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Ellis, Hanna
Publications (10 of 13) Show all publications
Gao, J., El-Zohry, A., Trilaksana, H., Gabrielsson, E., Leandri, V., Ellis, H., . . . Kloo, L. (2018). Light-Induced Interfacial Dynamics Dramatically Improve the Photocurrent in Dye-Sensitized Solar Cells: An Electrolyte Effect. ACS Applied Materials and Interfaces, 10(31), 26241-26247
Open this publication in new window or tab >>Light-Induced Interfacial Dynamics Dramatically Improve the Photocurrent in Dye-Sensitized Solar Cells: An Electrolyte Effect
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2018 (English)In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 10, no 31, p. 26241-26247Article in journal (Refereed) Published
Abstract [en]

A significant increase in the photocurrent generation during light soaking for solar cells sensitized by the triphenylamine-based D-pi-A organic dyes (PD2 and LEG1) and mediated by cobalt bipyridine redox complexes has been observed and investigated. The crucial role of the electrolyte has been identified in the performance improvement. Control experiments based on a pretreatment strategy reveals TBP as the origin. The increase in the current and IPCE has been interpreted by the interfacial charge-transfer kinetics studies. A slow component in the injection kinetics was exposed for this system. This change explains the increase in the electron lifetime and collection efficiency. Photoelectron spectroscopic measurements show energy shifts at the dye/TiO2 interface, leading us to formulate a hypothesis with respect to an electrolyte induced dye reorganization at the surface.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2018
Keywords
dye-sensitized solar cells, electrolyte, interface, dynamics, light soaking
National Category
Materials Chemistry Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-362697 (URN)10.1021/acsami.8b06897 (DOI)000441477800045 ()29996051 (PubMedID)
Funder
Swedish Research CouncilSwedish Energy Agency
Available from: 2018-10-11 Created: 2018-10-11 Last updated: 2018-10-11Bibliographically approved
Ellis, H. (2016). Developing Environmentally Friendly Dye-sensitized Solar Cells. (Doctoral dissertation). Uppsala: Acta Universitatis Upsaliensis
Open this publication in new window or tab >>Developing Environmentally Friendly Dye-sensitized Solar Cells
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Due to climate change and its effects, alternative renewable energy sources are needed in the future human society. In the work of this thesis, the Dye-sensitized Solar Cell (DSC) has been investigated and characterized.

DSCs are appealing as energy conversion devices, since they have high potential to provide low cost solar light to electricity conversion. The DSC is built up by a working electrode consisting of a conductive glass substrate with a dye-sensitized mesoporous TiO2 film, a counter electrode with a catalyst and, in between, the electrolyte which performs the charge transport by means of a redox mediator. The aim of this thesis was to develop and evaluate cheap and environmentally friendly materials for the DSC.

An alternative polymer-based counter electrode catalyst was fabricated and evaluated, showing that the PEDOT catalyst counter electrode outperformed the platinum catalyst counter electrode. Different organic dyes were evaluated and it was found that the dye architecture affected the performance of the assembled DSCs. A partly hydrophilic organic triphenylamine dye was developed and applied in water-based electrolyte DSCs. The partly hydrophilic dye outperformed the reference hydrophobic dye. Small changes in dye architecture were evaluated for two similar dyes, both by spectroscopic and electrochemical techniques. A change in the length of the dialkoxyphenyl units on a triphenylamine dye, affected the recombination and the regeneration electron transfer kinetics in the DSC system. Finally, three water soluble cobalt redox couples were developed and applied in water-based electrolyte DSCs. An average efficiency of 5.5% (record efficiency of 5.7%) for a 100% water-based electrolyte DSC was achieved with the polymer-based catalyst counter electrode and an organic dye with short dimethoxyphenyl units, improving the wetting and the regeneration process.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2016. p. 82
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1351
Keywords
dye-sensitized solar cells, dye, cobalt, triphenylamine, titanium dioxide, aqueous, PEDOT
National Category
Physical Chemistry
Research subject
Chemistry with specialization in Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-280291 (URN)978-91-554-9506-0 (ISBN)
Public defence
2016-04-29, Polhemsalen; Ång/10134, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 10:15 (English)
Opponent
Supervisors
Available from: 2016-04-06 Created: 2016-03-09 Last updated: 2016-05-24
Ellis, H., Jiang, R., Ye, S., Hagfeldt, A. & Boschloo, G. (2016). Development of high efficiency 100% aqueous cobalt electrolyte dye-sensitised solar cells. Physical Chemistry, Chemical Physics - PCCP, 18(12), 8419-8427
Open this publication in new window or tab >>Development of high efficiency 100% aqueous cobalt electrolyte dye-sensitised solar cells
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2016 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 18, no 12, p. 8419-8427Article in journal (Refereed) Published
Abstract [en]

