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  • 201.
    Elmgren, Maja
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Forsberg, Eva
    Uppsala universitet, Humanistisk-samhällsvetenskapliga vetenskapsområdet, Fakulteten för utbildningsvetenskaper, Institutionen för pedagogik, didaktik och utbildningsstudier.
    Management and leadership of doctoral education2011Konferansepaper (Annet vitenskapelig)
  • 202.
    Elmgren, Maja
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Forsberg, Eva
    Uppsala universitet, Humanistisk-samhällsvetenskapliga vetenskapsområdet, Fakulteten för utbildningsvetenskaper, Institutionen för pedagogik, didaktik och utbildningsstudier.
    Lindberg-Sand, Åsa
    Lund University.
    Sonesson, Anders
    Lund University.
    Doctoral education shapes the academy – what shapes doctoral education?2014Inngår i: Proc. ICED 2014: Educational development in a changing world, London: International Consortium for Educational Development , 2014Konferansepaper (Fagfellevurdert)
    Abstract [en]

    For universities all over the world, the strategic importance of doctoral education has increased over the last decades. Both locally and internationally we can observe growing activity in three interrelated areas of doctoral education: policy, knowledge formation and practice. Doctoral education is moving and has become a concern for the field of educational development.

    In a recent Swedish report on quality and leadership in doctoral education1 we elaborate on the many different ways in which doctoral education is essential for the regeneration, legitimacy and development of the academy and all its practices.

    We also describe how doctoral education to a large extent is built upon and integrated with other academic practices; primarily research but also undergraduate education and public outreach, and as a consequence is highly dependent on the organisation, infrastructure and quality enhancing processes of these.

    This reciprocal relationship and interdependence between the academy and doctoral education is under-studied and recent and future changes to doctoral education, at the policy as well as at the practice level, could mean considerable and unpredictable consequence for the academy. In our report we identify an on-going shift in power over Swedish doctoral education – away from the academy and towards the political arenas and funding bodies. This shift has reshaped both content and form of doctoral education. There is a marked risk that such changes could undermine the academy’s capacity to fulfil its mission.

    In this paper we will discuss conditions and recent developments in Sweden that is currently shaping doctoral education and describe the mechanisms at work.

    We will end by addressing a few areas of particular concern for educational development

  • 203.
    Elmgren, Maja
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Forsberg, Eva
    Uppsala universitet, Humanistisk-samhällsvetenskapliga vetenskapsområdet, Fakulteten för utbildningsvetenskaper, Institutionen för pedagogik, didaktik och utbildningsstudier.
    Lindberg-Sand, Åsa
    Lunds universitet.
    Sonesson, Anders
    Lunds universitet.
    The formation of doctoral education2016Rapport (Annet vitenskapelig)
    Fulltekst (pdf)
    fulltext
  • 204.
    Elmgren, Maja
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Henriksson, Ann-Sofie
    Academic teaching2018 (oppl. 2)Bok (Annet vitenskapelig)
  • 205.
    Elmgren, Maja
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi. Uppsala universitet, Universitetsförvaltningen.
    Henriksson, Ann-Sofie
    Uppsala universitet, Universitetsförvaltningen.
    Kvalitativt lärande på begränsad tid2008Inngår i: Proceedings NU2008: Kalmar, 16-18 Maj / [ed] Anders Sonesson & Maria Hedberg, 2008, s. 225-233Konferansepaper (Fagfellevurdert)
  • 206.
    Elmgren, Maja
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Henriksson, Ann-Sofie
    Universitetspedagogik2016 (oppl. 3)Bok (Annet vitenskapelig)
  • 207.
    Elmgren, Maja
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Ho, Felix M.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Åkesson, Eva
    Uppsala universitet, Universitetsförvaltningen.
    Schmid, Siegbert
    University of Sydney, School of Chemistry.
    Towns, Marcy
    Purdue University, Department of Chemistry.
    Comparison and Evaluation of Learning Outcomes from an International Perspective: Development of a Best-Practice Process2015Inngår i: Journal of Chemical Education, ISSN 0021-9584, E-ISSN 1938-1328, Vol. 92, nr 3, s. 427-432Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Chemistry education focused on learning outcomes is increasingly practiced, providing new opportunities for international comparisons. The interest in intended learning outcomes and constructive alignment has grown in many parts of the world due to both research in higher education and political decisions. In an International Union of Pure and Applied Chemistry (IUPAC) project, we have developed a method of using critical evaluation of learning outcomes and descriptors at international, national, and institutional levels to enhance learner-centered chemistry education. This method is process-focused, aimed at learning by sharing and comparing practices around the world. Three overarching documents for the chemistry bachelor from the USA, Europe and Australia were compared. The differences were found to be more in style than in content. A tool for self-analysis was constructed to evaluate how learning outcomes for courses and modules are linked to each other and to learning outcomes for educational programs and how the expected learning outcomes can be aligned with learning activities and assessment. We conclude that the method can be used to elucidate the correspondence between learning outcomes at different levels, and the constructive alignment between learning outcomes, learning activities and assessment. The process gives new perspectives and shared knowledge. Chemistry education may need to be different depending on local considerations, and awareness of these differences is of value for further development.

  • 208.
    Elmgren, Maja
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Åkesson, Eva
    Uppsala universitet, Universitetets ledning.
    Ho, Felix
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Schmid, Siegbert
    The University of Sydney.
    Parchmann, Ilka
    University of Kiel.
    Aremo, Nina
    University of Helsinki.
    Apotheker, Jan H.
    University of Groningen.
    Mimero, Pascal
    EI CESI.
    Namli, Hilmi
    Balikesir Universtitu.
    Reiners, Christiane S.
    Universität zu Köln.
    Towns, Marcy
    Purdue University.
    Best Practices in the Use of Learning Outcomes in Chemistry Education2013Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Guiding chemistry education for the future requires the exchange of perspectives on core knowledge, skills and competencies. Learning outcomes-driven chemistry education is increasingly practiced, providing new opportunities for international comparisons. The interest in intended learning outcomes and constructive alignment has grown in many parts of the world due to both research in higher education [1] and political decisions (e. g. the Bologna process in Europe). 

    We have developed a method for learning by sharing and comparing best practice of the use of these outcomes, to enhance learner-centered chemistry education both in the developed and developing countries. As a starting point, the overarching guidelines for chemistry education in Europe, North America and Australia were compared and discussed, with awareness of varying circumstances and terminology, which is necessary for this project to be useful in different settings. In focus were chemistry-specific and transferable skills as well as some higher order thinking skills (including aspects of conceptual, procedural and metacognitive knowledge [2]) rather than content and factual knowledge.

    The overarching guidelines were in turn compared with local learning outcomes for chemistry education at several universities. We evaluated how learning outcomes for courses and modules were linked to each other and to learning outcomes for educational programs. Furthermore we discussed how the expected learning outcomes were aligned with learning activities and assessment. A tool was designed to facilitate this, and used for self-analysis at the involved universities.

    We conclude that the method has promising features and can be used to elucidate the correspondence between learning outcomes at different levels, and the constructive alignment between learning outcomes, learning activities and assessment. A full electronic report and manual for the benchmarking procedure will be produced at the conclusion of the project, including a collection of examples of good/best practice for dissemination.

    References

    1. J. B. Biggs      and C. S. Tang, Teaching for quality learning at university: what the      student does. (Open University Press, Maidenhead, 2011).
    2. L. W. Anderson      and D. R. Krathwohl et al., Taxonomy for learning, teaching and assessing      – A revision of Bloom’s taxonomy of educational objectives (Longman, New      York, 2001)
  • 209.
    El-Zohry, Ahmed
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi. Stockholm Univ, Dept Phys, AlbaNova Univ Ctr, SE-10691 Stockholm, Sweden..
    Agrawal, Saurabh
    Ist CNR Sci & Tecnol Chim Giulio Natta CNR SCITEC, Computat Lab Hybrid Organ Photovolta CLHYO, I-06123 Perugia, Italy..
    De Angelis, Filippo
    Ist CNR Sci & Tecnol Chim Giulio Natta CNR SCITEC, Computat Lab Hybrid Organ Photovolta CLHYO, I-06123 Perugia, Italy.;Univ Perugia, Dept Chem Biol & Biotechnol, I-06123 Perugia, Italy.;Ist Italiano Tecnol, CompuNet, I-16163 Genoa, Italy..
    Pastore, Mariachiara
    Univ Lorraine, Lab Phys & Chim Theor LPCT, F-54000 Nancy, France.;CNRS, F-54000 Nancy, France..
    Zietz, Burkhard
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Critical Role of Protons for Emission Quenching of Indoline Dyes in Solution and on Semiconductor Surfaces2020Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 124, nr 39, s. 21346-21356Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    By combining time-correlated single photon counting (TCSPC) measurements, density functional theory (DFT), and time-dependent DFT (TD-DFT) calculations, we herein investigate the role of protons, in solutions and on semiconductor surfaces, for the emission quenching of indoline dyes. We show that the rhodanine acceptor moieties, and in particular the carbonyl oxygens, undergo protonation, leading to nonradiative excited-state deactivation. The presence of the carboxylic acid anchoring group, close to the rhodanine moiety, further facilitates the emission quenching, by establishing stable H-bond complexes with carboxylic acid quenchers, with high association constants, in both ground and excited states. This complexation favors the proton transfer process, at a low quencher concentration, in two ways: bringing close to the rhodanine unit the quencher and assisting the proton release from the acid by a partial-concerted proton donation from the close-by carboxylic group to the deprotonated acid. Esterification of the carboxylic group, indeed, inhibits the ground-state complex formation with carboxylic acids and thus the quenching at a low quencher concentration. However, the rhodanine moiety in the ester form can still be the source of emission quenching through dynamic quenching mechanism with higher concentrations of protic solvents or carboxylic acids. Investigating this quenching process on mesoporous ZrO2, for solar cell applications, also reveals the sensitivity of the adsorbed excited rhodanine dyes toward adsorbed protons on surfaces. This has been confirmed by using an organic base to remove surface protons and utilizing cynao-acrylic dye as a reference dye. Our study highlights the impact of selecting such acceptor group in the structural design of organic dyes for solar cell applications and the overlooked role of protons to quench the excited state for such chemical structures.

