The photoelectrochemical properties of tungsten oxide thin films with different stoichiometry (WO3-x) and thickness were investigated. The films were sputtered in O-2/Ar gas (ratio 0.43) on glass substrates coated with fluorine-doped tin dioxide at two sputter pressures, P-tot = 10 and 30 mTorr, yielding O/W ratios of the films, averaged over three samples, of 2.995 and 2.999 (x similar to 0.005 and x similar to 0.001), respectively. The films were characterized by 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. The concentration of oxygen vacancy band gap states was estimated from cyclic voltammetry and was found to correlate with the optical absorption in the NIR region. The incident photon to current efficiency for illumination from the electrolyte side (IPCEEE) and substrate electrode side (IPCESE) showed higher efficiency 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 transport take place ahnost throughout the entire film even for film electrodes as thick as 2 mu m. Analysis of the spectral distribution of the photoresponse (action spectra) using an extended Gartner Butler model to calculate the IPCE for front-side and back-side illumination was performed and showed that the diffusion length is large, of the order of the depletion layer thickness.

BiOCl microstructures that include microspheres stacked by nanosheet and microsized square nanosheets, with a large lateral size of 3-5 μm and a thickness of 35 nm (the side length/thickness ratio is ∼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.

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.

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.

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). Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

In this article, we discuss the use of photoelectrochemical cells for the production of hydrogen from water using sunlight as the energy source. This process, often termed photoelectrolysis or direct water splitting, offers the potential to produce hydrogen directly from sunlight without an expensive solid-state photovoltaic junction and without the losses associated with coupling to an external energy source. While the technology has been demonstrated, it is not yet economically competitive with other sources of hydrogen and will remain so until a number of technical challenges have been overcome. Here we introduce the basic operation of a solar water-splitting cell as well as issues that limit the efficiency and some common approaches to maximizing its performance.

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.

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.

Thin films of indium nitride, InN, were produced by reactive magnetron DC sputtering. By post treatment in dinitrogen, N-2, in the temperature range 350-500 degrees C a set of films gradually going from InN to indium oxide, In2O3 was obtained (due to dioxygen impurities in the annealing gas). Those films were characterized by X-ray diffraction, optical-, resistivity- and photoelectrochemical measurements for the aim of direct watersplitting in a photoelectrochemical cell.Surprisingly, the caused change in the film composition by annealing gave no significant change in the room temperature resistivity, but the free electron density and the optical properties were affected. In 0.1 M NaOH annealing improved the photoresponse of the thin films. A pronounced optimum was observed for films annealed at 425 degrees C. Even for those films the quantum efficiency was low; at most 2% of the photons at 350 nm were transformed into readable photoelectrons. The onset wavelength for photocurrent was located around 600 run (2.1 eV), which is far off from the onset of absorption 900 nni (1.4 eV). (c) 2005 Elsevier B.V. All rights reserved.

AbstractFor Abstract see ChemInform Abstract in Full Text.

DC sputter deposited TiO2 photoelectrodes: Effect of deposition angle on the efficiency of dye sensitized solar cell. ISES Solar World Congress 2003, Goteborg, Sweden, Paper W5.12. June 14-19, 2003.

The invention provides a device for obtaining an improved efficiency in a photovoltaic, nanostructured, dye sensitized cell structure, comprising a photoactive working electrode, a counter electrode and an electrolyte arranged there-between. The cell structure thereby forms a tandem cell in that the counter-electrode also is a photoactive electrode, whereby the photoactive working electrode and/or the photoactive electrode are built on a transparent substrate. Furthermore, both the photoactive working electrode and the photoactive electrode are made of porous nanostructured film and the photoactive working electrode is dye sensitized with a first dye. The first dye is selected such that the electron injection into the working electrode is so fast that the red-form of a redox-couple in the electrolyte as fast as possible replaces an injected electron. The second dye is selected such that it has a long lived excited state. In this case the material in the counter electrode is comprised of a semiconductor having a large band gap. In an alternative embodiment, the working electrode is dye sensitized corresponding to the first embodiment, whereas the counter electrode is comprised of a semiconductor with a band gap having absorption in the visible and/or IR region, whereby the light absorption in this electrode is further enhanced by a dye having been adsorbed onto the surface of the electrode.

A new concept 1 has been developed in order to achieve a new generation of materials (i.e. purpose-built nanomaterials), modelled and designed to match the physical and structural requirements of its applications. This concept, well sustained by a thermodynamic model 2 based on the monitoring of the nucleation, growth and ageing process through the control of the interfacial tension of the system allows to control the particle size and their surface morphology as well as the ability to thermodynamically stabilised metastable phases in solution 3 . The outcome of such concept is of great interest both for fundamental and applied research purposes since the influence of parameters such as particle size, orientation and surface morphology, film texture and porosity for instance on the electronic structure and/or catalytic activity of metal oxide materials may be probed and demonstrated. Moreover, designing well controlled materials allows to tune and optimise the physical properties of existing devices as well as creating novel improved devices. This concept, well illustrated on the controlled growth of spinel iron oxide (Fe3O4) nanoparticles in aqueous solution 4 , has been successfully applied to the development of novel designed materials such as large arrays of oriented nanofibers of iron(III) oxide (hematite) and ZnO (zincite) microtubes and microfibers on various substrate such as conducting glass, Si wafers for photovoltaic and photoelectrochemical devices 5 likewise large arrays of nanostructured hydrated ruthenium dioxide deposited on Teflon and polypropylene substrate as electrocatalysts and electrochemical capacitors 6 . New directions and applications such as, for instance, electrochromic devices 7 as well as nanostructured chemical and gas sensors are

A process for producing at least one epitaxial, nanostructured thin film of metal oxide and/or a hydrated metal oxide on at least one substrate placed in a container and a substrate/thin film thereof, comprises placing the substrate at any location in the container contg. a water soln., such that a covering area of the substrate being covered by the soln., contg. at least one metal salt and addnl. can contain other salts, pH-regulator(s), complexant(s), or mols., whereby from the substrate particles of a metal oxide of the metal from the metal salt is grown, forming the film on the covering area of the substrate. For a substrate (F-doped Sn oxide) for use as a solar cell, the oriented particles in the film have a photoactive component attached thereon, the fibers being arranged substantially perpendicular to the substrate.