In this study we report the application of three cobalt redox shuttles in 100% aqueous electrolyte dye-sensitised solar cells (DSCs). By using chloride as a counter-ion for cobalt bipyridine, cobalt phenanthroline and cobalt bipyridine pyrazole, the redox shuttles were made water soluble; no surfactant or further treatment was necessary. A simple system of merely the redox shuttles and 1-methylbenzimidazole (MBI) in water as an electrolyte in combination with an organic dye and a mesoporous PEDOT counter electrode was optimised. The optimisation resulted in an average efficiency of 5.5% (record efficiency of 5.7%) at 1 sun. The results of this study present promising routes for further improvements of aqueous cobalt electrolyte DSCs.

Keywords
Dye, solar cell, water, electrolyte, titanium dioxide
National Category
Physical Chemistry
Research subject
Chemistry with specialization in Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-280289 (URN)10.1039/C6CP00264A (DOI)000372249100012 ()26931779 (PubMedID)
Available from: 2016-03-09 Created: 2016-03-09 Last updated: 2018-08-16Bibliographically approved
Eriksson K., S., Josefsson, I., Ellis, H., Amat, A., Pastore, M., Oscarsson, J., . . . Rensmo, H. (2016). Geometrical and energetical structural changes in organic dyes for dye-sensitized solar cells probed with photoelectron spectroscopy and DFT. Physical Chemistry, Chemical Physics - PCCP, 18(1), 252-260
Open this publication in new window or tab >>Geometrical and energetical structural changes in organic dyes for dye-sensitized solar cells probed with photoelectron spectroscopy and DFT
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2016 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 18, no 1, p. 252-260Article in journal (Other academic) Published
Abstract [en]

The effects of alkoxy chain length in triarylamine based donor acceptor organic dyes are investigated with respect to the electronic and molecular surface structures on the performance of solar cells and the electron lifetime. The dyes were investigated when adsorbed on TiO2 in a configuration that can be used for dye sensitized solar cells (DSCs). Specifically, the two dyes D35 and D45 were compared using photoelectron spectroscopy (PES) and density functional theory (DFT) calculations. The differences in solar cell characteristics when longer alkoxy chains are introduced in the dye donor unit are attributed to geometrical changes in dye packing while only minor differences were observed in the electronic structure. A higher dye load was observed for D45 on TiO2. However, D35 based solar cells result in higher photocurrent although the dye load is lower. This is explained by different geometrical structures of the dyes on the surface.

National Category
Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-230853 (URN)10.1039/c5cp04589d (DOI)000368755500027 ()
Funder
Swedish Research CouncilCarl Tryggers foundation Swedish Energy AgencyStandUp
Available from: 2014-08-31 Created: 2014-08-31 Last updated: 2017-12-05Bibliographically approved
Schmidt, I., Plettenberg, I., Kimmich, D., Ellis, H., Witt, J., Dosche, C. & Wittstock, G. (2016). Spatially Resolved Analysis of Screen Printed Photoanodes of Dye-Sensitized Solar Cells by Scanning Electrochemical Microscopy. Electrochimica Acta, 222, 735-746
Open this publication in new window or tab >>Spatially Resolved Analysis of Screen Printed Photoanodes of Dye-Sensitized Solar Cells by Scanning Electrochemical Microscopy
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2016 (English)In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 222, p. 735-746Article in journal (Refereed) Published
Abstract [en]