  • 210.
    El-Zohry, Ahmed
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi. Stockholm Univ, Dept Phys, AlbaNova Univ Ctr, SE-10691 Stockholm, Sweden..
    Diez-Cabanes, Valentin
    Univ Lorraine, F-54000 Nancy, France.;CNRS, Lab Phys & Chim Theor LPCT, F-54000 Nancy, France..
    Pastore, Mariachiara
    Univ Lorraine, F-54000 Nancy, France.;CNRS, Lab Phys & Chim Theor LPCT, F-54000 Nancy, France..
    Ahmed, Taha
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Strukturkemi.
    Zietz, Burkhard
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström.
    Highly Emissive Biological Bilirubin Molecules: Shedding New Light on the Phototherapy Scheme2021Inngår i: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 125, nr 32, s. 9213-9222Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Bilirubin (BR) is the main end-product of the hemoglobin catabolism. For decades, its photophysics has been mainly discussed in terms of ultrafast deactivation of the excited state in solution, where, indeed, BR shows a very low green emission quantum yield (EQY), 0.03%, resulting from an efficient nonradiative isomerization process. Herein, we present, for the first time, unique and exceptional photophysical properties of solid-state BR, which amend by changing the type of crystal, from a closely packed alpha crystal to an amorphous loosely packed beta crystal. BR alpha crystals show a very bright red emission with an EQY of ca. 24%, whereas beta crystals present, in addition, a low green EQY of ca. 0.5%. By combining density functional theory (DFT) calculations and time-resolved emission spectroscopy, we trace back this dual emission to the presence of two types of BR molecules in the crystal: a "stiff" monomer, M1, distorted by particularly strong internal H-bonds and a "floppy" monomer, M2, having a structure close to that of BR in solution. We assign the red strong emission of BR crystals to M1 present in both the alpha and beta crystals, while the low green emission, only present in the amorphous (beta) crystal, is interpreted as M2 emission. Efficient energy-transfer processes from M2 to M1 in the closely packed a crystal are invoked to explain the absence of the green component in its emission spectrum. Interestingly, these unique photophysical properties of BR remain in polar solvents such as water. Based on these unprecedented findings, we propose a new model for the phototherapy scheme of BR inside the human body and highlight the usefulness of BR as a strong biological fluorescent probe.

    Fulltekst (pdf)
    FULLTEXT01
  • 211.
    El-Zohry, Ahmed
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Karlsson, Martin
    KTH Royal Inst Technol, Dept Chem, Appl Phys Chem, Teknikringen 30, SE-10044 Stockholm, Sweden.
    Gigantic Relevance of Twisted Intramolecular Charge Transfer for Organic Dyes Used in Solar Cells2018Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 122, nr 42, s. 23998-24003Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Within this work, we emphasis on the importance of twisted intramolecular charge transfer (TICT) process in organic dyes based on triphenyl amine moiety to achieve high performance in dye-sensitized solar cells. Through the comparison between two recent made dyes, Ll and L1Fc, on different semiconductors (TiO2, and ZrO2), we could spectrally and dynamically detect for the first time the formation of TICT state for Ll on ZrO2 after localized charge transfer (LCT) state population, and an electron injection process from TICT state on TiO2. However, for the excited L1Fc dye, the ultrafast electron transfer from ferrocene (Fc) moiety to the Ll unit quenched the formation of TICT state in L1Fc on semiconductors, leading instead to an electron injection process from the LCT state. The electron injection from TICT state in Ll associated with structural rearrangements on TiO2 leads to slow recombination process and an efficiency improvement of about 325%, compared to solar cells based on L1Fc dye, in which TICT state formation is hindered. Similar electron dynamics are obtained for Ll on TiO2 upon physically hindering the TICT process by adding polymer matrix. The presence of TICT state for Ll dye and similar triphenyl amine dyes aids to reconstruct the kinetic profile for these dyes on semiconductor surfaces, and to redesign organic dyes accordingly for higher efficiency in solar cells.

  • 212.
    El-Zohry, Ahmed M.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    The origin of slow electron injection rates for indoline dyes used in dye-sensitized solar cells2019Inngår i: Dyes and pigments, ISSN 0143-7208, E-ISSN 1873-3743, Vol. 160, s. 671-674Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This work highlights the direct impact of selecting acceptor moiety for organic dyes on the electron dynamics at faster time scales, in which overlooked photo-physical properties are present on semiconductor surfaces with specific acceptor moieties. Four top-performing dyes of indoline family (D131, D102, D149, and D205) sharing the same donor moiety, but through different acceptor groups, were selected and compared with respect of electron injection process, using ultrafast transient-infrared probe. The presence of rhodanine moiety at the acceptor unit in D102, D149 and D205, shows an additional slow electron injection process, of picosecond time-scale, on the low band-gap semiconductor, TiO2. This slow process is expected to be present due to a twisted intramolecular charge transfer/isomerized state of the excited dye prior to electron injection. This isomerized state reduces as well the detrimental electron recombination process rates, and results of high performance in solar cells based on these rhodanine dyes. Replacing the rhodanine moiety by a cyano-acrylic group in D131 dye shows faster electron injection and recombination processes, due to the lower dipole moment present in the excited state, hindering the formation of an isomerized state. These findings will aid to enhance the organic dyes design used in dye sensitized solar cells, in which designed photo-physical processes on semiconductor surfaces can increase the efficiencies of the solar cells.

  • 213.
    El-Zohry, Ahmed M.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Cong, Jiayan
    KTH Royal Inst Technol, Dept Chem, Appl Phys Chem, Teknikringen 30, SE-10044 Stockholm, Sweden..
    Karlsson, Martin
    KTH Royal Inst Technol, Dept Chem, Appl Phys Chem, Teknikringen 30, SE-10044 Stockholm, Sweden..
    Kloo, Lars
    KTH Royal Inst Technol, Dept Chem, Appl Phys Chem, Teknikringen 30, SE-10044 Stockholm, Sweden..
    Zietz, Burkhard
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Ferrocene as a rapid charge regenerator in dye-sensitized solar cells2016Inngår i: Dyes and pigments, ISSN 0143-7208, E-ISSN 1873-3743, Vol. 132, s. 360-368Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Using the reductive power of the ferrocene moiety (Fc), an ultrafast regeneration step via a covalent attachment of a Fc moiety to an organic triphenylamine-based dye (L1) when adsorbed on TiO2 is highlighted. Two modified dyes with one and two Fc moieties attached (L1Fc, and L1Fc2), respectively, were synthesized by addition to the L1 dye. These dyes have been studied spectroscopically using ultrafast transient absorption spectroscopy in the visible and the infrared (IR) regions. In acetonitrile, the results show an ultrafast excited state quenching of the modified dyes due to an expected electron transfer process from the Fc(s) to L1. Adsorbed onto TiO2, an electron transfer process is also detected from Fc to the oxidized dye (L1(+)). Despite the occurrence of an ultrafast regeneration step, the solar cell performance does not improve by the attachment of Fc(s) to the dye L1. Transient absorption measurements in the IR region revealed a fast electron recombination process to the Fc(+) moiety on an average time scale of ca. 300 ps, outcompeting the >12 ns process to L1(+). The reasons for the observed considerably faster recombination rate to Fc(+) than to L1(+) are discussed in detail. This study provides deep spectroscopic insights for such organic dyes utilized to afford ultrafast regeneration step without showing high performance in photovoltaic devices. In addition, this study will improve our understandings for the triangular relationship between the molecular design, electron kinetics, and the performance in photovoltaic devices.

  • 214.
    El-Zohry, Ahmed M.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Roca-Sanjuan, Daniel
    Zietz, Burkhard
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Ultrafast Twisting of the Indoline Donor Unit Utilized in Solar Cell Dyes: Experimental and Theoretical Studies2015Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 119, nr 5, s. 2249-2259Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Previous time-resolved measurements on D149, the most-studied dye of the indoline family, had shown a fast time-component of 20-40 ps that had tentatively been attributed to structural relaxation. Using femtosecond transient absorption, we have investigated the isolated indoline donor unit (i.e., without acceptor group) and found an ultrafast decay characterized by two lifetimes of 3.5 and 23 ps. Density functional theory calculations show p-bonding and p*-antibonding character of the central ethylene group for the highest occupied and lowest unoccupied molecular orbitals (HOMO and LUMO), respectively. The LUMO is localized on the flexible vinyl-diphenyl region of the donor unit and a twisting process is assumed to occur as a deactivation process for the excited molecule. This is confirmed by multireference second-order perturbation theory (CASSCF/CASPT2) calculations of the lowest-lying excited state, in which it is shown that torsion of the ethylene bond to 96 degrees and pyramidalization to ca. 100 degrees lead to a conical intersection with the ground state. Embedded in a plastic matrix, where double bond rotation is hindered, the decay is slowed down to nanoseconds. We have also investigated the dyes D102, D131, and D149, possessing the same indoline donor unit, by femtosecond transient absorption and found a similar decay component. The ca. 20 ps deactivation channel in D-family dyes is thus attributed to a twisting process of the donor unit. The fluorescence quantum yields of this unit and D149 were measured, and from comparison, the competition of the discovered twisting deactivation channel to the radiative decay of the excited indoline dyes could be confirmed. Blocking this deactivation channel is expected to further increase efficiency for the indoline dyes.

