Determination of the electronic density of states at a nanostructured TiO2/Ru-dye/electrolyte interface by means of photoelectron spectroscopy2002In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 285, no 1, p. 157-165Article in journal (Refereed)
    Abstract [en]

    In this work, photoelectron spectroscopy is used to measure the electronic density of states in the band gap region of a nanostructured TiO2 film. Such nanostructured films are used in dye-sensitized solar cells, and in this study a plain TiO2 film as well as a dye-sensitized film were examined. Further, to simulate the electrolyte effect on the energy levels at the oxide/dye/electrolyte interface in a solar cell, the density of states in the band gap region for an electrochemically prepared TiO2 film inserted with Li+ ions was measured. From the experimental findings we discuss the distribution and chemical nature of electron trap states in the band gap and the energy matching between the LUMO level of the adsorbed dye, cis-bis(4,4-dicarboxy-2,2-bipyridine)-bis(isothiocyanato)ruthenium(II), and the TiO2 conduction band edge.

  • 280.
    Westermark, Karin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Rensmo, Håkan
    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.
    Keis, Karin
    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.
    Ojamäe, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Persson, Petter
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    PES Studies of Ru(dcbpyH2)2(NCS)2 Adsorption on Nanostructured ZnO for Solar Cell Applications2002In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 106, no 39, p. 10102-10107Article in journal (Refereed)
    Abstract [en]

    The interaction between the dye cis-bis(4,4‘-dicarboxy-2,2‘-bipyridine)-bis(isothiocyanato)-ruthenium(II), Ru(dcbpyH2)2(NCS)2, and nanostructured ZnO was investigated by photoelectron spectroscopy (PES) using synchrotron radiation. The results are compared with those of nanostructured TiO2 sensitized with the same dye, which to date is the most efficient system for dye-sensitized photoelectrochemical solar cells. When comparing the two metal oxides, differences in the surface molecular structure were observed both for low and high dye coverages, as seen by comparing the oxygen, nitrogen and sulfur signals. The origin of these differences is discussed in terms of substrate-induced dye aggregation and in variations in surface bonding geometries. The measurements also provide information concerning the energy matching between the orbitals of the dye and the ZnO valence band, which is of importance in photoinduced charge transfer.

  • 281.
    Wiberg, Joanna
    et al.
    Chalmers University of Technology.
    Marinado, Tannia
    Physical Chemistry KTH and Division of Chemistry and Materials Shinshu University, Japan.
    Hagberg, Daniel P
    Organic Chemistry, KTH.
    Sun, Licheng
    Organic Chemistry, KTH.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Albinsson, Bo
    Chalmers University of Technology.
    Distance and driving force dependencies of electron injection and recombination dynamics in organic dye-sensitized solar cells.2010In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 114, no 45, p. 14358-14363Article in journal (Refereed)
    Abstract [en]

    A series of dyes based on a triphenylamine donor and a rhodanine acetic acid anchor/acceptor for solar cell application has been studied with regards to electron injection and recombination kinetics using femtosecond transient absorption. The series contains three dyes, with estimated electron transfer distances ranging from 17.2 to 11.0 Å, and which have shown significant differences in energy conversion efficiencies. The injection and recombination kinetics were studied in the NIR region where electrons in the conduction band of the TiO(2) are suggested to absorb. For all dyes, the injection rate is larger than (200 fs)(-1) which implicates a quantitative injection efficiency. Surprisingly, the subsequent recombination reaction has a rate that increases with increasing linker length. On the other hand, this behavior is consistent with the concomitant decrease in driving force for this series of dyes. Moreover, the lifetimes show exponential distance dependence when corrected for driving force and reorganization energy, which indicates a superexchange interaction between the electrons in TiO(2) and the radical cations of the dyes. A dependence on probe wavelength of the attenuation factor was found, giving a β value of 0.38 Å(-1) at 940 nm and 0.49 Å(-1) at 1040 nm. The difference is suggested to be due to the difference in electronic coupling between fully separated dye cations and injected electrons versus geminate electron-hole pairs. Addition of tert-butylpyridine, which from previous work is known to give a substantial drop in the IPCE values for the studied dyes, was found to decrease the amount of long-lived electrons in the TiO(2) without affecting the injection rate.