Different approaches are compared for imaging local differences in the performance of nanostructured dye-sensitized solar cells (DSCs) using scanning electrochemical microscopy (SECM). The DSCs were fabricated from TiO2 and the triphenylamine dye (E)-3-(5-(4-(bis(2',4'-dibutoxy-[1,1'-biphenyl]-4-yl) amino)phenyl)thiophen-2-yl)-2-cyanoacrylic acid, called D35. The components of the redox electrolytes cobalt trisbipyridine ([Co(bpy)(3)](3+/2+)) and iodide/triiodide (I-/I-3(-)) were used as SECM mediators. Imaging was performed by the feedback (FB) mode and the substrate-generation/tip collection (SG/TC) mode of SECM with additional options of local and temporal illumination. In FB mode, the SECM microelectrode (ME) reduces the mediator which is re-oxidized at the illuminated photoanode. In the SG/TC mode, the reduced form of the mediator is oxidized at the photoanode and the oxidized form is detected at the ME. It is expected that the SG/TC is more sensitive than the FB mode but provides lower lateral resolution. However, imaging is complicated by the strong light scattering in the nanoporous photoanode and the long residence time of charge carriers under the conditions of SECM imaging with low mediator concentrations. This prevents approaches based on local illumination or temporal illumination. Using shear force SECM (SF-SECM) in the FB mode, local differences in the morphology and performance of screen-printed photoanodes could be resolved that resulted from screen printing process. The morphological variations are also corroborated by scanning force microscopy and optical phase contrast microscopy. Furthermore, isolated irregularities were detected in which morphology and local performance were not correlated.

Keywords
photoelectrochemical shear force SECM, imaging, high resolution, cobalt mediator, all-organic-dyed photoanodes
National Category
Chemical Sciences
Identifiers
urn:nbn:se:uu:diva-316430 (URN)10.1016/j.electacta.2016.11.030 (DOI)000392566200083 ()
Funder
German Research Foundation (DFG), Wi 1617/20-1
Available from: 2017-03-01 Created: 2017-03-01 Last updated: 2017-11-29Bibliographically approved
Ellis, H., Schmidt, I., Hagfeldt, A., Wittstock, G. & Boschloo, G. (2015). Influence of Dye Architecture of Triphenylamine Based Organic Dyes on the Kinetics in Dye-Sensitized Solar Cells. The Journal of Physical Chemistry C, 119(38), 21775-21783
Open this publication in new window or tab >>Influence of Dye Architecture of Triphenylamine Based Organic Dyes on the Kinetics in Dye-Sensitized Solar Cells
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2015 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 119, no 38, p. 21775-21783Article in journal (Refereed) Published
Abstract [en]

The impact of the dye architecture on the kinetics in the dyesensitized solar cell (DSC) was investigated for two structurally similar organic dyes, adsorbed adsorbed to a mesoporous TiO2 film. Differences in the HOMO and LUMO levels of the triphenylamine dyes D35 and D45 were negligible, indicating that the changes in kinetics of the electron transfer processes in the solar cells can be attributed to structural differences of the organic dyes. The electron transfer kinetics of various processes was investigated by scanning electrochemical microscopy (SECM), transient absorption spectroscopy (TAS), and impedance spectroscopy (IS). SECM was used for the first time to determine the rate constants of the regeneration (reduction) of a photooiddized organic dye by a oneelectron cobalt mediator. Both TAS and IS measurements showed differences in recombination of electrons in TiO2, with oxidized D35 and D45. D45 with its shorter dimethoxyphenyl units yielded faster recombination and regeneration than D35, as measured by SECM and TAS. The results of this study show that small details in the dye structure significantly affect the kinetics of organic triphenylamine dye based dye-sensitized solar cells.