  • 215.
    El-Zohry, Ahmed M.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Roca-Sanjuán, Daniel
    Instituto de Ciencia Molecular, Universitat de València, P.O. Box 22085, ES-46071 València, Spain.
    Zietz, Burkhard
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Ultrafast Twisting of the Indoline Donor Unit Utilized in Solar Cell Dyes: Experimental and Theoretical Studies2015Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 119, nr 5, s. 2249-2259Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Previous time-resolved measurements on D149, the most-studied dye of the indoline family, had shown a fast time-component of 20–40 ps that had tentatively been attributed to structural relaxation. Using femtosecond transient absorption, we have investigated the isolated indoline donor unit (i.e., without acceptor group) and found an ultrafast decay characterized by two lifetimes of 3.5 and 23 ps. Density functional theory calculations show π-bonding and π*-antibonding character of the central ethylene group for the highest occupied and lowest unoccupied molecular orbitals (HOMO and LUMO), respectively. The LUMO is localized on the flexible vinyl-diphenyl region of the donor unit and a twisting process is assumed to occur as a deactivation process for the excited molecule. This is confirmed by multireference second-order perturbation theory (CASSCF/CASPT2) calculations of the lowest-lying excited state, in which it is shown that torsion of the ethylene bond to 96° and pyramidalization to ca. 100° lead to a conical intersection with the ground state. Embedded in a plastic matrix, where double bond rotation is hindered, the decay is slowed down to nanoseconds. We have also investigated the dyes D102, D131, and D149, possessing the same indoline donor unit, by femtosecond transient absorption and found a similar decay component. The ca. 20 ps deactivation channel in D-family dyes is thus attributed to a twisting process of the donor unit. The fluorescence quantum yields of this unit and D149 were measured, and from comparison, the competition of the discovered twisting deactivation channel to the radiative decay of the excited indoline dyes could be confirmed. Blocking this deactivation channel is expected to further increase efficiency for the indoline dyes.

  • 216.
    El-Zohry, Ahmed M.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Zietz, Burkhard
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Concentration and Solvent Effects on the Excited State Dynamics of the Solar Cell Dye D149: The Special Role of Protons2013Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 117, nr 13, s. 6544-6553Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    D149 is one of the best-performing metal-free, organic dyes for dye-sensitized solar cells. Excited state lifetimes strongly depend on the solvent used and have previously been reported to be between 100 and 700 ps, without any mechanistic explanation being given. We have earlier shown that photo-isomerization is one of several deactivation processes. Here, we report that lifetimes in certain solvents depend on concentration, even in very dilute (nanomolar) solutions. A detailed investigation of the concentration dependence enables us to assign a second, faster deactivation channel besides isomerization that reduces lifetimes further: a ground-state, hydrogen-bonded 1:1 complex of D149 with acids or interaction with protic solvents leads to excited state quenching, most probably through excited state proton transfer. This includes self-quenching caused by D149's own carboxylic group through intermolecular interaction, accounting for the concentration-dependent lifetimes. We are now able to dissect the complex excited state behavior into its components, allowing us to attribute rate constants to the isomerization and the excited-state proton transfer process. We are also able to explain the excited state of D149 in a wide range of environmental conditions, in the presence of acids/bases, at different concentrations as well as with varying temperatures. Furthermore, we determine the barrier for isomerization, a thermally activated process. The consequences of these effects on solar cells are discussed. Also we show that ultrafast techniques like femtosecond pump probe and upconversion inherently do not provide the required responsiveness for work with the concentration ranges required here, whereas single photon counting with its ultimate sensitivity is able to resolve the underlying processes.

  • 217.
    El-Zohry, Ahmed M.
    et al.
    Angstrom Labs, Dept Chem, SE-75120 Uppsala, Sweden.;Stockholm Univ, Dept Phys, AlbaNova Univ Ctr, SE-10691 Stockholm, Sweden..
    Zietz, Burkhard
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi. Angstrom Labs, Dept Chem, SE-75120 Uppsala, Sweden..
    Electron Dynamics in Dye-Sensitized Solar Cells Influenced by Dye-Electrolyte Complexation2020Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 124, nr 30, s. 16300-16307Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Herein, we present the effect of ground-state complexation between organic photosensitizers and the utilized electrolyte in dye-sensitized solar cells. To do so, we selected a well-known standard organic dye, D149, and the traditional iodide/triiodide redox couple as a case study. First, we detected the ground-state interactions between the D149 dye and the electrolyte components in acetonitrile. These interactions in acetonitrile have been identified as well for the donor molecule of D149 and the ester form of D149. All of these ground-state complexes have relatively high binding constants in solution. In addition, a charge-transfer state has been detected for the [D149/I-2] complex in acetonitrile, giving long-lived species with a lifetime of more than hundreds of nanoseconds. The presence of these adsorbed complexes on semiconductor surfaces such as ZrO2 and TiO2 have been confirmed via steady-state absorption and time-resolved emission. More importantly, these complexes adsorb on the semiconductor surfaces, showing different electron dynamics on the TiO2 in comparison to the adsorbed D149 itself, in which the electron injection and recombination processes have been greatly modulated. Such formed complexes on the semiconductor surfaces can certainly limit the efficiency of a working solar cell based on similar organic dyes. Thus, attention to the structural design of the photosensitizers to avoid such formed complexes should be highlighted, which opens a new pathway for improving the solar cell efficiencies based on organic dyes.

  • 218.
    El-Zohry, Ahmed
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi. Stockholm Univ, Dept Phys, AlbaNova Univ Ctr, SE-10691 Stockholm, Sweden..
    Orabi, Esam A.
    Univ Manitoba, Dept Chem, Winnipeg, MB R3T 2N2, Canada..
    Karlsson, Martin
    KTH Royal Inst Technol, Appl Phys Chem, SE-10044 Stockholm, Sweden..
    Zietz, Burkhard
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Twisted Intramolecular Charge Transfer (TICT) Controlled by Dimerization: An Overlooked Piece of the TICT Puzzle2021Inngår i: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 125, nr 14, s. 2885-2894Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Organic dyes have shown high efficiencies in solar cells, which is mainly attributed to the push-pull strategy present in such dyes upon attaching to the semiconductor surfaces. We deeply studied the fundamental photophysical properties of cyanoacrylic dyes, mostly the L1 dye, and found unique emission properties that depend on many factors such as the solvent polarity and the concentration of the dye and could present a complete emission picture about this family of dyes. The L1 dye shows an intramolecular charge transfer (ICT) emission state at low concentrations (approximately nanomolar scale) and shows a twisted intramolecular charge transfer (TICT) emission state in specific solvents upon increasing the concentration to the micromolar scale. Moreover, the associated emission lifetimes of the ICT and TICT states of the L1 dye depend on solvent basicity, highlighting the role of hydrogen bond formation on controlling such states. Density functional theory calculations are performed to gain insight into the photophysical properties of the dye and revealed that H-bonding between the carboxylic groups triggers the dimerization at low concentrations. Using femtosecond transient absorption, we assigned the rate of TICT formation to be in the range (160-650 fs)(-1), depending on the size of the studied cyanoacrylic dye. Therefore, we add herein a new dimension for controlling the formation of the TICT state, in addition to the solvent polarity and acceptor strength parameters. These findings are not limited to the studied dyes, and we expect that numerous organic carboxylic acids dyes show similar properties.

    Fulltekst (pdf)
    FULLTEXT01
  • 219.
    El-Zohry, Ahmed
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Orthaber, Andreas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström.
    Zietz, Burkhard
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Isomerization and Aggregation of the Solar Cell Dye D1492012Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 116, nr 50, s. 26144-26153Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    D149, a metal-free indoline dye, is one of the most promising sensitizers for dye-sensitized solar cells (DSSCs) and has shown very high solar energy conversion efficiencies of 9%. Effective electron injection from the excited state is a prerequisite for high efficiencies and is lowered by competing deactivation pathways. Previous investigations have shown surprisingly short-lived excited states for this dye, with maximum lifetime components of 100-720 ps in different solvents and less than 120 ps for surface-adsorbed D149. Using steady-state and time-resolved fluorescence, we have investigated the photochemical properties of D149 in nonpolar and polar solvents, polymer matrices, and adsorbed on ZrO2, partially including a coadsorbent. In solution, excitation to the S-2 state yields a product that is identified as a photoisomer. The reaction is reversible, and the involved double-bond is identified by NMR spectroscopy. Our results further show that lifetimes of 100-330 ps in the solvents used are increased to more than 2 ns for D149 in polymer matrices and on ZrO2. This is in part attributed to blocked internal motion due to steric constraint. Conversely, concentration-dependent aggregation leads to a dramatic reduction in lifetimes that can affect solar cell performance. Our results explain the unexpectedly short lifetimes observed previously. We also show that photochemical properties such as lifetimes determined in solution are different from the ones determined on semiconductor surfaces used in solar cells. The obtained mechanistic understanding should help develop design strategies for further improvement of solar cell dyes.

