| 1. |
- Nazeeruddin, M. K., et al.
(författare)
-
DFT-INDO/S modeling of new high molar extinction coefficient charge-transfer sensitizers for solar cell applications
- 2006
-
Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 45:2, s. 787-797
-
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.
|
|
| 2. |
- Boschloo, G., et al.
(författare)
-
A comparative study of a polyene-diphenylaniline dye and Ru(dcbpy)(2)(NCS)(2) in electrolyte-based and solid-state dye-sensitized solar cells
- 2008
-
Ingår i: Thin Solid Films. - : Elsevier BV. - 0040-6090 .- 1879-2731. ; 516:20, s. 7214-7217
-
Tidskriftsartikel (refereegranskat)abstract
- A small organic sensitizer, the polyene-diphenylaniline dye D5, was compared with the standard sensitizer N719 (Ru(dcbPY)(2)(NCS)(2)) in a dyesensitized solar cell investigation. In solar cells with relatively thin layers of mesoporous TiO2 (< 3 mu m) D5 outperformed N719 because of its high extinction coefficient. D5 showed also better performance than N719 in the case of sensitization of mesoporous ZnO. In solid-state solar cells, where the iodide/triiodide electrolyte was replaced by an amorphous hole conductor (spiro-OMeTAD), D5 gave promising preliminary results. The hole conductivity, observed in monolayers of D5 adsorbed at TiO2, may possibly lead to improved performance in such cells.
|
|
| 3. |
- Cappel, U. B., et al.
(författare)
-
Dye regeneration by Spiro-MeOTAD in solid state dye-sensitized solar cells studied by photoinduced absorption spectroscopy and spectroelectrochemistry
- 2009
-
Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 113:15, s. 6275-6281
-
Tidskriftsartikel (refereegranskat)abstract
- Photoinduced absorption (PIA) spectroscopy is presented as a tool for the systematic study of dye regeneration and pore filling in solid state dye-sensitized solar cells (DSC). Oxidation potentials and extinction coefficients for oxidized species of the perylene dye, ID28, on TiO(2) and of the hole conductor, 2,2'7,7'-tetrakis-(N,N-di-p-methoxyphenyl-amine)-9,9'-spirobifluorene (spiro-MeOTAD), were determined by spectroelectrochemistry. The onset of oxidation of a solid film of spiro-MeOTAD was found to be 0.15 V versus Fc/Fc(+) and extinction coefficients of spiro-MeOTAD(+) were found to be 33 000 M(-1) cm(-1) at 507 nm and 8500 M(-1) cm-' at 690 nm. Electrons in TiO(2) films were shown to alter the ground-state absorption spectra of ID28 attached to TiO(2)-PIA measurements indicated a good contact between ID28 and spiro-MeOTAD for different spiro-MeOTAD concentrations for both 2- and 6-mu m thick TiO(2) films. We discuss the possibility of estimating the quality of pore filling from the positions of absorption peaks. Results suggested that with a spiro-MeOTAD concentration of 300 mg mL(-1) in chlorobenzene, a uniform distribution of spiro-MeOTAD in the pores of the 6-mu m thick TiO(2) film could be achieved.
|
|
| 4. |
- Fischer, Andreas, et al.
(författare)
-
Crystal formation involving 1-methylbenzimidazole in iodide/triiodide electrolytes for dye-sensitized solar cells
- 2007
-
Ingår i: Solar Energy Materials and Solar Cells. - : Elsevier BV. - 0927-0248 .- 1879-3398. ; 91:12, s. 1062-1065
-
Tidskriftsartikel (refereegranskat)abstract
- Nitrogen heterocyclic compounds, such as N-methylbenzimidazole (MBI), are commonly used as additives to electrolytes for dye-sensitized solar cells (DSCs), but the chemical transformation of additives in electrolyte solutions remains poorly understood. Solid crystalline compound (MBI)(6)(MBI-H+)(2)(I-)(I-3(-)) (1) was isolated from different electrolytes for DSCs containing MBI as additive. The crystal structure of I was determined by single-crystal X-ray diffraction. In the crystal structure, 1 contains neutral and protonated MBI fragments; iodide and triiodide anions form infinite chains along the crystallographic a-axis. The role of the solvent and additives in the crystallization process in electrolytes is discussed.
|
|
| 5. |
- Gamstedt, Helene, et al.