National Category
Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-265912 (URN)10.1021/acs.jpcc.5b04436 (DOI)000361921600003 ()
Funder
Swedish Energy AgencyKnut and Alice Wallenberg FoundationSwedish Research CouncilStandUp
Available from: 2015-11-04 Created: 2015-11-04 Last updated: 2017-12-01Bibliographically approved
Ellis, H., Leandri, V., Hagfeldt, A., Boschloo, G., Bergquist, J. & Shevchenko, D.  . (2015). Laser desorption/ionization mass spectrometry of dye-sensitized solar cells: identification of the dye-electrolyte interaction. Journal of Mass Spectrometry, 50(5), 734-739
Open this publication in new window or tab >>Laser desorption/ionization mass spectrometry of dye-sensitized solar cells: identification of the dye-electrolyte interaction
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2015 (English)In: Journal of Mass Spectrometry, ISSN 1076-5174, E-ISSN 1096-9888, Vol. 50, no 5, p. 734-739Article in journal (Refereed) Published
Abstract [en]

Dye-sensitized solar cells (DSCs) have great potential to provide sustainable electricity from sunlight. The photoanode in DSCs consists of a dye-sensitized metal oxide film deposited on a conductive substrate. This configuration makes the photoanode a perfect sample for laser desorption/ionization mass spectrometry (LDI-MS). We applied LDI-MS for the study of molecular interactions between a dye and electrolyte on the surface of a TiO2 photoanode. We found that a dye containing polyoxyethylene groups forms complexes with alkali metal cations from the electrolyte, while a dye substituted with alkoxy groups does not. Guanidinium ion forms adducts with neither of the two dyes.

Keywords
laser desorption/ionization mass spectrometry, dye-sensitized solar cells, aqueous electrolytes, cyanoacrylic acid-based dyes, polyether chains
National Category
Physical Chemistry
Research subject
Chemistry with specialization in Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-229942 (URN)10.1002/jms.3582 (DOI)000355618200003 ()
Available from: 2014-08-18 Created: 2014-08-18 Last updated: 2017-12-05Bibliographically approved
Zhang, J., Ellis, H., Yang, L., Johansson, E. M. J., Boschloo, G., Vlachopoulos, N., . . . Shevchenko, D. (2015). Matrix-Assisted Laser Desorption/Ionization Mass Spectrometric Analysis of Poly(3,4-ethylenedioxythiophene) in Solid-State Dye-Sensitized Solar Cells: Comparison of In Situ Photoelectrochemical Polymerization in Aqueous Micellar and Organic Media. Analytical Chemistry, 87(7), 3942-3948
Open this publication in new window or tab >>Matrix-Assisted Laser Desorption/Ionization Mass Spectrometric Analysis of Poly(3,4-ethylenedioxythiophene) in Solid-State Dye-Sensitized Solar Cells: Comparison of In Situ Photoelectrochemical Polymerization in Aqueous Micellar and Organic Media
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2015 (English)In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 87, no 7, p. 3942-3948Article in journal (Refereed) Published
Abstract [en]

Solid-state dye-sensitized solar cells (sDSCs) are devoid of such issues as electrolyte evaporation or leakage and electrode corrosion, which are typical for traditional liquid electrolyte-based DSCs. Poly(3,4-ethylenedioxythiophene) (PEDOT) is one of the most popular and efficient p-type conducting polymers that are used in sDSCs as a solid-state hole-transporting material. The most convenient way to deposit this insoluble polymer into the dye-sensitized mesoporous working electrode is in situ photoelectrochemical polymerization. Apparently, the structure and the physicochemical properties of the generated conducting polymer, which determine the photovoltaic performance of the corresponding solar cell, can be significantly affected by the preparation conditions. Therefore, a simple and fast analytical method that can reveal information on polymer chain length, possible chemical modifications, and impurities is strongly required for the rapid development of efficient solar energy-converting devices. In this contribution, we applied matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS) for the analysis of PEDOT directly on sDSCs. It was found that the PEDOT generated in aqueous micellar medium possesses relatively shorter polymeric chains than the PEDOT deposited from an organic medium. Furthermore, the micellar electrolyte promotes a transformation of one of the thiophene terminal units to thiophenone. The introduction of a carbonyl group into the PEDOT molecule impedes the growth of the polymer chain and reduces the conductivity of the final polymer film. Both the simplicity of sample preparation (only application of the organic matrix onto the solar cell is needed) and the rapidity of analysis hold the promise of making MALDI MS an essential tool for the physicochemical characterization of conducting polymer-based sDSCs.