  • 220.
    Eriksson, Anna
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC, Analytisk kemi.
    Edwards, Katarina
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC, Analytisk kemi.
    Hagfeldt, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Agmo Hernández, Víctor
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC, Analytisk kemi.
    Physicochemical Characterization of Phosphopeptide/Titanium Dioxide Interactions Employing the Quartz Crystal Microbalance Technique2013Inngår i: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 117, nr 7, s. 2019-2025Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 221.
    Eriksson K., Susanna
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Hahlin, Maria
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Molekyl- och kondenserade materiens fysik.
    Axnanda, Stephanus
    Crumlin, Ethan
    Wilks, Regan
    Eriksson, Anna
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Liu, Zhi
    Åhlund, John
    Hagfeldt, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Siegbahn, Hans
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Molekyl- och kondenserade materiens fysik.
    Starr, David
    Bär, Marcus
    Rensmo, Håkan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Molekyl- och kondenserade materiens fysik.
    In-situ probing of H2O effects on a Ru-complex adsorbed on TiO2 using high pressure XPSManuskript (preprint) (Annet vitenskapelig)
  • 222.
    Eriksson K., Susanna
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Josefsson, Ida
    Ellis, Hanna
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Amat, Anna
    Pastore, Mariachiara
    Oscarsson, Johan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Molekyl- och kondenserade materiens fysik.
    Lindblad, Rebecka
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Molekyl- och kondenserade materiens fysik.
    Eriksson, Anna I. K.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Johansson, Erik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Boschloo, Gerrit
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Hagfeldt, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Fantacci, Simona
    Odelius, Michael
    Rensmo, Håkan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Molekyl- och kondenserade materiens fysik.
    Geometrical and energetical structural changes in organic dyes for dye-sensitized solar cells probed with photoelectron spectroscopy and DFT2016Inngår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 18, nr 1, s. 252-260Artikkel i tidsskrift (Annet vitenskapelig)
    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.

  • 223. Eriksson, Susanna K.
    et al.
    Hahlin, Maria
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Molekyl- och kondenserade materiens fysik.
    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 universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    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 universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    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 universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Molekyl- och kondenserade materiens fysik.
    Siegbahn, Hans
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Molekyl- och kondenserade materiens fysik.
    In-Situ Probing of H2O Effects on a Ru-Complex Adsorbed on TiO2 Using Ambient Pressure Photoelectron Spectroscopy2016Inngår i: Topics in catalysis, ISSN 1022-5528, E-ISSN 1572-9028, Vol. 59, nr 5-7, s. 583-590Artikkel i tidsskrift (Fagfellevurdert)
    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.

    Fulltekst (pdf)
    fulltext
  • 224.
    Eriksson, Susanna K
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Hahlin, Maria
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Molekyl- och kondenserade materiens fysik.
    Kahk, Juhan Matthias
    Villar-Garcia, Ignacio J
    Webb, Matthew J
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC, Fysikalisk-organisk kemi.
    Grennberg, Helena
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC, Fysikalisk-organisk kemi.
    Yakimova, Rositza
    Rensmo, Håkan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Molekyl- och kondenserade materiens fysik.
    Edström, Kristina
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Strukturkemi.
    Hagfeldt, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Siegbahn, Hans
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Molekyl- och kondenserade materiens fysik.
    Edwards, Mårten O M
    Karlsson, Patrik G
    Backlund, Klas
    Ahlund, John
    Payne, David J
    A versatile photoelectron spectrometer for pressures up to 30 mbar2014Inngår i: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 85, nr 7, s. 075119-Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 225.
    Eriksson, Susanna K.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Josefsson, Ida
    Ottosson, Niklas
    Ohrwall, Gunnar
    Bjorneholm, Olle
    Siegbahn, Hans
    Hagfeldt, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Odelius, Michael
    Rensmo, Hakan
    Solvent Dependence of the Electronic Structure of I- and I-3(-)2014Inngår i: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 118, nr 11, s. 3164-3174Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 226. Fan, Jiandong
    et al.
    Fabrega, Cristian
    Zamani, Reza R.
    Hao, Yan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Parra, Andres
    Andreu, Teresa
    Arbiol, Jordi
    Boschloo, Gerrit
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Hagfeldt, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    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 Electrolyte2013Inngår i: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 5, nr 20, s. 9872-9877Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 227. Fan, Jiandong
    et al.
    Hao, Yan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Cabot, Andreu
    Johansson, Erik M. J.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Boschloo, Gerrit
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Hagfeldt, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Cobalt(II/III) Redox Electrolyte in ZnO Nanowire-Based Dye-Sensitized Solar Cells2013Inngår i: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 5, nr 6, s. 1902-1906Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 228. Fan, Jiandong
    et al.
    Hao, Yan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Munuera, Carmen
    Garcia-Hernandez, Mar
    Gueell, Frank
    Johansson, Erik M. J.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Boschloo, Gerrit
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Hagfeldt, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Cabot, Andreu
    Influence of the Annealing Atmosphere on the Performance of ZnO Nanowire Dye-Sensitized Solar Cells2013Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 117, nr 32, s. 16349-16356Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 229.
    Farré, Yoann
    et al.
    Université de Nantes, France.
    Maschietto, Federica
    PSL Res Univ, Inst Chem Hlth & Life Sci I CLeHS, FRE 2027, 11 Rue P & M Curie, F-75005 Paris 05, France.
    Föhlinger, Jens
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Wykes, Mike
    PSL Res Univ, Inst Chem Hlth & Life Sci I CLeHS, FRE 2027, 11 Rue P & M Curie, F-75005 Paris 05, France.
    Planchat, Aurélien
    Univ Nantes, CNRS, CEISAM, UMR 6230, 2 Rue Houssiniere, F-44000 Nantes, France.
    Pellegrin, Yann
    Univ Nantes, CNRS, CEISAM, UMR 6230, 2 Rue Houssiniere, F-44000 Nantes, France.
    Blart, Errol
    Univ Nantes, CNRS, CEISAM, UMR 6230, 2 Rue Houssiniere, F-44000 Nantes, France.
    Ciofini, Ilaria
    PSL Res Univ, Inst Chem Hlth & Life Sci I CLeHS, FRE 2027, 11 Rue P & M Curie, F-75005 Paris 05, France.
    Hammarström, Leif
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Odobel, Fabrice
    Université de Nantes.
    A Comparative Investigation of the Role of the Anchoring Group on Perylene Monoimide Dyes in NiO-Based Dye-Sensitized Solar Cells2020Inngår i: ChemSusChem, ISSN 1864-5631, E-ISSN 1864-564X, Vol. 13, nr 7, s. 1844-1855Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The anchoring group of a sensitizer may strongly affect the overall properties and stability of the resulting dye-sensitized solar cells (DSSCs) and dye-sensitized photoelectrosynthetic solar cells (DSPECs). The properties of seven perylene monoimide (PMI) dyes have been comprehensively studied for their immobilization on nanocrystalline NiO film. The PMI dyes differ only by the nature of the anchoring group, which are: carboxylic acid (PMI-CO2H), phosphonic acid (PMI-PO3H2), acetyl acetone (PMI-acac), pyridine (PMI-Py), aniline (PMI-NH2), hydroxyquinoline (PMI-HQ), and dipicolinic acid (PMI-DPA). The dyes are investigated by cyclic voltammetry and spectroelectrochemistry and modeled by TD-DFT quantum chemical calculations. The mode of binding of these anchoring groups is investigated by infrared spectroscopy and the stability of the binding to NiO surface is studied by desorption experiments in acidic and basic media. The phosphonic acid group is found to offer the strongest binding to the NiO surface in terms of stability and dye loading. Finally, a photophysical study by ultrafast transient absorption spectroscopy shows that all dyes inject a hole in NiO with rate constants on a subpicosecond timescale and display similar charge recombination kinetics. The photovoltaic properties of the dyes show that PMI-HQ and PMI-acac give the highest photovoltaic performances, owing to a lower degree of aggregation on the surface.

  • 230. Farré, Yoann
    et al.
    Zhang, Lei
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Pellegrin, Yann
    Planchat, Aurelien
    Blart, Errol
    Boujtita, Mohammed
    Hammarström, Leif
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Jacquemin, Denis
    Odobel, Fabrice
    Second Generation of DiketopyrrolopyrroleDyes for NiO based Dye-Sensitized Solar Cells2016Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 120, nr 15, s. 7923-7940Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this study, four new diketopyrrolopyrrole (DPP) sensitizers, with a dicarboxylated triphenylamine anchoring group for attachment to NiO, were prepared and their electronic absorption, emission and electrochemical properties were recorded. The nature of the electronic excited-states was also modeled with TD-DFT quantum chemistry calculations. The photovoltaic performances of these new dyes were characterized in NiO-based dye-sensitized solar cells (DSCs) with the classical iodide/triiodide and cobaltII/III-polypyridine electrolytes, in which they proved to be quite active. Laser spectroscopy on dye/NiO/electrolyte films gave evidence for ultrafast hole injection into NiO (0.2-10 ps time scales). For the dyes with an appended naphtalenediimide (NDI) acceptor unit, ultrafast electron transfer to the NDI dramatically prolonged the lifetime of the charge separated state NiO(+)/dye-, from the ps time scale to an average lifetime ≈ 0.25 ms, which is among the slowest charge recombinations ever reported for dye/NiO systems. This allowed for efficient regeneration by CoIIIpolypyridine electrolytes, which translated into much improved PV-performance compared to the DPP dyes without appended NDI. Overall, these results underscore the suitability of DPP as sensitizers for NiO-based photoelectrochemical devices for photovoltaic and photocatalysis.

