A microscopic model for the current-voltage behaviour of the Na,K-pump

We have investigated the effect of the light‐induced deep‐level recombination centre specific to boron‐doped, oxygen‐contaminated Czochralski (Cz) silicon on the current–voltage characteristic of Cz silicon solar cells by means of numerical simulation and experiment. The device simulation predicts the occurrence of a shoulder in the current–voltage curve after activating the characteristic recombination centre. The physical reason for the non‐ideal diode behaviour, characterised by a local ideality factor greater unity, is the strongly injection‐level‐dependent bulk lifetime produced by the deep‐level centre. The increased ideality factor causes a degradation in fill factor with the magnitude of degradation depending on the doping concentration of the Cz silicon base. In order to verify the theoretical predictions experimentally, we have performed measurements on high‐efficiency Cz silicon solar cells. Current–voltage curves recorded before and after light degradation clearly show the theoretically predicted change in shape and the reduction in fill factor. An excellent quantitative agreement between calculation and experiment is obtained for the subtracted current–voltage curves measured after and before illumination. Copyright © 2001 John Wiley & Sons, Ltd.

A physical-chemistry study of a Nafion 117 membrane is undertaken and a correlation between the transport number and current–voltage data of this cation exchange membrane is established. The current–voltage characteristics of the membrane are obtained with the voltamperometric technique, by means of two feed platinised titanium electrodes and two measuring silver–silver chloride electrodes. Previous measurements show that the membrane presents low electrical resistance and weak permselectivity towards the proton in the presence of other metallic cations. However, its chemical modification with the conducting polymer highly improves the proton conduction and gives better selectivity towards the monovalent cation (Na+) against the divalent cation (Zn2+). The effects of the co-ion (anion), charge, solvent and chemical modification are made in evidence by the current–voltage curves. As a result of its pre-concentration near the anionic layer, the divalent cation increases the value of the limiting current density. Besides, the presence of an organic solvent inside the polymeric matrix of the membrane decreases the limiting current density. Different graphical methods are applied to deduce the limiting current density and the derivative method is found to be more reliable.

The main method for determining the semiconductor devices parameters is measuring and analytical processing of their current-voltage (CV) characteristics. Measuring complexes existing today for the implementation of this method are expensive and complex systems that are not economically profitable to use in the conditions of Ukraine production. In this work, an economical automated complex for CV characteristic measurement has been developed, based on a microcontroller control system with appropriate software, which, in connection with a computer, allows to provide express certification of solar cells and semiconductor devices by their current-voltage characteristics. The testing of the complex has been shown its ability to measure the CV characteristic with a sufficiently high accuracy with an average measurement error that does not exceed than 1%.

Analytical solutions using special trans functions theory for current–voltage expressions of perovskite solar cells and their approximate equivalent circuits

We report here the purification of glycerotoxin from the venom of Glycera convoluta, a novel 320 kDa protein capable of reversibly stimulating spontaneous and evoked neurotransmitter release at the frog neuromuscular junction. However, glycerotoxin is ineffective at the murine neuromuscular junction, which displays a different subtype of voltage- dependent Ca(2+) channels. By sequential and selective inhibition of various types of Ca(2+) channels, we found that glycerotoxin was acting via Ca(v)2.2 (N-type). In neuroendocrine cells, it elicits a robust, albeit transient, influx of Ca(2+) sensitive to the Ca(v)2.2 blockers omega-conotoxin GVIA and MVIIA. Moreover, glycerotoxin triggers a Ca(2+) transient in human embryonic kidney (HEK) cells over-expressing Ca(v)2.2 but not Ca(v)2.1 (P/Q-type). Whole-cell patch-clamp analysis of Ca(v)2.2 expressing HEK cells revealed an up-regulation of Ca(2+) currents due to a leftward shift of the activation peak upon glycerotoxin addition. A direct interaction between Ca(v)2.2 and this neurotoxin was revealed by co-immunoprecipitation experiments. Therefore, glycerotoxin is a unique addition to the arsenal of tools available to unravel the mechanism controlling Ca(2+)-regulated exocytosis via the specific activation of Ca(v)2.2.

A range of imaging agents for use in the positron emission tomography of Alzheimer's disease is currently under development. Each of the main compound classes, derived from thioflavin T (PIB), Congo Red (BSB), and aminonaphthalene (FDDNP) are believed to bind to mutually exclusive sites on the beta-amyloid (Abeta) peptide fibrils. We recently reported the presence of three classes of binding sites (BS1, BS2, BS3) on the Abeta fibrils for thioflavin T derivatives and now extend these findings to demonstrate that these sites are also able to accommodate ligands from the other chemotype classes. The results from competition assays using [3H]Me-BTA-1 (BS3 probe) indicated that both PIB and FDDNP were able to displace the radioligand with Ki values of 25 and 42 nM, respectively. BSB was unable to displace the radioligand tracer from the Abeta fibrils. In contrast, each of the compounds examined were able to displace thioflavin T (BS1 probe) from the Abeta fibrils when evaluated in a fluorescence competition assay with Ki values for PIB, FDDNP, and BSB of 1865, 335, and 600 nM, respectively. Finally, the Kd values for FDDNP and BSB binding to Abeta fibrils were directly determined by monitoring the increases in the ligand intrinsic fluorescence, which were 290 and 104 nM, respectively. The results from these assays indicate that (i) the three classes of thioflavin T binding sites are able to accommodate a wide range of chemotype structures, (ii) BSB binds to two sites on the Abeta fibrils, one of which is BS2, and the other is distinct from the thioflavin T derivative binding sites, and (iii) there is no independent binding site on the fibrils for FDDNP, and the ligand binds to both the BS1 and BS3 sites with significantly lower affinities than previously reported.

