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- Figgemeier, Egbert, et al.
(författare)
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Modification of electron transfer properties in photoelectrochemical solar cells by substituting {Ru(terpy)(2)}(2+) dyes with thiophene
- 2004
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Ingår i: Inorganic Chemistry Communications. - : Elsevier BV. - 1387-7003 .- 1879-0259. ; 7:1, s. 117-121
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Tidskriftsartikel (refereegranskat)abstract
- A comparison of the properties of the 2-thienyl-substituted carboxyphenyl {RuII(terpy)2} dyes with their non-substituted analogues has enabled us to gain insight into the electronic properties that are prerequisite for efficient electron injection into the TiO2 conduction band in photoelectrochemical solar cells. Introducing the thienyl group has a profound effect upon the efficiency of photoinduced electron injection. This effect can be explained by a significant shift in the LUMO position from the terpy ligand anchored on the TiO2 surface towards the 2-thienyl substituted ligand, which is shown by means of electrochemistry and semiempirical calculations.
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- Hagfeldt, A., et al.
(författare)
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A system approach to molecular solar cells
- 2004
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Ingår i: Coordination chemistry reviews. - : Elsevier BV. - 0010-8545 .- 1873-3840. ; 248:13-14, s. 1501-1509
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Forskningsöversikt (refereegranskat)abstract
- This paper gives an overview of the research and development of dye-sensitized solar cells (DSC) within the Swedish research program 'Angstrom Solar Center'. A path towards low production cost is the development of a continuous process, which allows the production of solar cells in large volumes and with a high productivity. We have developed a deposition method for the production of the mesoporous TiO2, electrode layer that is based on compression of a powder film at room temperature. This technique allows us to use flexible substrates-a prerequisite fora continuous process. A novel interconnect technology, compatible with a continuous production process, is described. Stability data of plastic DSC, exposed to indoor light for more than 10,000 h, demonstrates the possibility for the technology to be explored for various types of indoor applications. Optimization of the DSC is a challenging task as it is a complex highly interacting molecular system. A system approach is proposed, where the complete DSC is investigated with a series of measurement techniques ('toolbox') that allows the study of the internal processes under relevant conditions. Two examples of such techniques are given.
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- Johansson, Erik M .J., et al.
(författare)
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Interfacial properties of photovoltaic TiO2/dye/PEDOT-PSS heterojunctions
- 2005
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Ingår i: Synthetic metals. - : Elsevier BV. - 0379-6779 .- 1879-3290. ; 149:03-feb, s. 157-167
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Tidskriftsartikel (refereegranskat)abstract
- Systems comprising a dense TiO2 film electrode, a ruthenium polypyridine dye and a PEDOT-PSS (poly(3,4-ethylenedioxythiophene)-poly(4-styrenesulphonate)) film were prepared. The heterojunctions were shown to have photovoltaic properties, with the dye absorbing the light, the TiO2 acting as an electron conducting material and PEDOT-PSS acting as a hole transport material. A series of dyes was used to investigate their influence on the photocurrent and the photovoltage characteristics of the heterojunction. These results were compared to a photoelectrochemical system in which the PEDOT-PSS was replaced by a liquid electrolyte containing triiodide/iodide redox-couple. Photoelectron spectroscopy (PES) was used to monitor the interfacial properties of the heterojunction and the investigation points out effects of importance when assembling the materials together to a functional unit. Specifically, it was concluded that the interaction with the dye clearly affects the structure of PEDOT-PSS, both with respect to the surface composition of PSS relative to PEDOT and with respect to the chemical state of the sulphur in the polymers. Moreover, a comparison of the Ru3d and the valence band spectra of the two different interfaces (dye/TiO2 and dye/PEDOT-PSS) indicates that the energy level structure of the dyes compared to the substrate is different for the two surfaces. Thus, in the combined energy level picture under dark conditions, the energy levels in TiO2 relative to the energy levels in PEDOT-PSS depend on the dye.
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- Nazeeruddin, M. K., et al.
(författare)
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DFT-INDO/S modeling of new high molar extinction coefficient charge-transfer sensitizers for solar cell applications
- 2006
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 45:2, s. 787-797
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Tidskriftsartikel (refereegranskat)abstract
- A new ruthenium(II) complex, tetrabutylammonium [ruthenium (4-carboxylic acid-4'-carboxylate-2,2'-bipyridine)(4,4'-di(2-(3,6-dimethoxyphenyl)ethenyl)-2,2'-bipyridine)(NCS)(2)] (N945H), was synthesized and characterized by analytical, spectroscopic, and electrochemical techniques. The absorption spectrum of the N945H sensitizer is dominated by metal-to-ligand charge-transfer (MLCT) transitions in the visible region, with the lowest allowed MLCT bands appearing at 25 380 and 18 180 cm(-1). The molar extinction coefficients of these bands are 34 500 and 18 900 M-1 cm(-1), respectively, and are significantly higher when compared to than those of the standard sensitizer cis-dithiocyanatobis(4,4'-dicarboxylic acid-2,2'-bipyridine)ruthenium(II). An INDO/S and density functional theory study of the electronic and optical properties of N945H and of N945 adsorbed on TiO2 was performed. The calculations point out that the top three frontier-filled orbitals have essentially ruthenium 4d (t(2g) in the octahedral group) character with sizable contribution coming from the NCS ligand orbitals. Most critically the calculations reveal that, in the TiO2-bound N945 sensitizer, excitation directs charge into the carboxylbipyridine ligand bound to the TiO2 surface. The photovoltaic data of the N945 sensitizer using an electrolyte containing 0.60 M butylmethylimidazolium iodide, 0.03 M I-2, 0.10 M guanidinium thiocyanate, and 0.50 M tert-butylpyridine in a mixture of acetonitrile and valeronitrile (volume ratio = 85:15) exhibited a short-circuit photocurrent density of 16.50 +/- 0.2 mA cm(-2), an open-circuit voltage of 790 +/- 30 mV, and a fill factor of 0.72 +/- 0.03, corresponding to an overall conversion efficiency of 9.6% under standard AM (air mass) 1.5 sunlight, and demonstrated a stable performance under light and heat soaking at 80 degrees C.
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