Search results for "Current Density"
showing 10 items of 99 documents
Preferred Growth Direction by PbS Nanoplatelets Preserves Perovskite Infrared Light Harvesting for Stable, Reproducible, and Efficient Solar Cells
2020
Formamidinium-based perovskite solar cells (PSCs) present the maximum theoretical efficiency of the lead perovskite family. However, formamidinium perovskite exhibits significant degradation in air. The surface chemistry of PbS has been used to improve the formamidinium black phase stability. Here, the use of PbS nanoplatelets with (100) preferential crystal orientation is reported, to potentiate the repercussion on the crystal growth of perovskite grains and to improve the stability of the material and consequently of the solar cells. As a result, a vertical growth of perovskite grains, a stable current density of 23 mA cm(-2), and a stable incident photon to current efficiency in the infr…
Understanding the ring current effects on magnetic shielding of hydrogen and carbon nuclei in naphthalene and anthracene
2008
The local response to an external magnetic field normal to the molecular plane of naphthalene and anthracene was investigated via current density and magnetic shielding density maps. The Biot-Savart law shows that the deshielding caused by pi-ring currents in naphthalene is stronger for alpha- than for beta-protons due to geometrical factors. The shielding tensor of the carbon nuclei in both molecules is strongly anisotropic and its out-of-plane component determines the up-field chemical shift of (13)C in nuclear magnetic resonance spectra. The pi-ring currents flowing beyond the C-skeleton in front of a probe carbon nucleus, and on remote parts of the molecular perimeter, yield positive co…
Structural characterization and electrochemical hydrogen storage properties of Ti2LxZrxNi (x [ 0, 0.1, 0.2) alloys prepared by mechanical alloying
2013
International audience; Nominal Ti2Ni was synthesized under argon atmosphere at room temperature using a planetary high-energy ball mill. The effect of milling time and Zr substitution for Ti on the microstructure was characterized by XRD, SEM and TEM, and the discharge capacities of Ti2xZrxNi (x 1/4 0, 0.1, 0.2) were examined by electrochemical measurements at galvanostatic conditions. XRD analysis shows that amorphous phase of Ti2Ni can be elaborated by 60 h of milling, whereas Zr substitution hinders amorphization process of the system. The products of ball milling nominal Ti2xZrxNi (x 1/4 0.1, 0.2) were austenitic (Ti, Zr)Ni and partly TiO, despite the fact that the operation was carrie…
Current rectification in a single molecule diode: the role of electrode coupling.
2015
We demonstrate large rectification ratios (> 100) in single-molecule junctions based on a metal-oxide cluster (polyoxometalate), using a scanning tunneling microscope (STM) both at ambient conditions and at low temperature. These rectification ratios are the largest ever observed in a single-molecule junction, and in addition these junctions sustain current densities larger than 10^5 A/cm^2. By following the variation of the I-V characteristics with tip-molecule separation we demonstrate unambiguously that rectification is due to asymmetric coupling to the electrodes of a molecule with an asymmetric level structure. This mechanism can be implemented in other type of molecular junctions u…
Theoretical study on the influence of electric field direction on the photovoltaic performance of aryl amine organic dyes for dye-sensitized solar ce…
2019
It is very important to reveal the influence of different electric field directions on dye sensitizers. Thus, in this study, we investigated the electronic structures and optical properties of six designed aryl amine organic dye models under different electric fields using density functional theory (DFT) and time-dependent density functional theory (TD-DFT). Moreover, the electronic structures and optical properties of these studied dyes with different electric field in tetrahydrofuran (THF) were also calculated. The key parameters of the short-circuit current density (Jsc), including light harvesting efficiency (LHE) and intra-molecular charge transfer (ICT), are discussed in detail. With …
Effect of mode of operation, substrate and final electron acceptor on single-chamber membraneless microbial fuel cell operating with a mixed community
2018
Abstract Waste minimization and circular thinking are to be achieved in order to cope with the limited amount of resources of our planet. In this perspective, bio-electrochemical systems (BESs) can contribute to the global balance with their ability to extract chemical residual energy from wastewater and transform it directly into electrical current. BESs development has been limited by the cost connected to reactor design, in which membranes and cathode catalyst constituted a major drawback. In this paper we report the optimization process of a simple reactor without membranes or precious catalyst that produced 47.1 mW m−2, which is more than what achieved with configurations including mem…
Winding loss analysis and optimization of an AC inductor for a galvanically isolated PV inverter
2012
This paper describes simple treatments for fringing fields of air gaps in the core and bypass fluxes in the winding window area of an existing high frequency AC inductor used by a commercial developer of PV inverters. For this purpose, Maxwell (ANSOFT) electromagnetic software package is used for winding eddy current loss analysis. It is displayed that air gaps cause high flux strength and, therefore, induce significantly high eddy currents to the surrounded windings. Proximity effect also causes non uniform current density in the winding. Altogether, the inductor is affected by fringing fields, and proximity effect produces a very high AC resistance, consequently resulting in undesirable h…
The use of non-cavitating coupling fluids for intensifying sonoelectrochemical processes
2020
Abstract For the first time, we have investigated the beneficial effects of non-cavitating coupling fluids and their moderate overpressures in enhancing mass-transfer and acoustic energy transfer in a double cell micro-sonoreactor. Silicon and engine oils of different viscosities were used as non-cavitating coupling fluids. A formulated monoethylene glycol (FMG), which is a regular cooling fluid, was also used as reference. It was found that silicon oil yielded a maximum acoustic energy transfer (3.05 W/cm2) from the double jacketed cell to the inner cell volume, at 1 bar of coupling fluid overpressure which was 2.5 times higher than the regular FMG cooling fluid. It was also found that the…
CFD prediction of concentration polarization phenomena in spacer-filled channels for Reverse Electrodialysis
2014
Abstract Salinity Gradient Power generation through Reverse Electrodialysis (SGP-RE) is a promising technology to convert the chemical potential difference of a salinity gradient into electric energy. In SGP-RE systems, as in most membrane processes, concentration polarization phenomena may affect the theoretical driving force and thus the performance of the process. Operating conditions, including the feed solution flow rate and concentration and the channels׳ geometrical configuration, may greatly influence both the polarization effect and the pumping energy consumption. The present work uses CFD to investigate the dependence of concentration polarization and pressure drop on flow rate, f…
Relation between microstructure and transport properties of epitaxial YBa2Cu3O7-d thin films.
1997
Abstract In order to understand the origin of the high critical current densities observed in thin superconducting films compared to single crystals we measured in several epitaxial YBa 2 Cu 3 O 7−δ thin films the magnetic field and temperature dependence of the superconducting current density j s and the dynamical relaxation rate Q ≡ d ln j s / d ln( d B/ dt ). For all samples we found that (i) the superconducting current density j s is independent of magnetic field up to a certain field B Φ . The value of this field, which is sample dependent, decreases with increasing temperature; (ii) for fields B>B Φ , the superconducting current density falls off as B −1/2 over several decades; (iii) …