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| 2. |
- Westermark, Karin, et al.
(författare)
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Determination of the electronic density of states at a nanostructured TiO2/Ru-dye/electrolyte interface by means of photoelectron spectroscopy
- 2002
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Ingår i: Chemical Physics. - 0301-0104 .- 1873-4421. ; 285:1, s. 157-165
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Tidskriftsartikel (refereegranskat)abstract
- In this work, photoelectron spectroscopy is used to measure the electronic density of states in the band gap region of a nanostructured TiO2 film. Such nanostructured films are used in dye-sensitized solar cells, and in this study a plain TiO2 film as well as a dye-sensitized film were examined. Further, to simulate the electrolyte effect on the energy levels at the oxide/dye/electrolyte interface in a solar cell, the density of states in the band gap region for an electrochemically prepared TiO2 film inserted with Li+ ions was measured. From the experimental findings we discuss the distribution and chemical nature of electron trap states in the band gap and the energy matching between the LUMO level of the adsorbed dye, cis-bis(4,4′-dicarboxy-2,2′-bipyridine)-bis(isothiocyanato)ruthenium(II), and the TiO2 conduction band edge.
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| 3. |
- Agrell, H. G., et al.
(författare)
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Conductivity studies of nanostructured TiO2 films permeated with electrolyte
- 2004
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 108:33, s. 12388-12396
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Tidskriftsartikel (refereegranskat)abstract
- Charge transport in nanostructured TiO2 films permeated with an electrolyte was studied, using temperature-dependent conductivity and electron accumulation measurements. Two regions for charge transport were distinguished from the relationship between conductivity and electron concentration. In the first region (similar to1-20 electrons per TiO2 particle), the effective electron mobility is dependent on the electron concentration and values between 7 x 10(-4) and 78 x 10(-4) cm(2) V-1 s(-1) were determined. The activation energy of the mobility was similar to0.3 eV. The charge transport can be described with a trapping/detrapping model that involves localized band-gap states. In the second region (> 20 electrons per TiO2 particle), the effective electron mobility is independent of electron concentration and values of similar to150 x 10(-4) cm(2) V-1 s(-1) are calculated. The activation energy of mobility is in the range of 0-0.15 eV, depending on the electrolyte. Transport of electrons in the conduction band seems to be the most applicable model.
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| 5. |
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| 6. |
- Aranyos, Viviane, et al.
(författare)
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Electropolymerisable bipyridine ruthenium(II) complexes: synthesis, spectroscopic and electrochemical characterisation of 4-((2-thienyl)ethenyl)-and 4,4'-di((2-thienyl) ethenyl)-2,2'-bipyridine ruthenium complexes
- 2004
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Ingår i: Polyhedron. ; 23, s. 589-598
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Tidskriftsartikel (refereegranskat)abstract
- Four new ruthenium polypyridyl complexes with mono- or di-((2-thienyl) ethenyl) substituted bipyridines have been synthesized. The complexes were characterized by NMR, elemental analysis, UV-Vis absorption and electrochemistry (differentioal pulse and cyclic voltammetry). Electroactive polymer films of these complexes have been prepared by oxidative electropolymerisation and characterized by UV-Vis absorption spectroscopy and electrochemistry. The electrochemically induced polymerisation of the complexes resulted in a significant shift of the oxidation potential of the Ru(II)-Ru(III) process towards more positive potentials. Also, MLCT absorption band of the polymeric complexes is shifted towards shorter wavelengths. These results are interpreted in terms of an interrupiton of the conjugated system of the (2-thienyl)ethenyl-substituted bipyridine ligands due to a radical polymerisation mechanism affecting rather the ethenyl part of the ligand than the thienyl.
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| 7. |
- Aranyos, Viviane, et al.
(författare)
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Free-base tetra-arylphthalocyanines for dye-sensitised nanostructured solar cell applications
- 2001
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Ingår i: JOURNAL OF PORPHYRINS AND PHTHALOCYANINES. - : JOHN WILEY & SONS LTD. - 1088-4246. ; 5:8, s. 609-616
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Tidskriftsartikel (refereegranskat)abstract
- Adsorption of phthalocyanines lacking conventional attaching substituents onto nanostructured TiO2 electrodes has been studied, and some of the important factors for sensitisation have been identified. Tetra-dimethoxyphenyl phthalocyanine (2) and tetra-ph
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| 8. |
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| 9. |
- Bauer, Christophe, et al.
(författare)
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Electron injection and recombination in Ru(dcbpy)(2)(NCS)(2) sensitized nanostructured ZnO
- 2001
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Ingår i: JOURNAL OF PHYSICAL CHEMISTRY B. - : AMER CHEMICAL SOC. - 1089-5647. ; 105:24, s. 5585-5588
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Tidskriftsartikel (refereegranskat)abstract
- The dynamics of electron-transfer processes between bis(tetrabutylammonium) cis-bis(thiocyanato)bis(2,2'-bypiridine-4,4'-dicarboxylato)ruthenium(II) (called N719) and nanostructured ZnO films have been investigated by femtosecond and nanosecond spectrosco
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| 10. |
- Bauer, C., et al.
(författare)
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Interfacial electron-transfer dynamics in Ru(tcterpy)(NCS)(3)-sensitized TiO2 nanocrystalline solar cells
- 2002
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 106:49, s. 12693-12704
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Tidskriftsartikel (refereegranskat)abstract
- The anchoring of the ruthenium dye {(C4H9)(4)N}[Ru(Htcterpy)(NCS)(3)] (with tcterpy = 4,4',4-tricarboxy2,2':6',2-terpyridine), the so-called black dye, onto nanocrystalline TiO2 films has been characterized by UV-vis and FT-IR spectroscopies. FT-IR spectroscopy data suggest that dye molecules are bound to the surface by a bidentate binuclear coordination mode. The interfacial electron-transfer (ET) dynamics has been investigated by femtosecond pump-probe transient absorption spectroscopy and nanosecond laser flash photolysis. The electron-injection process from the dye excited state into the TiO2 conduction band is biexponential with a fast component (200 +/- 50 fs) and a slow component (20 ps). These two components can be attributed to the electron injection from the initially formed and the relaxed dye excited states, respectively. Nanosecond kinetic data suggest the existence of two distinguishable regimes (I and II) for the rates of reactions between injected electrons and oxidized dye molecules or oxidized redox species (D+ or I-2(.-)). The frontier between these two regimes is defined by the number of injected electrons per particle (Ne), which was determined to be about 1. The present kinetic study was undertaken within regime I (N-e > 1). Under these conditions, the back-electron-transfer kinetics is comparable to that in systems with other ruthenium complexes adsorbed onto TiO2. The reduction of oxidized dye molecules by iodide results in the formation of I-2(.-) on a very fast time scale (<20 ns). Within regime 1, the decay of I-2(.-) occurs in similar to100 ns via reaction with injected electrons (I-2(.-) + e(-) --> 2I(-)). In regime II (N-e less than or equal to 1), which corresponds to the normal operating conditions of dye-sensitized solar cells, the decay of I-2(.-) is very slow and likely occurs via the dismutation reaction (2I(2)(.-) --> I- + I-3(-)). Our results predict that, under high light intensity (N-e > 1), the quantum efficiency losses in dye-sensitized solar cells will be important because of the dramatic acceleration of the reaction between I-2(.-) and injected electrons. Mechanisms for the ET reactions involving injected electrons are proposed. The relevance of the present kinetic studies for dye-sensitized nanocrystalline solar cells is discussed.
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