Current-voltage Characteristic Curves Research Articles

A hybrid wind driven-based fruit fly optimization algorithm for identifying the parameters of a double-diode photovoltaic cell model considering degradation effects

The identification of unknown parameters of photovoltaic modules is the keystone to model their performance accurately. This paper introduces a novel hybrid wind driven-based fruit fly optimization algorithm to determine a double-diode photovoltaic cell model’s seven unknown parameters. Due to the limitations of reaching a matured convergence of the classical wind driven optimization for complex multi-modal optimization problems, this paper presents a hybrid algorithm by integrating the wind driven optimization algorithm’s exploitation and fruit fly optimization algorithm’s exploration capacities. The effectiveness of the proposed model is validated using real data from three photovoltaic technologies: mono-crystalline, poly-crystalline, and thin-film. Besides, its computational efficiency and precision are compared with those of various models: deterministic- and metaheuristic-based models. The average values of the standard deviation, normalized-root-mean-square error, mean absolute percentage error, coefficient of determination, and convergence speed of the proposed model were 8.1101 × 10-9, 0.0911%, 2.5661%, 99.0115%, and 10.0112 s. for mono-crystalline PV module, 7.1129 × 10-9, 0.1029%, 2.6334%, 98.9331%, and 8.1201 s. for poly-crystalline PV module, and 6.2212 × 10-9, 0.0871%, 2.3129%, 99.1256% and 9.3211 s. for thin-film PV module. Findings indicate that the proposed model outperforms the aforementioned models in accuracy, convergence speed and feasibility. In addition, it can work blindly with any current-voltage characteristic curve on a 15-min. basis under any weather condition without the need for any initial guess or previous information about any parameter.

Experimental study on improving silicon crystal discharge cutting efficiency based on laser irradiation method

The contact barrier formed between a metal and crystalline silicon during wire electrical discharge machining (wire-EDM) hinders improvements in the processing efficiency; thus, this paper proposes a workpiece pretreatment method that increases the doping concentration of the crystalline silicon surface. First, a silver layer was coated on a silicon surface by silk screen printing, then a laser marking machine was used to irradiate the coating surface. The mechanism of this method to form a heavily-doped layer was analyzed, and the current-voltage (I–V) characteristic curves under different pretreatment processes were compared. Finally, the influence of this method on the machining performance was studied by wire-EDM experiments. The results showed that the doping concentration of the silicon surface increased, and the contact resistance decreased. When the open voltage was 120 V, the cutting efficiency of the workpiece treated with laser irradiation and screen printing was 60% higher than that without pretreatment, and it was 28% higher than the workpiece with only the metal coating treatment; however, the treatment method had little effect on the kerf width or surface roughness. It is hoped that this work will provide useful guidance for improving the EDM efficiency of crystalline silicon.

Effect of Deposit Au thin Layer Between Layers of Perovskite Solar Cell on Cell's Performance

The present work aims to fabricate n-i-p forward perovskite solar cell (PSC) withئ structure (FTO/ compact TiO2/ compact TiO2/ MAPbI3 Perovskite/ hole transport layer/ Au). P3HT, CuI and Spiro-OMeTAD were used as hole transport layers. A nano film of 25 nm gold layer was deposited once between the electron transport layer and the perovskite layer, then between the hole transport layer and the perovskite layer. The performance of the forward-perovskite solar cell was studied. Also, the role of each electron transport layer and the hole transport layer in the perovskite solar cell was presented. The structural, morphological and electrical properties were studied with X-ray diffractometer, field emission scanning electron microscope and current-voltage (J-V) characteristic curves, respectively. J-V curves revealed that the deposition of the Au layer between the electron transport layer (ETL) and Perovskite layer (PSK) reduced the power conversion efficiency (PCE) from 3% to 0.08% when one layer of C. TiO2 is deposited in the PSC and to 0.11% with two layers of C. TiO2. Power conversion efficiency, with CuI as the hole transport layer (HTL), showed an increase from 0.5% to 2.7% when Au layer was deposited between PSK and CuI layers. Also, Isc increased from 6.8 mA to 17.4 mA and Voc from 0.3 V to 0.5V. With depositing Au layer between P3HT and PSK layers, the results showed an increase in the efficiency from 1% to 2.6% and an increase in Isc from 10.7 mA to 30.5 mA, while Voc decreased from 0.75 V to 0.5V

