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Design, Synthesis and Properties of Organic Sensitizers for Dye Sensitized Solar Cells
KTH, School of Chemical Science and Engineering (CHE), Chemistry. (Licheng Sun)ORCID iD: 0000-0003-1771-9401
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis gives a detailed description of the design and synthesis of new organic sensitizers for Dye sensitized Solar Cells (DSCs). It is divided in 7 chapters, where the first gives an introduction to the field of DSCs and the synthesis of organic sensitizers. Chapters 2 to 6 deal with the work of the author, starting with the first publication and the other following in chronological order. The thesis is completed with some concluding remarks (chapter 7).

The DSC is a fairly new solar cell concept, also known as the Grätzel cell, after its inventor Michael Grätzel. It uses a dye (sensitizer) to capture the incident light. The dye is chemically connected to a porous layer of a wide band-gap semiconductor. The separation of light absorption and charge separation is different from the conventional Si-based solar cells. Therefore, it does not require the very high purity materials necessary for the Si-solar cells. This opens up the possibility of easier manufacturing for future large scale production. Since the groundbreaking work reported in 1991, the interest within the field has grown rapidly. Large companies have taken up their own research and new companies have started with their focus on the DSC. So far the highest solar energy to electricity conversion efficiencies have reached ~12%.

The sensitizers in this thesis are based on triphenylamine or phenoxazine as the electron donating part in the molecule. A conjugated linker allows the electrons to flow from the donor to the acceptor, which will enable the electrons to inject into the semiconductor once they are excited. Changing the structure by introducing substituents, extending the conjugation and exchanging parts of the molecule, will influence the performance of the solar cell. By analyzing the performance, one can evaluate the importance of each component in the structure and thereby gain more insight into the complex nature of the dye sensitized solar cell.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology , 2011. , 80 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2011:31
Keyword [en]
Acceptor, chromophore, donor, dye, sensitized, energy level, HOMO/LUMO, linker, phenoxazine, sensitizer, solar cell, triphenylamine
National Category
Chemical Sciences Organic Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-33190ISBN: 978-91-7415-954-7OAI: oai:DiVA.org:kth-33190DiVA: diva2:413894
Public defence
2011-05-20, K2, Teknikringen 28, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC 20110505Available from: 2011-05-05 Created: 2011-04-29 Last updated: 2011-09-08Bibliographically approved
List of papers
1. Tuning the HOMO and LUMO Energy Levels of Organic Chromophores For Dye Sensitized Solar Cells
Open this publication in new window or tab >>Tuning the HOMO and LUMO Energy Levels of Organic Chromophores For Dye Sensitized Solar Cells
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2007 (English)In: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, no 72, 9550-9556 p.Article in journal (Refereed) Published
Abstract [en]

A series of organic chromophores have been synthesized in order to approach optimal energy level composition in the TiO2-dye-iodide/triiodide system in the dye-sensitized solar cells. HOMO and LUMO energy level tuning is achieved by varying the conjugation between the triphenylamine donor and the cyanoacetic acid acceptor. This is supported by spectral and electrochemical experiments and TDDFT calculations. These results show that energetic tuning of the chromophores was successful and fulfilled the thermodynamic criteria for dye-sensitized solar cells, electrical losses depending on the size and orientation of the chromophores were observed.

Keyword
high-efficiency, coumarin dyes, tio2, acid, performance, derivatives, design, light
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-7882 (URN)10.1021/jo701592x (DOI)000251313600017 ()
Note
QC 20100716Available from: 2008-01-09 Created: 2008-01-09 Last updated: 2012-02-28Bibliographically approved
2. Molecular Engineering of Organic Chromophores for Dye Sensitized Solar Cell Applications
Open this publication in new window or tab >>Molecular Engineering of Organic Chromophores for Dye Sensitized Solar Cell Applications
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2008 (English)In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 130, 6259-6266 p.Article in journal (Refereed) Published
Abstract [en]

Novel unsymmetrical organic sensitizers comprising donor, electron-conducting, and anchoring groups were engineered at a molecular level and synthesized for sensitization of mesoscopic titanium dioxide injection solar cells. The unsymmetrical organic sensitizers 3-(5-(4-(diphenylamino)styryl)thiophen-2-yl)-2-cyanoacrylic acid (D5), 3-(5-bis(4-(diphenylamino)styryl)thiophen-2-yl)-2-cyanoacrylic acid (D7), 5-(4-(bis(4-methoxyphenylamino)styryl)thiophen-2-yl)-2-cyanoacrylic acid (D9), and 3-(5-bis(4,4'-dimethoxydiphenylamino)styryl)thiophen-2-yl)-2-cyanoacrylic acid (D11) anchored onto TiO2 and were tested in dye-sensitized solar cell with a volatile electrolyte. The monochromatic incident photon-to-current conversion efficiency of these sensitizers is above 80%, and D11-sensitized solar cells yield a short-circuit photocurrent density of 13.90 +/- 0.2 mA/cm(2), an open-circuit voltage of 740 +/- 10 mV, and a fill factor of 0.70 +/- 0.02, corresponding to an overall conversion efficiency of 7.20% under standard AM 1.5 sun light. Detailed investigations of these sensitizers reveal that the long electron lifetime is responsible for differences in observed open-circuit potential of the cell. As an alternative to liquid electrolyte cells, a solid-state organic hole transporter is used in combination with the D9 sensitizer, which exhibited an efficiency of 3.25%. Density functional theory/time-dependent density functional theory calculations have been employed to gain insight into the electronic structure and excited states of the investigated species.

