Current-voltage Characteristic Curves Research Articles

Electric Response of a Negative Dielectric Anisotropy Nematic Liquid Crystal Doped with Ionic Dopant

The electrical properties measurements have been performed in a homogeneous alignment parallelepiped cell containing 4-methoxy benzylidene- 4-butylaniline (MBBA) liquid crystal doped with 0.02%wt tetrabutylammonium bromide (TBAB). The measurement of the complex permittivity was conducted in the nematic phase, covering a frequency range of 42 Hz to 5 MHz. A new relaxation mode was observed in the low-frequency region, which was not present in pure MBBA. The obtained dielectric dispersion could be fitted using the double Cole–Cole formula to determine the relaxation frequencies. The steady-state current exhibited a nonlinear dependence on the applied voltage, and hysteresis was observed in the transient current-voltage characteristic curve.

Exploring potential of lead-free KSn0.5Ge0.5I3 based perovskite solar cell: A combined first-principle DFT and SCAPS-1D study

Perovskite solar cells present a promising alternative to conventional silicon or lead-based solar cells, offering a synergistic blend of cost-effectiveness and potential for elevated power conversion efficiency. We investigated the potential of an innovative KSn0.5Ge0.5I3-based perovskite solar cell (PSC) using density functional theory (DFT) and SCAPS-1D simulation studies. Computational analysis via DFT probed the crystal structure, elastic, mechanical, and optoelectronic properties of KSn0.5Ge0.5I3. Tolerance factor computation (0.94) and negative formation energy (-3.16 eV) affirmed the thermodynamic stability of the orthorhombic phase in KSn0.5Ge0.5I3. Optical variables including refractive index, absorption coefficient, dielectric function, optical loss, and reflectivity, were computed to explore KSn0.5Ge0.5I3 viability in PV applications. Band structure analysis, density of states (DOS), and projected density of states (PDOS) have been used to determine the band gap (∼1.87 eV), effective masses, and mobility of e-/h+. We have conducted SCAPS-1D simulation for diverse PSCs configurations using various holes transport layers (HTLs) and electron transport layers (ETLs), identified IGZO (Eg = 3.05 eV) as a proficient ETL while CuSbS2 (Eg = 1.58 eV) as an effective HTL. A comprehensive investigation of parameters such as absorber layer thickness, shunt and series resistance, donor and acceptor density, absorber defect density, back contact metal, temperature, and interface characteristics was undertaken, and the impact on PV device performances was assessed through current-voltage (IV) and quantum efficiency (Q.E) characteristics curves. These findings underscore the potential of KSn0.5Ge0.5I3 as a promising material for PSCs, offering a sustainable and eco-friendly avenue for future renewable energy.

Parameters Estimation of Photovoltaic Modules Using Differential Evolution Metaheuristic Method

This paper presents the analysis of the differential evolution (DE) metaheuristic method, which is used to estimate some parameters employed in the equivalent electrical circuit that represents the photovoltaic (PV) cell model. The DE algorithm is an evolutionary algorithm that can be designed to search global optimal points with fast convergence time and present accurate results, requiring few control variables to be set. The accuracy of reproducing the characteristics of the PV module depends on the knowledge of some PV cell model parameters, such as series and shunt resistances, diode ideality factor, and diode reverse saturation current. Once the referred parameters are not usually given in the manufacturers' datasheet, their determination can be achieved by the DE algorithm, employing data and the current-voltage (I-V) characteristic curve provided by the PV module manufacturers. The technique is designed to minimize the error between the reference I-V curve and the I-V curve reproduced by the DE algorithm. Through simulation results, the feasibility of the DE algorithm to estimate the desired parameters of a PV cell is validated, and the algorithm's performance to reach the best solution with fast convergence and a small iteration number is evaluated.