  • 282. Wu, Mingxing
    et al.
    Bai, Jin
    Wang, Yudi
    Wang, Anjie
    Lin, Xiao
    Wang, Liang
    Shen, Yihua
    Wang, Zeqing
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Ma, Tingli
    High-performance phosphide/carbon counter electrode for both iodide and organic redox couples in dye-sensitized solar cells2012In: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 22, no 22, p. 11121-11127Article in journal (Refereed)
    Abstract [en]

    In the present study, molybdenum phosphide (MoP), nickel phosphide (Ni5P4), and carbon-supported Ni5P4 (Ni5P4/C) were proposed for use as counter electrode (CE) catalysts in dye-sensitized solar cells (DSCs) for the regeneration of both the conventional I-3(-)/I- redox couple and a new organic T-2/T- redox couple. For the I-3(-)/I- redox couple, the DSCs using MoP and Ni5P4 CE yielded a power conversion efficiency (PCE) of 4.92 and 5.71%, and the DSC using Ni5P4/C showed a high PCE of 7.54%, which was close to that of the DSC using Pt CE (7.76%). For the T-2/T- redox couple, Ni5P4/C performed much better than Pt and the DSC using Ni5P4/C CE showed a PCE of 4.75%, much higher than the photovoltaic performance of the DSC using Pt CE (3.38%).

  • 283. Wu, Mingxing
    et al.
    Guo, Hongyue
    Lin, Ya-nan
    Wu, Kezhong
    Ma, Tingli
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Synthesis of Highly Effective Vanadium Nitride (VN) Peas as a Counter Electrode Catalyst in Dye-Sensitized Solar Cells2014In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 118, no 24, p. 12625-12631Article in journal (Refereed)
    Abstract [en]

    Vanadium nitride (VN) peas and cubes were synthesized by regulating the molar ratio of the starting materials (urea/VOCl3) via the urea-metal chloride route. The as-prepared VN compounds were subsequently introduced into dye-sensitized solar cells (DSCs) as counter electrode (CE) catalysts for the regeneration of novel organic thiolate/disulfide (T-/T-2) and traditional iodide/triiodide (I-/I-3(-))redox couples. The cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and Tafel polarization curve results proved that the catalytic activity of the prepared VN was significantly affected by particle shape and particle size. The VN peas showed the highest catalytic activity, followed by the small VN cubes and large VN cubes. The I-/I-3(-)-electrolyte-based DSCs yielded a high power conversion efficiency (PCE) of 7.29%. The Pt-free VN CE catalysts are more suitable for the new organic redox couples of T-/T-2. The DSCs based on VN peas CE showed a PCE of 5.57%, an enhancement of 40.7% relative to the Pt-CE-based DSCs (3.96%).

  • 284. Wu, Mingxing
    et al.
    Lin, Xiao
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Ma, Tingli
    A novel catalyst of WO2 nanorod for the counter electrode of dye-sensitized solar cells2011In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 47, no 15, p. 4535-4537Article in journal (Refereed)
    Abstract [en]

    Tungsten dioxide (WO2) nanorods were synthesized, which showed excellent catalytic activity for the reduction of triiodide to iodide. The dye-sensitized solar cell (DSC) using WO2 as a counter electrode (CE) reached a high energy conversion efficiency of 7.25%, which can match the performance of the DSC based on a Pt CE.

  • 285. Wu, Mingxing
    et al.
    Lin, Xiao
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Ma, Tingli
    Low-Cost Molybdenum Carbide and Tungsten Carbide Counter Electrodes for Dye-Sensitized Solar Cells2011In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 50, no 15, p. 3520-3524Article in journal (Refereed)
  • 286. Wu, Mingxing
    et al.
    Lin, Xiao
    Wang, Liang
    Guo, Wei
    Wang, Yudi
    Xiao, Jinqiu
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry.
    Ma, Tingli
    In Situ Synthesized Economical Tungsten Dioxide Imbedded in Mesoporous Carbon for Dye-Sensitized Solar Cells As Counter Electrode Catalyst2011In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 115, no 45, p. 22598-22602Article in journal (Refereed)
    Abstract [en]

