Multicrystalline Silicon Cells Research Articles

Automated Defect Detection and Localization in Photovoltaic Cells Using Semantic Segmentation of Electroluminescence Images

In this article, we propose a deep learning based semantic segmentation model that identifies and segments defects in electroluminescence (EL) images of silicon photovoltaic (PV) cells. The proposed model can differentiate between cracks, contact interruptions, cell interconnect failures, and contact corrosion for both multicrystalline and monocrystalline silicon cells. Our model utilizes a segmentation Deeplabv3 model with a ResNet-50 backbone. It was trained on 17,064 EL images including 256 physically realistic simulated images of PV cells generated to deal with class imbalance. While performing semantic segmentation for five defect classes, this model achieves a weighted F1-score of 0.95, an unweighted F1-score of 0.69, a pixel-level global accuracy of 95.4%, and a mean intersection over union score of 57.3%. In addition, we introduce the UCF EL Defect dataset, a large-scale dataset consisting of 17,064 EL images, which will be publicly available for use by the PV and computer vision research communities.

A new model for a photovoltaic panel using Proteus software tool under arbitrary environmental conditions

The photovoltaic (PV) panel generates power based on different parameters, including environmental conditions such as solar irradiance, temperature, and internal electrical parameters of the PV panel. Thus, a PV model should be studied in advance to forecast and evaluate the impact of these factors on the PV performance, and this model should be matched with the PV panel's real behavior. For this reason, this paper developed a new model for a PV panel using the Proteus software. A flexible PV model with possibility of varying the weather conditions has been proposed using mathematical equations of a single-diode equivalent circuit, (i.e., photo-generated current, shunt-resistor current, and diode current). Moreover, these equations were modeled using “Pick Devices” in Proteus software library. To prove the effectiveness of the proposed model, it was applied on two types of monocrystalline, and multi-crystalline silicon cells of PV panel technologies. Subsequently, the corresponding current-voltage (I–V) and power-voltage (P–V) characteristics are obtained and compared with the manufacturer's data, PVsyst software, and other authors' results under arbitrary values of irradiance and temperature. The simulation results identified that the proposed model is flexible, simple, and suitable for different PV panel technologies under diverse weather conditions.

Estimation of future changes in photovoltaic potential in Australia due to climate change

Solar photovoltaic (PV) energy is one of the fastest growing renewable energy sources globally. However, the dependency of PV generation on climatological factors such as the intensity of radiation, temperature, wind speed, cloud cover, etc can impact future power generation capacity. Considering the future large-scale deployment of PV systems, accurate climate information is essential for PV site selection, stable grid regulation, planning and energy output projections. In this study, the long-term changes in the future PV potential are estimated over Australia using regional climate projections for the near-future (2020–2039) and far-future (2060–2079) periods under a high emission scenario that projects 3.4 °C warming by 2100. The effects of projected changes in shortwave downwelling radiation, temperature and wind speed on the future performance of PV systems over Australia is also examined. Results indicate decline in the future PV potential over most of the continent due to reduced insolation and increased temperature. Northern coastal Australia experiences negligible increase in PV potential during the far future period due to increase in radiation and wind speed in that region. On further investigation, we find that the cell temperatures are projected to increase in the future under a high emission scenario (2.5 °C by 2079), resulting in increased degradation and risks of failure. The elevated cell temperatures significantly contribute to cell efficiency losses, that are expected to increase in the future (6–13 d yr−1 for multi-crystalline silicon cells) mostly around Western and central Australia indicating further reductions in PV power generation. Therefore, long-term PV power projections can help understand the variations in future power generation and identify regions where PV systems will be highly susceptible to losses in Australia.

Investigation on Open-Circuit Voltage of an Efficiency-Boosting Solar Cell Technique Featuring V-Configuration

The V-Shaped Module (VSM) solar cell technology, which breaks the traditional concept of solar cell system, has been proven to enhance power conversion efficiency of some solar cells and has offered opportunities to increase generation power densities in area-limited applications. Compared to a planar cell system, the VSM has an additional opportunity to absorb photons and taps the potential of solar cells. In this study, the VSM, the proposed common technique enhancing efficiencies of various solar cells, was investigated by using commercially available multi-crystalline silicon solar cells. The VSM technique enables the efficiencies of the multi-crystalline silicon cells to increase from 13.4% to 20.2%, giving an efficiency boost of 51%. Though the efficiency of the cells increases, the open-circuit voltage of the cells decreases owing to the VSM technique. Furthermore, the obvious reduction in open-circuit voltage in the VSM was found and the phenomenon is explained for the first time.