  • 231.
    Favereau, Ludovic
    et al.
    Univ Nantes, CNRS, UMR CNRS 6230, CEISAM Chim & Interdisciplinarite Synth Anal Mode, 2 Rue Houssiniere,BP 92208, F-44322 Nantes 3, France..
    Makhal, Abhinandan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Pellegrin, Yann
    Univ Nantes, CNRS, UMR CNRS 6230, CEISAM Chim & Interdisciplinarite Synth Anal Mode, 2 Rue Houssiniere,BP 92208, F-44322 Nantes 3, France..
    Blart, Errol
    Univ Nantes, CNRS, UMR CNRS 6230, CEISAM Chim & Interdisciplinarite Synth Anal Mode, 2 Rue Houssiniere,BP 92208, F-44322 Nantes 3, France..
    Petersson, Jonas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Göransson, Erik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Hammarstrom, Leif
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Odobel, Fabrice
    Univ Nantes, CNRS, UMR CNRS 6230, CEISAM Chim & Interdisciplinarite Synth Anal Mode, 2 Rue Houssiniere,BP 92208, F-44322 Nantes 3, France..
    A Molecular Tetrad That Generates a High-Energy Charge-Separated State by Mimicking the Photosynthetic Z-Scheme2016Inngår i: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 138, nr 11, s. 3752-3760Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The oxygenic photosynthesis of green plants, green algae, and cyanobacteria is the major provider of energy rich compounds in the biosphere. The so-called "Z-scheme" is at the heart of this "engine of life". Two photosystems (photo system I and II) work in series to build up a higher redox ability than each photosystem alone can provide, which is necessary to drive water oxidation into oxygen and NADP(+) reduction into NADPH with visible light. Here we show a mimic of the Z-scheme with a molecular tetrad. The "tetrad Bodipy-NDI-TAPD-Ru is composed of two different dyes-4,4-difluoro-1,3,5,7-tetramethyl-2,6-diethy1-4-bora-3a,4a-diaza-s-indacene (Bodipy) and a Ru-II(bipyridine), (Ru) derivative-which are connected to a naphthalene diimide (NDI) electron acceptor and tetraalkylphenyldiamine (TAPD) playing the role of electron donor. A strong laser pulse excitation of visible light where the two dye molecules (Ru and Bodipy) absorb with equal probability leads to the cooperative formation of a highly energetic charge-separated state composed of an oxidized Bodipy and a reduced Ru. The latter state cannot be reached by one single photon absorption. The energy of the final charge-separated state (oxidized Bodipy/reduced Ru) in the tetrad lies higher than that in the reference dyads (Bodipy-NDI and TAPD-Ru), leading to the energy efficiency of the tetrad being 47% of the sum of the photon threshold energies. Its lifetime was increased by several orders of magnitude compared to that in the reference dyads Bodipy-NDI and TAPD-Ru, as it passes from about 3 ns in each dyad to 850 ns in the tetrad. The overall quantum yield formation of this extended charge-separated state is estimated to be 24%. Our proof-of-concept result demonstrates the capability to translate a crucial photosynthetic energy conversion principle into man-made molecular systems for solar fuel formation, to obtain products of higher energy content than those produced by a single photon absorption.

  • 232.
    Favereau, Ludovic
    et al.
    Univ Nantes, Univ LUNAM, CNRS, CEISAM,UMR CNRS 6230, 2 Rue Houssiniere BP 92208, F-44322 Nantes 3, France..
    Makhal, Abhinandan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Provost, David
    Univ Nantes, Univ LUNAM, CNRS, CEISAM,UMR CNRS 6230, 2 Rue Houssiniere BP 92208, F-44322 Nantes 3, France..
    Pellegrin, Yann
    Univ Nantes, Univ LUNAM, CNRS, CEISAM,UMR CNRS 6230, 2 Rue Houssiniere BP 92208, F-44322 Nantes 3, France..
    Blart, Errol
    Univ Nantes, Univ LUNAM, CNRS, CEISAM,UMR CNRS 6230, 2 Rue Houssiniere BP 92208, F-44322 Nantes 3, France..
    Göransson, Erik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Hammarström, Leif
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Odobel, Fabrice
    Univ Nantes, Univ LUNAM, CNRS, CEISAM,UMR CNRS 6230, 2 Rue Houssiniere BP 92208, F-44322 Nantes 3, France..
    Tris-bipyridine based dinuclear ruthenium(II)--osmium(III) complex dyads grafted onto TiO2 nanoparticles for mimicking the artificial photosynthetic Z-scheme2017Inngår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 19, nr 6, s. 4778-4786Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The Z-Scheme function within molecular systems has been rarely reported for solar energy conversion although it offers the possibility to achieve higher efficiency than single photon absorber photosystems due to the use of a wider range of visible light. In this study, we synthesized and investigated the electrochemical and spectroscopic properties of two new dyads based on ruthenium and osmium tris-bipyridine complexes covalently linked via a butane bridge to explore their ability to realize the Z-scheme function once immobilized on TiO2. These dyads can be grafted onto a nanocrystalline TiO2 film via the osmium complex bearing two dicarboxylic acid bipyridine ligands, while the ruthenium complex contains either two unsubstituted bipyridine ancillary ligands (RuH-Os) or two (4,4'-bis-trifluoro-methyl-bipyridine) ancillary ligands (RuCF3-Os). Transient absorption spectroscopy studies of the Ru(II)-Os(III) dyads with femtosecond and nanosecond lasers were conducted both in solution and on TiO2. For both conditions, the photophysical studies revealed that the MLCT excited state of the ruthenium complex is strongly quenched and predominantly decays by energy transfer to the LMCT of the adjacent Os(III) complex, in spite of the high driving force for electron transfer. This unexpected result, which is in sharp contrast to previously reported Ru(II)-Os(III) dyads, precluded us to achieve the expected Z-scheme function. However, the above results may be a guide for designing new artificial molecular systems reproducing the complex function of a Z-scheme with molecular systems grafted onto a TiO2 mesoporous film.

  • 233.
    Feldt, Sandra
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Alternative Redox Couples for Dye-Sensitized Solar Cells2013Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Dye-sensitized solar cells (DSCs) convert sunlight to electricity at a low cost. In the DSC, a dye anchored to a mesoporous TiO2 semiconductor is responsible for capturing the sunlight. The resulting excited dye injects an electron into the conduction band of the TiO2 and is in turn regenerated by a redox mediator, normally iodide/triiodide, in a surrounding electrolyte. The success of the iodide/triiodide redox couple is mainly attributed to its slow interception of electrons at the TiO2 surface, which suppresses recombination losses in the DSC.

    One of the main limitations with the iodide/triiodide redox couple is, however, the large driving force needed for regeneration, which minimizes the open circuit voltage and thus the energy conversion efficiency. In this thesis, alternative redox couples to the iodide/triiodide redox couple have been investigated. These redox couples include the one-electron transition metal complexes, ferrocene and cobalt polypyridine complexes. The use of one-electron redox couples in the DSC has previously been shown to lead to poor photovoltaic performances, because of increased recombination.

    Cobalt redox couples were here found to give surprisingly high efficiencies in combination with the triphenylamine-based organic dye, D35. The success of the D35 dye, in combination with cobalt redox couples, was mainly attributed to the introduction of steric alkoxy chains on the dye, which supress recombination losses. By introducing steric substituents on the dye, rather than on the redox couple, mass transport limitations could in addition be avoided, which previously has been suggested to limit the performance of cobalt complexes in the DSC. The result of this study formed the basis for the world record efficiency of DSCs of 12.3 % using cobalt redox couples.

    Interfacial electron-transfer processes in cobalt-based DSCs were investigated to gain information of advantages and limitations using cobalt redox couples in the DSC. The redox potentials of cobalt redox couples are easily tuned by changing the coordination sphere of the complexes, and regeneration and recombination kinetics were systematically investigated by increasing the redox potential of the cobalt complexes. Our hope is that this thesis can be a guideline for future design of new redox systems in DSCs. 

    Delarbeid
    1. Characterization of surface passivation by poly(methylsiloxane) for dye-sensitized solar cells employing the ferrocene redox couple.
    Åpne denne publikasjonen i ny fane eller vindu >>Characterization of surface passivation by poly(methylsiloxane) for dye-sensitized solar cells employing the ferrocene redox couple.
    Vise andre…
    2010 (engelsk)Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 114, nr 23, s. 10551-10558Artikkel i tidsskrift (Fagfellevurdert) Published
    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.

