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Ryuzi Katoh - One of the best experts on this subject based on the ideXlab platform.
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Electron Injection efficiency in dye-sensitized solar cells
Journal of Photochemistry and Photobiology C: Photochemistry Reviews, 2014Co-Authors: Ryuzi Katoh, Akihiro FurubeAbstract:Abstract Electron Injection processes in dye-sensitized solar cells (DSCs), which involve Electron transfer from an excited dye to a semiconductor nanoparticle, have been discussed in many previously reported studies. In this review we discuss the working principles and primary processes of DSCs, as well as these processes’ influence on basic properties of solar cells such as open-circuit voltage, short-circuit current, and incident photon-to-current conversion efficiency (IPCE). We focus our attention on the Electron Injection process, and we introduce methods to determine Electron Injection efficiency ( Φ inj ) using time-resolved fluorescence and absorption spectroscopy techniques. We present difficulties associated with obtaining Φ inj by means of such techniques, and we propose nanosecond time-resolved transient absorption spectroscopy as a reliable method. Then, Φ inj values obtained are summarized. Factors limiting Φ inj are discussed from the perspective of free energy changes for Electron Injection, the molecular structure of sensitizer dyes on the surface, and the presence of fast charge recombination pathways.
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Electron Injection dynamics in dye-sensitized semiconductor nanocrystalline films
Surface Science Reports, 2014Co-Authors: Akihiro Furube, Ryuzi Katoh, Kohjiro HaraAbstract:Abstract We have summarized recent ultrafast spectroscopic studies on phenomena associated with dye-sensitization of semiconductor metal oxide nanoparticles, especially TiO2 nanocrystalline film from a surface science perspective with a strong relation to mechanism of Electron Injection in dye-sensitized solar cells, which are attracting much interest from both viewpoints of pure science and applied science. A lot of chemical and physical processes are involved in this solar cell, such as light harvesting by molecules and nanostructures, interfacial Electron transfer, charge migration in solid and electrolyte, degradation of the materials, and so on. Among them, the very primary process initiated by photoabsorption by sensitizing dye molecules; that is, Electron Injection from excited adsorbates into the conduction band of semiconductor metal oxides is significantly important, because this process must be 100% efficient with a minimum driving force for high current and voltage generation. We have first focused on details of experimental methods used in this research area, and then in the following Sections, have organized this review by concentrating on each parameter that influences dynamics of Electron Injection in dye-sensitized semiconductors. Finally we have emphasized it is important to measure actual DSSCs for the precise comparison between Electron Injection dynamics and device performance.
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Quantitative study of solvent effects on Electron Injection efficiency for black-dye-sensitized nanocrystalline TiO2 films
Solar Energy Materials and Solar Cells, 2009Co-Authors: Ryuzi Katoh, Motohiro Kasuya, Akihiro Furube, Nobuhiro Fuke, Naoki Koide, Liyuan HanAbstract:The effects of various solvents on the Electron Injection efficiency for nanocrystalline TiO 2 films sensitized with the black dye trithiocyanato(4,4',4"-tricarboxy-2,2':6',2"-terpyridine)ruthenium(II) (Ru(tcterpy)(NCS) 3 ) have been studied quantitatively. The Electron Injection efficiency for the film dried in air was estimated as 0.4 using a time-resolved microwave conductivity technique. Using transient absorption measurements, we estimated the efficiency of Electron Injection for TiO 2 films in various solvents. Acetonitrile, which is widely considered to be the best solvent for solar cell performance, had the highest efficiency (∼0.65), and other solvents (3-methoxypropionitrile, γ-butyrolactone, and propylene carbonate) had lower efficiencies. These results suggest that characteristic interactions between the black dye and the -CN groups of solvents are important for achieving higher Electron Injection efficiency.