Place, publisher, year, edition, pages
ACS, 2008
Keyword
nanocrystalline tio2, electron-injection, recombination, semiconductor, chromophores, conductor, energies, dynamics, acceptor, model
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-10534 (URN)10.1021/ja800066y (DOI)000255620200032 ()2-s2.0-43249114905 (ScopusID)
Note
QC 20100716Available from: 2009-05-25 Created: 2009-05-25 Last updated: 2012-02-23Bibliographically approved
3. Highly efficient Organic Sensitizers for Solid State Dye Sensitized Solar Cells
Open this publication in new window or tab >>Highly efficient Organic Sensitizers for Solid State Dye Sensitized Solar Cells
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2009 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 113, no 38, 16816-16820 p.Article in journal (Refereed) Published
Abstract [en]

Organic sensitizers comprising of donor, electron-conducting, and anchoring groups designed and developed for dye-sensitized solar cell applications. The solar cell employing a spiro-OMeTAD hole transporting material exhibits a short circuit photocurrent density of 9.64 mA/cm2, the open circuit voltage of 798 mV and a fill factor of 0.57, corresponding to an overall conversion efficiency of 4.4% at standard AM 1.5 sunlight. Photo-induced absorption spectroscopy probes an efficient hole-transfer from dyes to the spiro-OMeTAD.

Keyword
PHOTOINDUCED ABSORPTION-SPECTROSCOPY; TIO2; CONVERSION
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-10545 (URN)10.1021/jp9033722 (DOI)000269745700037 ()2-s2.0-70349880505 (ScopusID)
Note
Uppdaterad från manuskrift 20100716 QC 20100716Available from: 2009-05-26 Created: 2009-05-26 Last updated: 2011-05-05Bibliographically approved
4. Triphenylamine Based Organic Chromophores Containing Two Anchoring Groups for Dye Sensitized Solar Cells
Open this publication in new window or tab >>Triphenylamine Based Organic Chromophores Containing Two Anchoring Groups for Dye Sensitized Solar Cells
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(English)Manuscript (preprint) (Other academic)
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-33337 (URN)
Note
QS 2011Available from: 2011-05-03 Created: 2011-05-03 Last updated: 2011-05-05Bibliographically approved
5. Phenoxazine Dyes for Dye-Sensitized Solar Cells: Relationship Between Molecular Structure and Electron Lifetime.
Open this publication in new window or tab >>Phenoxazine Dyes for Dye-Sensitized Solar Cells: Relationship Between Molecular Structure and Electron Lifetime.
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2011 (English)In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 17, no 23, 6415-6424 p.Article in journal (Refereed) Published
Abstract [en]

A series of metal-free organic dyes with a core phenoxazine chromophore have been synthesized and tested as sensitizers in dye-sensitized solar cells. Overall conversion efficiencies of 6.03-7.40 % were reached under standard AM 1.5G illumination at a light intensity of 100 mW cm(-2) . A clear trend in electron lifetime could be seen; a dye with a furan-conjugated linker showed a shorter lifetime relative to dyes with the acceptor group directly attached to the phenoxazine. The addition of an extra donor unit, which bore insulating alkoxyl chains, in the 7-position of the phenoxazine could increase the lifetime even further and, together with additives in the electrolyte to raise the conduction band, an open circuit voltage of 800 mV could be achieved. From photoelectron spectroscopy and X-ray absorption spectroscopy of the dyes adsorbed on TiO(2) particles, it can be concluded that the excitation is mainly of cyano character (i.e., on average, the dye molecules are standing on, and pointing out, from the surface of TiO(2) particles).

National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-33339 (URN)10.1002/chem.201003730 (DOI)000292095800018 ()21509836 (PubMedID)2-s2.0-79958204045 (ScopusID)
Note
Updated from submitted to published. QC 20110711Available from: 2011-05-03 Created: 2011-05-03 Last updated: 2012-03-20Bibliographically approved
6. Modifying the Energy Levels in Phenoxazine Based Sensitizers for Dye Sensitized Solar Cells
Open this publication in new window or tab >>Modifying the Energy Levels in Phenoxazine Based Sensitizers for Dye Sensitized Solar Cells
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(English)Manuscript (preprint) (Other academic)
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-33341 (URN)
Note

QS 2011

Available from: 2011-05-03 Created: 2011-05-03 Last updated: 2014-09-24Bibliographically approved

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