Jani Kallioinen

Publications (10)18.61 Total impact

• Source

  Available from: arxiv.org

  Article: Dye-Sensitized Nanostructured TiO2 Film Based Photoconductor

  Jani Kallioinen, M. R. Hassan, G. S. Paraoanu, Jouko Korppi-Tommola
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  ABSTRACT: Grooves were etched in a conductive layer of a conductive, transparent glass, and a nanoporous TiO2 film was deposited on both the conductive and nonconductive area. The width of the grooves was 100 $\mu$m and 150 $\mu$m. A transparent TiO2 film was dye-sensitized, covered with an electrolyte, and sandwiched with a cover glass. The conductivity of the dye-sensitized TiO2 film permeated with electrolyte was studied in the dark and under illumination, and was observed to be dependent on light intensity, wavelength and applied voltage. This study shows that dye-sensitized nanoporous films can be used as a wavelength dependent photoconductor.
  04/2008;
• Article: A dye-sensitized solar cell driven electrochromic device.

  Henriette Santa-Nokki, Jani Kallioinen, Jouko Korppi-Tommola
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  ABSTRACT: A new dye-sensitized solar cell driven electrochromic device has been fabricated. The device consists of an electrochromic display and a solar cell in a single nanocrystalline film. The optimization of the electrochromic and the solar cell functions was carried out. An applied potential of 1.0 V was required for coloring and the best solar energy conversion efficiency 1.1% was achieved. The efficiency may be compared to an efficiency of 4.6% obtained in a similar dye-sensitized solar cell without the display property. Coloring and bleaching times of the device were less than one second and a transmittance change from 38.7% (bleached) to 15.9% (colored) at best was achieved. The optimization of the electrochromic property of the device lead to decreasing efficiency of the solar cell and vice versa.
  Photochemical and Photobiological Sciences 02/2007; 6(1):63-6. · 2.58 Impact Factor
• Article: Quaternary ammonium polyiodides as ionic liquid/soft solid electrolytes in dye-sensitized solar cells.

  Henriette Santa-Nokki, Sara Busi, Jani Kallioinen, Manu Lahtinen, Jouko. Korppi-Tommola
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  ABSTRACT: Four new quaternary ammonium iodides, (Me2Pe2N)I, (Me2Hex2N)I, (Et2Pe2N)I and (Et2Hex2N)I, were synthesized and studied as electrolytes for dye-sensitized solar cells. All compds. were solids at room temp. The influence of varying amts. of elemental I and the effect of tert-butylpyridine (TBP) on the performance of a cell was also studied. Addn. of I lowered the m.ps. of the polyiodides. Of the NH4+ iodides only (Me2Hex2N)I:I2 (10:1) was liq. at room temp. and the others were soft solids. Under illumination from a halogen lamp at 10 mW/cm2, the highest power conversion efficiency of 2.4% was obtained with (Me2Hex2N)I:I2 (10:1) liq. electrolyte contg. TBP. This may be compared to an efficiency of 5.4% obtained from similar cells with traditional 3-methoxypropionitrile based electrolyte tested under identical conditions. The best efficiency with the soft solid electrolyte, (Et2Hex2N)I:I2 (10:1) with TBP, was 2.3%. [on SciFinder(R)]
  Journal of Photochemistry and Photobiology A Chemistry 01/2007; 186(1):29-33. · 2.42 Impact Factor
• Article: Photoinduced Ultrafast Dynamics of Ru(dcbpy)(2)(NCS)(2)-Sensitized Nanocrystalline TiO(2) Films: The Influence of Sample Preparation and Experimental Conditions.

