Search results for "electronics"
showing 10 items of 4340 documents
Metal Chalcohalides: Next Generation Photovoltaic Materials?
2021
Metal chalcohalides have recently been highlighted as so-far overlooked semiconductors that could play an important role in the future of photovoltaics (PV). Indeed, the blooming field of emergent PV technologies is still in search for stable, efficient, and environmentally-friendly light-harvesting materials to be used either in single-junction solar cells or multijunction devices in combination with silicon or another absorbers. Under the broad terms of metal chalcohalides, there exists a plethora of semiconductor materials with different chemical, structural, and optoelectronic characteristics. While some have already been implemented in solar cells with power conversion efficiencies up …
Sloped-wall thin-film photonic crystal waveguides
2005
The effect of the slope of the groove walls in the behavior of thin-film one-dimensional photonic crystal waveguides is extensively studied. In this respect, we point out its influence on the modal dispersion relations and then on the bandgap structure in general. Likewise, we also prove the lack of accuracy in the evaluation of the bandgap edges when material dispersion is ignored. The extreme importance of both facts, the wall slope and the material dispersion, in the analysis and design of realistic photonic crystal devices is emphasized. In particular, we exploit the wall slope as a new design parameter. By suitably choosing the value of the above parameter, sloped-wall photonic crystal…
Transmission anisotropy in triple-film opal photonic crystals
2006
Summary form only given: For photonic crystals (PhCs) to have successful impact on advancement of optical circuits and realisation of various functionalities, the incorporation of artificial defects into 3D PhCs is necessary. Opal films represent a convenient approach to the realisation of 3D PhCs. Taking into account the limited flexibility of the self-assembly, the first steps can be studies of planar defects in opals and hetero-opals. Characterisation of heteroPhCs should include the investigation of the dispersion of photonic bandgaps (PBG). While the dispersion of low-order PBGs in opal films is well known, the high order PBGs were hardly studied so far owing to high requirements to th…
Tuning the hole injection barrier in the intermolecular charge-transfer compoundDTBDT-F4TCNQ at metal interfaces
2014
Molecular monolayers of the charge-transfer salt dithienobenzodithiophene-tetrafluorotetracyanoquinodimethane (DTBDT-F${}_{4}$TCNQ) have been deposited on C(R$15\ifmmode\times\else\texttimes\fi{}3$)/W(110), Co/W(110), and hcp Co(0001) using molecular beam epitaxy in an ultrahigh vacuum. The integrity of the deposited molecules has been confirmed by scanning tunneling microscopy. Scanning tunneling spectroscopy has been used to determine the energetic positions of the highest occupied (HOMO) and lowest unoccupied (LUMO) molecular orbital of acceptor and donor in the pure and in the mixed phase. The mixed charge transfer phase exhibits a new HOMO close to the Fermi edge depicting a charge tra…
FAPb0.5Sn0.5I3: A Narrow Bandgap Perovskite Synthesized through Evaporation Methods for Solar Cell Applications
2020
The tunability of the optoelectrical properties upon compositional modification is a key characteristic of metal halide perovskites. In particular, bandgaps narrower than those in conventional lead‐based perovskites are essential to achieve the theoretical efficiency limit of single‐absorber solar cells, as well as develop multijunction tandem devices. Herein, the solvent‐free vacuum deposition of a narrow bandgap perovskite based on tin-lead metal and formamidinium cation is reported. Pinhole‐free films with 1.28 eV bandgap are obtained by thermal codeposition of precursors. The optoelectrical quality of these films is demonstrated by their use in solar cells with a power conversion effici…
Broadband microwave gas sensor: A coaxial design
2010
The method of gas detection by a broadband microwave gas sensor is presented in this article. The principle of this method is to use a sensitive material as substrate of a transmission coaxial line. The sensor represents an open line with an extreme surface in contact with gas. The interaction with the gas and the surface induces a dielectric variation of the substrate. From experimental results, the interaction between the sensitive material and each tested gas present a specific frequency spectrum of the reflection coefficient at the input of the line. The proposed method has the advantage of a compact size, wide bandwidth, simple structure, and capable with all sensitive materials. © 201…
Homogeneous and inhomogeneous broadening in single perovskite nanocrystals investigated by micro-photoluminescence
2021
Abstract Metal halides with perovskite crystalline structure have given rise to efficient optoelectronic and photonic devices. In the present work, we have studied the light emission properties of single CsPbBr3 and CsPbI3 semiconductor perovskite nanocrystals (PNCs), as the basis for a statistical analysis of micro-photoluminescence (micro-PL) spectra measured on tens of them. At room temperature, the linewidth extracted from PL spectra acquired in dense films of these nanocrystals is not very different from that of micro-PL measured in single nanocrystals. This means that the homogeneous linewidth due to exciton-phonon interaction is comparable or larger than the inhomogeneous effect asso…
Tuning the propagation constant by the anti-crossing bandgap prism coupling technique.
2012
A novel plasmonic structure based on an anticrossing bandgap prism coupling technique is proposed. The study has been carried out using photonic crystals based on diffraction gratings (bounded by dielectrics with identical dielectric functions) together with a high refractive index prism to couple the long-range surface plasmon polaritons to photons. We analyse the structure and demonstrate the ability for tuning the propagation constants of plasmon modes by changing the thickness of the gold grating. The comparison to non-bandgap techniques is studied, and the influence of the plasmonic configuration on the plasmon propagation constant is discussed as well. Experimental measurements were a…
Tenfold increase in efficiency from a reference blue OLED
2018
Abstract Starting from a reference single-layer light-emitting diode based on the blue phosphorescent bis-cyclometallated iridium complex FIrpic as guest, hosted in a PVK (non-conjugated poly(vynilcarbazole)) matrix, different strategies are followed to improve the efficiency of the devices through the combination of solution processed and evaporated layers. Injection of charges from the electrodes has been varied by using different conductive PEDOT: PSS as hole injection layer and a nanoscale Cs2CO3 interlayer as electron injection and hole-blocking film. Furthermore, a separated electron injection/hole blocking evaporated layer, TPBi or 3TPYMB, is introduced in double-layer devices to enh…
NEUTRON IRRADIATION EFFECTS IN PZ and PZT THIN FILMS
2005
ABSTRACT Neutron irradiation effects on highly oriented antiferroelectric PbZrO3 (PZ) and ferroelectric PbZr0.53Ti0.47O3 (PZT) thin films are investigated in view of their possible application as a temperature sensitive element in a new bolometer system for fusion devices like ITER. All investigated thin films were prepared by a sol-gel technique and by pulsed laser deposition (PLD) respectively. The dielectric properties were investigated in a frequency range from 1 to 250 kHz and at temperatures up to 400°C, prior to and after irradiation to a neutron fluence of 3 * 1022 m−2 (E > 0.1 MeV). After irradiation, the films were anneald in several steps up to 400°C in order to remove the radiat…