Two-diode Model Research Articles

Measurements and Modeling of III-V Solar Cells at High Temperatures up to 400 <inline-formula> <tex-math notation="latex">${}^{\circ}$</tex-math> </inline-formula>C

In this paper, we study the performance of 2.0 eV Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.12</sub> Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.39</sub> In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.49</sub> P and 1.4 eV GaAs solar cells over a temperature range of 25-400°C. The temperature-dependent J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">01</sub> and J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">02</sub> dark currents are extracted by fitting current-voltage measurements to a two-diode model. We find that the intrinsic carrier concentration n <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i</sub> dominates the temperature dependence of the dark currents, open-circuit voltage, and cell efficiency. To study the impact of temperature on the photocurrent and bandgap of the solar cells, we measure the quantum efficiency and illuminated current-voltage characteristics of the devices up to 400°C. As the temperature is increased, we observe no degradation to the internal quantum efficiency and a decrease in the bandgap. These two factors drive an increase in the short-circuit current density at high temperatures. Finally, we measure the devices at concentrations ranging from ~30 to 1500 suns and observe n = 1 recombination characteristics across the entire temperature range. These findings should be a valuable guide to the design of any system that requires high-temperature solar cell operation.

Effect of various model parameters on solar photovoltaic cell simulation: a SPICE analysis

In this paper, all the models of PV cell, namely ideal single-diode model, single-diode $$R_{\rm s}$$ model, single-diode $$R_{\rm p}$$ model, the two-diode model, and the three-diode model, have been discussed. SPICE simulation is done to evaluate the impact of model parameters on the operation of PV cell. The effects of the parameters are discussed. The photocurrent, $$I_{\rm L},$$ is proportional to irradiance, and the series resistance, $$R_{\rm s},$$ reduces the short-circuit current and fill factor. The parallel resistance, $$R_{\rm p},$$ reduces the open-circuit voltage, and both the diffusion diode and recombination diode reduce the open-circuit voltage value and fill factor. Finally, it is shown that an increase in cell operating temperature reduces the open-circuit voltage and fill factor and thus degrades the performance significantly.

Statistical analysis and engineering fit models for two-diode model parameters of large area silicon solar cells

In this paper, an attempt has been made to find the correlation between various parameters of the two-diode equivalent circuit model of silicon solar cells. The statistical analysis has been done to find the engineering fit models between these parameters. The solar cell parameter data of 82 solar cell samples has been estimated using the Particle Swarm Optimization method from the measured illuminated I-V characteristics of the cells. This data on estimated parameters has been used to find the Pearson’s correlation coefficient between different parameters and the significant outcome of this work is that it revealed a high correlation between the first diode’s reverse saturation current and its ideality factor and a medium correlation between the second diode’s reverse saturation current and its ideality factor in the two-diode equivalent circuit model of a silicon solar cell. An engineering fit model has been suggested between the reverse saturation current and ideality factor of the first diode, based on the data of 82 large area (∼154.8cm2) silicon solar cells with AM1.5 conversion efficiency between 15% and 18.4%. The suggested engineering fit between the two would be a method to reduce the number of parameters needed for silicon solar cell modeling and to make it easier for predicting the module output.

An accurate modelling of the two-diode model of PV module using a hybrid solution based on differential evolution

This paper proposes an accurate computational technique for the two-diode model of PV module. Unlike previous methods, it does not rely on assumptions that cause the accuracy to be compromised. The key to this improvement is the implementation of a hybrid solution, i.e. by incorporating the analytical method with the differential evolution (DE) optimization technique. Three parameters, i.e. IPV, Io1, and Rp are computed analytically, while the remaining, a1, a2, Io2 and Rs are optimized using the DE. To validate its accuracy, the proposed method is tested on three PV modules of different technologies: mono-crystalline, poly-crystalline and thin film. Furthermore, its performance is evaluated against two popular computational methods for the two-diode model. The proposed method is found to exhibit superior accuracy for the variation in irradiance and temperature for all module types. In particular, the improvement in accuracy is evident at low irradiance conditions; the root-mean-square error is one order of magnitude lower than that of the other methods. In addition, the values of the model parameters are consistent with the physics of PV cell. It is envisaged that the method can be very useful for PV simulation, in which accuracy of the model is of prime concern.