  Jani Kallioinen, Gabor Benkö, Pasi Myllyperkiö, Leonid Khriachtchev, Björn Skårman, Reine Wallenberg, Markus Tuomikoski, Jouko Korppi-Tommola, Villy Sundström, Arkady P Yartsev
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  ABSTRACT: In most of the previous ultrafast electron injection studies of Ru(dcbpy)2(NCS)2-sensitized nanocrystalline TiO2 films, experimental conditions and sample preparation have been different from study to study and no studies of how the differences affect the observed dynamics have been reported. In the present paper, we have investigated the influence of such modifications. Pump photon density, environment of the sensitized film (solvent and air), and parameters of the film preparation (crystallinity and quality of the film) were varied in a systematic way and the obtained dynamics were compared to that of a well-defined reference sample: Ru(dcbpy)2(NCS)2-TiO2 in acetonitrile. In some cases, the induced changes in the dynamics were uncorrelated to the electron injection process. High pump photon density (not in the linear response region) and exposure of the sensitized film to air altered the picosecond-time-scale kinetics considerably, and the changes were attributed mostly to degradation of the dye. In other cases, changes in the measured kinetics were related to the electron injection processes: reducing the firing temperature of the nanocrystalline film or making the film via electron beam evaporation (EBE) resulted in a decrease of the overall crystallinity of the film, and the electron injection slowed. In the sensitized EBE films, in addition to an increased contribution of triplet excited-state electron injection, a new electron transfer (ET) process with a time constant of 200 fs was observed.
  The Journal of Physical Chemistry B 06/2004; 108(20):6365-73. · 3.70 Impact Factor
• Article: Photoinduced Ultrafast Dynamics of Ru(dcbpy)2(NCS)2-Sensitized Nanocrystalline TiO2 Films:  The Influence of Sample Preparation and Experimental Conditions

  Jani Kallioinen, Gábor Benkö, Pasi Myllyperkiö, Leonid Khriachtchev, Björn Skårman, Reine Wallenberg, Markus Tuomikoski, Jouko Korppi-Tommola, Villy Sundström, Arkady P. Yartsev
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  ABSTRACT: In most of the previous ultrafast electron injection studies of Ru(dcbpy)2(NCS)2-sensitized nanocrystalline TiO2 films, experimental conditions and sample preparation have been different from study to study and no studies of how the differences affect the observed dynamics have been reported. In the present paper, we have investigated the influence of such modifications. Pump photon density, environment of the sensitized film (solvent and air), and parameters of the film preparation (crystallinity and quality of the film) were varied in a systematic way and the obtained dynamics were compared to that of a well-defined reference sample:  Ru(dcbpy)2(NCS)2−TiO2 in acetonitrile. In some cases, the induced changes in the dynamics were uncorrelated to the electron injection process. High pump photon density (not in the linear response region) and exposure of the sensitized film to air altered the picosecond-time-scale kinetics considerably, and the changes were attributed mostly to degradation of the dye. In other cases, changes in the measured kinetics were related to the electron injection processes:  reducing the firing temperature of the nanocrystalline film or making the film via electron beam evaporation (EBE) resulted in a decrease of the overall crystallinity of the film, and the electron injection slowed. In the sensitized EBE films, in addition to an increased contribution of triplet excited-state electron injection, a new electron transfer (ET) process with a time constant of 200 fs was observed.
  04/2004;
• Article: Interligand Electron Transfer Determines Triplet Excited State Electron Injection in RuN3−Sensitized TiO2 Films

  Gábor Benkö, Jani Kallioinen, Pasi Myllyperkiö, Florentina Trif, Jouko E. I. Korppi-Tommola, Arkady P. Yartsev, Villy Sundström
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  ABSTRACT: Electron injection from the transition metal complex Ru(dcbpy)2(NCS)2 (dcbpy = 2,2‘-bipyridine-4,4‘-dicarboxylate) into a titanium dioxide nanoparticle film occurs along two pathways. The dominating part of the electron injection proceeds from the initially excited singlet state of the sensitizer into the conduction band of the semiconductor on the sub-hundred-femtosecond time scale. The slower part of the injection occurs from the thermalized triplet excited state on the picosecond time scale in a nonexponential fashion, as was shown in a previous study (Benkö, G.; et al. J. Am. Chem. Soc. 2002, 124, 489). Here we show that the slower channel of injection is the result of the excited state being localized on a ligand of the sensitizer that is not attached to the semiconductor; hence, the electron cannot be injected directly from such an excited state into the semiconductor. Before being injected, it has to be transferred from the non-surface-attached ligand to the attached one. The results show that the interligand electron-transfer time is on the picosecond time scale, depends on the relative energies of the two ligands, and controls the electron injection from the excited triplet state of the sensitizer. The findings provide information relevant to the design of molecular-based assemblies and devices.
  02/2004;
• Article: Electron Transfer from the Singlet and Triplet Excited States of Ru(dcbpy)2(NCS)2 into Nanocrystalline TiO2 Thin Films

