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Photocurrent spectroscopy of thin passive films
2002
Publisher Summary This chapter reviews theoretical background on the photoelectrochemistry of metal and semiconductor electrodes on which photocurrent spectroscopy (PCS) relies, by focusing particularly on new features that are typical of the photoelectrochemical behavior of thin passive films and usually absent in the behavior of bulk crystalline semiconductors. The chapter also highlights the advantages of PCS in getting in situ information on the structure of the metal-passive-film-electrolyte systems and shows a more recent quantitative use of this technique in characterizing the composition of passive films. The formation of a protective film on a metallic surface is a key step in esta…
Low-Temperature Atomic Layer Deposition of Crystalline and Photoactive Ultrathin Hematite Films for Solar Water Splitting
2015
We developed a low-temperature atomic layer deposition route to deposit phase pure and crystalline hematite (alpha-Fe2O3) films at 230 degrees C without the need for postannealing. Homogenous and conformal deposition with good aspect ratio coverage was demonstrated on a nanostructured substrate and analyzed by transmission electron microscopy. These as-deposited alpha-Fe2O3 films were investigated as photoanodes for photoelectrochemical water oxidation and found to be highly photoactive. Combined with a TiO2 underlayer and a low-cost Ni(OH)(2) catalyst, hematite films of less than 10 nm in thickness reached photocurrent densities of 0.3 mA cm(-2) at 1.23 V vs RHE and a photocurrent onset po…
First-Principles Calculations of Angle-Resolved and Spin-Resolved Photoemission Spectra of Cr(110) Surfaces at the2p−3dCr Resonance
2013
A first principles approach for spin- and angle-resolved resonant photoemission is developed within multiple scattering theory and applied to a Cr(110) surface at the 2p-3d resonance. The resonant photocurrent from this nonferromagnetic system is found to be strongly spin polarized by circularly polarized light, in agreement with experiments on antiferromagnetic and magnetically disordered systems. By comparing the antiferromagnetic and Pauli-paramagnetic phases of Cr, we explicitly show that the spin polarization of the photocurrent is independent of the existence of local magnetic moments, solving a long-standing debate on the origin of such polarization. New spin polarization effects are…
Photoelectrical Properties of the SBN Relaxor Ceramics in the Range of the Broad Phase Transition
2014
AbstractA study of the effects of white light on photocurrent kinetics and the low and infra-low frequency relaxation of polarization in the barium-strontium niobate SBN‑75 ceramics is reported. It is found that at a low intensity illumination in the range of the relaxor phase the space charge is mainly responsible for manifestation of photo-electrical properties of SBN-75 ceramics.
Structured-light imaging through scattering
2016
We present a structured illumination technique to image objects hidden beneath scattering. The sample is computationally retrieved from a known ensemble of light patterns codified onto a digital micromirror device and photocurrent fluctuations provided by a detector with no spatial resolution. Results of laboratory experiments will be shown. Article not available.
Impact of the position isomer of the linkage in the double D–A branch-based organic dyes on the photovoltaic performance
2014
Abstract Three organic dyes with double D–A system were synthesized and applied in the dye-sensitized solar cells. These dyes contain phenothiazine as an electron donor and cyanoacetic acid as an acceptor/anchor. Linkages were incorporated at the ortho-, meta- and para-positions and their impact on the performance of photovoltaic was observed. Among them, the dye with a para-position linkage exhibited the highest short-circuit photocurrent density (12.26 mA cm−2) and open-circuit photovoltage (756 mV), leading to the best overall efficiency (6.14%) due to better light harvesting capacity under standard global 1.5 AM conditions. Under similar measuring conditions the dyes with ortho and meta…
The photoelectrochemistry of thin passive layers. Investigation of anodic oxide films on titanium metal
1993
Abstract A photoelectrochemical investigation has been performed on thin TiO2 films grown anodically in 0.5 M H2SO4 solution at high growth rates. The shape of the photocurrent vs. potential curves under monochromatic irradiation (photocharacteristics) depends on the photon energy of the incident light at energies above the optical band gap of the films (3.25 ± 0.05 eV). This finding has been explained by considering the presence of geminate recombination of the photogenerated electron-hole pairs. In order to fit the experimental photocharacteristics, an expression for the photocurrent is proposed which takes into account the low drift range of photocarriers and possible recombination in th…
Electrodes for GaOHPc:PCBM/P3HT:PCBM bulk heterojunction solar cell
2012
Abstract The bulk heterojunction approach appears to be one of the most promising concepts of creating efficient, low cost and easily producible organic solar cells. For this purpose one of the best materials was regioregular poly-3-hexylthiophene (P3HT), which is widely used as a donor molecule and a hole transporter, with soluble fullerene derivative (PCBM) as an acceptor and electron transporter. The main drawback of this highly efficient blend is its limited spectral range, covering only a 350–650 nm spectral interval. So the main aim of the present work was to extend the spectral range of the cell up to 850 nm by adding a second bulk heterojunction layer of complementary absorption spe…
ChemInform Abstract: A Photocurrent Spectroscopic Study of the Initial Stages of Anodic Oxide Film Formation on Niobium.
2010
Abstract An extensive electrochemical and photoelectrochemical investigation has been carried out with very thin anodic oxide layers grown on niobium metal in sulphuric acid solutions. From the experiments the presence of an initial suboxide layer on the metal surface was inferred. Upon anodic polarization a strongly non-stoichiometric pentoxide film is formed, which is subsequently oxidized to the normal amorphous pentoxide phase (a-Nb 2 O 5 ). The use of photocurrent spectroscopy (PCS) allowed this oxidation process to be followed at various potentials and polarization times. Moreover, from the experimental results we obtain information both on the composition and the solid-state structur…
Characterization of Thin Film Cig(S,Se)2 Submodules Using Solar Simulator and Laser Beam Induced Current Techniques
2015
In this work, the electrical and optical characterization of CIG(S,Se)2 sub-modules using both a solar simulator equipment and the Laser Beam Induced Current (LBIC) technique is presented. By using the solar simulator and a proper set-up, the electrical parameters of the modules at varying irradiance and temperatures are determined. In addition, the LBIC measurements are carried out to analyze the 2D photocurrent uniformity of the modules at two different wavelengths. Dispersion values of extracted parameters can be very useful for practically tuning the modelling stage at device/module level.