(författare)
-
Photoelectrochemical studies of ionic liquid-containing solar cells sensitized with different polypyridyl-ruthenium complexes
- 2009
-
Ingår i: Polyhedron. - : Elsevier BV. - 0277-5387 .- 1873-3719. ; 28:4, s. 757-762
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 6. |
- Gibson, Elizabeth A., et al.
(författare)
-
A p-Type NiO-Based Dye-Sensitized Solar Cell with an Open-Circuit Voltage of 0.35 V
- 2009
-
Ingår i: Angewandte Chemie International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 48:24, s. 4402-4405
-
Tidskriftsartikel (refereegranskat)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
|
|
| 7. |
- Gorlov, Mikhail, et al.
(författare)
-
Electrolytes for dye-sensitized solar cells based on interhalogen ionic salts and liquids
- 2007
-
Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 46:9, s. 3566-3575
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, we report on the preparation of interhalogen ionic liquids of the general formula [K+]XY2-, where K+ = 1,3-dialkylimidazolium, 1,2,3-trialkylimidazolium, or N-alkylpyridinium; XY2- = IBr2- or I2Br-. These compounds were characterized in solution and the solid state by NMR, IR, Raman, and mass spectroscopy. The crystal structure of the compound [Me(2)BuIm]IBr2 (7) shows that the IBr2- anion has a linear Br-I-Br structure. Indications of an equilibrium between different forms of XY2- anions in solution are observed. Interhalogen ionic salts and liquids were used as electrolyte components for encapsulated monolithic dye-sensitized solar cells. Overall light-to-electricity conversion efficiencies up to 6.4%, 5.0%, and 2.4% at 1000 W/m(2) were achieved by using electrolytes based on interhalogen ionic salts and gamma-butyrolactone, glutaronitrile, or native ionic liquids as solvents, respectively. Moreover, in terms of stability, the cell performance lost 9-14% of the initial performance after 1000 h illumination at 350 W/m(2).
|
|
| 8. |
- Paulsson, Heléne, et al.
(författare)
-
Electron transport and recombination in dye-sensitized solar cells with ionic liquid electrolytes
- 2006
-
Ingår i: Journal of Electroanalytical Chemistry. - : Elsevier BV. - 0022-0728 .- 1873-2569 .- 1572-6657. ; 586:1, s. 56-61
-
Tidskriftsartikel (refereegranskat)abstract
- The electron transport and recombination in dye-sensitized TiO2 solar cells with different electrolytes have been investigated. The electrolytes were based on iodine-doped ionic liquids (diethylmethylsulphonium, dibutylmethylsulphonium or 3-hexyl-1-methylimidazolium iodide) or an organic solvent (3-methoxypropionitrile with LiI, I-2 and 1-methylbenzimidazole). The most viscous electrolytes showed a clear limitation in photocurrent, which can be attributed to a low diffusion coefficient for the triiodide that transports positive charge to the counter electrode. No essential difference was found in the electron transport properties of the solar cells, which appear to be dominated by the properties of the nanostructured TiO2 film. The intensity-modulated photocurrent response was strongly affected by current saturation. This is proposed being caused by recombination processes. The electron lifetime is depending on the type of cation used in the ionic liquid, where bulky, less absorptive cations seem to give longer lifetimes.
|
|
| 9. |
|
|
| 10. |
|
|
| 11. |
- Pettersson, Henrik, et al.