    Tungsten dioxide imbedded in mesoporous carbon (WO(2)-MC) was obtained by in situ synthesis and then introduced into dye-sensitized solar cells (DSCs) as a counter electrode (CE) catalyst. Catalytic activity for redox couple regeneration was improved significantly through combining high electrical conductivity and catalytic activity into one material, WO(2)-MC, in which WO(2) served as a catalyst and MC served as an electrical conductor. This has been proved by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The triiodide/iodide-based DSC using WO(2)-MC as CE showed a high power conversion efficiency (PCE) of 7.76%, which surpassed the performance of the DSC using traditional Pt CE (7.55%). In addition, the WO(2)-MC and WO(2) nanorods exhibited higher catalytic activity than Pt for the regeneration of a new organic redox couple, di-5-(1-methyltetrazole) disulfide/5-mercapto-1-methyltetrazole N-tetramethylammonium salt (T(2)/T(-)). The PCE of the T(2)/T(-)-based DSCs using WO(2)-MC, WO(2), and Pt were 5.22, 4.66, and 3.09%, respectively.

  • 287. Wu, Mingxing
    et al.
    Lin, Xiao
    Wang, Yudi
    Wang, Liang
    Guo, Wei
    Qu, Daidi
    Peng, Xiaojun
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Graetzel, Michael
    Ma, Tingli
    Economical Pt-Free Catalysts for Counter Electrodes of Dye-Sensitized Solar Cells2012In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 134, no 7, p. 3419-3428Article in journal (Refereed)
    Abstract [en]

    Three classes (carbides, nitrides and oxides) of nanoscaled early-transition-metal catalysts have been proposed to replace the expensive Pt catalyst as counter electrodes (CEs) in dye-sensitized solar cells (DSCs). Of these catalysts, Cr3C2, CrN, VC(N), VN, TiC, TiC(N), TiN, and V2O3 all showed excellent catalytic activity for the reduction of I-3(-) to I- in the electrolyte. Further, VC embedded in mesoporous carbon (VC-MC) was prepared through in situ synthesis. The I-3(-)/I- DSC based on the VC-MC CE reached a high power conversion efficiency (PCE) of 7.63%, comparable to the photovoltaic performance of the DSC using a Pt CE (7.50%). In addition, the carbide catalysts demonstrated catalytic activity higher than that of Pt for the regeneration of a new organic redox couple of T-2/T-. The T-2/T- DSCs using TiC and VC-MC CEs showed PCEs of 4.96 and 5.15%, much higher than that of the DSC using a Pt CE (3.66%). This work expands the list of potential CE catalysts, which can help reduce the cost of DSCs and thereby encourage their fundamental research and commercial application.

  • 288. Wu, Mingxing
    et al.
    Lin, Ya-nan
    Guo, Hongyue
    Ma, Tingli
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Highly effective Pt/MoSi2 composite counter electrode catalyst for dye-sensitized solar cell2014In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 263, p. 154-157Article in journal (Refereed)
    Abstract [en]

    MoSi2 is introduced into dye-sensitized solar cell (DSC) as counter electrode (CE) catalyst for the first time, and the DSC produces power conversion efficiency (PCE) of 4.87%. To improve the catalytic activity, Pt/MoSi2 composite catalyst is synthesized and it is found that 1.13 wt% of Pt loading is enough for achieving high catalytic activity. After optimization, the DSC using the Pt/MoSi2 composite CE shows high PCE of 7.68%, close to the Pt CE based DSC (7.94%).  

  • 289. Wu, Mingxing
    et al.
    Wang, Yudi
    Lin, Xiao
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Ma, Tingli
    An Autocatalytic Factor in the Loss of Efficiency in Dye-Sensitized Solar Cells2012In: ChemCatChem, ISSN 1867-3880, E-ISSN 1867-3899, Vol. 4, no 9, p. 1255-1258Article in journal (Refereed)
  • 290. Wu, Mingxing
    et al.
    Wang, Yudi
    Lin, Xiao
    Yu, Naisen
    Wang, Liang
    Wang, Linlin
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Ma, Tingli
    Economical and effective sulfide catalysts for dye-sensitized solar cells as counter electrodes2011In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 13, no 43, p. 19298-19301Article in journal (Refereed)
    Abstract [en]

    Molybdenum sulfide (MoS(2)) and tungsten sulfide (WS(2)) are proposed as counter electrode (CE) catalysts in a I(3)(-)/I(-) and T(2)/T(-) based dye-sensitized solar cells (DSCs) system. The I(3)(-)/I(-) based DSCs using MoS(2) and WS(2) CEs achieved power conversion efficiencies of 7.59% and 7.73%, respectively.