Determination of subcell open circuit voltages and Iph–Voc curves in multijunction solar cells by sequentially pulsed, monochromatic illumination

The open circuit voltages Voc of individual subcells in a multijunction solar cell are measured by illuminating a given subcell with a pulse of spatially homogeneous, nearly monochromatic light with a rising edge in the μs regime. The influence of luminescent coupling and semi-transparency on Voc is eliminated by over-illuminating all subcells below this subcell with a preceding light pulse. By using a suns-Voc approach, the two-diode model dark saturation currents of each subcell are extracted. The proposed method is verified experimentally as well as through simulations on three and four-junction solar cells.

Investigation on the accurate parameter estimation of photovoltaic (PV) module based on simplified two-diode model

Purpose This paper aims to present a detailed investigation on the parameter estimation of a photovoltaic (PV) module by using a simplified two-diode model. Design/methodology/approach The studied PV module in this paper resembles an ideal two-diode model, and to reduce the computational time, the proposed model has a photocurrent source and two ideal-diodes and neglects the series and shunt resistances. Hence, for calculating the unknown parameters, only four parameters are required from the datasheet. Moreover, the studied model is simple and uses an easy modeling approach which is free from complexities. Findings The performance of the PV module is analyzed under non-standard test conditions by considering partial shading at different shaded levels, and it is found that the model has less computational time and gives accurate results. Originality/value The usefulness of this PV model is demonstrated with the help of several illustrative figures, and the performance of the PV module is evaluated.

Optimal laser wavelength for efficient laser power converter operation over temperature

A temperature dependent modeling study is conducted on a GaAs laser power converter to identify the optimal incident laser wavelength for optical power transmission. Furthermore, the respective temperature dependent maximal conversion efficiencies in the radiative limit as well as in a practically achievable limit are presented. The model is based on the transfer matrix method coupled to a two-diode model, and is calibrated to experimental data of a GaAs photovoltaic device over laser irradiance and temperature. Since the laser wavelength does not strongly influence the open circuit voltage of the laser power converter, the optimal laser wavelength is determined to be in the range where the external quantum efficiency is maximal, but weighted by the photon flux of the laser.

Thermodynamic analysis and optimization of densely-packed receiver assembly components in high-concentration CPVT solar collectors

Concentrated photovoltaic thermal (CPVT) solar collectors are one of the most promising solar concepts due to their compactness, multi-output nature, and high exergy efficiencies. However, accurate design models and clear simulation algorithms on the component-level are critical for the proper system-level engineering and evaluation of CPVT collectors. In this study, detailed design models and simulation algorithms of three state-of-the-art components commonly incorporated into the densely-packed receiver assemblies of high-concentration CPVT solar collectors are presented. These components, namely multi-junction photovoltaic cells, segmented thermoelectric generators with interconnectors, and finned minichannel heat extractors, could be integrated to form CPVT receiver assemblies in a number of different configurations. Thermodynamic component-level analyses that avoid oversimplified as well as computationally-expensive modeling approaches and provide clear and robust simulation algorithms with reasonable accuracy are separately developed for the three addressed components. Performance variations of InGaP/InGaAs/Ge cells with respect to cell temperature and flux concentration ratio are identified using a two-diode equivalent circuit model and relations for the irradiance-dependent temperature coefficients are provided. The effects of heat source/sink temperature and thermal impedance, load resistance, thermal and electrical contact resistance, and geometrical parameters on the performance of segmented thermoelectric generators are identified using a 1D thermoelectric model. The thermal and hydraulic performance of minichannel heat extractors when designed under fixed mass flowrate or fixed HTF velocity operation modes, as the number of minichannels is varied and using pure and nanoparticles-suspended HTFs, are studied to find their optimum geometries using a 1D total effective thermal resistance model. The obtained results provide valuable insight into the critical factors to be taken into account in the engineering of the addressed CPVT receiver assembly components. The separately-series equivalent thermal resistance network technique is employed in the thermal analyses in order to treat two-dimensional steady-state heat transfer in composite structures with different thermal conductivities as one-dimensional without a loss of accuracy. Finally, using the developed design models and simulation algorithms, constrained non-linear multi-variable geometric optimization of the assembly components has been carried out to obtain minimum pumping power, maximum extractor heat transfer coefficient, and maximum thermoelectric power output. Results show the existence of optimum geometrical design vectors, given a set of operation conditions, ensuring that the system-level performance of a CPVT employing the optimized components is maximized.

