Narrow Results

Au/P3HT (poly [3-hexylthiophene])/n-type crystalline silicon (n-c-Si) solar cells have been fabricated. The Aluminum back contact is obtained by evaporation on silicon substrate. An 80 nm P3HT layer thick was spin-coated on silicon substrate followed by thermal annealing. Finally golden contacts are deposited by sputtering. The best characteristics of this flawed solar cell are: V_oc=0.47 V, I_sc=7.42 mA/cm² and an efficiency of 1.29%. The area of this device is 0.07 cm². In order to get a deep understanding of the electrical properties of the heterojunction, capacitance-voltage and current-voltage-temperature measurements have been made. A compact electrical equivalent circuit has been used to describe the dark current-voltage characteristics. It is based on the combination of two exponential mechanisms, shunt and series resistances and space-charge limited current terms. From the temperature dependence of the extracted parameters we can obtain the limiting conduction mechanism. We found that the polymeric layer limits the current not only at low voltages, through Multi-Tunneling Capture Emission, but also at high voltages, through series resistance and Space-Charge Limited Current. On the other hand, the Silicon wafer limits the current at medium voltages, through the diffusion mechanism. In addition, the model is useful to estimate the open circuit voltage and built in voltage of the solar cell using only dark current voltage measurements.

Impedance spectroscopy studies of calcium doped (Ca=0.01, 0.05, 0.1) sodium bismuth titanate (NBT), that is, (Na_1/2Bi_1/2)_1-xCa_xTiO₃ (NBCT) solid solution are studied as a function of temperature (RT — 575°C) and frequency (100 Hz–1 MHz). The electrical properties and equivalent circuit parameters of Ca doped NBT, and it's bulk and grain boundary effects are studied with impedance spectroscopy as a non-destructive testing tool.

For film deposition, the substrate sheath properties, such as the plasma density, ion-to-atom ratios around the substrate, are more important for the film structure. In this paper, titanium thin films were deposited on grounded substrates by high-power pulsed magnetron sputtering (HPPMS) with the peak current in the range of 113–185 A. A simple and new equivalent circuit model of the sheath was established to study the plasma density around the substrate sheath. The Ti ion-to-atom ratios near substrate were studied by optical emission spectroscopy (OES), and the film structure was detected by transmission electron microscopy (TEM). The results showed that the calculated plasma density was from 0.8 × 10${}^{17}$ to 1.4 × 10${}^{17}$ m${}^{-3}$ at different peak current. These were consistent with the results measured by a modified one-grid ion collector using saturation current probe method, which proved our proposed equivalent circuit model was correct. The Ti ion-to-atom ratios around the substrate were estimated at about 24%–62%. The plasma density and ion to atom ratio around the substrate increased with the peak current, and this could lead to a higher film crystallization and preference growth on Ti (101) and (100).

The equivalent circuit of the p-i-n structure has been considered and developed for the quantum dot intermediate band solar cells where the nanoparticles are inserted in the active region of the diode. The admittance of the circuits are calculated consisting of frequency dependent capacitance and conductance. The presence of quantum dot layers in the active region of the diode increases the capacitance and conductance of the cell in lower frequencies. However, the number of QD cannot be increased and has an optimum.

Impedance measurement is a common method to study the electrical properties of thin film photovoltaics. For the first time, we use the MATLAB/Simulink environment to extract the complex impedance of the nanostructured heterojunction solar cells. The impedance magnitude, phase and Nyquist plot of the PV are simulated in LTI Viewer and Impedance versus Frequency analysis tools of SimPower GUI block of Simulink. We examined a variety of the equivalent circuits consisting of capacitance, series and shunt resistances representing the solar cell structure. The model uses the parameters with values reported in the literature at room temperature and zero bias. The effect of the additional capacitance and resistances in the equivalent circuits on the impedance components of the cells is considered by Simulink environment.

