| 1. |
- Ferdowsi, Parnian, et al.
(författare)
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Molecular Design of Efficient Organic D-A-pi-A Dye Featuring Triphenylamine as Donor Fragment for Application in Dye-Sensitized Solar Cells
- 2018
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Ingår i: ChemSusChem. - : WILEY-V C H VERLAG GMBH. - 1864-5631 .- 1864-564X. ; 11:2, s. 494-502
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Tidskriftsartikel (refereegranskat)abstract
- A metal-free organic sensitizer, suitable for the application in dye-sensitized solar cells (DSSCs), has been designed, synthesized and characterized both experimentally and theoretically. The structure of the novel donor-acceptor--bridge-acceptor (D-A-pi-A) dye incorporates a triphenylamine (TPA) segment and 4-(benzo[c][1,2,5]thiadiazol-4-ylethynyl)benzoic acid (BTEBA). The triphenylamine unit is widely used as an electron donor for photosensitizers, owing to its nonplanar molecular configuration and excellent electron-donating capability, whereas 4-(benzo[c][1,2,5]thiadiazol-4-ylethynyl)benzoic acid is used as an electron acceptor unit. The influences of I-3(-)/I-, [Co(bpy)(3)](3+/2+) and [Cu(tmby)(2)](2+/+) (tmby=4,4,6,6-tetramethyl-2,2-bipyridine) as redox electrolytes on the DSSC device performance were also investigated. The maximal monochromatic incident photon-to-current conversion efficiency (IPCE) reached 81% and the solar light to electrical energy conversion efficiency of devices with [Cu(tmby)(2)](2+/+) reached 7.15%. The devices with [Co(bpy)(3)](3+/2+) and I-3(-)/I- electrolytes gave efficiencies of 5.22% and 6.14%, respectively. The lowest device performance with a [Co(bpy)(3)](3+/2+)-based electrolyte is attributed to increased charge recombination.
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| 2. |
- Kavan, Ladislav, et al.
(författare)
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Electrochemical Properties of Cu(II/I)-Based Redox Mediators for Dye-Sensitized Solar Cells
- 2017
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Ingår i: Electrochimica Acta. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0013-4686 .- 1873-3859. ; 227, s. 194-202
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Tidskriftsartikel (refereegranskat)abstract
- Three Cu(II/I)-phenanthroline and Cu(II/I)-bipyridine redox mediators are studied on various electrodes and in variety of electrolyte solutions using cyclic voltammetry and impedance spectroscopy on symmetrical dummy cells. Graphene-based catalysts provide comparably high activity to PEDOT, and both catalysts outperform the activity of platinum. The charge-transfer kinetics and the diffusion rate significantly slowdown in the presence 4-tert-butylpyridine. This effect is specific only for Cu-mediators (is missing for Co-mediators), and is ascribed to a sensitivity of the coordination sphere of the Cu(II)-species to structural and substitutional changes. The 'Zombie Cells' made from symmetrical PEDOT/PEDOT devices exhibit enhanced charge-transfer rate and enhanced diffusion resistance. Electrochemically clean Cu(II)-bipyridine species are prepared, for the first time, by electrochemical oxidation of the parent Cu(I) complexes. Our preparative electrolysis brings numerous advantages over the standard chemical syntheses of the Cu(II)-bipyridine complexes. The superior performance of electrochemically grown clean Cu(II)-bipyridine complex is demonstrated on practical dye-sensitized solar cells. (C) 2016 Elsevier Ltd. All rights reserved.
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| 3. |
- Kavan, Ladislav, et al.
