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Light-induced cobalt tris(bipyridine) ligand exchange: a simple strategy towards efficient and durable dye-sensitized solar cells
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.ORCID iD: 0000-0001-5115-4593
(English)Manuscript (preprint) (Other academic)
National Category
Physical Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-187051OAI: oai:DiVA.org:kth-187051DiVA: diva2:928803
Note

QCR 20160517

Available from: 2016-05-16 Created: 2016-05-16 Last updated: 2016-05-17Bibliographically approved
In thesis
1. Electrolyte-Based Dynamics: Fundamental Studies for Stable Liquid Dye-Sensitized Solar Cells
Open this publication in new window or tab >>Electrolyte-Based Dynamics: Fundamental Studies for Stable Liquid Dye-Sensitized Solar Cells
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
Dye-sensitized solar cells, Stability, Electrolyte, Cobalt redox couples, Additives
National Category
Physical Chemistry
Research subject
Chemistry
Identifiers
urn:nbn:se:kth:diva-187025 (URN)978-91-7729-013-1 (ISBN)
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

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