Curves Of Solar Cells Research Articles

A Universal Extraction Method for Physical Parameters Applied for J–V Curves of Solar Cells

A Universal Extraction Method for Physical Parameters Applied for J–V Curves of Solar Cells

Heteroleptic Tin-Antimony Sulfoiodide for Stable and Lead-free Solar Cells

Summary The quaternary chalcogenide halides of group IV and V elements have attracted much attention due to their interesting semiconducting properties as well as a suitable band gap for solar cells. Here, for the first time, we report on solar cells using tin-antimony sulfoiodide (Sn2SbS2I3). Sn2SbS2I3 solar cells were fabricated using a chemical single-step deposition process with a solution containing a SbCl3-thiourea complex and SnI2 with the configuration of TiO2 and poly[2,6-(4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b′]dithiophene)-alt-4,7-(2,1,3-enzothiadiazole)] as the electron- and hole-transporting layers, respectively. The best-performing cell exhibits a power conversion efficiency of 4.04% under the illumination of standard AM 1.5G conditions (100 mW cm−2). These unencapsulated cells exhibited good stabilities at 80% relative humidity, 85°C in air, and under illumination, respectively. These results provide guidelines for fabrication of lead-free heteroleptic perovskite solar cells by hosting divalent or combinations of monovalent and trivalent metal cations.

Extraction of the minority carrier transport properties of solar cells using the Hovel model and genetic algorithms

In this paper, a quick and accurate method for extraction of the minority carrier transport properties of p-n or n-p junction solar cells, such as diffusion lengths and surface recombination velocities, is presented. The knowledge of these parameters is essential to investigating factors that limit the performance of photovoltaic devices. The proposed method, based on genetic algorithms and the analytical Hovel model, is used to fit the external quantum efficiency (EQE) curves of solar cells with different emitter thicknesses. As a demonstrative example of application of the procedure carried out in this work, theoretical and experimental EQE curves of n-p GaAs solar cells under the standard AM1.5G spectrum have been used in order to extract the desired parameters. Errors less than 2.4% have been obtained, which shows the capability of the developed tool. An analysis of the total number of iterations is presented. The results obtained can be used to improve the design, optimization, and manufacturing process of high-efficiency photovoltaic devices.

One-dimensional modeling for optoelectrical simulation of a mesoporous perovskite solar cell.

The metal-halide perovskite solar cell (PSC) has risen to the forefront of photovoltaic research, and presents the potential for low-cost fabrication with high-power conversion efficiency. Better understanding of the PSC operation mechanism is necessary and required to further improve the performance of the device. Therefore, in addition to numerous experimental studies, some number of optoelectrical simulations are necessary. However, usually, simulations are either electrical or optical and more in relation to one-dimensional (1D) structures such as planar cells. In this study, an approach to optoelectrical simulation of a 3D solar cell, such as the mesoporous PSC, has been presented. First, the 3D layers, such as the mesoporous layer, are modeled to a 1D effective layer using Bergman's effective medium theory. By using the spectral density function, this effective medium theory is able to introduce the 1D equivalent of the 3D layer. Then, the optical results by transfer matrix method are transferred to the SCAPS-1D code, in order to simulate the EQE spectrum and the JV curve of solar cells. The simulation results were compared with the experimental results for two mesoporous PSC, one without a capping perovskite layer and the other with the capping layer. The results of this study showed that the proposed procedure can simulate and therefore investigate the optoelectrical properties of 3D mesoporous solar cells, which can also be extended to similar 3D structures. This 1D simulation procedure, compared to 3D simulation, has a much lower execution time offering more simplicity and no need for commercial codes or specific hardware.

Visible Light Communication System for Indoor Positioning Using Solar Cell as Receiver

This article studies an indoor positioning system (IPS) based on visible light communication (VLC) using the solar cells as optical receivers. Due to the solar cell characteristics, the proposed system offers simultaneously communication and energy gathering. The current - voltage (I-V) and power - resistor (P-R) curves of solar cell under visible light is studied. The frequency response is investigated. The effect of solar irradiance interference on the VLC-based indoor positioning system (VLC-IPS) efficiency is also shown. A trilateration technique is used for estimating receiver's location. The obtained results show that the proposed system can simultaneously receive data and collect energy and it provides a suitable positioning accuracy with an average position error less than 3cm. The studied system can be considered an eco-friendly and promising technology.