Machine learning driven performance enhancement of perovskite solar cells with CNT as both hole transport layer and back contact

We propose a machine learning-based approach to enhance the performance of perovskite solar cells (PSCs) using carbon nanotubes as both hole transport layer (HTL) and back contact. Carbon-based PSCs offer low fabrication costs, long-term mechanical stability, high charge transport, and broad wavelength transparency. Our study estimates and enhances power conversion efficiency (PCE) of carbon-based PSCs through machine learning. PSC with single-walled carbon nanotube (SWCNT)-based HTL and back contact is investigated in simulations using SCAPS-1D and achieved 14.24% PCE, closely aligning with experimental data. Additionally, we explore the impact of various easily tunable fabrication parameters, such as the band gap and electron affinity of SWCNT in HTL, HTL thickness, active layer thickness, electron transport layer (ETL) thickness, HTL dopant concentration, absorber defect density, and ETL dopant concentration, on PCE. We generate a dataset of 20,480 samples to train classical and neural network-based machine learning models to predict performance parameters of PSCs, including short-circuit current density (JSC), open-circuit voltage (VOC), fill factor (FF), and PCE (η). The current density vs. voltage (J-V) characteristics curve is well-fitted by the predicted JSC, VOC, and FF, as evidenced by an average root mean squared error (RMSE) of 0.03 and a goodness of fit (R2) value of 0.99. The fully connected artificial neural network performs best, with RMSE of 0.05% and R2 of 0.99998 for predicting PCE. Genetic algorithm is used to optimize PCE, yielding a maximum PCE of 20.92%. Furthermore, an analysis of feature dimension and dataset size on prediction performance guides future modeling approaches.

Theoretical study of the thermoelectric properties through a single-molecule junction of Zinc Porphyrin

A theoretical analysis was performed to investigate the transport properties of the Zinc Porphyrin molecule and its response to thermal fluctuations. The renormalization method was used for this analysis, using the Green’s functions technique through the Dyson equation, focusing on first-neighbor interactions. This study produced various results, including energy-dependent transmission probability, current-voltage characteristic curves, electrical and thermal conductance assessments, Seebeck coefficient, and figure of merit (ZT). In order to validate the method used, both the profile results in the transmission probability and the I–V curves were compared with theoretical (DFT) and experimental results, respectively, obtaining significant agreements in the HOMO and LUMO of the molecule, as well as a characteristic behavior of a rectifying device. Complementing the above by calculating the ZT through the molecular system Zn(5,15-di(p-thiolphenyl)-10,20-di(p-tolyl)porphyrin) (ZnTPPdT), it was demonstrated that said molecule could be used as an efficient thermoelectric device that allows thermal energy to be converted into electrical energy.

X-ray Induced Electric Currents in Anodized Ta2O5: Towards a Large-Area Thin-Film Sensor.

We investigated the characteristics of radiation-induced current in nano-porous pellet and thin-film anodized tantalum exposed to kVp X-ray beams. We aim at developing a large area (≫cm2) thin-film radiation sensor for medical, national security and space applications. Large area (few cm2) micro-thin Ta foils were anodized and coated with a counter electrode made of conductive polymer. In addition, several types of commercial electrolytic porous tantalum capacitors were assembled and prepared for irradiation with kVp X-rays. We measured dark current (leakage) as well as transient radiation-induced currents as a function of external voltage bias. Large transient currents (up to 50 nA) under X-ray irradiation (dose rate of about 3 cGy/s) were measured in Ta2O5 capacitors. Small nano-porous Ta and large-area flat Ta foil capacitors show similar current-voltage characteristic curve after accounting for different X-ray attenuation in capacitor geometry. The signal is larger for thicker capacitor oxide. A non-negligible signal for null external voltage bias is observed, which is explained by fast electron production in Ta foils. Anodized tantalum is a promising material for use in large-area, self-powered radiation sensors for X-ray detection and for energy harvesting.