(författare)
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Novel highly active Pt/graphene catalyst for cathodes of Cu(II/I)-mediated dye-sensitized solar cells
- 2017
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Ingår i: Electrochimica Acta. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0013-4686 .- 1873-3859. ; 251, s. 167-175
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Tidskriftsartikel (refereegranskat)abstract
- Novel highly active, optically-transparent electrode catalyst containing Pt, PtOx, graphene oxide and stacked graphene platelet nanofibers is developed for a cathode of Cu(II/I)-mediated dye-sensitized solar cells. The catalyst layer is deposited on a FTO substrate, which thus becomes smoother than the parent FTO, but the button-like Pt/PtOx nanoparticles are still distinguishable. The found electrocatalytic activity for the Cu(tmby)(2)(2+/+) redox couple (tmby is 4,4', 6,6'-tetramethyl-2,2'-bipyridine) is outperforming that of alternative catalysts, such as PEDOT or platinum. Exchange current densities exceeding 20 mA/cm(2) are provided exclusively by our novel catalyst. The synergic boosting of electrocatalytic activity is seen, if we normalize it to the catalytic performance of individual components, i.e. Pt and graphene nanofibers. The outstanding properties of our cathode are reflected by the performance of the corresponding solar cells using the Y123-sensitized titania photoanode. Champion solar-conversion efficiency (11.3% at 0.1 sun) together with a fill factor of 0.783 compare favorably to all other so far reported best values for this kind of solar cells and the given experimental conditions.
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| 4. |
- Laskova, Barbora, et al.
(författare)
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Electron Kinetics in Dye Sensitized Solar Cells Employing Anatase with (101) and (001) Facets
- 2015
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Ingår i: Electrochimica Acta. - : Elsevier. - 0013-4686 .- 1873-3859. ; 160, s. 296-305
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Tidskriftsartikel (refereegranskat)abstract
- Two phase-pure nanocrystalline anatase materials differing in the exposed crystal facets (001) or (101) are studied by electrochemical impedance spectroscopy and by transient photovoltage and photocurrent decay in dye sensitized solar cells. A larger chemical capacitance, indicating larger density of states, is observed for anatase (001). The presence of deep electron traps in (001) nanosheets is further confirmed by optical (UV-Vis) and photoemission (XPS, UPS) spectra. The difference in chemical capacitance indicates a slower diffusion of electrons in the (001) anatase material, but also a higher electron lifetime compared to (101) anatase material. (C) 2015 Elsevier Ltd. All rights reserved.
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| 5. |
- Saygili, Yasemin, et al.
(författare)
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Copper Bipyridyl Redox Mediators for Dye-Sensitized Solar Cells with High Photovoltage
- 2016
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 138:45, s. 15087-15096
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Tidskriftsartikel (refereegranskat)abstract
- Redox mediators play a major role determining the photocurrent and the photovoltage in dye-sensitized solar cells (DSCs). To maintain the photocurrent, the reduction of oxidized dye by the redox mediator should be significantly faster than the electron back transfer between TiO2 and the oxidized dye. The driving force for dye regeneration with the redox mediator should be sufficiently low to provide high photovoltages. With the introduction of our new copper complexes as promising redox mediators in DSCs both criteria are satisfied to enhance power conversion efficiencies. In this study, two copper bipyridyl complexes, Cu-(II/I)(dmby)(2)TFSI2/1 (0.97 V vs SHE, dmby = 6,6'-dimethyl-2,2'-bipyridine) and Cu-(II/I)(tmby)(2)TFSI2/1 (0.87 V vs SHE, tmby = 4,4',6,6'-tetramethyl-2,2'-bipyridine), are presented as new redox couples for DSCs. They are compared to previously reported Cu-(II/I)(dmp)(2)TFSI2/1 (0.93 V vs SHE, dmp = bis(2,9-dimethyl-1,10-phenanthroline). Due to the small reorganization energy between Cu(I) and Cu(II) species, these copper complexes can sufficiently regenerate the oxidized dye molecules with close to unity yield at driving force potentials as low as 0.1 V. The high photovoltages of over 1.0 V were achieved by the series of copper complex based redox mediators without compromising photocurrent densities. Despite the small driving forces for dye regeneration, fast and efficient dye regeneration (2-3 mu s) was observed for both complexes. As another advantage, the electron back transfer (recombination) rates were slower with Cu-(II/I)(tmby)(2)TFSI2/1 as evidenced by longer lifetimes. The solar-to-electrical power conversion efficiencies for [Cu(tmby)(2)](2+/1+), [Cu(dmby)(2)](2+/1+) , and [Cu(dmp)(2)](2+/1+) based electrolytes were 10.3%, 10.0%, and 10.3%, respectively, using the organic Y123 dye under 1000 W m(-2) AM1.5G illumination. The high photovoltaic performance of Cu-based redox mediators underlines the significant potential of the new redox mediators and points to a new research and development direction for DSCs.
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