| 1. |
- Stashans, Arvids, et al.
(author)
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Theoretical study of lithium intercalation in rutile and anatase
- 1996
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In: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 53:1, s. 159-170
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Journal article (other academic/artistic)abstract
- Motivated by recent developments concerning coloration and energy storage in lithium intercalated nanostructural TiO2, quantum chemical Hartree-Fock calculations have been carried out to study lithium atom intercalation in rutile and anatase. Equilibrium geometries and effective atomic charges were obtained for the rutile (110) and anatase (101) clean surfaces. Li-induced local one-electron energy levels were found in the gap between the upper valence band and the conduction band and could be attributed to Ti3+ states. The absorption energies obtained are compared with available experimental data. The equilibrium positions of the Li atom and its surrounding host atoms have been calculated for both structures. The results predict a higher possibility of lithium intercalation in the anatase structure than in rutile.
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| 2. |
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| 3. |
- Beermann, Niclas, et al.
(author)
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Photoelectrochemical studies of oriented nanorod thin films of hematite
- 2000
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In: JOURNAL OF THE ELECTROCHEMICAL SOCIETY. - : ELECTROCHEMICAL SOC INC. - 0013-4651. ; 147:7, s. 2456-2461
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Journal article (peer-reviewed)abstract
- Thin films consisting of nanorods of hematite (alpha-Fe2O3) with controlled orientation onto transparent conductive glass substrates have been tested as photoelectrochemical cells. These films allow a more efficient transport and collection of photogenera
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| 4. |
- Ding, Bangfu, et al.
(author)
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Oxygen Vacancy Effect on Photoluminescence Properties of Self-Activated Yttrium Tungstate
- 2014
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In: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 118:44, s. 25633-25642
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Journal article (peer-reviewed)abstract
- A series of single-phase yttrium tungstate powders were synthesized through solid-state reaction under air or argon atmosphere. All powders showed broad band emission in the visible light region, and the argon-calcined samples presented strong near-infrared luminescence. Moreover, the long-wave excitation bands peaking at 340, 378, 380, 490, and 523 nm depended critically on the calcination atmosphere and temperature. The emergence of these new excitation bands was ascribed to different oxygen vacancy concentrations with the analysis of the first-principle calculation, Raman and X-ray absorption fine structure spectra. The oxygen vacancies caused the reduction of the average coordination number of tungsten, and the position of the localized energy band changed with the oxygen vacancy concentration. Finally, a schematic photoluminescence excitation model was proposed via anion and cation charge transfer. The obtained results promise to be very useful in interpreting self-activated tungstate luminescence mechanism. They can also serve as guide line for tuning the luminescence performance of yttrium tungstate and related materials.
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| 5. |
- Fredin, Kristofer, et al.
(author)
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Effect on Cell Efficiency following Thermal Degradation of Dye-Sensitized Mesoporous Electrodes Using N719 and D5 Sensitizers
- 2009
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In: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 113:43, s. 18902-18906
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Journal article (peer-reviewed)abstract
- This work examines the comparative durability of two common dyes at temperatures that may be experienced during fabrication of dye-sensitized solar cells (DSCs) such as through the application of thermoplastics for encapsulation or the use of a molten solid-state hole conductor. Dye-sensitized electrodes were heated in an atmosphere of air or nitrogen and thereafter used as working electrodes in DSCs. Electrodes sensitized with N719 appeared more sensitive to thermal degradation than electrodes sensitized with D5, although absorbance measurements suggest similar first-order degradation rates for the two dyes. Intensity modulated photovoltage spectroscopy and intensity modulated photocurrent spectroscopy were used to measure the effect of heating on electron lifetime and transport. It was found that the electron diffusion length may.. be as low as 10% for heated samples, compared to that of the unheated counterpart, and therefore, we assess recombination as an additional efficiency limiting process in our experiments.