Often, a depressed fill factor is observed in organic solar cells (OSCs), which is usually known as S-shaped current-voltage (J−V) characteristics. To investigate the origin of the depressed fill factor further, a poly[N-9-heptadecanyl-2,7-carbazole-alt-5,5-(4,7-di-2-thienyl-2,1,3-benzothiadiazole)]:[6,6]-phenyl C71 butyric acid methyl ester based OSC has been characterized through impedance spectroscopy. In addition, the photocurrent vs the applied effective bias plot reveals that the S-shaped J−V characteristics primarily reduce the diffusion current of the device. The present study shows that the diffusion current dominated section of photocurrent reduces with a slope of 2 in the depressed fill factor section given that the slope may further increase as per the impact of the S-shape. The reduction in the diffusion constant (Dn) in the S-shaped region supports the decrease in the diffusion current, which is observed through the photocurrent analysis. It is observed that, in the S-shaped section of the current-voltage characteristics, the transport time for free carriers increases up to 443 μs. The larger Urbach energy for the active layer of an S-shaped device demonstrates higher subbandgap disorder. Therefore, it is concluded that the accumulation of the charge carriers within the device and disorder in the active layer leads to the S-shaped current–voltage characteristics as well as poor carrier extraction.

The current–voltage characteristic of magnetospheric magnetic flux tubes is studied under rather general conditions, assuming the current to be carried by collision‐free particles experiencing inertia, electric forces, and magnetic mirror forces. The approach is that of the powerful kinetic “orbital motion” theory of current collectors in plasma as developed by H. M. Mott‐Smith and I. Langmuir in 1926. When C. Davisson's 1925 condition on particle access is fulfilled, the total voltage drop is uniquely determined from the current by kinetic/geometric considerations only, without considerations of the actual space charge and electrostatic potential distribution. For any velocity distribution that is isotropic within the source cone, the current–voltage characteristic is linear for sufficiently small currents. The nature of the corresponding global flux tube electric resistance is discussed. The current–voltage characteristic is given for a variety of distribution functions (where the Maxwellian case corresponds to that studied by S. Knight in 1973) including distributions with a reduced (nonisotropic) flux in the source cone. The current–voltage characteristic is also discussed for cases where the Davisson condition is not fulfilled, when the solution method provides a lower bound on the voltage for a given current. Making assumptions on the altitude extent of the voltage drop, we can also define an upper bound on the voltage for a particular current. The magnetospheric source of particles should be taken to be located at the top of the acceleration region in order to fulfill the Davisson condition. This may limit the effective magnetic mirror ratio, such that the applicability of the linear approximation to the current–voltage characteristic is more restricted, and the saturation current is moderately small, which may lead to overvoltages, a redistribution of the current, or an increased extent of the acceleration region. Joining solutions that piecewise fulfill the Davisson condition, we can derive the current flow for a rather wide range of prescribed potential distributions. Earlier works on the Knight mechanism and related theories for determining the voltage drop along a flux tube are discussed. Determination of the electrostatic potential distribution, and verification of the Davisson condition, requires considerations of the space charge (Poisson equation), to be discussed in a second paper.

Deposition of earth-abundant p-type CuBr films with high hole conductivity and realization of p-CuBr/n-Si heterojunction solar cell

Analysis of temperature dependent electrical properties of Au/perylene-diimide/n-Si Schottky diodes

The principle of super-regeneration can be applied to many electronic circuits to achieve large amplifications The advent of the tunnel diode has made available a device which, by virtue of its voltage controlled negative conductance region, can be used as the active element in a simple super-regenerative amplifier. In a tunnel diode super-regenerative amplifier the quenching process, necessary to start and interrupt the oscillations periodically, is simply accomplished by moving the operating point in the current-voltage characteristics from the negative conductance region to the positive conductance region The simplicity of the circuitry associated with the tunnel diode and its low noise capabilities make tunnel diodes super-regenerative amplifiers or detectors very attractive An analysis based on well-established super-regeneration theory shows that tunnel diodes can operate reliably in the super-regenerative mode. The results of the analysis compare with experimental results with good agreement The possibility of utilizing tunnel diode super-regenerative detectors or amplifiers in practical circuitry has boon demonstrated by their incorporation, with good performance, in actual communication circuits.

The electrical and photovoltaic properties of Al-doped and undoped polyacetylene-Electrodag +502 Schottky barrier diodes have been examined. The current-voltage and capacitance-voltage characteristics at different temperatures were investigated. The dependence of short-circuit current and open-circuit voltage on the light intensity, temperature, concentration of acceptors and oxygen was also determined. The yield of light energy transformed into electrical energy around 0.1% is obtained in the best case (Voc approximately=650 mV, Jsc approximately=200 mu A cm-2, FF approximately=0.3 and Pin approximately=50 mW cm-2).

Ferroelectric photovoltaic response to structural transformations in doped BiFeO3 derivative thin films

The authors report an enhanced infrared spectral response of GaAs-based solar cells that incorporate type II GaSb quantum dots (QDs) formed using interfacial misfit array growth mode. The material and devices, grown by molecular beam epitaxy, are characterized by current-voltage and spectral response characteristics. From 0.9to1.36μm, these solar cells show significantly more infrared response compared to reference GaAs cells and previously reported InAs QD solar cells. The short circuit current density and open circuit voltages of solar cells with and without dots measured under identical conditions are 1.29mA∕cm2, 0.37V and 1.17mA∕cm2, 0.6V, respectively.

Insight into traps at Al2O3/p-GaN metal-oxide-semiconductor interface fabricated on free-standing GaN substrate