Plasma diagnostic in a compact IEC-based nuclear fusion device

In this paper, the plasma parameters in the Iranian-Inertial Electrostatic Confinement Fusion (IR-IECF) device are measured using a Langmuir probe system. For this purpose, different parts of the Langmuir probe and necessary equipment are designed and constructed. The IR-IECF device, a compact IEC-based fusion device for nuclear fusion researches operating in pulsed or continuous mode, consists of two concentric or coaxial electrodes that the central one is negatively high voltage-biased and the outward electrode is grounded. In this configuration, the strong electric field between electrodes leads to ionization the filling gas resulting in hot and dense plasma formation in the center of the device. By applying voltage to the probe electrode being in direct contact with the plasma formed in the IR-IECF device, the current drawn from the probe is measured. Henceforth, by interpreting the obtained current-voltage (I-V) characteristic curve, the plasma parameters are determined for different conditions of discharge voltage and current. Moreover, by moving the probe between the electrodes, the plasma parameters at different distances from the IR-IECF device center are measured.

Electrical Conductivity of Multiwall Carbon Nanotube Bundles Contacting with Metal Electrodes by Nano Manipulators inside SEM.

Determining the metallicity and semiconductivity of a multi-walled carbon nanotube (MWCNT) bundle plays a particularly vital role in its interconnection with the metal electrode of an integrated circuit. In this paper, an effective method is proposed to determine the electrical transport properties of an MWCNT bundle using a current–voltage characteristic curve during its electrical breakdown. We established the reliable electrical nanoscale contact between the MWCNT bundle and metal electrode using a robotic manipulation system under scanning electron microscope (SEM) vacuum conditions. The experimental results show that the current–voltage curve appears as saw-tooth-like current changes including up and down steps, which signify the conductance and breakdown of carbon shells in the MWCNT bundle, respectively. Additionally, the power law nonlinear behavior of the current–voltage curve indicates that the MWCNT bundle is semiconducting. The molecular dynamics simulation explains that the electron transport between the inner carbon shells, between the outermost carbon shells and gold metal electrode and between the outermost carbons shells of two adjacent individual three-walled carbon nanotubes (TWCNTs) is through their radial deformation. Density functional theory (DFT) calculations elucidate the electron transport mechanism between the gold surface and double-wall carbon nanotube (DWCNT) and between the inner and outermost carbon shells of DWCNT using the charge density difference, electrostatic potential and partial density of states.

Resistive switching effect caused by oxygen vacancy migration in SrTiO3 ceramic

STO has been studied for many years and is mainly used in various fields such as ceramic capacitors, memristors and solar cells. The influence of oxygen vacancies on its physical properties is very important. In this article, we report the dielectric, impedance and current-voltage characteristics of STO ceramic at different temperatures. When the temperature is increased, the oxygen vacancy concentration of the STO ceramic increases, resulting in dielectric dispersion and dielectric relaxation behavior. In the analysis of impedance spectroscopy, oxygen vacancies mainly undergo secondary ionization and conduct grain conduction within the STO. The conductivity of STO ceramic increases with increasing temperature, mainly due to the increase in oxygen vacancy concentration. The STO ceramic at high temperature exhibits a current-voltage characteristic curve similar to the resistive switching effect, due to the migration of oxygen vacancies.