  • 291. Wu, Mingxing
    et al.
    Zhang, Qingyu
    Xiao, Jinqiu
    Ma, Chunyu
    Lin, Xiao
    Miao, Chunyu
    He, Youjing
    Gao, Yurong
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Ma, Tingli
    Two flexible counter electrodes based on molybdenum and tungsten nitrides for dye-sensitized solar cells2011In: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 21, no 29, p. 10761-10766Article in journal (Refereed)
    Abstract [en]

    Two novel flexible counter electrodes (CEs) on Ti sheets using molybdenum and tungsten nitrides (Mo(2)N, W(2)N) as catalysts were synthesized and used in a dye-sensitized solar cell (DSC) system. High catalytic activity of the two nitride CEs for the reduction of triiodide were proved by cyclic voltammetry, electrochemical impedance spectroscopy and Tafel-polarization measurements. The DSCs based on Mo(2)N and W(2)N CEs achieved power conversion efficiencies of 6.38 and 5.81%, reaching 91 and 83% of the photovoltaic performance of the DSC using a Pt CE, respectively. This research paves a promising way to develop new CE catalysts and reduce the cost of DSCs.

  • 292. Xu, Bo
    et al.
    Huang, Jing
    Agren, Hans
    Kloo, Lars
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Sun, Licheng
    AgTFSI as p-Type Dopant for Efficient and Stable Solid-State Dye-Sensitized and Perovskite Solar Cells2014In: ChemSusChem, ISSN 1864-5631, E-ISSN 1864-564X, Vol. 7, no 12, p. 3252-3256Article in journal (Refereed)
    Abstract [en]

    A silver-based organic salt, silver bis(trifluoromethane-sulfonyl) imide (AgTFSI), was employed as an effective p-type dopant for the triarylamine-based organic hole-transport material Spiro-MeOTAD, which has been successfully applied in solid-state dye-sensitized solar cells (ssDSCs) and perovskite solar cells (PSCs). The power conversion efficiencies (PCEs) of AgTFSI-doped devices improved by 20%, as compared to the device based on the commonly used oxygen doping both for ssDSCs and PSCs. Moreover, the solid-state dye-sensitized devices exposed to AgTFSI as dopant showed considerably better stability than those of oxygen doped, qualifying this p-type dopant as a promising alterative for the preparation of highly efficient as well as stable ssDSCs and PSCs for the future.

  • 293. Xu, Bo
    et al.
    Sheibani, Esmaeil
    Liu, Peng
    Zhang, Jinbao
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Tian, Haining
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Vlachopoulos, Nick
    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.
    Kloo, Lars
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Sun, Licheng
    Carbazole-Based Hole-Transport Materials for Efficient Solid-State Dye-Sensitized Solar Cells and Perovskite Solar Cells2014In: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 26, no 38, p. 6629-6634Article in journal (Refereed)
  • 294. Xu, Bo
    et al.
    Tian, Haining
    Bi, Dongqin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Gabrielsson, Erik
    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.
    Sun, Licheng
    Efficient solid state dye-sensitized solar cells based on an oligomer hole transport material and an organic dye2013In: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 1, no 46, p. 14467-14470Article in journal (Refereed)
    Abstract [en]

    A low-cost and easily-synthesized organic hole transport material (HTM) X3 bearing triphenylamine units and an organic dye was utilized for solid state dye sensitized solar cells (ssDSCs), which have achieved the power conversion efficiencies of 5.8% and 7.1% under 1 sun and 0.46 sun, respectively, outperforming the ssDSC based on Spiro-OMeTAD 5.4% (1 sun) and 6.4% (0.46 sun).

