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Electrolyte-Based Dynamics: Fundamental Studies for Stable Liquid Dye-Sensitized Solar Cells
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. (Lars Kloo)ORCID iD: 0000-0001-5115-4593
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The long-term outdoor durability of dye-sensitized solar cells (DSSCs) is still a challenging issue for the large-scale commercial application of this promising photovoltaic technique. In order to study the degradation mechanism of DSSCs, ageing tests under selected accelerating conditions were carried out. The electrolyte is a crucial component of the device. The interactions between the electrolyte and other device components were unraveled during the ageing test, and this is the focus of this thesis. The dynamics and the underlying effects of these interactions on the DSSC performance were studied.

Co(bpy)32+/3+-mediated solar cells sensitized by triphenylamine-based organic dyes are systems of main interest. The changes with respect to the configuration of both labile Co(bpy)32+ and apparently inert Co(bpy)33+ redox complexes under different ageing conditions have been characterized, emphasizing the ligand exchange problem due to the addition of Lewis-base-type electrolyte additives and the unavoidable presence of oxygen. Both beneficial and adverse effects on the DSSC performance have been separately discussed in the short-term and long-term ageing tests. The stability of dye molecules adsorbed on the TiO2 surface and dissolved in the electrolyte has been studied by monitoring the spectral change of the dye, revealing the crucial effect of cation-based additives and the cation-dependent stability of the device photovoltage. The dye/TiO2 interfacial electron transfer kinetics were compared for the bithiophene-linked dyes before and after ageing in the presence of Lewis base additives; the observed change being related to the light-promoted and Lewis-base-assisted performance enhancement. The effect of electrolyte co-additives on passivating the counter electrode was also observed. The final chapter shows the effect of electrolyte composition on the electrolyte diffusion limitation from the perspectives of cation additive options, cation concentration and solvent additives respectively. Based on a comprehensive analysis, suggestions have been made regarding lithium-ion-free and polymer-in-salt strategies, and also regarding cobalt complex degradation and the crucial role of Lewis base additives. The fundamental studies contribute to the understanding of DSSC chemistry and provide a guideline towards achieving efficient and stable DSSCs.

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2016. , 171 p.
Series
TRITA-CHE-Report, ISSN 1654-1081 ; 2016:27
Keyword [en]
Dye-sensitized solar cells, Stability, Electrolyte, Cobalt redox couples, Additives
National Category
Physical Chemistry
Research subject
Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-187025ISBN: 978-91-7729-013-1OAI: oai:DiVA.org:kth-187025DiVA: diva2:928820
Public defence
2016-06-15, Sal K2, Teknikringen 28, KTH, Stockholm, 13:00 (English)
Opponent
Supervisors
Funder
Swedish Energy AgencySwedish Research Council
Note

QC 20160517

Available from: 2016-05-17 Created: 2016-05-16 Last updated: 2016-05-17Bibliographically approved
List of papers
1. Crystallography as forensic tool for electrolyte degradation in dye-sensitized solar cells
Open this publication in new window or tab >>Crystallography as forensic tool for electrolyte degradation in dye-sensitized solar cells
(English)Manuscript (preprint) (Other academic)
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-187043 (URN)
Note

QCR 20160517

Available from: 2016-05-16 Created: 2016-05-16 Last updated: 2016-05-17Bibliographically approved
2. Light-induced cobalt tris(bipyridine) ligand exchange: a simple strategy towards efficient and durable dye-sensitized solar cells
Open this publication in new window or tab >>Light-induced cobalt tris(bipyridine) ligand exchange: a simple strategy towards efficient and durable dye-sensitized solar cells
(English)Manuscript (preprint) (Other academic)
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-187051 (URN)
Note

QCR 20160517

Available from: 2016-05-16 Created: 2016-05-16 Last updated: 2016-05-17Bibliographically approved
3. Long-term stability for cobalt-based dye-sensitized solar cells obtained by electrolyte optimization
Open this publication in new window or tab >>Long-term stability for cobalt-based dye-sensitized solar cells obtained by electrolyte optimization
2014 (English)In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 50, no 47, 6249-6251 p.Article in journal (Refereed) Published
Abstract [en]

A significant improvement in the long-term stability for cobalt-based dye-sensitized solar cells (DSCs) under light-soaking conditions has been achieved by optimization of the composition of tris(2,2'-bipyridine) Co(II)/Co(III) electrolytes. The effects of component exchanges and changes were also studied during the optimization process.