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Photoinduced Electron Injection in black dye sensitized nanocrystalline TiO2 films
Journal of Materials Chemistry, 2007Co-Authors: Ryuzi Katoh, Motohiro Kasuya, Akihiro Furube, Nobuhiro Fuke, Naoki Koide, Liyuan HanAbstract:Photoinduced Electron Injection in nanocrystalline TiO2 films sensitized with black dye [trithiocyanato(4,4′,4″-tricarboxy-2,2′:6′,2″-terpyridine)ruthenium(II), Ru(tcterpy)(NCS)3] was studied by means of transient absorption (TA) spectroscopy. We examined the effect of the additive 4-tert-butylpyridine (TBP) in acetonitrile, which is known to markedly improve the performance of solar cell devices. The efficiency of Electron Injection for the film immersed in acetonitrile was 50% higher than that for the film dried in air. Femtosecond TA measurements indicated that this efficiency enhancement was due to the opening of an additional Injection pathway from a lower-lying energy level. Upon the addition of 1 M TBP, which is known to raise the level of the conduction band of TiO2, the enhancement induced by acetonitrile disappeared. We discuss the mechanism of Electron Injection by comparing our results with results previously reported for the N3/TiO2 system.
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kinetics and mechanism of Electron Injection and charge recombination in dye sensitized nanocrystalline semiconductors
Coordination Chemistry Reviews, 2004Co-Authors: Ryuzi Katoh, Akihiro Furube, Alexander V Barzykin, Hironori Arakawa, M TachiyaAbstract:Our recent experimental and theoretical work on the kinetics and mechanism of Electron Injection and charge recombination in dye-sensitized nanocrystalline semiconductors is reviewed. In our experimental studies of Electron Injection, nanocrystalline ZnO films were chosen as the semiconductor. In order to reveal the kinetics and mechanism of Electron Injection we have developed several types of transient absorption spectrometers which enable us to observe the time profiles of the absorption spectra of the oxidized form of dyes and conducting Electrons with high sensitivity over a wavelength range from near IR to visible and over a time range from femtoseconds to submicroseconds. For N3 dye/ZnO system, the aggregation of N3 dyes and its effect on Electron Injection have been clarified spectroscopically. The Electron Injection process has been measured by a femtosecond pump-probe method and it has been found that a fraction of Electron Injection occurs via an intermediate state. The absolute efficiency of Electron Injection has been measured and a new theoretical model has been developed for Electron Injection to explain the dependence of the efficiency of Electron Injection on the free energy change for Injection. Concerning charge recombination a consistent theoretical model has been developed which explains not only the observed highly dispersive kinetics of charge recombination but also the effects of the light intensity, the applied bias and the dye structure on the kinetics.
Akihiro Furube - One of the best experts on this subject based on the ideXlab platform.
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Electron Injection efficiency in dye-sensitized solar cells
Journal of Photochemistry and Photobiology C: Photochemistry Reviews, 2014Co-Authors: Ryuzi Katoh, Akihiro FurubeAbstract:Abstract Electron Injection processes in dye-sensitized solar cells (DSCs), which involve Electron transfer from an excited dye to a semiconductor nanoparticle, have been discussed in many previously reported studies. In this review we discuss the working principles and primary processes of DSCs, as well as these processes’ influence on basic properties of solar cells such as open-circuit voltage, short-circuit current, and incident photon-to-current conversion efficiency (IPCE). We focus our attention on the Electron Injection process, and we introduce methods to determine Electron Injection efficiency ( Φ inj ) using time-resolved fluorescence and absorption spectroscopy techniques. We present difficulties associated with obtaining Φ inj by means of such techniques, and we propose nanosecond time-resolved transient absorption spectroscopy as a reliable method. Then, Φ inj values obtained are summarized. Factors limiting Φ inj are discussed from the perspective of free energy changes for Electron Injection, the molecular structure of sensitizer dyes on the surface, and the presence of fast charge recombination pathways.
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Electron Injection dynamics in dye-sensitized semiconductor nanocrystalline films
Surface Science Reports, 2014Co-Authors: Akihiro Furube, Ryuzi Katoh, Kohjiro HaraAbstract:Abstract We have summarized recent ultrafast spectroscopic studies on phenomena associated with dye-sensitization of semiconductor metal oxide nanoparticles, especially TiO2 nanocrystalline film from a surface science perspective with a strong relation to mechanism of Electron Injection in dye-sensitized solar cells, which are attracting much interest from both viewpoints of pure science and applied science. A lot of chemical and physical processes are involved in this solar cell, such as light harvesting by molecules and nanostructures, interfacial Electron transfer, charge migration in solid and electrolyte, degradation of the materials, and so on. Among them, the very primary process initiated by photoabsorption by sensitizing dye molecules; that is, Electron Injection from excited adsorbates into the conduction band of semiconductor metal oxides is significantly important, because this process must be 100% efficient with a minimum driving force for high current and voltage generation. We have first focused on details of experimental methods used in this research area, and then in the following Sections, have organized this review by concentrating on each parameter that influences dynamics of Electron Injection in dye-sensitized semiconductors. Finally we have emphasized it is important to measure actual DSSCs for the precise comparison between Electron Injection dynamics and device performance.