Simulation of solar cells by delocalized recombination model and its applications

For lattice-mismatch, high-defect-density solar cells, the current-voltage curve is not perfects, and it always has high ideality factor and low shunt resistance. In traditional one-dimension circuit model of solar cells, there is a paralleled resistor Rp and recombination diodes with high ideality factor to simulate this imperfection. In this research, a delocalized recombination model is built based on the assumption that recombination could occur between trapped electrons from n type sides and trapped holes from p type side. The model with different parameters (i.e. defect volume w and recombination parameter Cp) is then added into current continuity equations and I-V curves of solar cells were calculated. With the increase of Cp, fill factor (FF) decreases obviously, followed by the decrease of short-circuit current and open-circuit voltage. Larger defect volume w would cause higher ideality factor. The effects of mobility on I-V curves were also calculated, low mobility leads to decrease of shunt resistance and fill factor. Two type of solar cells with different configurations were irradiated by 70 keV and the I-V curves show different degradation behaviors. Type A cell shows large decrease of shunt resistance indicating loss of mobility while type B cell shows increase of n(V) due to delocalized recombination. The difference is related to different thicknesses of GaInP.

Study of validity of the single-diode model for solar cells by I–V curves parameters extraction using a simple numerical method

The I–V measurement of solar cells is one of the most employed electrical characterization techniques in the photovoltaics research field due to the valuable information one can obtain from such a curve. Parameters like Voc, Isc and the maximum power can be easily observed at a glance. Furthermore, additional information can be extracted by a more exhaustive analysis involving the equivalent electrical circuit of a solar cell which is based on ideal electrical components with a well-defined behavior. This equivalent circuit is typically assumed to be formed by a current source in parallel with a single diode and a shunt resistor, connected to a series resistor. However, this model does not take into account the separate contributions of the different carrier transport mechanisms in solar cells; for example, carrier diffusion and recombination-generation in the depletion region. Therefore, the single diode model may not be suitable in many practical cases. In this work, a simple numerical method was developed to extract the parameters for both single diode and double diode models from experimental I–V curves of solar cells. The developed numerical algorithm was applied to extract the parameters for a published benchmark solar cell which has been used for testing this kind of algorithms. The extracted parameters using our simple method are comparable with other more sophisticated and computer power demanding algorithms. Thereafter, we applied the developed algorithm to extract the single-diode parameters from simulated “experimental” I–V curves, where two carrier transport mechanisms are present, trying to understand under what conditions the single diode approximation would provide meaningful parameters for such experimental curves. It is shown that the extracted parameters can vary strongly, particularly for the dark saturation current and ideality factor, without much variation of the root mean square error between the experimental data and the model, causing these values to be unreliable and its physical interpretation misleading. We show that the same algorithm can be applied to a double diode (two exponentials) model providing physically meaningful parameters without much computing power requirements. In summary, there is no further justification for using a single diode model to interpret the experimental I–V curves of real solar cells.

Modeling and simulation of graphene-gated graphene-GaAs Schottky junction field-effect solar cell for its performance enhancement

Modeling and simulation of graphene-gated graphene-GaAs Schottky junction field-effect solar cell is performed using in-house developed algorithm based on finite-difference method, where Poisson and drift-diffusion equations are solved in an appropriate way. Our algorithm is verified by comparing the simulated $J$ – $V$ curve of solar cell with the previous experimental one. The carrier generation rate is calculated with light multireflection in the solar cell excluded, due to large optical absorption coefficient of GaAs, and the radiative recombination in GaAs leads to $\sim 5$ % light generated carrier loss. The charge transfer effect in graphene is investigated, which can affect open circuit voltage, and in particular for the semiconductor substrate with very low hole mobility. It is further numerically demonstrated that: 1) both open circuit voltage $V_{\textrm {OC}}$ and short circuit current $J_{\textrm {SC}}$ of the solar cell are governed by doping concentration through affecting Schottky barrier height and depletion width; 2) the value of $V_{\textrm {OC}}$ can be effectively adjusted by decreasing the thickness of gate oxide; however, it may result in oxide breakdown or reliability problem; and 3) there is tunability inertia for $V_{\textrm {OC}}$ with multilayer junction graphene implemented, but it can provide low series resistance.

