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Impact of Local Electric Fields on Charge-Transfer Processes at the TiO2/Dye/Electrolyte Interface
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry. (Gerrit Boschloo)ORCID iD: 0000-0002-3440-9416
Ecole Polytech Fed Lausanne, Inst Chem Sci & Engn, Lab Photomol Sci, EPFLFSB ISIC LSPM, Chemin Alamb,Stn 6, CH-1015 Lausanne, Switzerland.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
2017 (English)In: ACS Energy Letter, ISSN 2380-8195, Vol. 2, no 1, 161-167 p.Article in journal (Refereed) Accepted
Abstract [en]

Photoinduced electron -transfer processes at the TiO2/ dye/electrolyte interface are vital for various emerging technologies. Here, the impact of the local electric field at this interface on the charge -transfer processes was investigated in two aspects: (a) charge recombination between the electrons accumulated within TiO2 and the photoxidized dye and (b) regeneration of the dyes by the cobalt bipyridyl redox mediators. The amplitude of the local electric field was changed by use of different cations in the electrolytic environment, in the order E-Ca(2+) > E-Mg(2+)> E-Na(+) > E-u(+) characterized by the transient absorption spectroscopy. For the charge recombination process, the kinetic time constant showed a remarkable linear correlation with the relative electric field strength, while for the regeneration process, no evident dependence was observed. These results collectively suggest the spatial confinement of the effects of the local electric field on the interfacial electron -transfer processes.

Place, publisher, year, edition, pages
2017. Vol. 2, no 1, 161-167 p.
National Category
Physical Chemistry
Identifiers
URN: urn:nbn:se:uu:diva-310189DOI: 10.1021/acsenergylett.6b00568ISI: 000392260400025OAI: oai:DiVA.org:uu-310189DiVA: diva2:1055475
Funder
Swedish Energy AgencySwedish Research CouncilStandUp
Available from: 2016-12-12 Created: 2016-12-12 Last updated: 2017-02-27Bibliographically approved
In thesis
1. Exploring Electronic Processes at the Mesoporous TiO2/Dye/Electrolyte Interface
Open this publication in new window or tab >>Exploring Electronic Processes at the Mesoporous TiO2/Dye/Electrolyte Interface
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Dye sensitized solar cells (DSSCs) are an attractive way to convert light into electricity. Its development requires a detailed understanding and kinetic optimization of various electronic processes, especially those occurring at the mesoporous TiO2/dye/electrolyte interface. This dissertation work is focused on the exploration of the various electronic processes at the sensitized-electrode/electrolyte interface by using various electrochemical and photochemical methods.

Firstly, an alternative redox couple—TEMPO/TEMPO·+ with a relatively high positive redox potential—is explored, aiming to reduce the energy loss during the dye regeneration process. Despite the fast dye regeneration, the charge recombination between the electrons in the conduction band of mesoporous TiO2 and the oxidized redox species is found to be the limiting factor of the device. Further, a more efficient tandem-electrolyte system is developed, leading to DSSCs with the power conversion efficiency of 10.5 % and 11.7 % at 1 sun and 0.5-sun illumination, respectively. An electron-transfer cascade process during dye regeneration by the redox mediators is discovered to be beneficial. Further stability studies on the device suggest the crucial role of TiO2/dye/electrolyte interfaces in the long-term stability of cobalt bipyridyl electrolyte-based DSSCs.

On the fundamental level, the local electric field and Stark effects at the TiO2/dye/electrolyte interface are investigated in various aspects—including the charge compensation mechanism, the factors affecting the electric field strength, as well as its impact on charge transfer kinetics. These results give further insights about the TiO2/dye/electrolyte interface, and contribute to the further development and understanding of DSSCs.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2017. 86 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1464
Keyword
dye-sensitized solar cells, dye regeneration, Stark effect, the local electric field, cationic effect
National Category
Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-310191 (URN)978-91-554-9780-4 (ISBN)
Public defence
2017-02-10, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 10:15 (English)
Opponent
Supervisors
Available from: 2017-01-16 Created: 2016-12-12 Last updated: 2017-01-17

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