| 1. |
- Gamstedt, Helene, et al.
(author)
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Photoelectrochemical studies of ionic liquid-containing solar cells sensitized with different polypyridyl-ruthenium complexes
- 2009
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In: Polyhedron. - : Elsevier BV. - 0277-5387 .- 1873-3719. ; 28:4, s. 757-762
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Journal article (peer-reviewed)abstract
- The efficiency of dye-sensitized nanocryst. solar cells contg. ionic liqs., composed of org. sulfonium or imidazolium iodides, or a std. org.-liq.-based electrolyte was studied, while using sensitizers based on different polypyridyl-ruthenium complexes. The dyes N-719, [cis-Ru(II)(H2dcbpy)2(NCS)2(TBA)2] and Z-907, [cis-Ru(II)(H2dcbpy)(dnbpy)(NCS)2, Z-907 having a more hydrophobic character, as well as a bidentate beta -diketonato complex, [(dcbpy)2Ru(acetylacetonate)]Cl-, was studied. Solar cells sensitized with the dye N-719 were more efficient than the Z-907 cells, for all electrolytes studied. Adding a co-adsorbent, the amphiphilic hexadecylmalonic acid (HDMA), to Z-907 solar cells contg. an org.-liq. electrolyte resulted in increased overall light-to-electricity conversion efficiencies, from 3.7% to 4.0%, (100 W m-2, AM 1.5). Possibly, this is caused by an insulating hydrophobic barrier formed to suppress unwanted electron losses. By applying TiO2 (P25) nanoparticles, assumed to support electron transfer reactions, to the org.-liq. electrolyte, the conversion efficiency was increased from 4.1% to 4.6% (100 W m-2, AM 1.5). In 1000 W m-2 illumination, the highest overall short-circuit c.d., 9.3 mA cm-2, was achieved with the N-719 sensitized cells, with the TiO2 nanocomposite-contg. org.-liq.-based electrolyte. For solar cells sensitized with N-719, Z-907 or the beta -diketonato complex, and contg. imidazolium or sulfonium iodide ionic liqs., no improvements of the overall conversion efficiency could be noticed at addn. of HDMA to the dye or nanoparticles to the electrolyte.
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| 2. |
- Morandeira, Ana, et al.
(author)
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Improved photon-to-current conversion efficiency with a nanoporous p-type NiO electrode by the use of a sensitizer-acceptor dyad
- 2008
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In: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 112:5, s. 1721-1728
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Journal article (peer-reviewed)abstract
- A peryleneimide sensitizer and a covalently linked peryleneimide-naphthalenediimide dyad were prepared and characterized by absorption and emission spectroscopies, electrochemistry, and spectroelectrochemistry. These compounds were chemisorbed on nanoporous nickel oxide electrodes and then studied by femtosecond transient absorption spectroscopy in the presence of a redox active electrolyte (I-3(-)/I-). In both compounds, upon excitation of the peryleneimide unit, an electron is efficiently ejected from the valence band of NiO to the dye with an average time constant of approximately 0.5 ps. In the case of the dyad, the excess electron is shifted further onto the naphtalenediimide unit, creating a new charge separated state. The latter exhibits a substantial retardation of the charge recombination between the hole and the reduced molecule compared with the peryleneimide sensitizer. The photoaction spectra of a sandwich dye-sensitized solar cell (DSSC) composed of NiO films and these new dyes were recorded, and the absorbed-photon to current conversion efficiency (APCE) was three times higher with the dyad than with the peryleneimide dye: 45%. The maximum APCE of approximately 45% is the highest value reported for a DSSC based on a nanostructured metal oxide p-type semiconductor.
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| 3. |
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| 4. |
- Agrios, Alexander G., et al.