The shunt reactors located on both line terminals and substation bus-bars are commonly used on long extra high voltage (EHV) transmission systems for controlling voltage during load variations. In a small power system that appears in an early stage of a black start of a power system, an overvoltage could be caused by core saturation on the energization of a shunt reactor with residual flux. The most effective method for the limitation of the switching overvoltages is controlled switching since the magnitudes of the produced transients are strongly dependent on the closing instants of the switch. A harmonic index has been introduced that it's minimum value is corresponding to the best-case switching time. In addition, in this paper an artificial neural network (ANN) is used to estimate the optimum switching instants for real time applications. ANN is trained with equivalent circuit parameters of the network, so that developed ANN is applicable to every studied system. To verify the effectiveness of the proposed index and accuracy of the ANN-based approach, two case studies are presented and demonstrated.

In this work, we present a comprehensive study of the commutativity of fractional-order linear time-varying systems (LTVSs). Commutativity is a fundamental property in the analysis and control of dynamic systems and is often used to simplify the design of controllers. Fractional-order systems, which are characterized by a noninteger-order derivative, have been widely studied in recent years due to their ability to model a wide range of phenomena. However, the commutativity of fractional-order LTVSs has not been widely explored. In this work, we present a comprehensive study of the commutativity of fractional-order LTVSs. We first provide a mathematical definition of commutativity for these systems and demonstrate that it is equivalent to the commutativity of their transfer functions. We then propose a method for verifying the general condition for commutativity of fractional-order LTVSs under zero initial conditions (ICs) and prove it mathematically. Based on our findings, we realized that the commutative requirements, properties, theories, and conditions are general for fractional-order LTVSs, please observed that some fractional-order LTVSs are commutative, some are not commutative, while some are commutative under certain conditions. Based on this fact, we can say that not all fractional-order LTVSs are commutative.

We apply explicit commutative results to several examples of fractional-order LTVSs. Our theoretical and simulation results show a good agreement and prove that our fractional-order LTVSs are commutative under certain conditions, moreover, the commutativity property holds for certain conditions and classes of fractional-order LTVSs, but not for others. Because of the application of fraction commutativity in various fields of science and engineering, we find it necessary to come up with explicit results for the first time.

A new characterization method based on impedance frequency response analysis at different temperatures has been developed to assess and identify the dielectric and semiconductor materials for organic field-effect transistors (OFET). This method can not only characterize simultaneously dielectric and conductive behaviors of materials but also distinguish individual contributions to electrical conduction or to polarization from layers such as dielectric layer, semiconductor layer, and interfaces in OFET. Two kinds of materials, Urathan and DuPont 5018A as dielectric materials have been used to make a multilayer organic capacitor. It has been observed that Urathan, due to its lower conductivity, non-metallic conduction behavior at high temperature, and lower interfacial resistance, is more suitable as dielectric layer for OFET. Urathan appears an enhancement in conductivity by heating following an Arrhenius law with an activation energy transition from 0.002 to 0.24 eV at ~307 K, which originates from band tail hopping that occurs around the Fermi edge. At ~314 K, a dielectric transition also occurs, which is interpreted as a combination of electron polarization associated to the band tail hopping. The materials were used to fabricate OEFT, which performance was in agreement with that obtained from impedance analysis of the organic capacitor.

In this paper, AC and DC electrical properties of organic solar cells based on P3HT:PCBM active layer have been investigated. The performance of such solar cell has demonstrated the efficiency of 2.31% corresponding with short-circuit current density of 6.08 mA ⋅ cm${}^{-2}$, open circuit voltage of 0.64 V and fill factor of 60%. The equivalent circuit and the properties of the supposed interfaces between the layers in the P3HT:PCBM-based solar cell have been estimated. AC properties have demonstrated series capacitance increasing with increasing frequencies, which means series capacitance saves charges and parallel capacitance has decreased with increasing of frequency work as discharge part of charges stored in series capacitance. Also, equivalent series and parallel resistances have demonstrated a decrease from 7 $\mathrm{\Omega }$ and 120 k$\mathrm{\Omega }$ at low frequency to 1 $\mathrm{\Omega }$ and 43 k$\mathrm{\Omega }$ at high frequencies, respectively.

