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Tsuneo Fujii - One of the best experts on this subject based on the ideXlab platform.
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influence of dye content on the Conduction Band Edge of titania in the steam treated dye dispersing titania electrodes
Photochemistry and Photobiology, 2014Co-Authors: Rudi Agus Setiawan, Hiromasa Nishikiori, Nobuaki Tanaka, Tsuneo FujiiAbstract:The titania and dye-dispersing titania electrodes were prepared by a nitric acid-catalyzed sol-gel process. The dye-dispersing titania contains the dye molecules dispersed on the surface of the individual nanosized titania particles. The photo-cyclic voltammetry (Photo-CV) and photoelectric measurements of the dye-dispersing titania electrodes were conducted to clarify the factors changing the Conduction Band Edge of the titania and the open-circuit voltage (Voc ) of the electrodes. The remaining nitrate ions caused a negative shift of Conduction Band Edge of the titania of the dye-dispersing titania. The Conduction Band Edge of the titania was shifted in a negative direction in the electrode containing a greater amount of the dye. These results are due to the adsorption of nitrate ions and the dye-titania complex formation on the titania particle surface. The effect of the dye-titania complex formation on the shift in the titania Conduction Band Edge was greater than that of the adsorption of nitrate ions due to strong interaction between the dye and titania through the carboxylate and quinone-like groups of the dye. The shift in the titania Conduction Band Edge corresponded to the change in the Voc value.
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Influence of Dye Content on the Conduction Band Edge of Titania in the Steam‐treated Dye‐dispersing Titania Electrodes
Photochemistry and photobiology, 2014Co-Authors: Rudi Agus Setiawan, Hiromasa Nishikiori, Nobuaki Tanaka, Tsuneo FujiiAbstract:The titania and dye-dispersing titania electrodes were prepared by a nitric acid-catalyzed sol-gel process. The dye-dispersing titania contains the dye molecules dispersed on the surface of the individual nanosized titania particles. The photo-cyclic voltammetry (Photo-CV) and photoelectric measurements of the dye-dispersing titania electrodes were conducted to clarify the factors changing the Conduction Band Edge of the titania and the open-circuit voltage (Voc ) of the electrodes. The remaining nitrate ions caused a negative shift of Conduction Band Edge of the titania of the dye-dispersing titania. The Conduction Band Edge of the titania was shifted in a negative direction in the electrode containing a greater amount of the dye. These results are due to the adsorption of nitrate ions and the dye-titania complex formation on the titania particle surface. The effect of the dye-titania complex formation on the shift in the titania Conduction Band Edge was greater than that of the adsorption of nitrate ions due to strong interaction between the dye and titania through the carboxylate and quinone-like groups of the dye. The shift in the titania Conduction Band Edge corresponded to the change in the Voc value.
Joseph T. Hupp - One of the best experts on this subject based on the ideXlab platform.
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Determining the Conduction Band-Edge Potential of Solar-Cell-Relevant Nb2O5 Fabricated by Atomic Layer Deposition
Langmuir : the ACS journal of surfaces and colloids, 2017Co-Authors: William L. Hoffeditz, Michael J. Pellin, Omar K. Farha, Joseph T. HuppAbstract:Often key to boosting photovoltages in photoelectrochemical and related solar-energy-conversion devices is the preferential slowing of rates of charge recombination—especially recombination at semiconductor/solution, semiconductor/polymer, or semiconductor/perovskite interfaces. In devices featuring TiO2 as the semiconducting component, a common approach to slowing recombination is to install an ultrathin metal oxide barrier layer or trap-passivating layer atop the semiconductor, with the needed layer often being formed via atomic layer deposition (ALD). A particularly promising barrier layer material is Nb2O5. Its Conduction-Band-Edge potential ECB is low enough that charge injection from an adsorbed molecular, polymeric, or solid-state light absorber and into the semiconductor can still occur, but high enough that charge recombination is inhibited. While a few measurements of ECB have been reported for conventionally synthesized, bulk Nb2O5, none have been described for ALD-fabricated versions. Here, we...