Development of Temperature-Dependent SPICE Computer Models of Photovoltaic Cells

Parameterized computer models of photovoltaic (PV) cells and modules are proposed in the paper. Four-and five-parameter one-diode models, two-diode model, as well as behavioral models of the PV cell are considered. The temperature-dependence of the model parameters is taken into account. Parameter extraction approach is developed to determine the model parameters, based on nullor equivalent circuit and datasheet characteristics of the PV cells and modules. PSpice description of the developed PV model is given in the form of parameterized block. The accuracy of the computer PV models is investigated by comparison to the datasheet characteristics.

Fabrication of a 1.7-kV Schottky barrier diode with improved forward current-voltage characteristics

This paper presents the effects of thermal annealing performed at different temperatures on the forward current-voltage (I-V) characteristics to fabricate a 1.7-kV 4H-SiC Schottky barrier diode (SBD) with improved forward performances. To optimize the thermal annealing temperature, the SBDs were characterized by using precise low-current and high-current I-V measurements, a twodiode model analysis and grazing-incidence X-ray diffraction measurements. The results showed that a degradation in the ideality factor and a dramatic decrease in the turn-on resistance began at temperature above 550 °C. In particular, the turn-on resistance for the SBD annealed at 550 °C was reduced by 32% compared to that for the SBD without thermal annealing without any degradation in the Schottky barrier height. This was attributed to an expansion of Al crystallites caused by the thermal annealing.

Lead Halide Perovskite Photovoltaic as a Model p-i-n Diode.

The lead halide perovskite photovoltaic cells, especially the iodide compound CH3NH3PbI3 family, exhibited enormous progress in the energy conversion efficiency in the past few years. Although the first attempt to use the perovskite was as a sensitizer in a dye-sensitized solar cell, it has been recognized at the early stage of the development that the working of the perovskite photovoltaics is akin to that of the inorganic thin film solar cells. In fact, theoretically perovskite is always treated as an ordinary direct band gap semiconductor and hence the perovskite photovoltaics as a p-i-n diode. Despite this recognition, research effort along this line of thought is still in pieces and incomplete. Different measurements have been applied to different types of devices (different not only in the materials but also in the cell structures), making it difficult to have a coherent picture. To make the situation worse, the perovskite photovoltaics have been plagued by the irreproducible optoelectronic properties, most notably the sweep direction dependent current-voltage relationship, the hysteresis problem. Under such circumstances, it is naturally very difficult to analyze the data. Therefore, we set out to make hysteresis-free samples and apply time-tested models and numerical tools developed in the field of inorganic semiconductors. A series of electrical measurements have been performed on one type of CH3NH3PbI3 photovoltaic cells, in which a special attention was paid to ensure that their electronic reproducibility was better than the fitting error in the numerical analysis. The data can be quantitatively explained in terms of the established models of inorganic semiconductors: current/voltage relationship can be very well described by a two-diode model, while impedance spectroscopy revealed the presence of a thick intrinsic layer with the help of a numerical solver, SCAPS, developed for thin film solar cell analysis. These results point to that CH3NH3PbI3 is an ideal intrinsic semiconductor, which happens to be very robust against accidental doping, and that the perovskite photovoltaic cell is in fact a model p-i-n diode. The analytical methods and diagnostic tools available in the inorganic semiconductor PV cells are useful and should be fully exploited in the effort of improving the efficiency. One outstanding question is why the perovskite stays intrinsic. Considering the defects and impurities that must abound in the perovskite layers formed by the spin-coating process, for example, there must be physicochemical mechanism keeping it from being doped. This may be related to the special band structure making up the band gap in this ionic solid. Understanding the mechanism may open a door for the wider utility of this class of solid.