(author)
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Low-temperature TiO2 Films for Dye-sensitized Solar Cells : Factors Affecting Energy Conversion Efficiency
- 2008
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In: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 112:27, s. 10021-10026
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Journal article (peer-reviewed)abstract
- Semiconductor films prepd. by electrostatic layer-by-layer deposition can be used to fabricate dye-sensitized solar cells after low-temp. treatment (150 DegC). However, the resulting photocurrent is much less than when the film is sintered at 500 DegC. The difference in short-circuit current is a factor of 2.2 with the Ru-based dye N719 and is 3.5 with the org. dye D5. The photocurrent at a given wavelength is proportional to the light-harvesting efficiency, charge injection effciency, and charge collection efficiency. Sintered films take up more than 60% more of either dye than unsintered films and therefore absorb more photons. Electron injection is hindered in unsintered films due to a conduction band edge potential 100 mV more neg. than in a sintered electrode. Addnl. injection effects could be due to adsorption of the dye to polymer rather than to TiO2 in unsintered films, although our measurements were inconclusive on this point. Kinetic studies show electron transport times (ttr) an order of magnitude faster then electron lifetimes (te) in both sintered and unsintered electrodes. Furthermore, a Li+ insertion expt. shows that both films have good elec. connectivity between TiO2 nanoparticles. Unsintered films thus exhibit efficient charge transport despite the presence of polymer and the lack of heat treatment to induce necking.
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| 5. |
- Boschloo, Gerrit, et al.
(author)
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Characteristics of the Iodide/Triiodide Redox Mediator in Dye-Sensitized Solar Cells
- 2009
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In: Accounts of Chemical Research. - : American Chemical Society (ACS). - 0001-4842 .- 1520-4898. ; 42:11, s. 1819-1826
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Research review (peer-reviewed)abstract
- Dye-sensitized solar cells (DSCs) have gained widespread interest because of their potential for low-cost solar energy conversion. Currently, the certified record efficiency of these solar cells is 11.1%, and measurements of their durability and stability suggest lifetimes exceeding 10 years under operational conditions, The DSC is a photoelectrochemical system: a monolayer of sensitizing dye is adsorbed onto a mesoporous TiO2 electrode, and the electrode is sandwiched together with a counter electrode. An electrolyte containing a redox couple fills the gap between the electrodes. The redox couple is a key component of the DSC. The reduced part of the couple regenerates the photo-oxidized dye. The formed oxidized species diffuses to the counter electrode, where it is reduced. The photovoltage of the device depends on the redox couple because it sets the electrochemical potential at the counter electrode. The redox couple also affects the electrochemical potential of the TiO2 electrode through the recombination kinetics between electrons in TiO2 and oxidized redox species. This Account focuses on the special properties of the iodide/triiodide (I-/I-3(-)) redox couple in dye-sensitized solar cells. It has been the preferred redox couple since the beginning of DSC development and still yields the most stable and efficient DSCs. Overall, the iodide/triiodide couple has good solubility, does not absorb too much light, has a suitable redox potential, and provides rapid dye regeneration. But what distinguishes I-/I-3(-) from most redox mediators is the very slow recombination kinetics between electrons in TiO2 and the oxidized part of the redox couple, triiodide. Certain dyes adsorbed at TiO2 catalyze this recombination reaction, presumably by binding iodine or triiodide. The standard potential of the iodide/triiodide redox couple is 0.35 V (versus the normal hydrogen electrode, NHE), and the oxidation potential of the standard DSC-sensitizer (Ru(dcbpy)(2)(NCS)(2)) is 1.1 V. The driving force for reduction of oxidized dye is therefore as large as 0.75 V. This process leads to the largest internal potential loss in DSC devices. We expect that overall efficiencies above 15% might be achieved if half of this internal potential loss could be gained. The regeneration of oxidized dye with iodide leads to the formation of the diiodide radical (I-2(-center dot)). The redox potential of the I-2(-center dot)/I- couple must therefore be considered when determining the actual driving force for dye regeneration. The formed I-2(-center dot) disproportionates to I-3(-) and I-, which leads to a large loss in potential energy.
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| 6. |
- Bruder, Ingmar, et al.
(author)
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Efficient organic tandem cell combining a solid state dye-sensitized and a vacuum deposited bulk heterojunction solar cell
- 2009
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In: Solar Energy Materials and Solar Cells. - : Elsevier BV. - 0927-0248 .- 1879-3398. ; 93:10, s. 1896-1899
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Journal article (peer-reviewed)abstract
- In this letter, we report on an efficient organic tandem solar cell combining a solid state dye-sensitized with a ZnPc/C60-based, vacuum deposited bulk heterojunction solar cell. Due to an effective serial connection of both subcells and to the complementary absorption of the dyes used, a power conversion efficiency of ηp=(6.0±0.1)% was achieved under simulated AM 1.5 illumination. The device parameters are , and FF=(54±1)%.