Hydrogenation and Gettering Compatiblep-Type Contacts for Multicrystalline Silicon Cells, Free of Light, and Elevated Temperature Induced Degradation

Results for a room temperature contacting method applied to the p -type rear surface of monocrystalline and multicrystalline solar cell structures are presented. Monocrystalline silicon devices with the rear contacts prepared using the point contacting by localized dielectric breakdown method are reported with an efficiency of 19.2%. The devices show improved measurements of key performance metrics of ρc of 1.6 ± 0.8 mΩcm2 and J 0 c of 2100 ± 650 fAcm−2. This contacting approach is also demonstrated for multicrystalline silicon cells, with no evidence of parasitic breakdown at grain boundary sites. The multicrystalline device implementation highlights a key advantage of this contacting method, namely a relatively free choice of annealing temperature. This flexibility allows process optimization such that the activation of light-and-elevated-temperature-induced degradation is prevented in hydrogenated multicrystalline silicon, while still maximizing the benefits to bulk lifetime.

Photoluminescence-Based Spatially Resolved Temperature Coefficient Maps of Silicon Wafers and Solar Cells

In this article, we present a method to obtain implied open-circuit voltage images of silicon wafers and cells at different temperatures. The proposed method is then demonstrated by investigating the temperature coefficients of various regions across multicrystalline silicon wafers and cells from different heights of two bricks with different dislocation densities. Interestingly, both low and high temperature coefficients are found in dislocated regions on the wafers. A large spread of temperature coefficient is observed at regions with similar performance at 298 K. Reduced temperature sensitivity is found to be correlated with the increasing brick height and is exhibited by both wafers and cells. This may indicate that cells made from the top of the brick, although having higher defect concentration, actually suffer relatively less degradation in the performance at higher temperatures.

Prospecting technologies for photovoltaic solar energy: Overview of its technical‐commercial viability

There are many technologies that may emerge and eventually disappear over the years. This fact makes the monitoring of technological trends as well as the anticipation of the direction of technological change paramount. This article aims to carry out the prospection of technologies, focusing on its technical-commercial viability, for solar photovoltaic energy. The research method had a qualititative-quantitative approach with application of the Delphi technique. In the conduction of the Delphi technique, seven steps were followed, ranging from the selection of the specialists to the considerations of their opinions regarding the future of nine photovoltaic technologies. The results of the research indicate that in 2020, the cells monocrystalline, multicrystalline, and amorphous silicon; cadmium telluride; indium/copper selenide, indium, and gallium diselenide; and multicompound III-V cells will have technical and commercial viability and that dye-sensitized silicon nanowire and carbon nanostructure-based cells will not be viable. For the year 2025, monocrystalline and multicrystalline silicon cells and those of multicompounds III-V will still be technically and commercially viable. Silicon nanowire; amorphous silicon; cadmium telluride; indium/copper, selenium, and gallium diselenide dye-sensitized cells; and organic photovoltaic cells, including those based on carbon nanostructure, may be viable. This study is important, because the technological prospecting of the photovoltaic cells determines the possible trajectories of these cells, in a way that helps the companies of the sector to anticipate the strategic scenarios, thus facilitating the decision making process.

The Artificial Mixed Fused Quartz Particles and Silicon Particles-Assisted High-Performance Multicrystalline Silicon

Mixed seeds of fused quartz particles and silicon particles were laid at the bottom of the crucible to assist the growth of multicrystalline silicon crystals. The full melting process was used, and then we found that the grown crystals had higher quality. The effect of mixed seeds on the growth of multicrystalline silicon was studied. The results showed that fine and uniform initial grains could be obtained by mixed seeds assisting the growth of crystals. Increasing the number of grain boundaries can better release thermal stress and inhibit the proliferation and diffusion of dislocations. The defect density of multicrystalline silicon decreased and the minority carrier lifetime increased, thus improving the conversion efficiency of multicrystalline silicon cells.

Broadband antireflection Mie scatterers revisited-a solar cell and module analysis.

Reflectance, reduction, and light trapping enhancement are essential to maximize the absorption of silicon solar cells. The industrial state of the art method to improve the solar cell optics is wet chemical texturization of the front surface in combination with the deposition of antireflection coatings. This work analyzes an alternative route, namely a TiO2 pillar structure on the front side of a planar silicon solar cell encapsulated in ethylene vinyl acetate (EVA) and glass. It focuses on parameter variations of the structured TiO2 layer while taking the module encapsulation into account. It is shown that internal reflections at the front interface of the module play a crucial role for the structure design. This leads to optimized structures working in a different optical regime. While state of the art structures optimized for a half infinite encapsulation act as effective media, structures optimized for the full module show an improved performance by making use of diffractive effects. It could be shown that weighted reflectance of 4.7% can be reached for a solar module with TiO2 pillar structure on top of the silicon surface compared to 5.5% for a two-layer ARC with a TiO2 bottom layer and 2.3% for an isotexture, which is the state of the art structure for multicrystalline silicon cells.