Tribovoltaic performance of the Schottky contact between metal and PZT ceramic

The sliding contact between a metal or semiconductor with another semiconductor can lead to a new charge generation mechanism known as the tribovoltaic effect. This effect has several advantage over the more common triboelectric effect, such as a higher rate of charge transfer and the ability to produce a direct current (DC) output directly via the junction interface. During operation, the junction interface produces a built-in electric field. In this study, we investigate the tribovoltaic effect on sliding between copper and unpoled lead zirconate titanate (PZT) ceramic. It was found that the contact between the metal and semiconducting oxide ceramic leads to the Schottky junction effect, which can effectively drive frictionally excited charges to an external load. By increasing the applied stress to PZT, we observed different current-voltage characteristic curves. The proposed electronic band behavior determines the electrical output direction in the tribovoltaic nanogenerator (TVNG). This direction depends on the built-in electric fields formed at the junction. The performance of the TVNG was tested in both series and parallel connections, observing clearly improved electrical outputs for both. The proposed TVNG can efficiently power small electronic devices, such as LEDs, and charge capacitors in a short period of time. This work expands the understanding of unconventional transport mechanisms through the Schottky contact of PZT and metal, and provides fundamental knowledge for the future development of tribovoltaic devices.

Analytical model of light current-voltage characteristics of a solar cell based on experimental data

In this work, a modified experimental method for calculating the parameters of the one-exponential equation of the light current-voltage characteristic of solar cells has been developed using approximation and verification of experimental data. This approach allowed us to create a more accurate mathematical model of such characteristics. It has been confirmed that the approximation equation of the open circuit voltage versus short circuit current contains the necessary data to establish the numerical values of the p-n junction parameters: the imperfection factor and the saturation current of the one-exponential model of the light current-voltage characteristics of a solar cell. A comparison between the experimentally measured results and those predicted by the mathematical model results allowed not only to correctly determine the values of the parameters of the one-exponential equation of light current-voltage characteristics, but also to identify instrumental and computational errors in the experimental studies. An expression for calculating the series resistance based on verified current and voltage values at the point of maximum power was derived. In cases where the current or voltage values at the maximum power point are questionable, the determination of the series resistance value is possible using numerical methods for solving the equation of the single-exponential model in a narrow range of the light current-voltage characteristic curve in the vicinity of the maximum power point. The use of algorithms in maximum power point tracking systems that more reliably determine its coordinates increases the efficiency of these systems and the output power delivered to the load.

ANALYSIS OF PERFORMANCE OF A PV SOLAR CELL AND EFFECT OF PHYSICAL PARAMETER

In recent days, PV solar systems have been commercialized in almost the whole world because of its advantageous efforts like a long-term supply of power at a very lower cost and various governments are also encouraging consumers to use sustainable green energy. The purpose of this study was to develop a model that allows the user to predict PV cell’s current-voltage (I-V) and power-voltage (P-V) characteristic curves by varying irradiance, cell temperature, and diode ideality factor, and the value of series resistance. The characteristic curves obtained from the simulation of the MATLAB/Simulink model are matched with the data given by the manufacturers by changing the value of mentioned internal parameters. Comparative results of one and two diode models with different electrophysical parameters are shown. There are analyses for photocurrent, voltage and power, as well as their dependence on single and two diode models. Block diagram models for diodes are also presented. Keywords: Irradiance, Temperature, Ideality Factor, Series Resistance, current-voltage characteristics.

Design, Transport/Molecular Scale Electronics, Electric Properties, and a Conventional Quantum Study of a New Potential Molecular Switch for Nanoelectronic Devices.

In this study, we examined the influence of an external electric field applied in two directions: horizontal (X-axis) and vertical (Y-axis) on the electronic and vibrational properties of a field-effect molecular switch, denoted as M. We employed density functional theory and quantum theory of atoms in molecules for this analysis. The current-voltage (I-V) characteristic curve of molecular switch system M was computed by applying the Landauer formula. The results showed that the switching mechanism depends on the direction of the electric field. When the electric field is applied along the X-axis and its intensity is around 0.01 au, OFF/ON switching mechanisms occur. By utilizing electronic localization functions and localized-orbital locator topological analysis, we observed significant intramolecular electronic charge transfer "back and forth" in Au-M-Au systems when compared to the isolated system. The noncovalent interaction revealed that the Au-M-Au complex is also stabilized by electrostatic interactions. However, if the electric field is applied along the Y-axis, a switching mechanism (OFF/ON) occurs when the electric field intensity reaches 0.008 au. Additionally, the local electronic phenomenological coefficients (Lelec) of this field-effect molecular switch were determined by using the Onsager phenomenological approach. It can also be predicted that the molecular electrical conductance (G) increases as Lelec increases. Finally, the electronic and vibrational properties of the proposed models M and Au-M-Au exhibit a powerful switching mechanism that may potentially be employed in a new generation of electronic devices.