    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-135563 (URN)10.1021/jp100957p (DOI)000278479700032 ()
    Tilgjengelig fra: 2010-12-14 Laget: 2010-12-07 Sist oppdatert: 2017-12-11bibliografisk kontrollert
    2. Design of organic dyes and cobalt polypyridine redox mediators for high-efficiency dye-sensitized solar cells
    Åpne denne publikasjonen i ny fane eller vindu >>Design of organic dyes and cobalt polypyridine redox mediators for high-efficiency dye-sensitized solar cells
    Vise andre…
    2010 (engelsk)Inngår i: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 132, nr 46, s. 16714-16724Artikkel i tidsskrift (Fagfellevurdert) Published
    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.

    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-139393 (URN)10.1021/ja1088869 (DOI)000284792000064 ()21047080 (PubMedID)
    Tilgjengelig fra: 2010-12-27 Laget: 2010-12-23 Sist oppdatert: 2017-12-11bibliografisk kontrollert
    3. Effects of Driving Forces for Recombination and Regeneration on the Photovoltaic Performance of Dye-Sensitized Solar Cells using Cobalt Polypyridine Redox Couples
    Åpne denne publikasjonen i ny fane eller vindu >>Effects of Driving Forces for Recombination and Regeneration on the Photovoltaic Performance of Dye-Sensitized Solar Cells using Cobalt Polypyridine Redox Couples
    2011 (engelsk)Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 115, nr 43, s. 21500-21507Artikkel i tidsskrift (Fagfellevurdert) Published
    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.

    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-161433 (URN)10.1021/jp2061392 (DOI)000296172800087 ()
    Tilgjengelig fra: 2011-11-16 Laget: 2011-11-14 Sist oppdatert: 2017-12-08bibliografisk kontrollert
    4. Regeneration and Recombination kinetics in Cobalt Polypyridine based Dye-Sensitized Solar Cells, explained using Marcus theory
    Åpne denne publikasjonen i ny fane eller vindu >>Regeneration and Recombination kinetics in Cobalt Polypyridine based Dye-Sensitized Solar Cells, explained using Marcus theory
    Vise andre…
    2013 (engelsk)Inngår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 15, nr 19, s. 7087-7097Artikkel i tidsskrift (Fagfellevurdert) Published
    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.

    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-192668 (URN)10.1039/c3cp50997d (DOI)000317980600013 ()
    Tilgjengelig fra: 2013-01-24 Laget: 2013-01-24 Sist oppdatert: 2017-12-06bibliografisk kontrollert
    5. Linker Unit Modification of Triphenylamine-based Organic Dyes for Efficient Cobalt Mediated Dye-Sensitized Solar Cells
    Åpne denne publikasjonen i ny fane eller vindu >>Linker Unit Modification of Triphenylamine-based Organic Dyes for Efficient Cobalt Mediated Dye-Sensitized Solar Cells
    Vise andre…
    2013 (engelsk)Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 117, nr 41, s. 21029-21036Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

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

    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-192688 (URN)10.1021/jp403619c (DOI)000326125800001 ()
    Tilgjengelig fra: 2013-01-24 Laget: 2013-01-24 Sist oppdatert: 2017-12-06bibliografisk kontrollert
    6. Carbon Counter Electrodes Efficient Catalysts for the Reduction of Co(III) in Cobalt Mediated Dye-Sensitized Solar Cells
    Åpne denne publikasjonen i ny fane eller vindu >>Carbon Counter Electrodes Efficient Catalysts for the Reduction of Co(III) in Cobalt Mediated Dye-Sensitized Solar Cells
    Vise andre…
    (engelsk)Manuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    The photovoltaic performance of cobalt-based dye-sensitized solar cells using carbon materials as the catalyst for the reduction of Co(III) was found similar or better than that of platinum. The charge transfer resistance at the counter electrode decreased, as the catalytic activity increased with increasing surface area of the carbon material.

    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-192690 (URN)
    Tilgjengelig fra: 2013-01-24 Laget: 2013-01-24 Sist oppdatert: 2013-03-05
    Fulltekst (pdf)
    fulltext
  • 234.
    Feldt, Sandra
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Gibsson, Elizabeth
    School of chemistry, University of Nottingham.
    Wang, Gang
    Fabregat, Guillermo
    Boschloo, Gerrit
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Hagfeldt, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Carbon Counter Electrodes Efficient Catalysts for the Reduction of Co(III) in Cobalt Mediated Dye-Sensitized Solar CellsManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    The photovoltaic performance of cobalt-based dye-sensitized solar cells using carbon materials as the catalyst for the reduction of Co(III) was found similar or better than that of platinum. The charge transfer resistance at the counter electrode decreased, as the catalytic activity increased with increasing surface area of the carbon material.

  • 235.
    Feldt, Sandra
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Lohse, Peter
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - 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 universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Hagfeldt, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Regeneration and Recombination kinetics in Cobalt Polypyridine based Dye-Sensitized Solar Cells, explained using Marcus theory2013Inngår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 15, nr 19, s. 7087-7097Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 236.
    Feldt, Sandra M.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Gibson, Elizabeth A.
    Wang, Gang
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Fabregat, Guillermo
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Boschloo, Gerrit
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Hagfeldt, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Carbon counter electrodes efficient catalysts for the reduction of Co(III) in cobalt mediated dye-sensitized solar cells2014Inngår i: Polyhedron, ISSN 0277-5387, E-ISSN 1873-3719, Vol. 82, s. 154-157Artikkel i tidsskrift (Fagfellevurdert)
    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. 

  • 237.
    Fernandes, Arthur B.
    et al.
    Univ Sao Paulo, Inst Quim, Dept Quim Fundamental, BR-05508000 Sao Paulo, SP, Brazil.
    Pavliuk, Mariia V.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Paun, Cristina
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Carvalho, Alexandrina C.
    Univ Sao Paulo, Inst Quim, Dept Quim Fundamental, BR-05508000 Sao Paulo, SP, Brazil.
    Nomura, Cassiana S.
    Univ Sao Paulo, Inst Quim, Dept Quim Fundamental, BR-05508000 Sao Paulo, SP, Brazil.
    Lewin, Erik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Oorganisk kemi.
    Lindblad, Rebecka
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Oorganisk kemi.
    Camargo, Pedro H. C.
    Univ Sao Paulo, Inst Quim, Dept Quim Fundamental, BR-05508000 Sao Paulo, SP, Brazil;Univ Helsinki, Dept Chem, FI-00014 Helsinki, Finland.
    Sá, Jacinto
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi. Polish Acad Sci, Inst Phys Chem, PL-01224 Warsaw, Poland.
    Bastos, Erick L.
    Univ Sao Paulo, Inst Quim, Dept Quim Fundamental, BR-05508000 Sao Paulo, SP, Brazil.
    Recoverable and Reusable Polymer Microbead-Supported Metal Nanocatalysts for Redox Chemical Transformations2020Inngår i: ACS APPLIED NANO MATERIALS, ISSN 2574-0970, Vol. 3, nr 2, s. 1722-1730Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Metal nanoparticles have been widely exploited in catalysis, but their full impact on the environment and human health is still under debate. Here we describe the one-step fabrication of recoverable and reusable polymer microbead-supported metal and metal oxide nanocatalysts for application in batch reactions and flow systems. Au, Ag, and Fe3O4 nanoparticles were prepared directly at the surface of commercial benzylamine-coated spherical polymer beads in water by using low-energy microwave radiation for 5 min. The functionalization of microbead surface with betalamic acid, an antioxidant from plant origin, before irradiation changes the morphology and catalytic properties of the grafted nanoparticles. No leaching of the active phase was observed during the application of these effective and ready-to-use nanocatalysts on the reduction of 4-nitrophenol and oxidation of dihydrorhodamine 123. The supported nanocatalysts were recovered by filtration and/or magnetic separation and reused up to three times without significant drop in catalytic performance. These results can stimulate the controlled and facile synthesis of recoverable microbead-supported magnetic and nonmagnetic nanocatalysts that can be applied under myriad reaction conditions and reused multiple times.

  • 238.
    Fernandes, Daniel L. A.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Budinska, Alena
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Pavliuk, Mariia V.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Sá, Jacinto
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi. Polish Acad Sci, Inst Phys Chem, PL-01224 Warsaw, Poland..
    Novel photo-reactor for fast screening of photo-catalytic systems2017Inngår i: Journal of Photochemistry and Photobiology A: Chemistry, ISSN 1010-6030, E-ISSN 1873-2666, Vol. 335, s. 36-39Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Photo-catalysis is an emerging technology for clean energy production, organic synthesis and environmental protection, etc. While there is a hydrogen of systems and schemes to attain these objectives, there is a paucity of photo-reactors capable of determine catalytic abilities in real time with reduce amounts of samples, i.e., fast-screening of catalyst and reaction parameters. Herein, we report a novel photo-reactor for simultaneous online monitoring of gaseous products with quadrupole mass spectrometry and photo-physics with fibre optic UV/Vis with millisecond time resolution on 4 mL cuvettes.

  • 239.
    Fernandes, Daniel L. A.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Paun, Cristina
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Pavliuk, Mariia V.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Fernandes, Arthur B.
    Univ Sao Paulo, Inst Chem, Dept Fundamental Chem, BR-05508000 Sao Paulo, Brazil..
    Bastos, Erick L.
    Univ Sao Paulo, Inst Chem, Dept Fundamental Chem, BR-05508000 Sao Paulo, Brazil..
    Sá, Jacinto
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi. Polish Acad Sci, Inst Phys Chem, PL-01224 Warsaw, Poland..
    Green microfluidic synthesis of monodisperse silver nanoparticles via genetic algorithm optimization2016Inngår i: RSC Advances, E-ISSN 2046-2069, Vol. 6, nr 98, s. 95693-95697Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A scalable and green procedure for the microfluidic flow synthesis of monodisperse silver nanoparticles is reported. Beetroot extract is used both as a reducing and growth-regulating agent. A multi-objective genetic algorithm was used to automate the optimization of the reaction and reduce sample polydispersity observed in previous reports. The proposed methodology ensures high-quality nanoparticles in a rapidly manner and devoid of human skill or intuition, essential for method standardization and implementation.