Tunable three-dimensional (3D) electromagnetic (EM) metasurfaces are critical for dynamic modulation of EM responses but their construction and tuning mechanism are still complex. Here, we report a simple yet effective 3D reconfigurable EM metasurface, which was obtained from a planar kirigami polyimide substrate printed with periodically arranged copper split-ring resonator. Under mechanical stretch, the two-dimensional (2D) planar metasurface can be uniformly deformed into a 3D state, which is effective for tuning its EM transmission characteristic. By combining mechanics and EM simulations as well as experimental measurements, we revealed the deformation mode and active EM transmission modulation capability of the metasurface. It is shown that at the initial state, the planar kirigami metasurface exhibits ideal frequency selective transmission to transverse electric (TE) wave but allows for complete transmission for transverse magnetic (TM) wave. As the applied strain increases from 0% to 20%, the transmission was adjusted from −17.74dB to −9.74dB for TE wave but merely from 0dB to −3.25dB for TM wave. Meanwhile, the resonant frequency experienced a visible shift for both TE and TM waves. Finally, the equivalent circuit analysis and simulated surface current density were conducted to reveal the tuning mechanism of the proposed metasurface.

This paper reports the effect of surface morphology on the electrochemical performance of electrodeposited manganese oxide films. These films were deposited on stainless steel substrate by chronoamperometry for different deposition time (30s, 60s, and 120s). Morphology of deposited films were studied by scanning electron microscopy and decrease in surface area was observed with variation in deposition time. Cyclic voltammetry revealed decrease in specific capacitance with decrease in surface area of films. This effect was analyzed by electrochemical impedance spectroscopy (EIS) study. Further, the EIS data were fitted with equivalent circuit of electrochemical capacitor electrode and investigating electrolyte ion interaction with electrode during charge storage process. EIS fitted data were analyzed to study the electrode characteristics such as series resistance, double layer charge storage and charge transfer resistance. The variation in these characteristics was due to change in diffusion length with increased deposited electrode material content on substrate.

The objective of this study is to characterize the pH sensing performance of carbon nanotube-based thin films and compare them to their non-carbon nanotube-based counterparts. A layer-by-layer technique is employed for fabricating the nanocomposites, and pH sensitivity is encoded by incorporating polyaniline (PANI) by itself or with single-walled carbon nanotubes during film fabrication. In particular, polyaniline is doped with different counter ions such as hydrochloric acid (HCl) and methane sulfonic acid (MeSA) for fabricating four different thin film sample sets. The as fabricated films are subjected to various pH buffer solutions ranging from pH 1 to 13 while their electrical properties are simultaneously measured using two different techniques. First, time-domain bulk film resistance measurements have been conducted, and the findings show that all four types of films exhibit pH sensitivity. Their bulk film resistances increase in tandem with increasing pH. Second, frequency-domain electrical impedance spectroscopy (EIS) has also been conducted when the films are exposed to different pH buffers. The recorded EIS spectra have been fit to a proposed equivalent circuit model consisting of resistors, capacitors and a constant-phase element. The results suggest that the MeSA-based films exhibit linear sensitivity, whereas the HCl-based films exhibit a bilinear sensitivity in the time-domain case. Both HCl- and MeSA-based films exhibit a bilinear pH response in the frequency domain. The equivalent circuit has also revealed that the equivalent parallel capacitor and the constant-phase element of the HCl-and MeSA-doped films also exhibit an inverse bilinear sensitivity to pH buffer solutions.

The electrical and dielectric properties of the compound C₇H₁₂N₂[H₂PO₄]₂ ⋅ 1/2H₂O were investigated by the complex impedance spectroscopy, over a wide range of frequencies and temperatures, 600 Hz–5 MHz and 303–408 K, respectively. Besides, a detailed analysis of the impedance spectrum suggested that the electrical properties of the material at several temperatures and the electrical equivalent circuit have been proposed to explain the impedance results. Concerning the Nyquist plots, they clearly showed the presence of bulk and grain boundary. As for the imaginary part of modulus at several temperatures, it shows double relaxation peaks, thus suggesting the presence of grains and grain boundary conductions in the sample.