Conclusive Model-Fit Current–Voltage Characteristic Curves with Kink Effects

Current–voltage characteristic curves of NFinFET are presented and fitted with modified current–voltage (I-V) formulas, where the modified term in the triode region is demonstrated to be indispensable. In the as-known I-V formula, important parameters need to be determined to make both the measured data and the fitting data as close as possible. These parameters include kN (associated with the sizes of the transistor and mobility), λ (associated with early voltage), and Vth (the threshold voltage). The differences between the measured data and the fitting data vary with the applied source–drain bias, proving that the mobility of the carriers is not consistently constant. On the other hand, a modified formula, called the kink effect factor, is negatively or positively added, simulating solitary heat waves or lattice vibration, which disturb the propagation of carriers and thus influence the source–drain current (IDS). The new statistical standard deviations (δ) are then found to be effectively suppressed as the kink effect is taken into account.

The effect of metal Ag nanoparticles on CdS/ZnTe heterojunction solar cells

Recent research on organic and inorganic solar cells has demonstrated that adding metal nanoparticles to the active layer can dramatically boost the performance of thin-film cells. In this research, Silver (Ag) nanoparticles have been added in CdS/ZnTe thin films that were prepared using the pulsed laser deposition (PLD) technique with laser energy ranging from (200-300 mJ). X-ray diffraction (XRD) analysis was used to examine the thin films of CdS and ZnTe for structural details. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) were also employed to examine the morphology of the films. The typical rectifier behavior was seen using the current-voltage (I-V) characteristic curves. Furthermore, by studying the effect of adding silver (Ag) nanoparticles on the capacitance-voltage (C-V) characteristics.

Nanofluidic sensing platform for PNK assay using nonlinear hybridization chain reaction and its application in DNA logic circuit

In this study, a polyethyleneimine (PEI)/Zr4+-functionalized nanofluidic sensing platform based on nonlinear hybridization chain reaction (NHCR) was developed for PNK activity assay. With the existence of PNK, the hairpin HPNK was cleaved by λ exonuclease, liberating the initiator T-DNA. Then T-DNA triggered the nonlinear HCR in solution and the reaction products were absorbed onto the nanopore, which changed the surface charge of nanofluidic device and could be detected by current-voltage characteristic curves. Compared to traditional linear HCR, the nonlinear HCR exhibits a higher sensitivity and order of growth kinetics, making it a powerful signal amplifier in bioanalysis. Due to the powerful amplification efficiency of nonlinear HCR, high sensitivity of the nanopore and specific recognition site of PNK/λ-Exo, an ultrasensitive and selective PNK sensing approach had been developed and applied to precisely quantitate the PNK activity with a LOD of 0.0001 U/mL. Moreover, utilizing this nanofluidic system as a foundation, we constructed a logic circuit that utilized PNK, adenosine diphosphate (ADP), and (NH4)2SO4 as input elements. ADP and (NH4)2SO4 had a crucial function in facilitating the PNK to regulate the DNA logic gate. By modifying the target and inhibitors, the nanofluidic device could detect a variety of stimuli and execute more advanced logical operations.