  • 240.
    Fernandes, Daniel L. A.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Pavliuk, Maria V.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Sa, Jacinto
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    A 3D printed microliquid jet with an adjustable nozzle diameter2015Inngår i: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 140, nr 18, s. 6234-6238Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Microliquid jets have many applications, in particular in the fields of spectroscopy/analysis of samples susceptible to beam damage. Herein, we report a microliquid jet, manufactured with 3D printing technology, with a tuneable nozzle diameter output. This strategy increases the breadth of techniques that can be covered with a single microliquid jet.

  • 241.
    Flores-Diaz, Natalie
    et al.
    Univ Costa Rica, Ctr Electroquim & Energia Quim CELEQ, San Jose 2060, Costa Rica;Univ Costa Rica, Escuela Quim, San Jose 2060, Costa Rica.
    Soto-Navarro, Andrea
    Univ Costa Rica, Ctr Electroquim & Energia Quim CELEQ, San Jose 2060, Costa Rica.
    Freitag, Marina
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Lamoureux, Guy
    Univ Costa Rica, Escuela Quim, San Jose 2060, Costa Rica;Univ Costa Rica, Ctr Invest Prod Nat CIPRONA, San Jose 2060, Costa Rica.
    Pineda, Leslie W.
    Univ Costa Rica, Ctr Electroquim & Energia Quim CELEQ, San Jose 2060, Costa Rica;Univ Costa Rica, Escuela Quim, San Jose 2060, Costa Rica.
    Neutral organic redox pairs based on sterically hindered hydroquinone/benzoquinone derivatives for dye-sensitized solar cells2018Inngår i: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 167, s. 76-83Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Substituted derivatives of hydroquinone/benzoquinone were studied as organic redox mediators in the electrolyte for dye-sensitized solar cells (DSSCs). Thus, di-tert-butylhydroquinone (DTHQ), thymohydroquinone (ThymHQ) and phenylhydroquinone (PhHQ), were combined with their oxidized counterparts to form the pairs DTHQ/DTBQ, ThymHQ/ThymBQ, and PhHQ/PhBQ. In general, the characteristic parameters of the DSSCs with the substituted derivatives surpassed those of the DSSC with the unsubstituted hydroquinone/benzoquinone electrolyte. The short-circuit current (J(sc)) of the devices using DTHQ/DTBQ and ThymHQ/ThymBQ (13.61 mA cm(-2) and 12.56 mA cm(-2), respectively) are comparable to the J(sc) obtained for cobalt(II/III) tris (bipyridine) as a reference electrolyte (14.54 mA cm(-2)). However, parameters such as open-circuit voltage (V-oc) and fill factor (FF) (547 mV and 0.48, respectively) are far from competitive. The best photovoltaic performance was obtained for the pair ThymHQ/ThymBQ using a triphenylamine (TPA)-based organic dye (LEG4) as sensitizer and a hybrid counter electrode with poly(3,4-ethylenedioxythiophene) (PEDOT) and graphene. These experimental conditions give under 1 sun (98%) the highest efficiency (eta = 3.19%); low-light intensities of 12.3% and 51.8% suns lead to efficiencies of 3.34% and 3.29%, respectively. Electrochemical impedance spectroscopy (EIS) revealed that the main cause for loss in photocurrent is the low recombination resistance compared to Co(II/III) as reference electrolyte. Based on the EIS analysis, a down-shift of the conduction band of TiO2 was found for all assembled devices containing the organic redox mediators, which explains the low V-oc values for these derivatives.

  • 242.
    Forooqi Motlaq, Vahid
    et al.
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Farmaceutiska fakulteten, Institutionen för läkemedelskemi.
    Gedda, Lars
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Edwards, Katarina
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Doutch, James
    STFC, ISIS Neutron & Muon Source, Rutherford Appleton Lab, Didcot OX11 0QX, England..
    Bergström, L. Magnus
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Farmaceutiska fakulteten, Institutionen för läkemedelskemi.
    Spontaneous Formation of Ultrasmall Unilamellar Vesicles in Mixtures of an Amphiphilic Drug and a Phospholipid2023Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 39, nr 32, s. 11337-11344Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have observed ultrasmall unilamellar vesicles, withdiametersof less than 20 nm, in mixtures of the tricyclic antidepressant drugamitriptyline hydrochloride (AMT) and the unsaturated zwitterionicphospholipid 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) in physiologicalsaline solution. The size and shape of spontaneously formed self-assembledaggregates have been characterized using complementary techniques,i.e., small-angle neutron and X-ray scattering (SANS and SAXS) andcryo-transmission electron microscopy (cryo-TEM). We observe rodlikemixed micelles in more concentrated samples that grow considerablyin length upon dilution, and a transition from micelles to vesiclesis observed as the concentration approaches the critical micelle concentrationof AMT. Unlike the micelles, the spontaneously formed vesicles decreasein size with each step of dilution, and ultrasmall unilamellar vesicles,with diameters as small as about 15 nm, were observed at the lowestconcentrations. The spontaneously formed ultrasmall unilamellar vesiclesmaintain their size for as long we have investigated them (i.e., severalmonths). To the best of our knowledge, such small vesicles have neverbefore been reported to form spontaneously in a biocompatible phospholipid-basedsystem. Most interestingly, the size of the vesicles was observedto be strongly dependent on the chemical structure of the phospholipid,and in mixtures of AMT and the phospholipid 1,2-dimyristoyl-sn-glycero-3-phosphocholine(DMPC), the vesicles were observed to be considerably larger in size.The self-assembly behavior in the phospholipid-drug surfactantsystem in many ways resembles the formation of equilibrium micellesand vesicles in mixed anionic/cationic surfactant systems.

    Fulltekst (pdf)
    fulltext
  • 243.
    Fredin, Lisa
    et al.
    NIST, Mat Measurement Lab, Chem Sci, Rockville, MD USA..
    Chabera, Pavel
    Lund Univ, Dept Chem, Chem Phys, Lund, Sweden..
    Lomoth, Reiner
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Sundstrom, Villy
    Lund Univ, Lund, Sweden..
    Warnmark, Kenneth
    Lund Univ, Lund, Sweden..
    Persson, Petter
    Lund Univ, Theoret Chem, Lund, Sweden..
    Photochemistry of iron(III) carbenes2017Inngår i: Abstracts of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 254Artikkel i tidsskrift (Annet vitenskapelig)
  • 244.
    Freitag, Marina
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Boschloo, Gerrit
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    The revival of dye-sensitized solar cells2017Inngår i: Current Opinion in Electrochemistry, E-ISSN 2451-9103, Vol. 2, nr 1, s. 111-119Artikkel, forskningsoversikt (Fagfellevurdert)
    Abstract [en]

    The scientific progress in the field of dye-sensitized solar cells (DSCs) is marked by a recent number of important breakthroughs. DSCs provide a technically and economically credible alternative concept to present-day p-n junction photovoltaic devices. Relentless efforts helped to achieve high efficiencies with DSCs. Some of the major progress was made by developing new panchromatic rigid structure dye systems, new redox shuttles and hole transport materials. Under full sun illumination (standard AM 1.5 G), conversion efficiencies have reached over 13% with Zn porphyrins and 14% with co-sensitized organic dyes. The new redox couples and electrolytes are able to regenerate the dye at less than 0.2 V. Current research and development is the perquisite to improve efficiencies beyond 20% for future applications with improved stability and sustainability.