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effects of adsorbed pyridine derivatives and ultrathin atomic layer deposited alumina coatings on the Conduction Band Edge energy of tio2 and on redox shuttle derived dark currents
Langmuir, 2013Co-Authors: Michael J Katz, Michael J. Pellin, Omar K. Farha, Michael J D Vermeer, Joseph T. HuppAbstract:Both the adsorption of t-butylpyridine and the atomic-layer deposition of ultrathin conformal coatings of insulators (such as alumina) are known to boost open-circuit photovoltages substantially for dye-sensitized solar cells. One attractive interpretation is that these modifiers significantly shift the Conduction-Edge energy of the electrode, thereby shifting the onset potential for dark current arising from the interception of injected electrons by solution-phase redox shuttle components such as Co(phenanthroline)(3)(3+) and triiodide. For standard, high-area, nanoporous photoelectrodes, Band-Edge energies are difficult to measure directly. In contrast, for flat electrodes they are readily accessible from Mott-Schottky analyses of impedance data. Using such electrodes (specifically TiO(2)), we find that neither organic nor inorganic electrode-surface modifiers shift the Conduction-Band-Edge energy sufficiently to account fully for the beneficial effects on electrode behavior (i.e., the suppression of dark current). Additional experiments reveal that the efficacy of ultrathin coatings of Al(2)O(3) arises chiefly from the passivation of redox-catalytic surface states. In contrast, adsorbed t-butylpyridine appears to suppress dark currents mainly by physically blocking access of shuttle molecules to the electrode surface. Studies with other derivatives of pyridine, including sterically and/or electronically diverse derivatives, show that heterocycle adsorption and the concomitant suppression of dark current does not require the coordination of surface Ti(IV) or Al(III) atoms. Notably, the favorable (i.e., negative) shifts in onset potential for the flow of dark current engendered by organic and inorganic surface modifiers are additive. Furthermore, they appear to be largely insensitive to the identity of shuttle molecules.
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electrochemical spectral and quartz crystal microgravimetric assessment of Conduction Band Edge energies for nanocrystalline zirconium dioxide solution interfaces
Coordination Chemistry Reviews, 2004Co-Authors: Buford I. Lemon, Fang Liu, Joseph T. HuppAbstract:Abstract Electrochemical quartz crystal microgravimetry studies of porous nanocrystalline ZrO 2 electrodes in acetonitrile containing 1 M LiClO 4 show that surface electronic states can be accessed at potentials as far positive as 0 V versus Ag/AgCl, as evidenced by uptake of charge-compensating cations. A much higher density of surface states is encountered beginning at about −1.3 V. Based on previous work with TiO 2 , SnO 2 , and ZnO, this potential is tentatively identified with E cb for ZrO 2 and is about 0.5 V more negative than E cb for TiO 2 . In water, cation uptake is replaced by efficient reduction of H 3 O + or water to hydrogen, a finding that has interesting parallels in radiation chemistry. Identifying the onset potential for hydrogen evolution with either E cb or a potential characteristic of a high density of trap states, the value obtained is about 0.3 V negative of E cb for TiO 2 . Like the Conduction Band Edge energy for titanium dioxide, the putative E cb value for ZrO 2 shifts negatively with increasing pH. Comparisons of surface-based ligand-to-metal charge-transfer Band energies point to an E cb value for colloidal ZrO 2 in water that is about 0.4 V negative of the value for colloidal TiO 2 . Consistent with three recent literature reports, empty states should lie low enough in energy to permit efficient injection from photoexcited dyes under certain conditions.
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Electrochemical, spectral, and quartz crystal microgravimetric assessment of Conduction Band Edge energies for nanocrystalline zirconium dioxide/solution interfaces
Coordination Chemistry Reviews, 2004Co-Authors: Buford I. Lemon, Fang Liu, Joseph T. HuppAbstract:Abstract Electrochemical quartz crystal microgravimetry studies of porous nanocrystalline ZrO 2 electrodes in acetonitrile containing 1 M LiClO 4 show that surface electronic states can be accessed at potentials as far positive as 0 V versus Ag/AgCl, as evidenced by uptake of charge-compensating cations. A much higher density of surface states is encountered beginning at about −1.3 V. Based on previous work with TiO 2 , SnO 2 , and ZnO, this potential is tentatively identified with E cb for ZrO 2 and is about 0.5 V more negative than E cb for TiO 2 . In water, cation uptake is replaced by efficient reduction of H 3 O + or water to hydrogen, a finding that has interesting parallels in radiation chemistry. Identifying the onset potential for hydrogen evolution with either E cb or a potential characteristic of a high density of trap states, the value obtained is about 0.3 V negative of E cb for TiO 2 . Like the Conduction Band Edge energy for titanium dioxide, the putative E cb value for ZrO 2 shifts negatively with increasing pH. Comparisons of surface-based ligand-to-metal charge-transfer Band energies point to an E cb value for colloidal ZrO 2 in water that is about 0.4 V negative of the value for colloidal TiO 2 . Consistent with three recent literature reports, empty states should lie low enough in energy to permit efficient injection from photoexcited dyes under certain conditions.