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Quantitative study of solvent effects on Electron Injection efficiency for black-dye-sensitized nanocrystalline TiO2 films
Solar Energy Materials and Solar Cells, 2009Co-Authors: Ryuzi Katoh, Motohiro Kasuya, Akihiro Furube, Nobuhiro Fuke, Naoki Koide, Liyuan HanAbstract:The effects of various solvents on the Electron Injection efficiency for nanocrystalline TiO 2 films sensitized with the black dye trithiocyanato(4,4',4"-tricarboxy-2,2':6',2"-terpyridine)ruthenium(II) (Ru(tcterpy)(NCS) 3 ) have been studied quantitatively. The Electron Injection efficiency for the film dried in air was estimated as 0.4 using a time-resolved microwave conductivity technique. Using transient absorption measurements, we estimated the efficiency of Electron Injection for TiO 2 films in various solvents. Acetonitrile, which is widely considered to be the best solvent for solar cell performance, had the highest efficiency (∼0.65), and other solvents (3-methoxypropionitrile, γ-butyrolactone, and propylene carbonate) had lower efficiencies. These results suggest that characteristic interactions between the black dye and the -CN groups of solvents are important for achieving higher Electron Injection efficiency.
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Photoinduced Electron Injection in black dye sensitized nanocrystalline TiO2 films
Journal of Materials Chemistry, 2007Co-Authors: Ryuzi Katoh, Motohiro Kasuya, Akihiro Furube, Nobuhiro Fuke, Naoki Koide, Liyuan HanAbstract:Photoinduced Electron Injection in nanocrystalline TiO2 films sensitized with black dye [trithiocyanato(4,4′,4″-tricarboxy-2,2′:6′,2″-terpyridine)ruthenium(II), Ru(tcterpy)(NCS)3] was studied by means of transient absorption (TA) spectroscopy. We examined the effect of the additive 4-tert-butylpyridine (TBP) in acetonitrile, which is known to markedly improve the performance of solar cell devices. The efficiency of Electron Injection for the film immersed in acetonitrile was 50% higher than that for the film dried in air. Femtosecond TA measurements indicated that this efficiency enhancement was due to the opening of an additional Injection pathway from a lower-lying energy level. Upon the addition of 1 M TBP, which is known to raise the level of the conduction band of TiO2, the enhancement induced by acetonitrile disappeared. We discuss the mechanism of Electron Injection by comparing our results with results previously reported for the N3/TiO2 system.
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kinetics and mechanism of Electron Injection and charge recombination in dye sensitized nanocrystalline semiconductors
Coordination Chemistry Reviews, 2004Co-Authors: Ryuzi Katoh, Akihiro Furube, Alexander V Barzykin, Hironori Arakawa, M TachiyaAbstract:Our recent experimental and theoretical work on the kinetics and mechanism of Electron Injection and charge recombination in dye-sensitized nanocrystalline semiconductors is reviewed. In our experimental studies of Electron Injection, nanocrystalline ZnO films were chosen as the semiconductor. In order to reveal the kinetics and mechanism of Electron Injection we have developed several types of transient absorption spectrometers which enable us to observe the time profiles of the absorption spectra of the oxidized form of dyes and conducting Electrons with high sensitivity over a wavelength range from near IR to visible and over a time range from femtoseconds to submicroseconds. For N3 dye/ZnO system, the aggregation of N3 dyes and its effect on Electron Injection have been clarified spectroscopically. The Electron Injection process has been measured by a femtosecond pump-probe method and it has been found that a fraction of Electron Injection occurs via an intermediate state. The absolute efficiency of Electron Injection has been measured and a new theoretical model has been developed for Electron Injection to explain the dependence of the efficiency of Electron Injection on the free energy change for Injection. Concerning charge recombination a consistent theoretical model has been developed which explains not only the observed highly dispersive kinetics of charge recombination but also the effects of the light intensity, the applied bias and the dye structure on the kinetics.