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| 6. |
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| 7. |
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| 8. |
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| 9. |
- Greijer, Helena, et al.
(author)
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Environmental aspects of electricity generation from a nanocrystalline dye-sensitized solar cell system
- 2001
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In: Renewable Energy. ; 23, s. 27-39
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Journal article (peer-reviewed)abstract
- A Life Cycle Assessment, LCA, of a nanocrystalline dye sensitized solar cell (ncDSC) system has been performed, according to the ISO14040 standard. In brief, LCA is a tool to analyse the total environmental impact of a product or system from cradle to grave. Six different weighing methods were used to rank and select the significant environmental aspects to study further. The most significant environmental aspects according to the weighing methods are emission of sulphur dioxide and carbon dioxide. Carbon dioxide emission was selected as the environmental indicator depending on the growing attention on the global warming effect. In an environmental comparison of electricity generation from a ncDSC system and a natural gas/combined cycle power plant, the gas power plant would result in 450 g CO2/kWh and the ncDSC system in between 19–47 g CO2/kWh. The latter can be compared with 42 g CO2/kWh, according to van Brummelen et al. “Life Cycle Assessment of Roof Integrated Solar Cell Systems, (Report: Department of Science, Technology and Society, Utrecht University, The Netherlands, 1994)” for another thin film solar cell system made of amorphous silicon. The most significant activity/component contributing to environmental impact over the life cycle of the ncDSC system is the process energy for producing the solar cell module. Secondly comes the components; glass substrate, frame and junction box. The main improvement from an environmental point of view of the current technology would be an increase in the conversion efficiency from solar radiation to electricity generation and still use low energy demanding production technologies. Also the amount of material in the solar cell system should be minimised and designed to maximise recycling.
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| 10. |
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| 11. |
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| 12. |
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| 13. |
- He, JJ, et al.
(author)
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Dye-sensitized nanostructured p-type nickel oxide film as a photocathode for a solar cell
- 1999
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In: JOURNAL OF PHYSICAL CHEMISTRY B. - : AMER CHEMICAL SOC. - 1089-5647. ; 103:42, s. 8940-8943
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Journal article (peer-reviewed)abstract
- Nanostructured NiO film was prepared by depositing nickel hydroxide slurry on conducting glass and sintering at 500 degrees C to a thickness of about 1 mu m. The photocurrent-voltage (IV) characteristics of the plain nanostructured NiO electrode recorded
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| 14. |
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| 15. |
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| 16. |
- Hinkley, James T., et al.
(author)
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Prospects for solar only operation of the hybrid sulphur cycle for hydrogen production
- 2011
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In: International journal of hydrogen energy. - : Elsevier BV. - 0360-3199 .- 1879-3487. ; 36:18, s. 11596-11603
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Journal article (peer-reviewed)abstract
- The hybrid sulphur process is one of the most promising thermochemical water splitting cycles for large scale hydrogen production. While the process includes an electrolysis step, the use of sulphur dioxide in the electrolyser significantly reduces the electrical demand compared to conventional alkaline electrolysis. Solar operation of the cycle with zero emissions is possible if the electricity for the electrolyser and the high temperature thermal energy to complete the cycle are provided by solar technologies. This paper explores the possible use of photovoltaics (PV) to supply the electrical demand and examines a number of configurations. Production costs are determined for several scenarios and compared with base cases using conventional technologies. The hybrid sulphur cycle has promise in the medium term as a viable zero carbon production process if PV power is used to supply the electrolyser. However, the viability of this process is dependent on a market for hydrogen and a significant reduction in PV costs to around $1/W(p).
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| 17. |
- Johansson, Malin B., et al.