National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-147440 (URN)10.1039/c4cc00698d (DOI)000336793100017 ()2-s2.0-84901044564 (ScopusID)
Funder
Swedish Research CouncilSwedish Energy Agency
Note

QC 20140627

Available from: 2014-06-27 Created: 2014-06-27 Last updated: 2016-05-17Bibliographically approved
4. Cation-Dependent Photostability of Co(II/III)-Mediated Dye-Sensitized Solar Cells
Open this publication in new window or tab >>Cation-Dependent Photostability of Co(II/III)-Mediated Dye-Sensitized Solar Cells
Show others...
2015 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 119, no 44, 24704-24713 p.Article in journal (Refereed) Published
Abstract [en]

The electrolyte composition has a significant effect on the performance and stability of cobalt-based, dye-sensitized solar cells (DSSCs). The stability of DSSCs incorporating Co(II/III) tris(bipyridine) redox mediator has been investigated over 1000 h under full solar irradiation (with UV cutoff) at a temperature of 60 °C, the main focus being on monitoring the photovoltaic performance of the device and analyzing the internal charge-transfer dynamics in the presence of different cation coadditives (preferably added as tetracyanoborate salts). A clear cation-dependence is shown, not only of the early light-induced performance but also of the long-term photostability of the photovoltage of the device. These light-induced changes, which are attributed to the promotion of electron injection and less electron recombination loss, by transient spectral and electrochemical studies at the TiO2/dye/electrolyte interface, indicate that the main cation effects involve the TiO2 surface electric field and energy-state distribution. By examining the stability of adsorbed and solvated dye during aging, it has been found that the dye photodegradation is probably responsible for the decline in the photovoltage and that this is extremely dependent on the nature of the cation coadditives in the electrolyte. It is therefore suggested that optimization of the electrolyte cation composition is essential for improving the stability of cobalt-based DSSCs.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2015
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-181971 (URN)10.1021/acs.jpcc.5b06310 (DOI)000364435200003 ()2-s2.0-84946547956 (ScopusID)
Funder
Swedish Research CouncilSwedish Energy Agency
Note

QC 20160212

Available from: 2016-02-12 Created: 2016-02-11 Last updated: 2016-05-17Bibliographically approved
5. Interfacial dye/electrolyte interaction dramatically improving the photocurrent in dye-sensitized solar cells
Open this publication in new window or tab >>Interfacial dye/electrolyte interaction dramatically improving the photocurrent in dye-sensitized solar cells
(English)Manuscript (preprint) (Other academic)
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-187052 (URN)
Note

QCR 20160517

Available from: 2016-05-16 Created: 2016-05-16 Last updated: 2016-05-17Bibliographically approved
6. A quasi-liquid polymer-based cobalt redox mediator electrolyte for dye-sensitized solar cells
Open this publication in new window or tab >>A quasi-liquid polymer-based cobalt redox mediator electrolyte for dye-sensitized solar cells
Show others...
2013 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 15, no 40, 17419-17425 p.Article in journal (Refereed) Published
Abstract [en]

Recently, cobalt redox electrolyte mediators have emerged as a promising alternative to the commonly used iodide/triiodide redox shuttle in dye-sensitized solar cells (DSCs). Here, we report the successful use of a new quasi-liquid, polymer-based electrolyte containing the Co3+/Co2+ redox mediator in 3-methoxy propionitrile solvent in order to overcome the limitations of high cell resistance, low diffusion coefficient and rapid recombination losses. The performance of the solar cells containing the polymer based electrolytes increased by a factor of 1.2 with respect to an analogous electrolyte without the polymer. The performances of the fabricated DSCs have been investigated in detail by photovoltaic, transient electron measurements, EIS, Raman and UV-vis spectroscopy. This approach offers an effective way to make high-performance and long-lasting DSCs.

Keyword
Mass-Transport, Organic-Dyes, Couple, Complexes, Recombination, Performance, Efficiency, Shuttles
National Category
Other Chemistry Topics
Identifiers
urn:nbn:se:kth:diva-133669 (URN)10.1039/c3cp52869c (DOI)000325398500047 ()2-s2.0-84886894701 (ScopusID)
Funder
StandUp
Note

QC 20150626

Available from: 2013-11-08 Created: 2013-11-08 Last updated: 2016-05-17Bibliographically approved
7. Impedance spectroscopic analysis of electrolyte diffusion in aged dye-sensitized solar cells containing cobalt tris(bipyridine) redox shuttles
Open this publication in new window or tab >>Impedance spectroscopic analysis of electrolyte diffusion in aged dye-sensitized solar cells containing cobalt tris(bipyridine) redox shuttles
(English)Manuscript (preprint) (Other academic)
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-187053 (URN)
Note

QCR 20160517

Available from: 2016-05-16 Created: 2016-05-16 Last updated: 2016-05-17Bibliographically approved

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Available from 2017-05-03 16:17

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