Impact of Cracks in Multicrystalline Silicon Solar Cells on PV Module Power—A Simulation Study Based on Field Data

In this paper, we present a methodology to exploit the crack statistics of solar cells in photovoltaic (PV) modules assessed in field for simulating the power output of PV modules and module strings. The measured probability of a crack and the type of crack, depending on the position of the cell in the module, are used to simulate a statistical distribution of modules made up of cells represented by an extended two-diode model. We show that cracks have a significative effect on module power when the break resistance is higher than 0.01 Ω. We compare the modeled break resistances with the specific break resistances measured at cracks in minimodules caused by mechanical bending tests. In the range of measured break resistances, 19% of the individual modules lose more than 20% of their initial power, and up to 5% of strings consisting of 20 modules show a power loss of more than 20%.

Research on the Output Characteristics of Photovoltaic Array under the Non-Uniform Light

The output characteristics of photovoltaic array was related with the topology of array, shadow distribution and illumination level. The theoretical analysis and simulation modeling of output characteristics of photovoltaic array including series array, parallel array and series-parallel array were made under the non-uniform illumination environment based on the circuit analysis. The photovoltaic cell was modeled by use of the improved two-diode model. Non uniform illumination is expanded from two illumination levels of traditional to N illumination levels and from the single series array to any number series-parallel array. The different analysis methods were adopted in different arrays for mathematical modeling and simulation. The current analysis was used in series arrays and voltage analysis used in parallel arrays. Analysis of current in branches and voltage between branches was used in series-parallel array. Then the mathematical models were established and programmed in m-file by MATLAB. The simulation models had a high computational accuracy, and were suitable for any simulation output characteristics of PV in different light environment and array topology. They could provide a theoretical basis for constructing the topological structure on the same condition and studying MPPT of PV array under non-uniform illumination.

Application of Equivalent Circuit Models to Monitor the Degradation of Organic Photovoltaic Cells

Organic photovoltaic (OPV) devices have lower efficiency, shorter lifetimes, faster degradation, and poorer stability than inorganic photovoltaics (IPV) in ambient conditions. In this paper, the equivalent electrical circuit of a two-diode model effectively extracts the model-fit electrical photovoltaic (PV) parameters from degraded OPV devices, especially the series (R s ) and shunt (R sh ) resistances. The result shows a better correlation between the resistances of the devices and performance of the devices over the degradation process where the devices are deliberately exposed to ambient conditions under constant illumination. The degradation of the devices is mostly caused by the degradation of the aluminum (Al) electrode from water and oxygen, which correlates to the R s . However, it is possible that the degradation of the bulk active layer can also occur due to the constant illumination on the device, which causes a reduction of photocurrent.

A high-accuracy photovoltaic emulator system using ARM processors

In this paper, an embedded design for implementing a real-time photovoltaic (PV) system emulator with user-defined environmental conditions is proposed. The design implemented on a Sitara Cortex 9 ARM processor allows the evaluation of PV cells in a low-cost, portable and affordable system. This embedded PV emulation system uses an LCD screen to establish a human-system interface (HSI), and it contains an extensible database of commercial PV cells with their manufacturer’s datasheet parameters. Based on the accurate two-diode model, the proposed design allows the generation of high precision I–V,P–V characteristic curves with the embedded ARM, which represents an affordable and simple solution. Experimental results demonstrate the accuracy of the real-time embedded system for different solar cells and environmental conditions.

A procedure to calculate the I – V characteristics of thin-film photovoltaic modules using an explicit rational form

Abstract Accurate models of the electrical behaviour of photovoltaic modules are effective tools for system design. One or two diode equivalent circuits have been widely used even though some mathematical difficulties were found dealing with implicit equations. In this paper, a new model based on a simple rational function, which does not contain any implicit exponential form, is presented. The model was conceived in order to be used with thin-film photovoltaic modules, whose current–voltage curves are characterised by very smooth shapes. The parameters of the model are evaluated by means of the derivatives of the issued characteristics in the short circuit and open circuit points at standard rating conditions, and assuming that the calculated current–voltage curve contains the rated maximum power point of the simulated panel. The capability of the model to calculate the current–voltage characteristic for values of the solar irradiance and cell temperature far from the standard rating conditions was verified for various thin-film technologies, such as CIS, CIGS, amorphous silicon, tandem and triple-junctions photovoltaic modules. A comparison with the results obtained by another rational model and other two-diode models, which were used to simulate the electrical behaviour of thin-film photovoltaic modules, is also presented.

