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Tuning the HOMO and LUMO Energy Levels of Organic Chromophores For Dye Sensitized Solar Cells
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.ORCID iD: 0000-0003-1771-9401
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
Show others and affiliations
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.

Place, publisher, year, edition, pages
2007. no 72, 9550-9556 p.
Keyword [en]
high-efficiency, coumarin dyes, tio2, acid, performance, derivatives, design, light
National Category
Chemical Sciences
Identifiers
URN: urn:nbn:se:kth:diva-7882DOI: 10.1021/jo701592xISI: 000251313600017OAI: oai:DiVA.org:kth-7882DiVA: diva2:13041
Note
QC 20100716Available from: 2008-01-09 Created: 2008-01-09 Last updated: 2012-02-28Bibliographically approved
In thesis
1. Synthesis of Organic Chromophores for Dye Sensitized Solar Cells
Open this publication in new window or tab >>Synthesis of Organic Chromophores for Dye Sensitized Solar Cells
2007 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [en]

This thesis is divided into four parts with organic chromophores for dye sensitized solar cells as the common feature and an introduction with general concepts of the dye sensitized solar cells.

The first part of the thesis describes the development of an efficient organic chromophore for dye sensitized solar cells. The chromophore consists of a triphenylamine moiety as an electron donor, a conjugated linker with a thiophene moiety and cyanoacrylic acid as an electron acceptor and anchoring group. During this work a strategy to obtain an efficient sensitizer was developed. Alternating the donor, linker or acceptor moieties independently, would give us the tool to tune the HOMO and LUMO energy levels of the chromophores. The following parts of this thesis regard this development strategy.

The second part describes the contributions to the HOMO and LUMO energy levels when alternating the linker moiety. By varying the linker the HOMO and LUMO energy levels was indeed shifted. Unexpected effects of the solar cell performances when increasing the linker length were revealed, however.

The third part describes the investigation of an alternative acceptor group, rhodanine-3-acetic acid, in combination with different linker lengths. The HOMO and LUMO energy level tuning was once again successfully shifted. The poor electronic coupling of the acceptor group to the semiconductor surface proved to be a problem for the overall efficiency of the solar cell, however.

The fourth part describes the contributions from different donor groups to the HOMO and LUMO energy levels and has so far been the most successful in terms of reaching high efficiencies in the solar cell. A top overall efficiency of 7.1 % was achieved.

Place, publisher, year, edition, pages
Stockholm: KTH, 2007. 43 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2007:86
Keyword
Organic Chromophores, Dye Sensitized Solar Cells
National Category
Organic Chemistry
Identifiers
urn:nbn:se:kth:diva-4600 (URN)978-91-7178-833-7 (ISBN)
Presentation
2008-01-25, D3, Lindstedtsvägen 5, Stockholm, 13:00
Opponent
Supervisors
Note
QC 20101108Available from: 2008-01-09 Created: 2008-01-09 Last updated: 2010-11-08Bibliographically approved
2. Synthesis of Organic Chromophores for Dye Sensitized Solar Cells.
Open this publication in new window or tab >>Synthesis of Organic Chromophores for Dye Sensitized Solar Cells.
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

 

This thesis deals with development and synthesis of organic chromophores for dye sensitized solar cells. The chromophores are divided into three components; donor, linker and acceptor.

The development of efficient organic chromophores for dye sensitized solar cells starts off with one new organic chromophore, D5. This chromophore consists of a triphenylamine moiety as an electron donor, a conjugated linker with a thiophene moiety and cyanoacrylic acid as an electron acceptor and anchoring group. Alternating the donor, linker or acceptor moieties independently, would give us the tool to tune the HOMO and LUMO energy levels of the chromophores. The following parts of this thesis regard this development strategy.

The contributions to the HOMO and LUMO energy levels were investigated when alternating the linker moiety. Unexpected effects of the solar cell performances when increasing the linker length were revealed, however.

In addition, the effect of an alternative acceptor group, rhodanine-3-acetic acid, in combination with different linker lengths was investigated. The HOMO and LUMO energy level tuning was once again successful. Electron recombination from the semiconductor to the electrolyte is probably the cause of the poor efficiencies obtained for this series of dyes.

Finally, the development of functionalized triphenylamine based donors and the contributions from different substituents to the HOMO and LUMO energy levels and as insulating layers were investigated. This strategy has so far been the most successful in terms of reaching high efficiencies in the solar cell. A top overall efficiency of 7.79 % was achieved.

 

Place, publisher, year, edition, pages
Stockholm: KTH, 2009. 73 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2009:18
Keyword
Acceptor, chromophore, donor, dye sensitized solar cells, HOMO and LUMO energy level tuning, linker, organic dye.
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-10547 (URN)978-91-7415-328-6 (ISBN)
Public defence
2009-08-28, F3, KTH, Lindstedtsvägen 26, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC 20100716Available from: 2009-06-12 Created: 2009-05-26 Last updated: 2010-07-16Bibliographically approved
3. 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
4. Design, Synthesis and Properties of Organic Sensitizers for Dye Sensitized Solar Cells
Open this publication in new window or tab >>Design, Synthesis and Properties of Organic Sensitizers for Dye Sensitized Solar Cells
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
Acceptor, chromophore, donor, dye, sensitized, energy level, HOMO/LUMO, linker, phenoxazine, sensitizer, solar cell, triphenylamine
National Category
Chemical Sciences Organic Chemistry
Identifiers
urn:nbn:se:kth:diva-33190 (URN)978-91-7415-954-7 (ISBN)
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

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