Polaronic conduction and switching phenomena of amorphous Li2O–CuO–P2O5

This study investigates electrical conductivity of bulk phosphate glasses containing Li2O and CuO, prepared by standard melt quenching technique. Furthermore, static current–voltage characteristic curves at high fields for memory switching behavior were examined. X-ray diffraction patterns for the studied materials revealed the amorphicity of the prepared films. It was observed that the activation energy of the samples lies in the range of 0.53–0.98 eV, depending on composition. The electrical conductivity at room temperature showed a minimum at a certain ratio of Li2O/CuO. Conduction mechanism and observed minimum were explained by small polaron hopping and interaction between polarons and ions. Current–voltage characteristics at high electric field showed memory switching. The mean value of the threshold voltage was found to be dependent on composition which decreased with increase in CuO content. Values of the threshold voltage and activation energy were obtained for the investigated compositions. The observed switching phenomenon was explained by thermal model. • Phosphate glasses with Li2O and CuO were prepared. • Electrical conductivity at room temperature was showed a minimum at a certain ratio of Li2O/CuO. • Current–voltage characteristic of the samples was showed memory switching at high electric field.

Combined electro-thermal model for PV panels

AbstractThis paper presents a combined electro-thermal model to serve the aim of accurate output power prediction of photovoltaic systems, based on the concept of the thermal energy balance. The electrical sub-model is built based on fitting a surface to the current-voltage curves collected under wide range temperatures and irradiances. For this purpose, the current-voltage characteristic curves are reproduced using two different methods. The thermal sub-model considers all the effective heat transfer mechanisms to estimate the photovoltaic module junction temperature. The Newton-Raphson iterative method is used as a solving algorithm to calculate the photovoltaic junction temperature. The collected results prove the applicability of the model under a wide range of environmental conditions.

Bayesian estimation of equivalent circuit parameters of photovoltaic cells

The equivalent circuit model of a photovoltaic cell is useful for understanding device loss mechanisms as well as the design and analysis of systems using photovoltaic cells. Although nonlinear least-squares methods are routinely applied for the extraction of equivalent circuit parameters using current–voltage characteristic curves, they only yield a point estimation sensitive to the initial value and do not provide an estimation error. In this study, a data-driven approach using Bayesian estimation is proposed to extract equivalent circuit parameters. Contrary to the conventional least-squares method, this method does not require tedious initial value adjustments and provides an estimation error.

Parameters estimation of solar photovoltaic module using camel behavior search algorithm

Finding accurate mathematical model of electrical equivalent circuit of solar photovoltaic (PV) cell is crucial to achieve and improve maximum power point, simulation design and efficiency computations for solar energy system. Due to the nonlinearity of the characteristic of solar PV cell, optimization methods are the best for estimating the electrical model parameters which lead to accurate estimating I-V curve. In this paper, camel behavior search algorithm is proposed as a new method for estimating the five different parameters for single diode model of PV solar module. This is tested on multicrystalline KC 200GT PV module. A measurement data of the module is used to verify and test the consistency of accurately estimating the set of parameters that govern the characteristics I-V relationship of solar cell. The simulation results show that the current-voltage characteristic and power-voltage curve obtained are matching to the measured experimental data set. For performance evaluation, the proposed method is simple, fast in convergence response and has an acceptable accuracy in obtaining the five estimated parameters.

High-Performance PANI-Based Ammonia Gas Sensor Promoted by Surface Nanostructuralization

In the area of conductive polymer-based sensors, polyaniline (PANI) has been widely studied for NH3 gas detection and a lot of effort has been devoted to improving its sensing performance. In this work, PANI thin film was prepared by chemical oxidation polymerization and spinning coating approach. By further etching via reactive ion etching (RIE), a nanostructuralized PANI thin film was obtained. All of the morphology characterization, current-voltage (I–V) characteristics curves, and XPS analysis suggest that etching via RIE with O2 gas could not only effectively increase the sensitive area and chemical diffusion pathway but also introduce extra oxygen-containing functional groups to adsorb more NH3 molecules by hydrogen bond. The gas sensing performance of the PANI thin film sensor to NH3 was examined. When the concentration of NH3 gas increased from 3 ppm to 990 ppm, the response of pristine film-based PANI sensor increased from 1.07 to 1.48, while, the response of nanostructuralized film-based PANI sensor increased from 1.16 to 3.19. All the response, reproducibility, and selectivity to NH3 results showed that the PANI sensor of nanostructuralized thin film to NH3 was superior to the PANI sensor of pristine film. This work demonstrates a convenient and effective way that can be beneficially utilized for improving the gas sensing performance.