Effect of Electrical Model, Temperature, and Generation Rate on the Photovoltaic Module Parameters

AbstractThis paper proposes a two-diode model to represent the photovoltaic cell. This model requires only three parameters (photocurrent, diffusion, and recombination of the dark current). The analytical resolution of continuity equations in each region of a crystalline solar cell enabled the determination of the expressions of diffusion and recombination of dark currents. New relationships are proposed giving the expressions of these currents as a function of their reference values, which are determined from both the data provided by the manufacturer and the different temperature values. This study indicated how the parameters of the proposed model were determined. Predicted current–voltage curves were compared with the De Soto one-diode model and experimental data from a building integrated photovoltaic facility at the National Institute of Standards and Technology (NIST) for two different cell technologies (single crystalline, polycrystalline). The maximum power calculated by the proposed model was ca...

CIGS P3 scribing using ultrashort laser pulses and thermal annealing

In general, laser structuring of CIGS solar modules causes material modifications in the vicinity of the processed area. The irradiated region often reveals high densities of defect states or melt that affect the electrical properties dramatically. In particular, this is a problem for laser P3 scribing where trenches should isolate the front from the back electrode. In this paper, we demonstrate optimized P3 scribes using ultrashort-pulse laser processing in combination with thermal annealing yielding permanently increased solar cell performance. We further investigate this behavior with the help of a two-diode equivalent circuit model. The simulations correlate very well to our obtained experimental results. We show that basically two main effects are responsible for the performance increase after thermal annealing. Firstly, the recombination current within the p–n junction decreases over orders of magnitudes, and secondly, the overall shunt resistance rises significantly.

Universal analytical solution to the optimum load of the solar cell

Accurate performance model of solar cells is very crucial for embedded power applications. At low irradiance levels, the two-diode model for PV model is well known for its excellent accuracy. Using the two-diode model, we provide the generic expression of the optimum load RmL which holds for both the single-diode and two-diode model. Also, we obtain an explicit solution based on elementary analytical functions to seek the optimum diode-voltage VmD using dichotomy method. Furthermore, the values of Im and RmL can be calculated based on the explicit expression of Im and RmL in terms of VmD. However, the computation for RmL is difficult, so we create a user-friendly program by Matlab/GUI to make it easier. As predicted, the results computed by the proposed method agree well with the experimental data of four real solar cells. Finally, the impacts of the series and shunt resistance on the optimum load are studied. It turns out that the results of the single-diode model in literature have the same tendency as that of the two-diode model.

Quantum Dot Solar Cells with Nanoscale Barriers Around Dots: Experiment and Two-Diode Model Analysis

Incorporation of quantum dots into the p-n junction of the photovoltaic device provides numerous possibilities for nanoscale control of photoelectron processes via engineering the band structure and nanoscale potential profile. The band structure is determined by the size and shape of quantum dots and width of the wetting layer. The potential profile is formed by selective doping, which leads to the built-in dot charge. To study the effects of the band structure and nanoscale potential barriers on the photovoltaic performance we fabricated and investigated 3-μm base GaAs devices with various InAs quantum dot media and selective doping. All quantum dot devices show significant improvement in conversion efficiency in comparison with the reference cell. The data obtained have been analyzed in frame of the diode model. It was found that the two-diode model with the ideality factors of [Formula: see text] and [Formula: see text] well describes the scope of data. The essential [Formula: see text] component evidences that the Shockley-Read-Hall recombination plays a substantial role in recombination losses. Further optimization of solar cells should be aimed at the formation of potential profile with large barriers that separate quantum dot areas from high mobility conducting channels.