(author)
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The Importance of Oxygen Vacancies in Nanocrystalline WO3−x ThinFilms Prepared by DC Magnetron Sputtering for Achieving High Photoelectrochemical Efficiency
- 2017
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In: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 121:13, s. 7412-7420
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Journal article (peer-reviewed)abstract
- The photoelectrochemical properties of tungsten oxide thinfilms with different stoichiometry (WO3−x) and thickness were investigated.The films were sputtered in O2/Ar gas (ratio 0.43) on glass substrates coatedwith fluorine-doped tin dioxide at two sputter pressures, Ptot = 10 and 30mTorr, yielding O/W ratios of the films, averaged over three samples, of 2.995and 2.999 (x ∼ 0.005 and x ∼ 0.001), respectively. The films were characterizedby X-ray diffraction, scanning electron microscopy, and spectrophotometry.The 10 mTorr samples showed large absorption in the near-infrared (NIR)range, whereas the 30 mTorr samples had a small absorption in this region. Theconcentration of oxygen vacancy band gap states was estimated from cyclicvoltammetry and was found to correlate with the optical absorption in the NIRregion. The incident photon to current efficiency for illumination from theelectrolyte side (IPCEEE) and substrate electrode side (IPCESE) showed higherefficiency for the more stoichiometric films, indicating that oxygen vacancies in the band gap act as recombination centers.Surprisingly high values of IPCEEE and IPCESE were found, and it was concluded that efficient charge separation and transporttake place almost throughout the entire film even for film electrodes as thick as 2 μm. Analysis of the spectral distribution of thephotoresponse (action spectra) using an extended Gärtner−Butler model to calculate the IPCE for front-side and back-sideillumination was performed and showed that the diffusion length is large, of the order of the depletion layer thickness.
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| 18. |
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| 19. |
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| 21. |
- Larsson, Ted, et al.
(author)
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Electron transfer between cellobiose dehydrogenase and graphite electrodes
- 1996
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In: Analytica Chimica Acta. - : Elsevier. - 0003-2670 .- 1873-4324. ; 331:3, s. 207-215
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Journal article (peer-reviewed)abstract
- Electron transfer between the enzyme cellobiose dehydrogenase (CDH) and a flavin adenine dinucleotide (FAD) containing a catalytic active fragment of CDH (FAD-fragment) and a graphite electrode, respectively, was established. The current response in the presence of the enzyme substrate for graphite electrodes with CDH or the FAD-fragment adsorbed on the freshly polished graphite surface were compared with that of electrodes where CDH or the FAD-fragment were crosslinked in a redox polymer at the electrode surface. The initial slope, dj/d[S](S=0), where j is the current density and [S](S=0) the zero substrate concentration, was taken as a measure of the substrate response. For the electrodes with enzymes adsorbed directly on the surface, dj/d[S](S=0), was a factor of 3 lower than for electrodes prepared with the polymer mixture. The redox polymer based electrodes, with CDH and with FAD-fragment, both showed a high and close to equal substrate response. In contrast the surface adsorbed CDH gave a much higher substrate response than the FAD-fragment.
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| 22. |
- Li, Min, et al.
(author)
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Microsized BiOCl Square Nanosheets as Ultraviolet Photodetectors and Photocatalysts
- 2016
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In: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 8:10, s. 6662-6668
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Journal article (peer-reviewed)abstract
- BiOCl microstructures that include microspheres stacked by nanosheet and microsized square nanosheets, with a large lateral size of 3-5 mu m and a thickness of 35 nm (the side length/thickness ratio is similar to 100), are synthesized by a solvothermal method with the assistance of polyvinylpyrrolidone. The exposed face of the large square nanosheet is {001} facet. The BiOCl microstructures show good photocatalytic activity toward decomposition of Rhodamine B under ultraviolet-visible light irradiation. Moreover, individual microsized BiOCl square nanosheets are employed as the building block for construction of an ultraviolet photodetector. Because of its large size, thin thickness, and high surface-to-volume ratio, a BiOCl nanosheet shows high sensitivity and fast transient response to ultraviolet light in the spectral range 200-380 nm.