National Category
Physical Chemistry Analytical Chemistry
Identifiers
urn:nbn:se:uu:diva-252689 (URN)10.1021/ac504851f (DOI)000352659500056 ()25751409 (PubMedID)
Funder
Swedish Research Council, 621-2011-4423Swedish Institute, 00814/2011Knut and Alice Wallenberg Foundation
Available from: 2015-05-25 Created: 2015-05-11 Last updated: 2017-12-04
Leandri, V., Ellis, H., Gabrielsson, E., Sun, L., Boschloo, G. & Hagfeldt, A. (2014). An organic hydrophilic dye for water-based dye-sensitized solar cells. Physical Chemistry, Chemical Physics - PCCP, 16(37), 19964-19971
Open this publication in new window or tab >>An organic hydrophilic dye for water-based dye-sensitized solar cells
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2014 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 16, no 37, p. 19964-19971Article in journal (Refereed) Published
Abstract [en]

In this study we report the first organic hydrophilic dye employed for 100% water-based electrolyte DSSCs. We show that the replacement of alkyl by glycolic chains in the dye structure is able to provide excellent wettability, resulting in an efficient system with remarkably reduced desorption problems that allowed us to perform tests over a wide pH range. By changing the electrolyte composition, employing chenodeoxycholic acid as a co-adsorbent and using PEDOT counter-electrodes, 3% power conversion efficiency under 1-sun illumination was obtained. We show that chenodeoxycholic acid does not significantly increase the wettability, and we provide new insights into the higher performance resulting from its co-adsorption.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2014
National Category
Physical Chemistry
Research subject
Chemistry with specialization in Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-229941 (URN)10.1039/c4cp02774d (DOI)000341359700022 ()
Available from: 2014-08-18 Created: 2014-08-18 Last updated: 2017-12-05Bibliographically approved
Ellis, H. (2014). Characterization of dye-sensitized solar cells: Components for environmentally friendly photovoltaics. (Licentiate dissertation). Uppsala: Ångström
Open this publication in new window or tab >>Characterization of dye-sensitized solar cells: Components for environmentally friendly photovoltaics
2014 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

As fossil fuels, the major source of energy used today, create the greenhouse gas carbon dioxide which causes global warming, alternative energy sources are necessary in the future. There is a need for different types of renewable energy sources such as hydropower, windpower, wave- power and photovoltaics since different parts of the world have different possibilities. The sun is a never ending energy source. Photovoltaics use the energy of the sun and converts it into electricity. There are different types of photovoltaics and a combination of them could provide humankind with energy in a sustainable way. In this thesis dye-sensitized solar cells are investigated. Materials for the counter electrode have been investigated and resulting in a polymer based cathode outperforming the traditionally used platinized counter electrode in a cobalt-based redox mediator system (paper I). The sensitizer of the TiO2 was investigated, in this study by modifications of the π-linker unit in an organic donor-linker-acceptor based dye. Four new dyes were synthesized, all four showing extended absorption spectra compared to the reference dye. However, it was found that increasing the absorption spectrum does not neces- sarily increase the power conversion efficiency of the solar cell (paper II). In the last part of this thesis, water-based electrolyte dye-sensitized solar cells were investigated. A hydrophilic dye with glycolic chains close to the center of regeneration was synthesized. The results show increased wettability by water-based electrolyte for the sensitized surface, increased regenera- tion and performance for the hydrophilic dye compared to a hydrophobic dye (paper III). The glycolic chains complex with small cations such as Na+ and K+ in the electrolyte, this proba- bly facilitate the regeneration of the hydrophilic dye even further (paper IV). In this thesis new materials for a more environmentally friendly dye-sensitized solar cell are investigated.

Place, publisher, year, edition, pages
Uppsala: Ångström, 2014. p. 67
Keywords
solar cells, dye-sensitized solar cells
National Category
Physical Chemistry
Research subject
Chemistry with specialization in Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-229939 (URN)
Presentation
2014-09-08, Room 80121, Ångström, 10:00 (English)
Opponent
Supervisors
Available from: 2014-08-18 Created: 2014-08-18 Last updated: 2014-09-22Bibliographically approved
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