Lock-in thermography based local solar cell analysis for high efficiency monocrystalline hetero junction type solar cells

Until now the Dark Lock-in Thermography (DLIT) based "Local I-V" method for analyzing the inhomogeneity of the two-diode parameters of solar cells was applied mostly to multicrystalline silicon cells. In this contribution it is applied to three high-efficiency monocrystalline cells of the hetero junction type (HJT), one showing very good and two showing slightly degraded cell parameters. It is shown that the degradation of the lower performing cells is mainly due to additional local J02-type current contributions, which are partly stemming from surface injuries and mainly degrade the fill factor. It can be estimated that the local inhomogeneous dark current contributions, which can be imaged and quantified by DLIT, degrade the efficiency of the best cell only by 0.1%, but that of the stronger degraded cells by 0.3% and 0.6% (absolute) respectively. Under reduced illumination intensity the differences between the cells are even higher. The possibilities and limitations of the "Local I-V" evaluation of solar cells for investigating high-efficiency cells are discussed.

The Role of Inhomogeneities for Understanding Current–Voltage Characteristics of Solar Cells

All solar cells show more or less inhomogeneous electronic properties. This holds in particular for multicrystalline silicon cells, where local differences of the lifetime of more than an order of magnitude exist. This contribution explains how these inhomogeneities can be imaged and quantified, and the physical origins and the efficiency degradation potential of J 01-, J 02-, and ohmic inhomogeneities are reviewed. It is found that J 02 and ohmic currents are always highly localized, in contrast with J 01 currents. Hence, for describing most of the area of silicon solar cells, a one-diode model is sufficient, but J 02 and ohmic currents reduce the efficiency at low illumination intensity. Moreover, the physical origins of known prebreakdown phenomena are reviewed and a new breakdown type dominating in monocrystalline silicon cells is proposed.

Two‐Dimensional Hot Spot Temperature Simulation for c‐Si Photovoltaic Modules

A two‐step method to simulate the spatially resolved temperature of a partially shaded cell in a crystalline silicon photovoltaic (PV) module is presented and tested. First, an efficient module electronic simulation tool computes the operating conditions of a module's constituent cells. Second, a two‐dimensional finite‐element analysis simulation, utilizing forward‐, and revers‐bias electroluminescence measurements, is performed to spatially resolved cell temperature. With an outdoor experiment, un‐encapsulated cell temperatures are directly measured under controlled heat transfer conditions. A peak local cell temperature of 144 °C is observed on a multi crystalline silicon cell dissipating 54 W heat in the experiment, 57 °C higher than the result from a non‐spatially resolved simulation. Experimental results indicate cells without significant Ohmic shunts are suitable for temperature simulation with the aid of reverse bias electroluminescence imaging, which yields a maximum temperature prediction error of less than 15 °C. However, simulation for cells with significant Ohmic shunts is prone to underestimate the cell temperature by up to 45 °C. Multiple shading fractions from 12 to 80% lead to severe heating scenarios in such case.

Quantitative Prediction of Power Loss for Damaged Photovoltaic Modules Using Electroluminescence

Electroluminescence (EL) is a powerful tool for the qualitative mapping of the electronic properties of solar modules, where electronic and electrical defects are easily detected. However, a direct quantitative prediction of electrical module performance purely based on electroluminescence images has yet to be accomplished. Our novel approach, called “EL power prediction of modules” (ELMO) as presented here, used just two electroluminescence images to predict the electrical loss of mechanically damaged modules when compared to their original (data sheet) power. First, using this method, two EL images taken at different excitation currents were converted into locally resolved (relative) series resistance images. From the known, total applied voltage to the module, we were then able to calculate absolute series resistance values and the real distribution of voltages and currents. Then, we reconstructed the complete current/voltage curve of the damaged module. We experimentally validated and confirmed the simulation model via the characterization of a commercially available photovoltaic module containing 60 multicrystalline silicon cells, which were mechanically damaged by hail. Deviation between the directly measured and predicted current/voltage curve was less than 4.3% at the maximum power point. For multiple modules of the same type, the level of error dropped below 1% by calibrating the simulation. We approximated the ideality factor from a module with a known current/voltage curve and then expand the application to modules of the same type. In addition to yielding series resistance mapping, our new ELMO method was also capable of yielding parallel resistance mapping. We analyzed the electrical properties of a commercially available module, containing 72 monocrystalline high-efficiency back contact solar cells, which suffered from potential induced degradation. For this module, we predicted electrical performance with an accuracy of better than 1% at the maximum power point.