Surface and interface effects on the current–voltage characteristic curves of multiwall carbon nanotube-Si hybrid junctions selectively probed through exposure to HF vapors and ppm-NO2

The possibility to increase the efficiency of photovoltaic (PV) cells based on hybrid carbon nanotube (CNT)–Si heterojunctions is related to the ability to control the chemical properties of the CNT–Si interface and of the CNT bundle layer. In spite of the encouraging performances of PV cells based on multiwall (MW) CNT, so far few efforts have been made in the study of this device compared to single wall (SW) CNT–Si interfaces. Here, surface and interface effects on the current–voltage characteristic curves of MW CNT–Si hybrid junctions are investigated through exposure to HF vapors and to 10 ppm-NO2 and compared to the effects detected in SW CNT–Si junctions. Quite similar results in terms of open circuit voltage, short circuit current density, and efficiency are found for both cells, suggesting that exposure to HF vapors mostly affects the interface chemical properties, i.e., the silicon oxidation state, that in both junctions reach an optimal state about 50 h after etching. In turn, NO2 exposure has larger effects on the SW-based cell, consistently with the larger surface-to-volume ratio of SW with respect to MW. In both cases, the efficiency value reaches a maximum after 28 min, before dropping when the NO2 molecules desorb from the surface. A combined analysis of current–voltage curves and photoemission data collected along the different phases of gas exposures allowed us to relate changes in the electrical properties to the chemistry of Si at the interface.

Modeling and Simulation of Lead-Free Perovskite Solar Cell Using SCAPS-1D

In this work, the effect of some parameters on tin-based perovskite (CH3NH3SnI3) solar cell were studied through device simulation with respect to adjusting the doping concentration of the perovskite absorption layer, its thickness and the electron affinities of the electron transport medium and hole transport medium, as well as the defect density of the perovskite absorption layer and hole mobility of hole transport material (HTM). A device simulator; the one-dimensional Solar Cells Capacitance Simulator (SCAPS‑1D) program was used for simulating the tin-based perovskite solar cells. The current-voltage (J-V) characteristic curve obtained by simulating the device without optimization shows output cell parameters which include; open circuit voltage (Voc) = 0.64V, short circuit current density (Isc) = 28.50mA/, fill factor (FF) = 61.10%, and power conversion efficiency (PCE) = 11.30% under AM1.5 simulated sunlight of 100mW/cm2 at 300K. After optimization, values of the doping concentration, defect density, electron affinity of electron transport material and hole transport material were determined to be: 1.0x1016cm-3, 1.0x1015cm-3, 3.7 eV and 2.3 eV respectively. Appreciable values of solar cell parameters were obtained with Jsc of 31.38 mA/cm2, Voc of 0.84 V, FF of 76.94% and PCE of 20.35%. when compared with the initial device without optimization, it shows improvement of ~1.10 times in Jsc, ~1.80 times in PCE, ~1.31 times in Voc and ~1.26 time in FF. The results show that the lead-free CH3NH3SnI3 perovskite solar cell which is environmentally friendly is a potential solar cell with high theoretical efficiency of 20.35%.

Modelling effect of temperature and irradiance changes of Assa, Morocco on photovoltaic modules’ performance

A mathematical representation of a photovoltaic (PV) solar cell and module performances is demonstrated in this paper. One diode based on the Shockley diode equation model is adopted for simulation and extract the performance indications. The simulated solar module is a particular 235W solar module operating in an existing 806.52 kWp grid connected photovoltaic power plant located at Assa, southern Morocco. The model demonstrates power-voltage (P-V) and current-voltage (I-V) characteristic curves with weather conditions changes. These external conditions include temperature and solar irradiance level (represented by sun unit 1sun=1000w/m2) which greatly affect the performance of the PV system. This paper also presents PV simulation with a maximum power point tracking (MPPT) converter and the general model was implemented in Matlab/Simulink software and used as an example verifying the performance of the tested module under Assa city weather variable.