  Jani Kallioinen, Gábor Benkö, Villy Sundström, Jouko E. I. Korppi-Tommola, Arkady P. Yartsev
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  ABSTRACT: Time-resolved absorption spectroscopy was used to study the femtosecond and picosecond time scale electron injection from the excited singlet and triplet states of Ru(dcbpy)2(NCS)2 (RuN3) into titanium dioxide (TiO2) nanocrystalline particle film in acetonitrile. The fastest resolved time constant of 30 fs was shown to reflect a sum of two parallel ultrafast processes, nonergodic electron transfer (ET) from the initially excited singlet state of RuN3 to the conduction band of TiO2 and intersystem crossing (ISC). The branching ratio of 1.5 between the two competing processes gives rate constants of 1/50 fs-1 for ET and 1/75 fs-1 for ISC. Following the ultrafast processes, a minor part of the electron injection (40%) occurs from the thermalized triplet state of RuN3 on the picosecond time scale. The kinetics of this slower phase of electron injection is nonexponential and can be fitted with time constants ranging from 1 to 60 ps.
  04/2002;
• Article: Photoinduced ultrafast dye-to-semiconductor electron injection from nonthermalized and thermalized donor states.

  Gábor Benkö, Jani Kallioinen, Jouko E I Korppi-Tommola, Arkady P Yartsev, Villy Sundström
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  ABSTRACT: Electron injection from the transition metal complex Ru(dcbpy)(2)(NCS)(2) (dcbpy = 4,4'-dicarboxy-2,2'-bipyridine) into a titanium dioxide nanocrystalline film occurs on the femto- and picosecond time scales. Here we show that the dominating part of the electron transfer proceeds extremely rapidly from the initially populated, vibronically nonthermalized, singlet excited state, prior to electronic and nuclear relaxation of the molecule. The results are especially relevant to the understanding and design of molecular-based photovoltaic devices and artificial photosynthetic assemblies.
  Journal of the American Chemical Society 02/2002; 124(3):489-93. · 9.91 Impact Factor
• Article: Dynamic preparation of TiO2 films for fabrication of dye-sensitized solar cells

  Henriette Santa-Nokki, Jani Kallioinen, Terho Kololuoma, Vladimir Tuboltsev, Jouko Korppi-Tommola
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  ABSTRACT: Preparation of nanocrystalline porous titanium dioxide (TiO2) films with roll-to-roll compatible methods was studied. Gravure printing was used for spreading TiO2 paste and paper calendering for pressing TiO2 nanoparticle films. Influence of different preparation methods on performance of fabricated dye-sensitized solar cells (DSSCs) was investigated. The attained light into electricity conversion efficiency was compared with DSSCs fabricated on conductive plastic substrates by doctor-blading spreading with subsequent static pressing. The latter method achieved a light conversion efficiency as high as 5.1%. The efficiency of the cells with a gravure printed TiO2 film was found to be rather low. The highest conversion efficiency was 1.7%; this is concluded to be due to insufficient thickness of the gravure printed TiO2 films. Calendering of the doctor-bladed films on the other hand attained a light conversion efficiency of 4.7%.
  Journal of Photochemistry and Photobiology A: Chemistry.
• Article: Photoinduced dynamics of Ru(dcbpy)[sub2](NCS)[sub2] : in solution and on nanocrystalline titanium dioxide thin films /

  Jani. Kallioinen
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  ABSTRACT: Diss. -- Jyväskylän yliopisto.