James R Durrant - One of the best experts on this subject based on the ideXlab platform.
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parameters influencing the efficiency of Electron Injection in dye sensitized solar cells
Journal of the American Chemical Society, 2009Co-Authors: Sara Koops, Brian Oregan, Piers R F Barnes, James R DurrantAbstract:In this paper we focus upon the Electron Injection dynamics in complete nanocrystalline titanium dioxide dye-sensitized solar cells (DSSCs) employing the ruthenium bipyridyl sensitizer dye N719. Electron Injection dynamics and quantum yields are studied by time-resolved single photon counting, and the results are correlated with device performance. In typical DSSC devices, Electron Injection kinetics were found to proceed from the N719 triplet state with a half-time of 200 ± 60 ps and quantum yield of 84 ± 5%. We find that these Injection dynamics are independent of presence of iodide/triiodide redox couple and of the pH of the peptization step used in the synthesis of the TiO2 nanoparticles. They are furthermore found to be only weakly dependent upon the application of electrical bias to the device. In contrast, we find these dynamics to be strongly dependent upon the concentration of tert-butylpyridine (tBP) and lithium cations in the electrolyte. This dependence is correlated with shifts of the TiO2 co...
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slow Electron Injection on ru phthalocyanine sensitized tio2
Journal of the American Chemical Society, 2007Co-Authors: Ana Morandeira, Ismael Lopezduarte, Victoria M Martinezdiaz, Brian Oregan, Chris G Shuttle, Nor A Hajizainulabidin, Tomas Torres, Emilio Palomares, James R DurrantAbstract:Photoinduced Electron Injection in dye sensitized TiO2 is a critical step in the function of dye sensitized solar cells. High Electron Injection quantum yields are a requirement to obtain efficient devices. While high Electron Injection quantum yields are usually linked to ultrafast Electron-transfer dynamics (in the fs−ps timescales), the latter are not a requirement. We present here a system, Ru-phthalocyanine sensitized TiO2, where slow Electron Injection (kinj ≈ 450 ns-1) and efficient Electron Injection are compatible owing to the long lifetime of the injecting state, the Ru-phthalocyanine triplet state. Ru-phthalocyanine dyes are attractive sensitizers because they absorb strongly in the red and their axial ligands hinder the formation of aggregates.
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Transient luminescence studies of Electron Injection in dye sensitised nanocrystalline TiO2 films
Journal of Photochemistry and Photobiology A-chemistry, 2001Co-Authors: Yasuhiro Tachibana, Igor V. Rubtsov, Ivan Montanari, Keitaro Yoshihara, David R. Klug, James R DurrantAbstract:Abstract We employ fluorescence upconversion spectroscopy to monitor the dynamics of Electron Injection in tetracarboxyphenyl zinc porphyin (ZnTCPP) sensitised nanocrystalline TiO 2 films. A good agreement is found between these measurements and previous studies of Electron Injection employing transient absorption spectroscopy. In both case, nonexponential kinetics are observed, with Electron Injection occurring on timescales ranging from
Villy Sundström - One of the best experts on this subject based on the ideXlab platform.
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Photoinduced Electron Injection from Ru(dcbpy)2(NCS)2 to SnO2 and TiO2 nanocrystalline films.