Optimization of a Fuzzy-Logic-Control-Based MPPT Algorithm Using the Particle Swarm Optimization Technique

In this paper, an asymmetrical fuzzy-logic-control (FLC)-based maximum power point tracking (MPPT) algorithm for photovoltaic (PV) systems is presented. Two membership function (MF) design methodologies that can improve the effectiveness of the proposed asymmetrical FLC-based MPPT methods are then proposed. The first method can quickly determine the input MF setting values via the power–voltage (P–V) curve of solar cells under standard test conditions (STC). The second method uses the particle swarm optimization (PSO) technique to optimize the input MF setting values. Because the PSO approach must target and optimize a cost function, a cost function design methodology that meets the performance requirements of practical photovoltaic generation systems (PGSs) is also proposed. According to the simulated and experimental results, the proposed asymmetrical FLC-based MPPT method has the highest fitness value, therefore, it can successfully address the tracking speed/tracking accuracy dilemma compared with the traditional perturb and observe (P&O) and symmetrical FLC-based MPPT algorithms. Compared to the conventional FLC-based MPPT method, the obtained optimal asymmetrical FLC-based MPPT can improve the transient time and the MPPT tracking accuracy by 25.8% and 0.98% under STC, respectively.

Leakage of photocurrent: an alternative view on I–V curves of solar cells**Project supported by the Union Innovation Projects of Jiangsu Province (No. BY2011182) and CAS, the National Basic Research Program (No. 2012CB619305), and the National Natural Science Foundation of China (Nos. 51272275, 51302305, 61376065).

An alternative way is proposed to interpret I–V characteristics of GaInP single-junction solar cells by position-dependent leakage of photocurrent. With this approach, the I–V curves of solar cells under non-uniform illumination are well analyzed. The effective spreading resistance is also extracted to understand the dynamic behavior of between the open-circuit voltage and short-circuit current points. The conditions under which the one-diode model will fail are addressed in detail. These analyses are also applicable for a characterization of the I–V curves with lateral voltage distribution under uniform illumination.

The Solar Cell Mathematical Model Simulation and Verification

The output characteristics of solar cell that researched as the target is analysed at different temperatures and light intensity .Combining with the equivalent circuit of solar cell, mathematical model is established .The system is simulated through MATLAB/Simulink and the data is compared with the actual one. The experimental results show that the model can well reproduce the output characteristics curve of solar cell at arbitrary condition and the error between the model and the actual output is decreased because of the series resistance. The system can satisfy the requirements of engineering design, in addition, the system can provides theoretical basis for simulation study of solar power generation system.

Determining diode parameters of illuminated current density-voltage curves considering the voltage-dependent photo current density

Suitable procedures for the determination of diode parameters of illuminated and dark current density-voltage ( j - V ) curves of solar cells are investigated. Within these procedures we avoid misinterpretations by the commonly used shifting approximation which assumes a voltage-independent photo carrier collection. To this end, the voltage-dependent collection efficiency is determined by j - V measurements under incremental illumination. After that, illuminated curves can be converted into dark curves taking the voltage-dependent photo current density into account. The converted dark curve next is consigned into a program that numerically solves the implicit equation of the current density and derives the diode parameters by means of a weighted least-squares minimization. Only if fluctuations of the illumination are noticeably high this procedure cannot be used, since the converted dark curve also reveals a high noise level. Then, the determination of diode parameters is performed stepwise with the help of commonly used methods.

Parameter identification for solar cell models using harmony search-based algorithms

Recently, accurate modeling of current vs. voltage (I–V) characteristics of solar cells has attracted the main focus of various researches. The main drawback in accurate modeling is the lack of information about the precise values of the models parameters, namely, photo-generated current, diode saturation current, series resistance, shunt resistance and diode ideality factor. In order to make a good agreement between experimental data and the models results, parameter identification with the help of an optimization technique is necessary. Because I–V curve of solar cells is extremely non-linear, an excellent optimization technique is required. In this paper, harmony search (HS)-based parameter identification methods are proposed to identify the unknown parameters of the solar cell single and double diode models. Simple concept, easy implementation and high performance are the main reasons of HS popularity to solve complex optimization problems. For this aim, three state-of-the-art HS variants are used to determine the unknown parameters of the models. The effectiveness of the HS variants is investigated with comparative study among different techniques. Simulation results manifest the superiority of the HS-based algorithms over the other studied algorithms in modeling solar cell systems.