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energetics of the nanocrystalline titanium dioxide aqueous solution interface approximate Conduction Band Edge variations between h0 10 and h 26
Journal of Physical Chemistry B, 1999Co-Authors: Andrew L Lyon, Joseph T. HuppAbstract:A reflectance method has been used to assess Conduction Band Edge energies (Ecb) for nanocrystalline TiO2(anatase) electrodes in contact with aqueous electrolytes. The measurements, which were made over a range of nearly 40 pH units, reveal a Nernstian dependence of Ecb upon pH over most of this range, i.e., a −64 mV shift per unit decrease in log(proton activity) between H0 = −8 and H- = +23. Electrochemical quartz crystal microbalance (EQCM) measurements have established that charge compensating proton uptake occurs at potentials negative of Ecb. Uptake occurs over the entire EQCM-accessible pH range (H0 = −5 to pH = +11). The combined findings are inconsistent with Ecb control solely via surface protonation and deprotonation reactions, whose pKa's occur in the vicinity of pH 4 and 10. They are consistent, however, with a mechanism whereby: (a) electrochemical generation of Ti(III) trap sites, in the log(proton activity) range from H0 = −8 to H- = +23, is accompanied quantitatively by proton intercalat...
Rudi Agus Setiawan - One of the best experts on this subject based on the ideXlab platform.
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influence of dye content on the Conduction Band Edge of titania in the steam treated dye dispersing titania electrodes
Photochemistry and Photobiology, 2014Co-Authors: Rudi Agus Setiawan, Hiromasa Nishikiori, Nobuaki Tanaka, Tsuneo FujiiAbstract:The titania and dye-dispersing titania electrodes were prepared by a nitric acid-catalyzed sol-gel process. The dye-dispersing titania contains the dye molecules dispersed on the surface of the individual nanosized titania particles. The photo-cyclic voltammetry (Photo-CV) and photoelectric measurements of the dye-dispersing titania electrodes were conducted to clarify the factors changing the Conduction Band Edge of the titania and the open-circuit voltage (Voc ) of the electrodes. The remaining nitrate ions caused a negative shift of Conduction Band Edge of the titania of the dye-dispersing titania. The Conduction Band Edge of the titania was shifted in a negative direction in the electrode containing a greater amount of the dye. These results are due to the adsorption of nitrate ions and the dye-titania complex formation on the titania particle surface. The effect of the dye-titania complex formation on the shift in the titania Conduction Band Edge was greater than that of the adsorption of nitrate ions due to strong interaction between the dye and titania through the carboxylate and quinone-like groups of the dye. The shift in the titania Conduction Band Edge corresponded to the change in the Voc value.
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Influence of Dye Content on the Conduction Band Edge of Titania in the Steam‐treated Dye‐dispersing Titania Electrodes
Photochemistry and photobiology, 2014Co-Authors: Rudi Agus Setiawan, Hiromasa Nishikiori, Nobuaki Tanaka, Tsuneo FujiiAbstract:The titania and dye-dispersing titania electrodes were prepared by a nitric acid-catalyzed sol-gel process. The dye-dispersing titania contains the dye molecules dispersed on the surface of the individual nanosized titania particles. The photo-cyclic voltammetry (Photo-CV) and photoelectric measurements of the dye-dispersing titania electrodes were conducted to clarify the factors changing the Conduction Band Edge of the titania and the open-circuit voltage (Voc ) of the electrodes. The remaining nitrate ions caused a negative shift of Conduction Band Edge of the titania of the dye-dispersing titania. The Conduction Band Edge of the titania was shifted in a negative direction in the electrode containing a greater amount of the dye. These results are due to the adsorption of nitrate ions and the dye-titania complex formation on the titania particle surface. The effect of the dye-titania complex formation on the shift in the titania Conduction Band Edge was greater than that of the adsorption of nitrate ions due to strong interaction between the dye and titania through the carboxylate and quinone-like groups of the dye. The shift in the titania Conduction Band Edge corresponded to the change in the Voc value.
Serge Biesemans - One of the best experts on this subject based on the ideXlab platform.