Journal of the American Chemical Society, 2003Co-Authors: Gabor Benkö, Pasi Myllyperkiö, Jie Pan, And Arkady P. Yartsev, Villy SundströmAbstract:Photoinduced Electron Injection from the sensitizer Ru(dcbpy)2(NCS)2 (RuN3) into SnO2 and TiO2 nanocrystalline films occurs by two distinct channels on the femto- and picosecond time scales. The faster Electron Injection into the conduction band of the different semiconductors originates from the initially excited singlet state of RuN3, and occurs in competition with intersystem crossing. The rate of singlet Electron Injection is faster to TiO2 (1/55 fs-1) than to SnO2 (1/145 fs-1), in agreement with higher density of conduction band acceptor states in the former semiconductor. As a result of competition between the ultrafast processes, for TiO2 singlet, whereas for SnO2 triplet Electron Injection is dominant. Electron Injection from the triplet state is nonexponential and can be fitted with time constants ranging from ~1 ps (2.5 ps for SnO2) to ~50 ps for both semiconductors. The major part of triplet Injection is independent of the semiconductor and is most likely controlled by intramolecular dynamics in RuN3. The overall time scale and the yield of Electron Injection to the two semiconductors are very similar, suggesting that processes other than Electron Injection are responsible for the difference in efficiencies of solar cells made of these materials. (Less)
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particle size and crystallinity dependent Electron Injection in fluorescein 27 sensitized tio2 films
Journal of Physical Chemistry B, 2003Co-Authors: Gabor Benkö, Anders Hagfeldt, Villy Sundström, Bjorn Skarman, Reine Wallenberg, Arkady YartsevAbstract:Influence of processing parameters, such as autoclaving and firing temperature, on the optical properties of nanocrystalline anatase TiO2 film and on the process of Electron Injection from the dye fluorescein 27 to the as-prepared films is studied. Transmission Electron microscopy and steady-state and time-resolved femtosecond spectroscopy measurements indicate that the larger the TiO2 particle and the better its overall crystallinity, the faster the process of Electron Injection. Unraveling factors that control the properties of the sub-20-nm sized semiconductor particles, and by this the Electron Injection to them, is important for understanding the process of interfacial Electron transfer from the dye to the semiconductor, as well as future optimization of the function of the photoelectrochemical cell based on dye-sensitized TiO2 films.
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ULTRAFAST Electron Injection AND RECOMBINATION DYNAMICS OF DYE SENSITISED TIO2 PARTICLES
Chemical Physics Letters, 1998Co-Authors: Marcus Hilgendorff, Villy SundströmAbstract:Abstract We report studies of Electron Injection and recombination dynamics of the Electronically excited laser dye fluorescein 27 adsorbed on nanometer-sized TiO 2 colloidal particles in aqueous solution. Using femtosecond pump–probe spectroscopy, we show that Electron Injection occurs in ∼300 fs. This time scale for the Electron Injection process was confirmed recording the signal of the stimulated emission decay of the dye and the simultaneous rise of the absorption of the injected Electron. In addition, our results provide strong evidence that the subsequent recombination process is controlled by cooling of the hot semi-oxidised radical anion initially prepared by ultrafast Electron Injection.
Gerald J Meyer - One of the best experts on this subject based on the ideXlab platform.
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Electron Injection AT DYE-SENSITIZED SEMICONDUCTOR ELECTRODES
Annual Review of Physical Chemistry, 2005Co-Authors: David F Watson, Gerald J MeyerAbstract:Electron Injection at dye-sensitized semiconductors is reviewed. Particular emphasis is placed on theoretical and photoelectrochemical studies of dye-sensitized planar and single-crystal electrodes. The accepted mechanism of Electron Injection, which was derived from these classical studies, is introduced. Selected photoelectrochemical studies of dye-sensitized nanocrystalline semiconductors are reviewed; emphasis is given to factors that influence the efficiencies of Electron Injection and charge recombination. The development of quasi-solid-state nanocrystalline dye-sensitized solar cells is also discussed. Recent time-resolved spectroscopic studies of Electron Injection and charge recombination are reviewed. These studies have led to a better understanding of Electron Injection mechanisms, and have revealed the limitations of the classical models.
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Electron Injection recombination and halide oxidation dynamics at dye sensitized metal oxide interfaces
Journal of Physical Chemistry A, 2000Co-Authors: Todd A Heimer, Edwin J Heilweil, Carlo Alberto Bignozzi, Gerald J MeyerAbstract:Time-resolved infrared measurements indicate ultrafast, <350 fs, Electron Injection from (4,4‘dcb)2Ru(NCS)2 (1) and (5,5‘dcb)2Ru(NCS)2 (2) to nanostructured TiO2 electrodes (where 4,4‘dcb = 4,4‘-(COOH)2-2,2‘-bipyridine). Although rapid, the Injection from 2 apparently occurs with a lower quantum yield than that from 1, explaining a lower overall photon-to-current efficiency for 2/TiO2 solar cells. Transient visible spectroscopy reveals similar rates of both halide oxidation and injected Electron-oxidized dye recombination for the two sensitizers. Substituting SnO2 for TiO2 increases the Electron Injection yield from 2 in the case of transparent metal oxide films and improves the photon-to-current efficiency. Results indicate a wavelength-dependent Electron Injection yield.