Search results for "electromagnetic"
showing 10 items of 1595 documents
Structural Analysis and Photocurrent Spectroscopy of CCCs on 99.99% Aluminum
2003
A characterization of chromate conversion coatings (CCCs) formed in the presence and in the absence of accelerator (ferroferricyanide redox couple) has been performed by various techniques (transmission electron microscopy, TEM, glow discharge optical emission spectrometry, GDOES, X-ray absorption near-end structure, XANES, and photon correlation spectroscopy). The results of a detailed investigation on morphological, compositional, and solid-state properties of freshly converted aluminum samples at different immersion times (30 s-90 min) are reported. The TEM and GDOES data suggest the presence of iron-cyanide species only in the external layer of CCC of nearly constant thickness. The XANE…
Photoconductivity of Germanium Nanowire Arrays Incorporated in Anodic Aluminum Oxide
2007
Photoconductivity of germanium nanowire arrays of 50 and 100 nm diameter incorporated into Anodic Aluminum Oxide (AAO) membranes illuminated with visible light is investigated. Photocurrent response to excitation radiation with time constants faster than 10−4 s were governed by absorption of incident light by nanowires, while photokinetics with time constants of the order of 10−3 s originates from the photoluminescence of the AAO matrix. Possible applications of nanowire arrays inside AAO as photoresistors are discussed.
Photoelectrochemical investigation of passive layers formed on Fe in different electrolytic solutions
2004
Abstract The passive films formed on Fe in different electrolytic solutions, spanning almost the overall pH range, and with different growth procedures were investigated systematically by photocurrent spectroscopy. The potentiodynamic growth curves are compared both in aerated and de-aerated electrolytes and a potentiostatic growth procedure is also employed. For high positive formation potentials, similar anodic spectra are recorded in all solutions giving an optical gap very close to that expected for crystalline Fe2O3. The origin of photocurrent spikes is also investigated and the effect of the formation potential upon the measured absorption threshold is discussed taking into account th…
Impact of π-conjugation configurations on the photovoltaic performance of the quinoxaline-based organic dyes
2017
Abstract Three novel quinoxaline-based donor-π-acceptor type organic dyes were synthesized and explored as sensitizers in dye-sensitized solar cells (DSSCs). The impacts of various π-conjugation configurations which contain different quinoxaline derivatives on the absorption properties, electrochemical properties and photovoltaic performances, as well as theoretical calculations have been investigated systematically. The photovoltaic performances of these dyes were found to be highly relevant to the π-conjugated configurations. In particular, the DSSC based on the dye with 2,3-dioctylquinoxaline as the spacer exhibited the highest efficiency of 8.20% with a short-circuit photocurrent densit…
Direct measurement of optical losses in plasmon-enhanced thin silicon films (Conference Presentation)
2018
Plasmon-enhanced absorption, often considered as a promising solution for efficient light trapping in thin film silicon solar cells, suffers from pronounced optical losses i.e. parasitic absorption, which do not contribute to the obtainable photocurrent. Direct measurements of such losses are therefore essential to optimize the design of plasmonic nanostructures and supporting layers. Importantly, contributions of useful and parasitic absorption cannot be measured separately with commonly used optical spectrophotometry. In this study we apply a novel strategy consisting in a combination of photocurrent and photothermal spectroscopic techniques to experimentally quantify the trade-off betwee…
Polymer Halide Perovskites-Waveguides Integrated in Nanocellulose as a Wearable Amplifier-Photodetector System
2018
Semiconductor organometallic halide (CH 3 NH 3 PbX 3 , X=Cl, Br, I) perovskites (MHP) have emerged as a very high promising material for optoelectronics. Their large absorption coefficients, high electronic mobilities, excellent quantum yield of emission at room temperature and tunable band-gap with the composition resulted in a new generation of photovoltaics and electronic devices. In this work, HPVK materials are successfully incorporated on a nanocellulose (NC) substrate with the intention to exploit the interesting properties of HPVK materials to construct wearable devices. In particular, a bilayer Poly(methyl methacrylate) /HPVK deposited on NC resulted in a suitable waveguide to demo…
Synthesis and photovoltaic performance of asymmetric di-anchoring organic dyes
2015
Abstract Two novel metal-free organic dyes bearing two asymmetric double donor–acceptor segments were synthesized. Their physical, optical, electrochemical properties and photovoltaic performances were investigated. Compared with the mono-anchoring dye containing single donor–acceptor chain, these new dyes exhibited a broader and much stronger absorption in the light wavelength ranging from 400 to 600 nm, showed higher IPCE values and short-circuit current density, which led to more efficient photovoltaic performance. The dye with triphenylamine and phenothiazine as two electron donors and two cyanoacrylic acids as two electron acceptors exhibited an impressive power conversion efficiency o…
<title>Localized excitons in fluoroperovskite LiBaF<formula><inf><roman>3</roman></inf></formula> crystals&…
2003
Two radiating processes in LiBaF3 crystals, fast valence-core transitions (5.4 - 6.5 eV) and slow, so called self-trapped exciton luminescence (about 4.3 eV), are important for practical application. Here we present a study of 4.3 eV luminescence under X-ray excitation and photoexcitation as well as under photostimulation after X-irradiation of undoped and Ag-doped LiBaF3 crystals at various temperatures. It is shown that 4.3 eV luminescence appears under X-ray excitation at least from 85 K to 400 K in both undoped and doped crystals. In all samples studied the excitation spectra of 4.3 eV luminescence contain both the main exciton like band at the edge of fundamental absorption at about 10…
Photoluminescence activity in natural silica excited in the vacuum-UV range
1999
Abstract We report an experimental study on the optical absorption and photoluminescence detected in samples of natural silica. Our results show that the two emission bands, β (∼3.1 eV) and α E (∼4.3 eV), have an excitation profile in the vacuum ultraviolet region with a maximum at ∼7.5 eV. This excitation profile indicates that, in terms of energy levels of the luminescent defect, there is a transition from a ground state, S 0 , to a second excited state, S 2 , able to excite PL emission, in addition to the well known transition corresponding to the optical absorption band, B 2β . Our data are in a quantitative agreement with `ab initio' calculations carried out for a two-fold coordinated …
X‐ray and pulsed electron beam excited luminescence and optical absorption in KTaO 3 crystals
2005
Pulsed electron beam excited time-resolved transient absorption and luminescence have been studied in nominally pure and Li-doped KTaO3 single crystals. It is found that under electron beam excitation in nominally pure KTaO3 the absorption bands peaks at ∼0.8 eV, ∼1.1 eV and 1.7 eV whereas in KTaO3:Li at ∼1.1 eV and ∼1.7 eV. The transient absorption decay varies over the spectrum thus revealing several short-lived centers. The main luminescence peak is centred at ∼2.7 eV in all KTaO3 specimens. Luminescence decay kinetics observed for the two bands slightly differ indicating different kinds of excited states are involved. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)