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achieving Conduction Band Edge effective work functions by hbox la _ 2 hbox o _ 3 capping of hafnium silicates
IEEE Electron Device Letters, 2007Co-Authors: Lars-ake Ragnarsson, Hong Yu Yu, Annelies Delabie, Johan Swerts, Tom Schram, Vincent S Chang, Thierry Conard, Stefan De Gendt, Serge BiesemansAbstract:Conduction Band-Edge effective work functions (phim,eff ) are demonstrated with TaCx and TiN by means of La2O3 capping of HfSiOx in a gate-first process flow with CMOS-compatible thermal budget. With TaCx, a 10- Aring-thick La2O3 cap results in a phi m,eff of 3.9 eV with a low equivalent oxide thickness (EOT) increase (1-2 Aring) and unaffected electron mobility. With TiN, non-nitrided La2O3 capping results in a smaller phim,eff reduction at a larger EOT increase, while with post-cap nitridation, the TiN phim,eff is lower at a smaller EOT increase. Results show that the choice of metal and nitridation conditions have significant effects on La2O3 capped stacks
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Achieving Conduction Band-Edge Effective Work Functions by $\hbox{La}_{2}\hbox{O}_{3}$ Capping of Hafnium Silicates
IEEE Electron Device Letters, 2007Co-Authors: Lars-ake Ragnarsson, Hong Yu Yu, Annelies Delabie, Johan Swerts, Tom Schram, Vincent S Chang, Thierry Conard, Stefan De Gendt, Serge BiesemansAbstract:Conduction Band-Edge effective work functions (phim,eff ) are demonstrated with TaCx and TiN by means of La2O3 capping of HfSiOx in a gate-first process flow with CMOS-compatible thermal budget. With TaCx, a 10- Aring-thick La2O3 cap results in a phi m,eff of 3.9 eV with a low equivalent oxide thickness (EOT) increase (1-2 Aring) and unaffected electron mobility. With TiN, non-nitrided La2O3 capping results in a smaller phim,eff reduction at a larger EOT increase, while with post-cap nitridation, the TiN phim,eff is lower at a smaller EOT increase. Results show that the choice of metal and nitridation conditions have significant effects on La2O3 capped stacks
Nobuaki Tanaka - One of the best experts on this subject based on the ideXlab platform.
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influence of dye content on the Conduction Band Edge of titania in the steam treated dye dispersing titania electrodes
Photochemistry and Photobiology, 2014Co-Authors: Rudi Agus Setiawan, Hiromasa Nishikiori, Nobuaki Tanaka, Tsuneo FujiiAbstract:The titania and dye-dispersing titania electrodes were prepared by a nitric acid-catalyzed sol-gel process. The dye-dispersing titania contains the dye molecules dispersed on the surface of the individual nanosized titania particles. The photo-cyclic voltammetry (Photo-CV) and photoelectric measurements of the dye-dispersing titania electrodes were conducted to clarify the factors changing the Conduction Band Edge of the titania and the open-circuit voltage (Voc ) of the electrodes. The remaining nitrate ions caused a negative shift of Conduction Band Edge of the titania of the dye-dispersing titania. The Conduction Band Edge of the titania was shifted in a negative direction in the electrode containing a greater amount of the dye. These results are due to the adsorption of nitrate ions and the dye-titania complex formation on the titania particle surface. The effect of the dye-titania complex formation on the shift in the titania Conduction Band Edge was greater than that of the adsorption of nitrate ions due to strong interaction between the dye and titania through the carboxylate and quinone-like groups of the dye. The shift in the titania Conduction Band Edge corresponded to the change in the Voc value.
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Influence of Dye Content on the Conduction Band Edge of Titania in the Steam‐treated Dye‐dispersing Titania Electrodes
Photochemistry and photobiology, 2014Co-Authors: Rudi Agus Setiawan, Hiromasa Nishikiori, Nobuaki Tanaka, Tsuneo FujiiAbstract:The titania and dye-dispersing titania electrodes were prepared by a nitric acid-catalyzed sol-gel process. The dye-dispersing titania contains the dye molecules dispersed on the surface of the individual nanosized titania particles. The photo-cyclic voltammetry (Photo-CV) and photoelectric measurements of the dye-dispersing titania electrodes were conducted to clarify the factors changing the Conduction Band Edge of the titania and the open-circuit voltage (Voc ) of the electrodes. The remaining nitrate ions caused a negative shift of Conduction Band Edge of the titania of the dye-dispersing titania. The Conduction Band Edge of the titania was shifted in a negative direction in the electrode containing a greater amount of the dye. These results are due to the adsorption of nitrate ions and the dye-titania complex formation on the titania particle surface. The effect of the dye-titania complex formation on the shift in the titania Conduction Band Edge was greater than that of the adsorption of nitrate ions due to strong interaction between the dye and titania through the carboxylate and quinone-like groups of the dye. The shift in the titania Conduction Band Edge corresponded to the change in the Voc value.