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| 7. |
- Gibson, Elizabeth A., et al.
(author)
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A p-Type NiO-Based Dye-Sensitized Solar Cell with an Open-Circuit Voltage of 0.35 V
- 2009
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In: Angewandte Chemie International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 48:24, s. 4402-4405
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Journal article (peer-reviewed)abstract
- In tandem: Employing a molecular dyad and a cobalt-based electrolyte gives a threefold-increase in open-circuit voltage (VOC) for a p-type NiO device (VOC=0.35 V), and a fourfold better energy conversion efficiency. Incorporating these improvements in a TiO2/NiO tandem dye-sensitized solar cell (TDSC), results in a TDSC with a VOC=0.91 V
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| 8. |
- Hagberg, Daniel, 1977-, et al.
(author)
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Symmetric and unsymmetric donor functionalization : Comparing structural and spectral benefits of chromophores for dye-sensitized solar cells
- 2009
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In: Journal of Materials Chemistry. - : Royal Society of Chemistry (RSC). - 0959-9428 .- 1364-5501. ; 19:39, s. 7232-7238
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Journal article (peer-reviewed)abstract
- A series of organic chromophores have been synthesized in order to investigate the benefits of structural versus spectral properties as well as the absorption properties and solar cell performance with unsymmetrically introduced substituents in the chromophore. Exceptionally high open-circuit voltage, Voc, was found for the symmetrical structurally benefited dye, which also gave the best overall solar cell performance.
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| 9. |
- Moon, Soo-Jin, et al.
(author)
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Highly Efficient Organic Sensitizers for Solid-State Dye-Sensitized Solar Cells
- 2009
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In: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 113:38, s. 16816-16820
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Journal article (peer-reviewed)abstract
- Org. sensitizers comprising of donor, electron-conducting, and anchoring groups are designed and developed for dye-sensitized solar cell applications. A solar cell employing 3-(5'-{4-[bis-(4-hexyloxy-phenyl)-amino]-phenyl}-[2,2']bithiophenyl-5-yl)-2-cyano-acrylic acid dye spiro-OMeTAD as a hole-transporting material exhibits a short circuit photocurrent d. of 9.64 mA/cm2, an open-circuit voltage of 798 mV, and a fill factor of 0.57, corresponding to an overall conversion efficiency of 4.4% at std. AM 1.5 sunlight. Photoinduced absorption spectroscopy probes an efficient hole-transfer from dyes to the spiro-OMeTAD.
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| 10. |
- Nonomura, Kazuteru, et al.
(author)
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The effect of UV-irradiation (under short-circuit condition) on dye-sensitized solar cells sensitized with a Ru-complex dye functionalized with a (diphenylamino)styryl-thiophen group
- 2009
-
In: International Journal of Photoenergy (Online). - : Hindawi Limited. - 1110-662X .- 1687-529X. ; :471828
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Journal article (peer-reviewed)abstract
- A new ruthenium complex, cis-di(thiocyanato)(2,2'-bipyridine-4,4'-dicarboxylic acid)(4,4'-bis(2-(5-(2-(4-diphenylaminophenyl) ethenyl)-thiophen-2-yl)ethenyl)-2,2'-bipyridine)ruthenium(II) (named E322) has been synthesized for use in dye-sensitized solar cells (DSCs). Higher extinction coeff. and a broader absorption compared to the std. Ru-dye, N719, were aimed. DSCs were fabricated with E322, and the efficiency was 0.12% initially (4.06% for N719, as ref.). The efficiency was enhanced to 1.83% by exposing the cell under simulated sunlight contg. UV-irradn. at short-circuit condition. The reasons of this enhancement are (1) enhanceing electron injection from sensitizer to TiO2 following a shift toward pos. potentials of the conduction band of TiO2 by the adsorption of protons or cations from the sensitizer, or from the redox electrolyte and (2) improving the regeneration reaction of the oxidized dye by the redox electrolyte by the dissoln. of aggregated dye from the surface of TiO2 following the treatment.
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