(författare)
-
The monolithic multicell : A tool for testing material components in dye-sensitized solar cells
- 2007
-
Ingår i: Progress in Photovoltaics. - : Wiley. - 1062-7995 .- 1099-159X. ; 15:2, s. 113-121
-
Tidskriftsartikel (refereegranskat)abstract
- A multicell is presented as a tool for testing material components in encapsulated dye-sensitized solar cells. The multicell is based on a four-layer monolithic cell structure and an industrial process technology. Each multicell plate includes 24 individual well-encapsulated cells. A sulfur lamp corrected to the solar spectrum has been used to characterize the cells. Efficiencies up to 6.8% at a light-intensity of 1000 W/m(2) (up to 7.5% at 250 W/m(2)) have been obtained with an electrolyte solution based on gamma-butyrolactone. Additionally, a promising long-term stability at cell efficiencies close to 5% at 1000 W/m(2) has been obtained with an electrolyte based on glutaronitrile. The reproducibility of the cell performance before and after exposure to accelerated testing has been high. This means that the multicell can be used as an efficient tool for comparative performance and stability tests.
|
|
| 12. |
- Privalov, Timofei, et al.
(författare)
-
A Study of the Interactions between I−/I3− Redox Mediators and Organometallic Sensitizing Dyes in Solar Cells
- 2009
-
Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 113:2, s. 783-790
-
Tidskriftsartikel (refereegranskat)abstract
- Specific interactions of the I−/I3− redox mediators with the reduced and oxidized dye, Ru(4,4′-dicarboxy-2,2′-bipyridyl)2(NCS)2, referred to as N3 or Ru(dcbpy)2(NCS)2, have been studied by means of density functional theory (DFT) with the focus on the charge transfer process involving {dye+ I−} adducts; computations had been performed with a series of density functionals (gradient-corrected density functional BP86, and the hybrid density functionals B3LYP, MPW1K, B3PW1K, and MPW1PW91). Different pathways leading to {dye+ I−} adducts have been studied. First, mechanistic insights into the interaction of I− with RuIII(dcbpy)2(NCS)2 via an SCN− ligand directly giving rise to RuII(dcbpy)2(NCS)2I⌉0 have been obtained with the distinctive S−I bonding. Second, the binding of I− to the N3 dye cation via I−−dcbpy interactions has been analyzed. We also report experimental and computational evidence that sheds light on the interaction of the redox mediator with bipyridyl moieties. Evidence for a charge transfer process in the presence of only one I− anion in the outer coordination sphere of the ruthenium center has been identified. Finally, geometries and electronic structures of plausible intermediates have been computationally analyzed based on an inner-sphere interaction between the metal center and the redox mediator, including a two-step regeneration reaction: RuIII(dcbpy)2(NCS)2⌉+ + I− → RuIII(dcbpy)2(NCS)I⌉+ + SCN−, followed by the interaction of a second I− with the intermediate RuIII(dcbpy)2(NCS)I⌉+ complex. Conclusive evidence of a charge-transfer process that gives rise to the regenerated RuII complex, where I− interacts with the intermediate RuIII(dcbpy)2(NCS)I⌉+ complex has been identified.
|
|
| 13. |
- Waita, Sebastian M., et al.
(författare)
-
Electron transport and recombination in dye sensitized solar cells fabricated from obliquely sputter deposited and thermally annealed TiO2 films
- 2007
-
Ingår i: Journal of Electroanalytical Chemistry. - : Elsevier BV. - 1572-6657 .- 0022-0728 .- 1873-2569. ; 605:2, s. 151-156
-
Tidskriftsartikel (refereegranskat)abstract
- Dye sensitized solar cells based on annealed titanium dioxide films prepared by oblique reactive DC magnetron sputtering have been investigated in detail. Electron transport and recombination were studied using intensity-modulated photocurrent and photovoltage spectroscopy. Electron transport time as well as lifetime were found to increase upon lowering of the light intensity and to increase upon increasing the thickness of the TiO2 film. The properties are very similar to those observed for solar cells based on colloidal TiO2 films despite the morphologies being very different. In all cases, films are composed of a porous assembly of TiO2 nanocrystals. Grain boundaries with associated trap and/or energy barriers may explain the observed transport properties.
|
|