  • 245.
    Freitag, Marina
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Daniel, Quentin
    KTH Royal Inst Technol, Sch Chem Sci & Engn, Dept Chem, S-10044 Stockholm, Sweden..
    Pazoki, Meysam
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Sveinbjörnsson, Kári
    Zhang, Jinbao
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    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 universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Boschloo, Gerrit
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    High-efficiency dye-sensitized solar cells with molecular copper phenanthroline as solid hole conductor2015Inngår i: Energy & Environmental Science, ISSN 1754-5692, E-ISSN 1754-5706, Vol. 8, nr 9, s. 2634-2637Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 246.
    Freitag, Marina
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi. 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 universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Pazoki, Meysam
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Strukturkemi.
    Hao, Yan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Zietz, Burkhard
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Graetzel, Michael
    Ecole Polytech Fed Lausanne, Inst Chem Sci & Engn, Lab Photon & Interfaces, CH-1015 Lausanne, Switzerland..
    Hagfeldt, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi. Ecole Polytech Fed Lausanne, Inst Chem Sci & Engn, Lab Photomol Sci, CH-1015 Lausanne, Switzerland..
    Boschloo, Gerrit
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Copper Phenanthroline as a Fast and High-Performance Redox Mediator for Dye-Sensitized Solar Cells2016Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 120, nr 18, s. 9595-9603Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 247.
    Freitag, Marina
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi. École Polytechnique Fédérale de Lausanne .
    Teuscher, Joel
    École Polytechnique Fédérale de Lausanne .
    Saygili, Yasemin
    École Polytechnique Fédérale de Lausanne .
    Zhang, Xiaoyu
    East China Univ Sci & Technol.
    Giordano, Fabrizio
    Ecole Polytech Fed Lausanne.
    Liska, Paul
    Ecole Polytech Fed Lausanne.
    Hua, Jianli
    East China Univ Sci & Technol.
    Zakeeruddin, Shaik M.
    Ecole Polytech Fed Lausanne.
    Moser, Jacques-E.
    École Polytechnique Fédérale de Lausanne .
    Grätzel, Michael
    Ecole Polytech Fed Lausanne.
    Hagfeldt, Anders
    Ecole Polytech Fed Lausanne.
    Dye-sensitized solar cells for efficient power generation under ambient lighting2017Inngår i: Nature Photonics, ISSN 1749-4885, E-ISSN 1749-4893, Vol. 11, nr 6, s. 372-+Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Solar cells that operate efficiently under indoor lighting are of great practical interest as they can serve as electric power sources for portable electronics and devices for wireless sensor networks or the Internet of Things. Here, we demonstrate a dye-sensitized solar cell (DSC) that achieves very high power-conversion efficiencies (PCEs) under ambient light conditions. Our photosystem combines two judiciously designed sensitizers, coded D35 and XY1, with the copper complex Cu(II/I)(tmby) as a redox shuttle (tmby, 4,4', 6,6'-tetramethyl-2,2'-bipyridine), and features a high open-circuit photovoltage of 1.1 V. The DSC achieves an external quantum efficiency for photocurrent generation that exceeds 90% across the whole visible domain from 400 to 650 nm, and achieves power outputs of 15.6 and 88.5 mu W cm(-2) at 200 and 1,000 lux, respectively, under illumination from a model Osram 930 warm-white fluorescent light tube. This translates into a PCE of 28.9%.

  • 248.
    Freitag, Marina
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi. Ecole Polytech Fed Lausanne, Lab Photomol Sci, Inst Chem Sci & Engn, Stn 6, CH-1015 Lausanne, Switzerland.
    Yang, Wenxing
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Fredin, Lisa A.
    NIST, Chem Informat Res Grp, Div Chem Sci, Mat Measurement Lab, 100 Bur Dr,Stop 8320, Gaithersburg, MD 20899 USA..
    D'Amario, Luca
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Karlsson, K. Martin
    Dyenamo AB, Tekn Ringen 38 A, S-11428 Stockholm, Sweden..
    Hagfeldt, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi. Ecole Polytech Fed Lausanne, Lab Photomol Sci, Inst Chem Sci & Engn, Stn 6, CH-1015 Lausanne, Switzerland.
    Boschloo, Gerrit
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Supramolecular Hemicage Cobalt Mediators for Dye-Sensitized Solar Cells2016Inngår i: ChemPhysChem, ISSN 1439-4235, E-ISSN 1439-7641, Vol. 17, nr 23, s. 3845-3852Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A new class of dye-sensitized solar cells (DSSCs) using the hemicage cobalt-based mediator [Co(ttb)](2+/3+) with the highly preorganized hexadentate ligand 5,5 '', 5 ''''-((2,4,6-triethyl benzene-1,3,5-triyl)tris(ethane-2,1-diyl))tri-2,2'-bipyridine (ttb) has been fully investigated. The performances of DSSCs sensitized with organic D-p-A dyes utilizing either [Co(ttb)](2+/3+) or the conventional [Co(bpy)(3)](2+/3+) (bpy = 2,2'-bipyridine) redox mediator are comparable under 1000 Wm(-2) AM 1.5 G illumination. However, the hemicage complexes exhibit exceptional stability under thermal and light stress. In particular, a 120-hour continuous light illumination stability test for DSSCs using [Co(ttb)](2+/3+) resulted in a 10% increase in the performance, whereas a 40% decrease in performance was found for [Co(bpy)(3)](2+/3+) electrolyte-based DSSCs under the same conditions. These results demonstrate the great promise of [Co(ttb)](2+/3+) complexes as redox mediators for efficient, cost-effective, large-scale DSSC devices.

  • 249.
    Freitas-Dörr, B. C.
    et al.
    Univ Sao Paulo, Inst Quim, Dept Quim Fundamental, BR-05508000 Sao Paulo, SP, Brazil..
    Machado, C. O.
    Univ Sao Paulo, Inst Quim, Dept Quim Fundamental, BR-05508000 Sao Paulo, SP, Brazil..
    Pinheiro, A. C.
    Univ Sao Paulo, Inst Quim, Dept Quim Fundamental, BR-05508000 Sao Paulo, SP, Brazil..
    Fernandes, A. B.
    Univ Sao Paulo, Inst Quim, Dept Quim Fundamental, BR-05508000 Sao Paulo, SP, Brazil..
    Dorr, F. A.
    Univ Sao Paulo, Fac Ciencias Farmaceut, Dept Anal Clin & Toxicol, BR-05508000 Sao Paulo, SP, Brazil..
    Pinto, E.
    Univ Sao Paulo, Fac Ciencias Farmaceut, Dept Anal Clin & Toxicol, BR-05508000 Sao Paulo, SP, Brazil..
    Lopes-Ferreira, M.
    Butantan Inst, Immunoregulat Unit, Special Lab Appl Toxinol, Ctr Toxins Immune Response & Cell Signaling CEPID, BR-05503900 Sao Paulo, SP, Brazil..
    Abdellah, M.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi. South Valley Univ, Qena Fac Sci, Dept Chem, Qena 83523, Egypt..
    Sa, J.
    Uppsala Univ, Dept Chem, Phys Chem Div, Angstrom Lab, S-75120 Uppsala, Sweden.;Polish Acad Sci, Inst Phys Chem, PL-01224 Warsaw, Poland..
    Russo, L. C.
    Univ Sao Paulo, Dept Bioquim, Inst Quim, BR-05508000 Sao Paulo, SP, Brazil..
    Forti, F. L.
    Univ Sao Paulo, Dept Bioquim, Inst Quim, BR-05508000 Sao Paulo, SP, Brazil..
    Goncalves, L. C. P.
    Univ Sao Paulo, Inst Quim, Dept Quim Fundamental, BR-05508000 Sao Paulo, SP, Brazil..
    Bastos, L. L.
    Univ Sao Paulo, Inst Quim, Dept Quim Fundamental, BR-05508000 Sao Paulo, SP, Brazil..
    A metal-free blue chromophore derived from plant pigments2020Inngår i: Science Advances, E-ISSN 2375-2548, Vol. 6, nr 14, artikkel-id eaaz0421Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Blue natural pigments are rare, especially among plants. However, flowering species that evolved to attract Hymenoptera pollinators are colored by blue anthocyanin-metal complexes. Plants lacking anthocyanins are pigmented by betalains but are unable to produce blue hues. By extending the pi-system of betalains, we designed a photostable and metal-free blue dye named BeetBlue that did not show toxicity to human hepatic and retinal pigment epithelial cells and does not affect zebrafish embryonal development. This chiral dye can be conveniently synthesized from betalamic acid obtained from hydrolyzed red beetroot juice or by enzymatic oxidation of L-dopa. BeetBlue is blue in the solid form and in solution of acidified polar molecular solvents, including water. Its capacity to dye natural matrices makes BeetBlue the prototype of a new class of low-cost bioinspired chromophores suitable for a myriad of applications requiring a blue hue.

    Fulltekst (pdf)
    FULLTEXT01
  • 250.
    Freys, Jonathan C.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Gardner, James M.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström.
    D'Amario, Luca
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström.
    Brown, Allison M.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Hammarström, Leif
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Ru-based donor-acceptor photosensitizer that retards charge recombination in a p-type dye-sensitized solar cell2012Inngår i: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 41, nr 42, s. 13105-13111Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report on the synthesis and characterization of a donor-acceptor ruthenium polypyridyl complex as a photosensitizer for p-type dye-sensitized solar cells (DSSCs). The electrochemical, photophysical, and photovoltaic performance of two ruthenium-based photosensitizers were tested in NiO-based DSSCs; bis-(2,2′-bipyridine-4,4′-dicarboxylic acid) 2N-(1,10-phenanthroline)-4-nitronaphthalene-1,8-dicarboximide ruthenium(ii), ([Ru(dcb) 2(NMI-phen)](PF 6) 2) and tris-(2,2′-bipyridine-4,4′-dicarboxylic acid) 3 ruthenium(ii), [(Ru(dcb) 3)Cl 2]. The presence of an electron-accepting group, 4-nitronaphthalene-1,8-dicarboximide (NMI), attached to the phenanthroline of [Ru(dcb) 2(NMI-phen)] 2+ resulted in long-lived charge separation between reduced [Ru(dcb) 2(NMI-phen)] 2+ and NiO valence band holes; 10-50 μs. In the reduced state for [Ru(dcb) 2(NMI-phen)] 2+, the electron localized on the distal NMI group. In tests with I 3 -/I - and Co(4,4′-di-tert-butyl-bipyridine) 3 2+/3+ electrolytes, [Ru(dcb) 2(NMI-phen)] 2+ outperformed [Ru(dcb) 3] 2+ in solar cell efficiency in devices. A record APCE (25%) was achieved for a ruthenium photosensitizer in a p-type DSSC. Insights on photosensitizer regeneration kinetics are included.

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