Electronic Transport Properties of Phenalenyl Molecular Devices via Gated Modulation

By applying nonequilibrium Green’s functions (NEGF) in combination with the density functional theory (DFT), we investigate the electronic transport properties of gated phenalenyl molecular devices with two different contact geometries. The calculated results show that electronic transport properties of the two different devices can be modulated by external transverse gates. When the molecule contacts the Au electrodes through two second-nearest sites, the current-voltage (I-V) characteristic curves are symmetric and suppressed by the gate electrodes. However, a rectifying behavior will occur when the electrodes connect the molecule on both sides, one second-nearest site and one third-nearest site, respectively. Mechanisms for such phenomena are proposed and these findings suggest a new opportunity for developing molecular devices.

Synthesis of conductive polyaniline-carbon nanofiber nanocomposite with chenille like morphology for photocatalytic coatings applications

Pristine carbon nanofibers (CNF) have been dispersed with a non-ionic surfactant, Triton X-100 and then acid oxidized (in H2SO4: HNO3, acid ratio 3:1). This ensures a consistent dispersion with attachments of water soluble functional groups (−COOH and OSO3H). Subsequently polyaniline (PANICNF) based nanocomposites, were prepared at low temperature (0–5) ˚C via in-situ polymerization approach. Triton X-100 facilitates the dispersion of bundled CNF, thereby assisting PANI molecules to uniformly coat the edge and surface sites of CNF. This gives rise to a unique core-shell structure with chenille like appearance (PANI@CNF), implying emeraldine PANICNF nanocomposite forms an interpenetrating network. A bandgap of∼1.37 eV as compared to PANI (3.17 eV) calculated using UV–vis Tauc plot curve fit shows that this unique morphology proves to be a boon for the photocatalytic coating formulation. Spectroscopic study also show that the obtained quinoid to benzenoid ring peak ratio for PANI is 1:0.992 and for PANI/CNF is 1:0.996 which is almost equal to one and is thus highly conductive. CNF prompts enhanced polaron movement from valence to conduction band in PANI/CNF while also acting as the acceptor layer to the quinoid rings in PANI which is the donor layer. A linear ohmic graph for PANI/CNF coatings was obtained using I–V (current-voltage) characteristic curves. Thus PANI/CNF nanocomposite coatings possessing a unique fuzzy fabric (chenille) like core-shell morphology has a tunable band gap, enhanced surface area and improved charge transfer properties and are potentially active photovoltaic coatings for environmentally exposed surfaces.

In-Situ Measurement of Power Loss for Crystalline Silicon Modules Undergoing Thermal Cycling and Mechanical Loading Stress Testing

An in-situ method is proposed for monitoring and estimating the power degradation of mc-Si photovoltaic (PV) modules undergoing thermo-mechanical degradation tests that primarily manifest through cell cracking, such as mechanical load tests, thermal cycling and humidity freeze tests. The method is based on in-situ measurement of the module’s dark current-voltage (I-V) characteristic curve during the stress test, as well as initial and final module flash testing on a Sun simulator. The method uses superposition of the dark I-V curve with final flash test module short-circuit current to account for shunt and junction recombination losses, as well as series resistance estimation from the in-situ measured dark I-Vs and final flash test measurements. The method is developed based on mc-Si standard modules undergoing several stages of thermo-mechanical stress testing and degradation, for which we investigate the impact of the degradation on the modules light I-V curve parameters, and equivalent solar cell model parameters. Experimental validation of the method on the modules tested shows good agreement between the in-situ estimated power degradation and the flash test measured power loss of the modules, of up to 4.31 % error (RMSE), as the modules experience primarily junction defect recombination and increased series resistance losses. However, the application of the method will be limited for modules experiencing extensive photo-current degradation or delamination, which are not well reflected in the dark I-V characteristic of the PV module.