The complex impedance of the bis(2-amino-6-methylpyridine) tetrachloridozincate compound (C₆H₉N₂)₂ZnCl₄ has been investigated in the temperature range 313–403 K and in the frequency range 200 Hz–5 MHz. The impedance plots show semicircle arcs at different temperatures and an electrical equivalent circuit has been proposed to explain the impedance results. The circuits consist of the parallel combination of bulk resistance R_p and constant phase elements (CPE). The bulk resistance of the material decreases with rise in temperature. dc conduction activation energies are estimated from Arrhenius plots. The frequency-dependent conductivity data are fitted in the modified power law: σ_ac(ω) = σ_dc + A₁ω^s1 + A₂ω^s2. Dielectric data were analyzed using complex electrical modulus M* at various temperatures. The modulus plot can be characterized by full width at half height or by β values of Kohlrausch–William–Watts (KWW) function. Activation energy of hopping is almost close to the activation energy of conduction suggesting a hopping transport mechanism.

The impedance properties in polarized piezoelectric can be described by electric equivalent circuits. The classic circuit used in the literature to describe real systems is formed by one resistor (R), one inductance (L) and one capacitance C connected in series and one capacity ($C_0$) connected in parallel with the formers. Nevertheless, the equation that describe the resonance and anti-resonance frequencies depends on a complex manner of R, L, C and $C_0$. In this work is proposed a simpler model formed by one inductance (L) and one capacity (C) in series; one capacity ($C_0$) in parallel; one resistor ($R_P$) in parallel and one resistor ($R_S$) in series with other components. Unlike the traditional circuit, the equivalent circuit elements in the proposed model can be simply determined by knowing the experimental values of the resonance frequency $f_r$, anti-resonance frequency $f_a$, impedance module at resonance frequency $|Z_r|$, impedance module at anti-resonance frequency $|Z_a|$ and low frequency capacitance $C_0$, without fitting the impedance experimental data to the obtained equation.

Polycrystalline ${\text{Na}}_{0.9}$${\text{Ba}}_{0.1}$${\text{Nb}}_{0.9}$(${\text{Sn}}_{0.5}$${\text{Ti}}_{0.5}{)}_{0.1}$O₃ is prepared by the solid-state reaction technique. The formation of single-phase material was confirmed by an X-ray diffraction study and it was found to be a tetragonal phase at room temperature. Nyquist plots ($Z^{\prime \prime }$ versus $Z^{\prime })$ show that the conductivity behavior is accurately represented by an equivalent circuit model which consists of a parallel combination of bulk resistance and constant phase elements (CPE). The frequency dependence of the conductivity is interpreted in terms of Jonscher’s law. The conductivity ${\sigma }_{dc}$ follows the Arrhenius relation. The modulus plots can be characterized by the empirical Kohlrausch–Williams–Watts (KWW), $\phi (t)$ = exp($-(t$/$\tau {)}^{\beta })$ function and the value of the stretched exponent ($\beta )$ is found to be almost independent of temperature. The near value of activation energies obtained from the analyses of modulus and conductivity data confirms that the transport is through an ion hopping mechanism dominated by the motion of the (${\text{O}}^{2-})$ ions in the structure of the investigated material.

This paper reviews the interpretation of impedance and capacitance spectra for different capacitor technologies and discusses how basic electrical characteristics can be inferred from them. The basis of the interpretation is the equivalent circuit for capacitors. It is demonstrated how the model parameters, such as capacitance and equivalent series resistance, can be extracted from the measured spectra. The aspects of measurement accuracy are exemplarily discussed on the measured spectra.

Based on the classical lumped parameter model, using two-port network admittance Y-parameter matrix, the electrical characteristic of voltage gain, output power and efficiency of parallel-parallel connected piezoelectric transformers is analyzed in detail. In addition, how the number of paralleled identical Rosen type piezoelectric transformers contributes to the voltage gain and output power is simulated by the Pspice. The theoretical analysis and the simulation results show that, parallel connection of piezoelectric transformer is an effective way to improve the output power. Compared single piezoelectric transformer, the parallel connection of piezoelectric transformer can not only supply more power but also improve the voltage gain.

This paper proposes a novel method of Travelling-wave Rotation Ultrasonic Motor (TRUMs) modeling of the motor's two energy transmitting processes. Two sub-models are built, where one is an Electric-Vibration equivalent circuit model and the other is a Vibration-Force discrete contact model. A mixed model composed of these two earlier models is then derived. Finally, the characteristics of the model are tested and verified by simulations and experiments.