Experimental Study of Light Intensity on I-V Characteristic of Single Crystalline Silicon Solar Cell

It is important to understand the effect of the light intensity on output performance of the solar cell, in order to evaluate the I-V curve of solar cell under various environment conditions. Based on the method of sun-light sources simulation and the linear interpolation method, this paper dissused the I-V characteristics of single crystalline silicon solar cell under different light intensity. The experiment results show that with the increasing of light intensity of solar simulator, the open circuit voltage VOC changed very little，the characteristics parameters short circuit current Isc increased linearly, the maximum power output Pm increased linearly, and the photoelectric transgormation efficiency η kept a constant appromixaly after increasing to a certain level.

Explanation of commonly observed shunt currents in c-Si solar cells by means of recombination statistics beyond the Shockley-Read-Hall approximation

The current-voltage (I–V) characteristics of industrially fabricated, crystalline silicon solar cells are often influenced by non-linear shunts that originate from localized, highly disturbed regions and cause ideality factors n > 2. We show that recombination within such locations needs model descriptions that go beyond the Shockley-Read-Hall (SRH) approximation, because the density of defects is so high that recombination does not occur via isolated, but coupled defect states. We use a variant of coupled defect level (CDL) recombination, the donor-acceptor-pair (DAP) recombination, but via deep levels (as opposed to shallow levels). With this model, we quantitatively reproduce the I–V curves of solar cells that we subjected to various degrees of cleaving, laser scribing or diamond scratching to form shunt locations in a controlled manner. The suggested model explains the transition from ideality factors n < 2 to n > 2 when going from low to high defect densities. We also explain the non-saturating reverse I–V characteristics. We show that an additional source of currents with n > 2 is SRH recombination in an inversion layer that extends from the front p-n junction to the rear contact along the cell’s edge or along a micro-crack.

3D Analysis of the performances degradation caused by series resistance in concentrator solar cells

This paper deals with the modeling of series resistance components in silicon concentrator solar cells. The main components of the macroscopic series resistance are analyzed by means of one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D) numerical simulations. It is shown that the contribution of the lateral current flux, flowing along the emitter region, and of the transverse current flux, flowing along the metal grid, cannot be neglected and, hence, the operation of solar cells subjected to high current densities cannot be described by simple one-dimensional models. The percentage weight of 2D and 3D components on the total value of the series resistance is evaluated and rules for the proper design of the cell geometries are given. An analysis of the effectiveness of the most popular methods for the extraction of the series resistance from the I–V curves of solar cells is also proposed.

Modeling of the I– V curves of the PV modules using linear interpolation/extrapolation

Translation of the I– V curves of solar cells and modules for irradiance G and device temperature T is investigated. A new translation procedure based on the linear interpolation/extrapolation is proposed, in order to translate the I– V curves to target conditions of G and T. The accuracy of the method is investigated based on the indoor and outdoor experimental I– V curves of various kinds of photovoltaic (PV) cells and modules. The calculated the I– V curves over a wide range of G and T well agree with experimental results for various kinds of PV cells and modules. These results indicate that the translation of the I– V curve based on the method is effective for estimating the performance of the PV devices under various climatic conditions.

Simulating solar cells with a microcomputer

Designing modern silicon solar cells in order to get the maximum efficiency requires the inclusion of effects such as the variation of diffusion length, and electric field as a function of impurity concentration in nonhomogeneous silicon. In this paper, it is shown that it is possible to develop an efficient computer program to simulate the I–V curves of solar cells, which takes into account such effects, when low-injection conditions apply to the semiconductor. The program can be run in any PC microcomputer, without any coprocessor, giving results similar to larger programs, in a fraction of the time usually required for this purpose. The program allows the inclusion of internal resistances (series and shunt) in order to compare the ideal and real behavior of a given solar cell. Conversion efficiency, open circuit voltage, short circuit current, and filling factor are obtained for a set of fabrication parameters, such as substrate and emitter dopings, thicknesses, and surface recombination velocities. The results are in agreement with recent experimental results.