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Influence of π-Conjugation Units in Organic Dyes for Dye-Sensitized Solar Cells
KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.ORCID iD: 0000-0002-4521-2870
2007 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 111, no 4, 1853-1860 p.Article in journal (Refereed) Published
Abstract [en]

Two organic dyes with the general structure donor-conjugated chain-acceptor (D-pi-A) have been investigated as sensitizers for nanocrystalline TiO2 solar cells. The electron donor and acceptor groups were pyrrolidine and cyano acrylic acid, respectively. The conjugated chain of 2-cyano-3-{5-[2-(4-pyrrolidin-1-ylphenyl)vinyl]thiophen-2-yl}acrylic acid contains one phenyl ring and a thiophene unit and is therefore denoted PT, while for 2-cyano-3-{5 -[2-(5-pyrrolidin-1-ylthiophen-2-yl)vinyl]thiophen-2-yl}acrylic acid the phenyl ring is replaced by a second thiophene unit (TT). Solar-to-electrical energy conversion efficiencies under simulated AM 1.5 irradiation (1000 W m(-2)) of 2.3% were obtained for solar cells based on PT but of less than 0.05% for those based on TT. The reasons for the dramatic difference of the efficiencies were analyzed. Photoinduced absorption measurements revealed that the TT dye was not properly regenerated by redox electrolyte after electron injection. This sluggish regeneration is probably due to the 0.3 V less positive HOMO level for TT dye compared to the PT dye, resulting in a lower driving force for regeneration of the oxidized dye by iodide in the electrolyte. In addition, regeneration of the oxidized TT dye and electron injection from the excited TT dye may be poor due to formation of dye aggregates/complexes, as FT-IR measurements show an excess of not properly and/or unidentate bound TT dye molecules instead of bidentate bound PT dye molecules. The results highlight that small structural change of dyes results in significant changes in redox energies and binding features, affecting dramatically the performance of these dyes in dye-sensitized solar cells.

Place, publisher, year, edition, pages
2007. Vol. 111, no 4, 1853-1860 p.
Keyword [en]
density-functional thermochemistry; tio2 electrodes; conversion; efficiency; electricity; potentials; absorption; complexes; exchange; light
National Category
Physical Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-11294DOI: 10.1021/jp065550jISI: 000245005500044Scopus ID: 2-s2.0-33847351205OAI: oai:DiVA.org:kth-11294DiVA: diva2:272217
Note
QC 20100730Available from: 2009-10-14 Created: 2009-10-14 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Photoelectrochemical studies of dye-sensitized solar cells using organic dyes
Open this publication in new window or tab >>Photoelectrochemical studies of dye-sensitized solar cells using organic dyes
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The dye-sensitized solar cell (DSC) is a promising efficient low-cost molecular photovoltaic device. One of the key components in DSCs is the dye, as it is responsible for the capture of sunlight.

State-of-the-art DSC devices, based on ruthenium dyes, show record efficiencies of 10-12 %. During the last decade, metal-free organic dyes have been extensively explored as sensitizers for DSC application. The use of organic dyes is particularly attractive as it enables easy structural modifications, due to fairly short synthetic routes and reduced material cost. Novel dye should in addition to the light-harvesting properties also be compatible with the DSC components.

In this thesis, a series of new organic dyes are investigated, both when integrated in the DSC device and as individual components. The evaluation methods consisted of different electrochemical and photoelectrochemical techniques. Whereas the light-harvesting properties of the dyes were fairly easily improved, the behavior of the dye integrated in the DSC showed less predictable photovoltaic results.

The dye series studied in Papers II and IV revealed that their dye energetics limited vital electron-transfer processes, the dye regeneration (Paper II) and injection quantum yield (Paper IV). Further, in Papers III-VI, it was observed that different dye structures seemed to alter the interfacial electron recombination with the electrolyte. In addition to the dye structure sterics, some organic dyes appear to enhance the interfacial recombination, possibly due to specific dye-redox acceptor interaction (Paper V).

The impact of dye sterical modifications versus the use of coadsorbent was explored in Paper VI. The dye layer properties in the presence and absence of various coadsorbents were further investigated in Paper VII.

The core of this thesis is the identification of the processes and properties limiting the performance of the DSC device, aiming at an overall understanding of the compatibility between the DSC components and novel organic dyes.

Place, publisher, year, edition, pages
Stockholm: KTH, 2009. 84 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2009 : 50
Keyword
additive, charge recombination, coadsorbent, conduction band shift, dye-sensitized, electron lifetime, electron-transfer, organic dye, photoelectrochemical, photovoltaic, sensitizer, semiconductor, solar cell, solar cell efficiency, titanium dioxide
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-11248 (URN)978-91-7415-461-0 (ISBN)
Public defence
2009-10-30, F3, Lindstedtsvägen 26, KTH, Stcokholm, 10:00 (English)
Opponent
Supervisors
Note
QC 20100730Available from: 2009-10-14 Created: 2009-10-09 Last updated: 2010-07-30Bibliographically approved

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Sun, Licheng

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