A Fast-Dynamic Control Scheme for a Power-Electronics-Based PV Emulator

The dynamic performance of a photovoltaic (PV) emulator is critical for testing applications with fast maximum power point tracking (MPPT) algorithms. In this article, a power-electronics-based PV emulator (PVE) is proposed to achieve fast-dynamic response, as well as, to emulate accurately in all regions of the current-voltage (I-V) characteristic curve. The control scheme of the proposed PVE consists of an instantaneous output impedance matching (IOIM) controller based on load resistance feedback to generate the voltage reference signal and an inner boundary control (BC) scheme to regulate the converter at a given reference within a short period of time. The IOIM controller overcomes the drawback of conventional PVEs that suffer from oscillating reference signal in a certain region of the I-V characteristic curve. Moreover, use of load resistance feedback in the reference generation algorithm allows the decoupling of the reference signal generator from the inner control loop. The BC scheme adapts a corrected second-order switching surface to achieve a faster response time and robust operation with switching converter loads. Detailed small signal model of the PVE is derived to design the IOIM control loop and to ensure a stable and fast convergent emulation in the entire I-V characteristic curve. Experimental results of a 130 W (VMPP = 35.2 V, IMPP = 3.69 A) prototype are presented with both resistive loads and an MPPT converter to verify its performance under fast varying irradiance and load conditions.

Development of a photovoltaic characteristics generator based on mathematical models for four PV panel technologies

A good study of photovoltaic system requests to have very precise 
 current-voltage characteristic curves of photovoltaic modules for different technologies. The photovoltaic emulator provides an efficient solution to maintain the same current-voltage output of photovoltaic module. It includes three parts: the PV model, the control strategy, and the power converter. This paper provides three classes of modeling and simulation of photovoltaic arrays and presents the synthesis results of the current-voltage characteristic performances obtained by the modeling approaches. The models of the first class are based on electrical circuit model, those of the second class are based on multiple straight lines model, and for the third class, it is based on the look up table. The mathematical model is built using MATLAB/ Simulink, and an experimental bench was carried out to acquire an up-to-date and representative experimental database of four PV panels. This database is used for the validation of these models for the different PV panel technologies under Moroccan meteorological conditions. Following this comparative study, we came to a high agreement between the experimental and simulated current-voltage characteristics for the emulator under study.

Novel rare earth yttrium doping effect on physical properties of PbS nanostructures: facile synthesis and characterization

The dielectric properties of pure and yttrium-doped PbS nanoparticles synthesized by the coprecipitation chemical synthesis route have been studied by several characterizations. X-ray diffraction patterns of samples were employed to estimate the crystallite sizes and intrinsic microstrains using Williamson–Hall (W–H) plot analysis. The crystallite size and intrinsic macrostrain values were evaluated in the range of 13.7–15.9 nm and 1.09 × 10–3–1.72 × 10–3, respectively, using W–H plots. The formation of nanoparticles, nanoflakes, sponge, and nanosheets were seen via scanning electron microscope (SEM). Energy dispersive spectroscopy (EDS) of 5.0 wt% confirms the Y: PbS sample elements' chemical composition and stoichiometry. The optical band gaps increase in the range of (0.93–1.17 eV) with an increase in the dislocation density. The higher values of dielectric constant (23.6–28.0), dielectric loss (37.6–176.8), loss tangent (2.7–8.6), and electrical conductivity [ 10.2 to ( 11.7) S/m] have been reported at the lower frequency. The highest electrical conductivity values were obtained in the range of [ 4.71 to ( 4.81) S/m] for as-prepared samples. The greater capacitance and impedance values were found at 3 kHz and decrease with increasing the frequency up to 10 MHz. The current–voltage characteristic curves of undoped and Y: PbS NPs were performed under biased voltage. The space charge current density was noticed in the range of (8.7 × 10–4–4.2 × 10–4 amp/cm2) at 1.0, 2.5, and 5.0 wt% of Y: PbS samples. The enhancement in the optical band gap and dielectric and electric properties on yttrium doping in PbS compared to pristine PbS NPs makes them suitable for optoelectronic applications.