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| 23. |
- Lindblom, Torbjörn, 1938-
(author)
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Reactions in the System Nitro-cellulose/ Diphenylamine with Special Reference to the Formation of a Stabilizing Product Bonded to Nitro-cellulose
- 2004
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Doctoral thesis (other academic/artistic)abstract
- The methods HPLC, microcalorimetry and FTIR together with chemometry, provide good analytical tools to follow the degradation of nitro-cellulose.The degradation products formed from diphenylamine (DPA) during storage can be followed with HPLC. FTIR, together with chemometry, also gives the precision needed for safety control of propellants.Nitro-cellulose (NC) containing DPA obtained a green colour already after 1 day storage at 70°C. About 10% of the stabilizer, and its derivatives, added were not extractable giving an extended time to autocatalysis. This time could be extended up to 70 days at 70°C for an extracted sample compared to about 3 days for non-stabilized NC. This was not shown before.Aged and extracted NC samples contained a non-extractable nitro compound. The most likely compound is 2,4´-dinitroDPA, probably bonded to NC via the amine nitrogen. The bonding to NC occurs after the formation of NNODPA. This is something not described before.Using another batch of nitro-cellulose to find out if a chemical bonding occurs gave inconclusive results as a blue NC was formed. Low molecular NC with high stability was obtained. A chemical bonding probably occurs when using NNODPA as a stabilizer, indicating NNODPA plays a key role.The use of FTIR/chemometry is a promising method to use when studying small chemical changes. The described methodology should be used to find out more about the compound(s) being bonded to NC.
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| 24. |
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| 26. |
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| 27. |
- Lindgren, Torbjörn, 1972-
(author)
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In Search of the Holy Grail of Photoelectrochemistry : A Study of Thin Film Electrodes for Solar Hydrogen Generation
- 2004
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Doctoral thesis (other academic/artistic)abstract
- Hydrogen is a wanted energy carrier in a future society less dependent of fossil fuels. This thesis investigates the possibilities of using solar energy to convert water into hydrogen and oxygen, so called artificial photosynthesis. Through this work multiple inexpensive and stable thin film semiconductor electrodes have been produced and used as solar energy absorbers and active sites for direct watersplitting in photoelectrochemical cells. The electrodes have mainly been of nanostructured metal oxide character but also nitrides have been studied. Detailed back ground theory on photoelectrochemistry of semiconductors for hydrogen evolution is given in the summary of the thesis.Nanostructured WO3 electrodes with a quantum yield close to unity were designed and photoelectrochemically characterized. Hematite, α-Fe2O3, nanorods were synthesized and characterized for the aim of water oxidation. The morphology of the hematite nanorods was found to be in favor of the traditional isotropic nanostructured electrodes. Moreover, a unique porous nitrogen doped TiO2 material, photoactive in visible light, was obtained by reactive sputtering. The nitrogen doped material has interesting photoelectrochemical properties and is also promising for related applications such as pollution degradation by photocatalysis. Polycrystalline indium nitride, InN, was produced by reactive sputtering. Electrodes of the as prepared InN as well as electrodes annealed in nitrogen were studied for the aim of photooxidation of water.The electrodes studied are interesting candidates as potential watersplitting electrodes in photoelectrochemical cells, even if all had in common that further improvements and optimizations need to be done.
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| 28. |
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| 29. |
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| 30. |
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| 31. |
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| 32. |
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| 33. |
- Lindquist, Sten-Eric
(author)
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Wired Enzyme Electrodes : A Retroperspective Story about an Exciting Time at University of Texas at Austin and Its Impact on My Scientific Career
- 2013
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In: ChemPhysChem. - : Wiley. - 1439-4235 .- 1439-7641. ; 14:10, s. 2081-2088
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Journal article (peer-reviewed)abstract
- The present paper features an exciting time in the late 1980s when I, as a visiting scientist, had the privilege to participate in the early and very exciting development of the in vivo redox-polymer-wired glucose sensor in Professor Adam Heller's laboratory at the Department of Chemical Engineering at University of Texas at Austin. This story is followed by an overview of the research my visit initiated at Uppsala University. In collaboration with Swedish colleagues, we explored a few of the many possibilities to form new biosensors by utilizing Prof. Heller's concept of cross-linked redox-polymer/redox-enzyme electrodes.