  • 295. Xu, Bo
    et al.
    Tian, Haining
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Lin, Lili
    Qian, Deping
    Chen, Hong
    Zhang, Jinbao
    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.
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Luo, Yi
    Zhang, Fengling
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Sun, Licheng
    Integrated Design of Organic Hole Transport Materials for Efficient Solid-State Dye-Sensitized Solar Cells2015In: ADVANCED ENERGY MATERIALS, ISSN 1614-6832, Vol. 5, no 3, article id 1401185Article in journal (Refereed)
    Abstract [en]

    A series of triphenylamine-based small molecule organic hole transport materials (HTMs) with low crystallinity and high hole mobility are systematically investigated in solid-state dye-sensitized solar cells (ssDSCs). By using the organic dye LEG4 as a photosensitizer, devices with X3 and X35 as the HTMs exhibit desirable power conversion efficiencies (PCEs) of 5.8% and 5.5%, respectively. These values are slightly higher than the PCE of 5.4% obtained by using the state-of-the-art HTM Spiro-OMeTAD. Meanwhile, transient photovoltage decay measurement is used to gain insight into the complex influences of the HTMs on the performance of devices. The results demonstrate that smaller HTMs induce faster electron recombination in the devices and suggest that the size of a HTM plays a crucial role in device performance, which is reported for the first time.

  • 296. Yanagisawa, Masaru
    et al.
    Korodi, Ferenc
    Bergquist, Jonas
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry. Department of Physical and Analytical Chemistry, Physical Chemistry. Analytical Chemistry. Analytisk kemi.
    Holmberg, Anna
    Hagfeldt, Anders
    Department of Physical Chemistry. Department of Physical and Analytical Chemistry, Physical Chemistry. Analytical Chemistry.
    Åkermark, Björn
    Sun, Licheng
    Synthesis of phthalocyanines with two carboxylic acid groups and their utilization in solar cells based on nano-structured TiO22004In: Journal of Porphyrins and Phthalocyanines, Vol. 8, no 10, p. 1228-1235Article in journal (Refereed)
  • 297.
    Yang, Lei
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry.
    Cappel, Ute B.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry.
    Unger, Eva L.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry.
    Karlsson, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry.
    Karlsson, Karl Martin
    Gabrielsson, Erik
    Sun, Licheng
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry.
    Johansson, Erik M. J.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry.
    Comparing spiro-OMeTAD and P3HT hole conductors in efficient solid state dye-sensitized solar cells2012In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 14, no 2, p. 779-789Article in journal (Refereed)
    Abstract [en]

    Two hole conductor materials, spiro-OMeTAD and P3HT, were compared in solid-state dye-sensitized solar cells. Two organic dyes containing one anchor unit (D35) or two anchor units (M3) were used in the comparison. Absorbed photon to current conversion efficiency close to unity was obtained for the devices with spiro-OMeTAD. Energy conversion efficiencies of 4.7% and 4.9% were measured for the devices with spiro-OMeTAD and the dyes D35 and M3, respectively. For the devices using the P3HT hole conductor the results were rather different comparing the two dye molecules, with energy conversion efficiencies of 3.2% and 0.5% for D35 and M3, respectively. Photo-induced absorption measurements suggest that the regeneration of the dyes, and the polymer infiltration, is not complete using P3HT, while spiro-OMeTAD regenerates the dyes efficiently. However, the TiO(2)/D35/P3HT system shows rather high energy conversion efficiency and electrochemical oxidation of the dyes on TiO(2) indicates that D35 have a more efficient dye to dye hole conduction than M3, which thereby might explain the higher performance. The dye hole conduction may therefore be of significant importance for optimizing the energy conversion in such hybrid TiO(2)/dye/polymer systems.

