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Ultrafast dye regeneration in a core-shell NiO-dye-TiO2 mesoporous film
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.ORCID iD: 0000-0003-0244-8565
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2018 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 20, no 1, p. 36-40Article in journal (Refereed) Published
Abstract [en]

In this study, a core-shell NiO-dye-TiO2 mesoporous film was fabricated for the first time, utilizing atomic layer deposition technique and a newly designed triphenylamine dye. The structure of the film was confirmed by SEM, TEM, and EDX. Excitation of the dye led to efficient and fast charge separation, by hole injection into NiO, followed by an unprecedentedly fast dye regeneration (t1/2 [less-than-or-equal] 500 fs) by electron transfer to TiO2. The resulting charge separated state showed a pronounced transient absorption spectrum caused by the Stark effect, and no significant decay was found within 1.9 ns. This indicates that charge recombination between NiO and TiO2 is much slower than that between the NiO and the reduced dye in the absence of the TiO2 layer (t1/2 [approximate] 100 ps).

Place, publisher, year, edition, pages
The Royal Society of Chemistry , 2018. Vol. 20, no 1, p. 36-40
National Category
Natural Sciences Engineering and Technology
Identifiers
URN: urn:nbn:se:uu:diva-335974DOI: 10.1039/C7CP07088HISI: 000418374800002OAI: oai:DiVA.org:uu-335974DiVA, id: diva2:1164543
Funder
Knut and Alice Wallenberg Foundation, 2011.0067Swedish Energy Agency, 43599-1Available from: 2017-12-11 Created: 2017-12-11 Last updated: 2018-03-14Bibliographically approved
In thesis
1. Shining Light on Molecules: Electron Transfer Processes in Model Systems for Solar Energy Conversion Investigated by Transient Absorption Spectroscopy
Open this publication in new window or tab >>Shining Light on Molecules: Electron Transfer Processes in Model Systems for Solar Energy Conversion Investigated by Transient Absorption Spectroscopy
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In the recent years, solar energy conversion has attracted a huge research interest due to the potential application for limiting the greenhouse effect. In many solar cells and solar fuel cells, understanding of charge transfer (CT) and recombination is important for future improvement of the overall efficiency. One important tool for that is transient absorption spectroscopy (TAS).

Mesoporous nickel oxide films were investigated due to their potential application in p-type dye-sensitized solar cells (DSSCs), tandem DSSCs and dye sensitized solar fuel cells (DSSFC:s). Firstly, it was found that the hole generated by band gap excitation is trapped on an ultrafast time scale by Ni3+ states. It was possible to observe a direct signal from the holes by transient mid-IR absorption spectroscopy allowing for direct detection of hole injection and trapping. On a ns time scale, the trapped holes relaxed to much less reactive holes which favored long lived NiO-dye charge separation (CS).

A series of perylene monoimide (PMI) dyes with different anchoring groups was studied. Differences in binding affinity and stability were found. Nevertheless, all PMIs showed ultrafast charge separation and similar recombination kinetics. Furthermore, the effect of MLCT localization of ruthenium polypyridyl complexes was investigated. All those dyes showed slow or no hole injection. At the same time, a self-quenching process was found for all compounds that limited the photoconversion efficiency.

Furthermore, a new core-shell structure of p-type DSSCs was proposed and investigated. Here, the liquid electrolyte was replaced by a layer of TiO2. That system was found to undergo both injection and regeneration of the dye on an ultrafast time scale (below 1 ps). Furthermore, the CS state did not show any decay within 2 ns making this structure interesting for application in DSSCs.

A pentad consisting of a known Ru-based (electro)chemical water oxidation catalyst (WOC) linked to two zinc-porphyrin-fullerene dyads (ZnP-C60) was investigated. The charge transfer processes leading to the first oxidation of the WOC were understood. Low levels of water oxidation were detected in presence of a sacrificial electron acceptor.

The gained understanding of the CT dynamics and recombination processes thus allows new strategies to improve the efficiency in molecular systems for solar energy conversion.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2018. p. 74
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1645
Keywords
photophysics, photoinduced electron transfer, transient absorption spectroscopy, laser spectroscopy, solar energy conversion, p-type DSSCs, Charge separation, recombination, mesoporous NiO
National Category
Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-343443 (URN)978-91-513-0273-7 (ISBN)
Public defence
2018-05-04, Siegbahnsalen, Lägerhyddsvägen 1, Uppsala, 09:15 (English)
Opponent
Supervisors
Available from: 2018-04-13 Created: 2018-03-14 Last updated: 2018-04-24

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Tian, LeiFöhlinger, JensZhang, Zhi-BinYang, WenxingJohansson, Malin BKubart, TomasBoschloo, GerritHammarström, LeifTian, Haining
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