Evaluation of front and backside performances of a large surface organic photovoltaic module under bifacial illumination

Semitransparency is one of the attractive characteristics of thin-film solar modules as it allows electricity generation while providing building illumination. However, enhancing transparency can result in lower energy generation efficiency. An effective way to improve energy production in semitransparent modules is through bifacial illumination. This work aims to evaluate, experimentally, and discuss the optical and electrical properties of a commercial, semitransparent organic photovoltaic (OPV) module under bifacial illumination. With that purpose, current-voltage characteristic curves were obtained under the following conditions: a) front, b) rear illumination and c) simultaneous illumination on both faces. The module was placed inside a V-trough cavity to implement electrical measurements with the module's both faces simultaneously illuminated by natural sunlight. Results show that bifacial illumination is an effective way to enhance energy production in semitransparent OPV devices, and a 46% increase in power generation compared to traditional illumination (frontal illumination) was achieved in the experiments. The backside illumination performance differs by over 40%, compared with the front side, due to electrode shading, optics, and differences in the energy conversion processes taking place in the active layer. The OPV module operation under bifacial illumination is equivalent to a parallel connection between the front and backside illumination performances. Optical modeling shows that the active layer absorbs a large part of the incoming light within the cell spectral response. Nevertheless, in the case of frontal illumination, a significant fraction of solar radiation in the visible region is transmitted and remains available, for instance, for building illumination purposes.

The effect of step cooling treatment on the microstructure of Cu2ZnSnS4 film and its electric property

Flexible Cu2ZnSnS4 (CZTS) thin-film solar cells have the advantages of high flexibility, lightweight, and easy storage, which can provide portable and clean energy for various portable electronic and communication devices and vehicles. In this work, CZTS thin film deposited on flexible aluminum foil were prepared by vacuum magnetron sputtering and sulfide annealing in a tubular furnace. A step-by-step cooling way was applied to the annealing stage aiming at tuning the formation of CZTS, that is, when the slow cooling reached a target temperature (400 °C, 350 °C, 300 °C, 250 °C), a rapid cooling was triggered by opening the tube furnace lid. The effects of step cooling on the micro structure and property of CZTS film were studied by X-ray diffraction, Raman scattering, energy dispersive spectroscopy, scanning electron microscopy and current-voltage (I-V) characteristic curve test. The experimental results showed that all samples have CZTS phase and the Al/CZTS interface exhibited ohmic contact. And the formation of secondary phases like SnS, Sn2S3 and Cu31S16 in the sample film can be tuned by the step cooling treatments. The sample treated at 300 °C had the highest CZTS content, the average grain size of CZTS was 45 nm and the number of secondary phases was fewer. Beside, the I-V curve revealed that this sample had the lowest resistance. The experimental results in this work indicate the feasibility of Al as a substrate and back electrode for CZTS thin film.

Current, photocurrent and thermocurrent of borophene-black phosphorus heterostructures

In this paper, we calculated current–voltage characteristic curves (IV curves), Conductivity, real space charge distribution, transmission spectrum, photocurrent, and thermal current of the borophene-black phosphorus heterostructure. Our results show that the zigzag device has excellent photocurrent characteristics. The direction of photocurrent can be adjusted by changing the wavelength of incident light and adding gate voltage. The armchair device has excellent IV curve characteristics and good linear characteristics at low voltage. The armchair device also has good thermoelectric current properties. The position distribution of covalent bonds formed between atoms in this heterostructure is revealed by the real space charge distribution. Our results are significant for applying borophene-black phosphorus heterostructure in electric transport devices.

Spectroscopic study on size-dependent optoelectronics of N-type ultra-high conductive polymer PBFDO

Single-molecule plasmas are widely used in spectroscopic studies and plasma devices, and the organic conjugated molecular chain of poly (benzodifurandione) (PBFDO) has excellent electrical conductivity and unique electronic structure. Therefore, an in-depth theoretical study of the spectroscopic, charge transfer and electron transport properties of PBFDO polymers and the analysis of physical mechanisms are essential. In this work, the absorption spectra of neutral and charged PBFDO polymers of different sizes and periodic systems of PBFDO polymers are studied theoretically. The charge transfer modes of the different absorption peaks are also given. The Raman and resonance Raman properties of long-chain PBFDO polymers under 514 nm laser were revealed. The electron transport properties and Current-Voltage Characteristic (I-V) Curves of PBFDO devices were also investigated. This work will provide the necessary theoretical guidance for the application of PBFDO in the field of nanoscale optoelectronics and the design of devices.

