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Photovoltaic and Interfacial Properties of Heterojunctions Containing Dye-sensitized Dense TiO2 and Triarylamine derivatives
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics I.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics I.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics I.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics I.
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2007 (English)In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 19, no 8, 2071-2078 p.Article in journal (Refereed) Published
Abstract [en]

A series of solid-state heterojunctions comprising a dense TiO2 film electrode as an electron conductor, a ruthenium polypyridine complex (Ru(dcbpy)2(NCS)2) as a light-absorbing dye, and different triarylamine derivatives as hole conductors were prepared, and their photovoltaic properties as well as the molecular and electronic interfacial structures were investigated. The photovoltaic properties were compared to systems containing the hole conductors dissolved in an organic solvent as well as to a system containing a liquid electrolyte containing the iodide/tri-iodide redox couple. Two of the solid-state heterojunctions showed conversion efficiencies close to those of the system containing the iodide/tri-iodide redox couple, while one system was clearly less efficient. To explain the differences in photovoltaic properties the electronic and molecular interfacial structures of the solid-state heterojunctions were investigated by photoelectron spectroscopy (PES). By valence level PES the electronic energy levels highest in energy for the dye and the hole conductors were mapped, and the differences in energy matching partly explain the trends in photovoltaic properties. Differences in the molecular surface structure of the heterojunctions were also observed from the N Is core level measurements. Specifically it was found that the smaller hole conductor, showing low photocurrent yield, is inserted into the dye layer.

Place, publisher, year, edition, pages
2007. Vol. 19, no 8, 2071-2078 p.
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:uu:diva-94531DOI: 10.1021/cm062498vISI: 000245549500028OAI: oai:DiVA.org:uu-94531DiVA: diva2:168408
Available from: 2006-05-08 Created: 2006-05-08 Last updated: 2017-12-14Bibliographically approved
In thesis
1. Interfaces in Dye-Sensitized Oxide / Hole-Conductor Heterojunctions for Solar Cell Applications
Open this publication in new window or tab >>Interfaces in Dye-Sensitized Oxide / Hole-Conductor Heterojunctions for Solar Cell Applications
2006 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Nanoporous dye-sensitized solar cells (DSSC) are promising devices for solar to electric energy conversion. In this thesis photoelectron spectroscopy (PES), x-ray absorption spectroscopy (XAS) and photovoltaic measurements are used for studies of the key interfaces in the DSSC.

Photovoltaic properties of new combinations of TiO2/dye/hole-conductor heterojunctions were demonstrated and their interfacial structures were studied. Three different types of hole-conductor materials were investigated: Triarylamine derivatives, a conducting polymer and CuI. The difference in photocurrent and photovoltage properties of the heterojunction due to small changes in the hole-conductor material was followed. Also a series of dye molecules were used to measure the influence of the dye on the photovoltaic properties. Differences in both the energy-level matching and the geometric structure of the interfaces in the different heterojunctions were studied by PES. This combination of photovoltaic and PES measurements shows the possibility to link the interfacial electronic and molecular structure to the functional properties of the device.

Three effective dyes used in the DSSC, Ru(dcbpy)2(NCS)2, Ru(tcterpy)(NCS)3 and an organic dye were studied in detail using PES and XAS and resonant core hole decay spectroscopy. The results gave information of the frontier electronic structure of the dyes and how the dyes are bonded to the TiO2 surface.

Finally, the hole-conductor mechanism in a conducting polymer was investigated theoretically using semi-empirical and ab-initio methods.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2006. 53 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 188
Keyword
Physics, Photoelectron spectroscopy, Solar cells, Heterojunction, Fysik
Identifiers
urn:nbn:se:uu:diva-6892 (URN)91-554-6575-7 (ISBN)
Public defence
2006-05-29, Polhemsalen, Ångströmlaboratoriet, Lägerhyddsv.1, Uppsala, 13:15
Opponent
Supervisors
Available from: 2006-05-08 Created: 2006-05-08 Last updated: 2012-10-09Bibliographically approved
2. Surface Science Studies of Metal Oxides Formed by Chemical Vapour Deposition on Silicon
Open this publication in new window or tab >>Surface Science Studies of Metal Oxides Formed by Chemical Vapour Deposition on Silicon
2006 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

For an electronic device well-designed interfaces are critical for the performance. Studies of interfaces down to an atomic level are thus highly motivated both from a fundamental and technological point of view. In this thesis, a surface science approach has been employed to study the formation of interfaces in systems relevant for transistor and solar cell applications. Surface science methodology entails ultra high vacuum environment, single crystalline surfaces, submonolayer control of deposited material, surface sensitive spectroscopy and atomic resolution microscopy.

The primary experimental method for characterization is electron spectroscopy. This is a family of very powerful experimental techniques capable of giving information on the atomic level. Additionally, studies have been performed using scanning tunnelling microscopy. Combined these two methods can provide an atomic level characterisation of the geometric and electronic properties of the surface.

The emphasis of this work is placed on ultra thin TiO2 and ZrO2 films grown on silicon substrates by means of ultra-high vacuum metal-organic chemical vapour deposition. ZrO2 has also been grown on SiC and FeCrAl. Deposition has been performed with different process parameters. The interface region of each film has been characterised. The band alignment, a most important issue with regard to the development of new transistor devices, for the ZrO2/Si(100) system has been explored. Decomposition pathways of the metal organic precursors have been studied in detail. Changing process parameters is shown to alter both the precursor decomposition pathway and the nature of the interface region, thus opening the possibility to tailor the material function.

The titanium dioxide films grown in situ have shown to be excellent models of nanostructured electrode materials. In this spirit, interfaces of model systems for the solid-state dye-sensitized solar cell have been studied. Links between device performance and interface structure have been elucidated.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2006. 58 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 203
Keyword
Physics, chemical vapour deposition, high-k, metal oxides, silicon, dye-solid interface, metal organic, electron spectroscopy, scanning tunnelling microscopy, Fysik
Identifiers
urn:nbn:se:uu:diva-7088 (URN)91-554-6622-2 (ISBN)
Public defence
2006-09-29, Polhemsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:15 (English)
Opponent
Supervisors
Available from: 2006-09-04 Created: 2006-09-04 Last updated: 2012-10-09Bibliographically approved

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Hedlund, MariaRyan, DeclanSiegbahn, HansRensmo, Håkan

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