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| 34. |
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| 35. |
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| 36. |
- Mwabora, Julius M., et al.
(author)
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Structure, Composition and Morphology of Photoelectrochemically Active TiO2-xNx Thin Films Deposited by Reactive DC Magnetron Sputtering
- 2004
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In: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 108:52, s. 20193-20198
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Journal article (peer-reviewed)abstract
- Films of nitrogen-doped TiO2 were made by reactive DC magnetron sputtering in a mixture of argon, oxygen, and nitrogen. The nitrogen gas ratio Φ was varied in the 0 < Φ < 0.025 range during the depositions, resulting in TiO2-xNx films with 0 ≤ x ≤ 0.022 as determined by X-ray photoelectron spectroscopy. Structural and morphological properties of the films were investigated by X-ray diffraction, atomic force microscopy, and scanning and transmission electron microscopy. Films prepared without nitrogen had a rutile structure, while the nitrogen-doped films were either rutile or anatase depending on Φ being below or above ∼0.007. Deposition rate, effective grain size, root-mean-square roughness, morphology, and optical absorption were also found to depend on Φ. The films were photoelectrochemically active, as reported in an earlier papers of ours [J. Phys. Chem. B 2003, 107, 5709-5716 and J. Phys. Chem. B 2004, 108, 5995-6003].
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| 37. |
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| 38. |
- Rensmo, Håkan, et al.
(author)
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High light-to-energy conversion efficiencies for solar cells based on nanostructured ZnO electrodes
- 1997
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In: Journal of Physical Chemistry B. - : AMER CHEMICAL SOC. - 1520-6106 .- 1520-5207. ; 101:14, s. 2598-2601
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Journal article (other academic/artistic)abstract
- Photoelectrochemical properties of nanostructured ZnO thin film electrodes have been investigated in the UV and visible regions. For films consisting of 15 nm large undoped crystallites a maximum monochromatic current conversion efficiency of 58% was obtained in the visible using a ruthenium-based dye as a sensitizer. The overall solar energy conversion efficiency for this film was 2%. In comparison, sensitized films consisting of 150 nm large Al-doped crystallites yield a monochromatic current conversion efficiency of 31% and an overall solar energy conversion efficiency of 0.5%. The study also shows that nanostructured ZnO may give high efficiencies in the UV region, approaching unity for the Al-doped films.
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| 39. |
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| 40. |
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| 41. |
- Vayssieres, Lionel, et al.
(author)
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Three-dimensional array of highly oriented crystalline ZnO microtubes
- 2001
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In: Chemistry of Materials. - : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 13:12, s. 4395-4398
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Journal article (peer-reviewed)abstract
- The ability to generate homogeneous particulate thin films of highly orientedand highly porous microparticles of a post transition metal oxide onto polycrystalline and single-crystalline substrates, at low cost, by a template-free, aqueous low-temperature coating process is demonstrated by the fabrication of a large three-dimensional array ofperpendicularly oriented hexagonal microtubes of crystalline zincite ZnO from an aqueous solution of zinc nitrate and methenamine.
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| 42. |
- Waita, Sebastian M., et al.
(author)
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Electron transport and recombination in dye sensitized solar cells fabricated from obliquely sputter deposited and thermally annealed TiO2 films
- 2007
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In: Journal of Electroanalytical Chemistry. - : Elsevier BV. - 1572-6657 .- 0022-0728 .- 1873-2569. ; 605:2, s. 151-156
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Journal article (peer-reviewed)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.
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| 43. |
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