Theoretical investigation of silicon thin film solar cell for improving short and long wavelength response

Theoretical investigation or numerical simulation of performance of a solar cell can provide useful information to maximize power conversion efficiency. In that respect we carried out a set of numerical simulation using AFORS-HET simulation program. Separately the optical absorption of the individual layers of thin film solar cell was analyzed. Current-voltage characteristic curve of a reference cell (Cell-A) was used as the starting device. The power conversion efficiency (PCE) of the reference device was 8.85% with short circuit current density (Jsc) of 15.43 mA/cm2 and fill factor (FF) of 68.3%. After suitable optimization the PCE of this device (Cell-B2) improves to 11.59% (Jsc and FF became 13.0 mA/cm2 and 87% respectively). The results show that the effective optical absorption in the active layer can be improved significantly by optimizing the device structure. The short wavelength response can be improved by reducing the parasitic optical absorption of the doped window layer, while the long wavelength response improves by raising effective absorption length of the active layer. Furthermore, optimum thickness of the active layer, for the highest possible PCE, is found to be dependent upon its defect density.

Influence of Eu3+ on the structural, optical and electrical properties of PEO–PVA: dual bandgap materials for optoelectronic applications

Solid-polymer electrolytes (SPE) based on rare-earth doping is a growing approach for the development of various optoelectronic and ion-conducting devices. Eu3+/PEO–PVA SPE was prepared by solution casting. The impacts of Eu3+ content on the microstructure, chemical composition, and complexation with the functional groups of the blend as well as on the film morphology were evaluated by X-ray diffraction, FT-IR spectroscopy, and FE-SEM microscopy. It was revealed that the film's crystallinity and optical transmittance can be tailored by Eu3+ content. Tauc's method illustrated that the films exhibit dual band gaps on both the low energy side (2.0–2.8 eV) and the high energy side (4.0–4.38 eV). In addition, the refractive index and optical conductivity of SPE were greatly enhanced with increasing Eu3+ content. The current–voltage characteristic curves were recorded at an applied voltage range of 0–10 V, and temperature range of 30–100 °C. The materials exhibited non-Ohmic behavior. The DC conductivity ({sigma }_{mathrm{dc}}) values of the pure and 6 wt% Eu3+-doped blend were in the range of 1.16 × 10–6–2.05 × 10–6 S/cm and 1.73 × 10–6–3.36 × 10–6 S/cm, respectively. The relations between the current density and the electric field revealed that the Schottky emission is the most suitable conduction mechanism. The results indicate that Eu3+/PEO–PVA SPE is suitable for some optoelectronic applications and ion-conducting devices.

Brownian dynamics simulation of electrical properties of KcsA potassium ion channel

As one of the regulators of cationic concentration in cells, potassium channels play an important role in the depolarization and repolarization of nerve cell. KcsA (K<sup>+</sup> conduction and selectivity architecture) channel is simple and has the commonness of potassium ion channel, which is often used as a template for potassium channel research. In this paper, Brownian dynamics (BD) method is used to simulate the electrical characteristics of the actual KcsA potassium channel systematically. The potential mean force (PMF) of ions in the channel under electrostatic field, the current-voltage characteristic curve of symmetric solution and asymmetric solution, the ion concentration distribution curve in the axial direction of the channel, and the conduction-concentration curve are obtained. The results show that the selectivity filter region of KcsA potassium channel blocks the passage of Cl<sup>–</sup> basically, showing a special selection characteristic of the passage of K<sup>+</sup>, that its current-voltage curve presents a basically linear distribution, and that the conductivity-concentration curve presents a trend of first increasing and then flattening. The basic characteristic is consistent with the experimental phenomenon. In addition, the influence of the THz field on the channel K<sup>+</sup> current is also simulated and analyzed. Compared with applying only the same amplitude electrostatic field, the selected terahertz field of 0.6 THz, 1.2 THz, and 5 THz can reduce the PMF by affecting the interaction potential energy between ion pairs, thereby increasing the K<sup>+</sup> current. The research in this paper not only deepens the understanding of the regularity of KcsA potassium ion channels, but also provides a new idea for studying other types of ion channels and the influence of terahertz field on the characteristics of ion channels.