  • 298.
    Yang, Lei
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Xu, Bo
    Bi, Dongqin
    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.
    Sun, Licheng
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Johansson, Erik M. J.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Initial Light Soaking Treatment Enables Hole Transport Material to Outperform Spiro-OMeTAD in Solid-State Dye-Sensitized Solar Cells2013In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 135, no 19, p. 7378-7385Article in journal (Refereed)
    Abstract [en]

    Efficient solid state dye-sensitized solar cells (sDSCs) were obtained using a small hole transport material, MeO-TPD (N,N,N',N'-tetrakis(4-methoxyphenyl)benzidine), after an initial light soaking treatment. It was discovered that the light soaking treatment for the MeO-TPD based solar cells is essential in order to achieve the high efficiency (4.9%), which outperforms spiro-OMeTAD based sDSCs using the same dye and device preparation parameters. A mechanism based on Li+ ion migration is suggested to explain the light soaking effect. It was observed that the electron lifetime for the MeO-TPD based sDSC strongly increases after the light soaking treatment, which explains the higher efficiency. After the initial light soaking treatment the device efficiency remains considerably stable with only 0.2% decrease after around 1 month (unsealed cells stored in dark).

  • 299.
    Yang, Lei
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Zhang, Jinbao
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Shen, Yang
    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.
    Bi, Dongqin
    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.
    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.
    Vlachopoulos, Nick
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Snedden, Alan
    Kloo, Lars
    Jarboui, Adel
    Chams, Amani
    Perruchot, Christian
    Jouini, Mohamed
    New Approach for Preparation of Efficient Solid-State Dye-Sensitized Solar Cells by Photoelectrochemical Polymerization in Aqueous Micellar Solution2013In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 4, no 23, p. 4026-4031Article in journal (Refereed)
    Abstract [en]

    Hereby, we present a new, cost-effective, and environmentally friendly method of preparing an efficient solid-state dye-sensitized solar cell (sDSC) using a PEDOT conducting polymer as the hole conductor and a recently developed organic sensitizer. PEDOT is generated and deposited on the dye-sensitized TiO2 electrode by in situ photoelectropolymerization of bis-EDOT in aqueous micellar solution. The advantages of this approach are the use of water as the solvent and the obtainment of a sDSC simply by adding a silver layer on the as-obtained polymer film deposited on dye/TiO2 without the need for electrolytic solution. The sDSC containing the film prepared as above is compared to those where the organic dye is used to generate the same polymer film but in organic solvent. The energy conversion efficiency values of the two cells appear comparable, 4.8% for sDSC prepared in the aqueous-phase polymerized PEDOT and 6% for the sDSC prepared with in organic-phase polymerized PEDOT.

  • 300.
    Yang, Wenxing
    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.
    Hao, Yan
    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.
    Efficient dye regeneration at low driving force achieved in triphenylamine dye LEG4 and TEMPO redox mediator based dye-sensitized solar cells2015In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 17, no 24, p. 15868-15875Article in journal (Refereed)
    Abstract [en]

    Minimizing the driving force required for the regeneration of oxidized dyes using redox mediators in an electrolyte is essential to further improve the open-circuit voltage and efficiency of dye-sensitized solar cells (DSSCs). Appropriate combinations of redox mediators and dye molecules should be explored to achieve this goal. Herein, we present a triphenylamine dye, LEG4, in combination with a TEMPO-based electrolyte in acetonitrile (E-0 = 0.89 V vs. NHE), reaching an efficiency of up to 5.4% under one sun illumination and 40% performance improvement compared to the previously and widely used indoline dye D149. The origin of this improvement was found to be the increased dye regeneration efficiency of LEG4 using the TEMPO redox mediator, which regenerated more than 80% of the oxidized dye with a driving force of only similar to 0.2 eV. Detailed mechanistic studies further revealed that in addition to electron recombination to oxidized dyes, recombination of electrons from the conducting substrate and the mesoporous TiO2 film to the TEMPO+ redox species in the electrolyte accounts for the reduced short circuit current, compared to the state-of-the-art cobalt tris(bipyridine) electrolyte system. The diffusion length of the TEMPO-electrolyte based DSSCs was determined to be similar to 0.5 mu m, which is smaller than the similar to 2.8 mu m found for cobalt-electrolyte based DSSCs. These results show the advantages of using LEG4 as a sensitizer, compared to previously record indoline dyes, in combination with a TEMPO-based electrolyte. The low driving force for efficient dye regeneration presented by these results shows the potential to further improve the power conversion efficiency (PCE) of DSSCs by utilizing redox couples and dyes with a minimal need of driving force for high regeneration yields.

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