How cell textures impact angular cell-to-module ratios and the annual yield of crystalline solar modules

Two emerging trends in multicrystalline silicon cell texturing are plasma texturing, and metal catalyzed chemical etching. Both processes roughen silicon surfaces in order to increase light absorption. These processes are attractive as they are applicable to diamond-wire sawn wafers. This work investigates the optical properties of these surfaces, and other conventionally textured surfaces like isotropic acidic and random pyramid textures, are investigated for cells in air and after encapsulation for a large range of angles of incidence. We find that the angular optical performance in air varies strongly with cell texture, but when embedded in a module structure these variations are significantly mitigated: the advantages of a high angular absorption of solar cells are not fully transferred to the module level. This is especially notable for plasma etched, black silicon cell structures which suffer comparatively from poorer index matching and light recycling inside a module structure. The losses caused explicitly by the module embedding (described in the cell to module ratio) are in the range of 1–5% for perpendicular incoming light, and increase to 6–15% at an angle of incidence of 70°. Based on these angular performances, we calculate the annual yield of the modules and find that it varies by less than 2% for the cell textures. Nevertheless, the annual optical yield for the black silicon cell structures are the highest, whereas the metal catalyzed chemical etching cell structures show the lowest performance. Further, we find that different annual distributions of the incoming light at the two investigated locations (Melbourne and Alice Springs) only impact the relative performance of the cell textures at high module tilt angles.

Lighting performance of multifunctional PV windows: A numeric simulation to explain illuminance distribution and glare control in offices

To show how much photovoltaic windows improve daylight distribution of a deep-plan office by both reducing glare and powering supplementary lighting, a numerical experiment based on radiosity and raytracing methods was conducted. The chosen model geometry was a laterally lit, deep-plan office room. A desk 7.50 m away from the window provides a work plane for illuminance analysis. Ten scenarios were considered: A) single colourless, transparent single-glazed window; B) PV window as an array of multicrystalline separate silicon cells, mounted on a transparent glazing; C) transparent thin-film PV window. Respectively, A1, B1 and C1 are under direct solar radiation; B2 and C2 with net-zero electric lighting based on two luminaires; and B3 and C3 based on a single luminaire. Static analysis yields illuminance distribution on the horizontal plane at 0.75 m above floor along a central axis. Advantages were observed on scenarios B2, C2, B3 and C3, as shown by realistic images. Dynamic analysis was conducted for the scenarios A1*, B1*, C1*, B2* and C2*. Whole-year calculation of work plane illuminance, continuous Daylight Autonomy (cDA) and Daylight Glare Index (DGI) results show the superiority thin-film PV with supplementary lighting, (scenario C2*).

Performance Evaluation of Two Photovoltaic Cell Technologies in Fluctuating Weather Conditions, Using EN50530 Test Procedure

Generally, photovoltaic (PV) cell manufacturers provide technical information, at standard test conditions (STCs) and nominal operating cell temperature (NOCT) ratings. However, this information is not sufficient to accurately predict the module operations under dynamic weather. In this study, test is conducted under fluctuating irradiance conditions, provided by EN50530 test procedure, to evaluate the performance of multi crystalline silicon and thin-film PV cells. Particular attention is given to the influence that the level and the slope of irradiance change have on the energy yield of PV technologies. This analysis aimed at revealing the appropriate selection of PV technology for obtaining maximum power under dynamic weather conditions.

Comparison of the indoor performance of 12 commercial PV products by a simple model

AbstractThis article presents a simple comparative model which has been developed for the estimation of the performance of photovoltaic (PV) products' cells in indoor environments. The model predicts the performance of PV solar cells, as a function of the distance from a spectrum of artificial (fluorescent light, halogen light, and light‐emitting diodes) and natural light. It intends to support designers, while creating PV‐integrated products for indoor use. For the model's validation, PV cells of 12 commercially available PV‐powered products with power ranging from 0.8 to 4 mWp were tested indoors under artificial illumination and natural light. The model is based on the physical measurements of natural and artificial irradiance indoors, along with literature data of PV technologies under low irradiance conditions. The input data of the model are the surface of the solar cell (in m2), the wavelength‐dependent spectral response (SR) of the PV cell, the spectral irradiance indoors, and solar cell's distance from light sources. The model calculates solar cells' efficiency and power produced under the specific indoor conditions. If using the measured SR of a PV cell and the irradiance as measured indoors, the model can predict the performance of a PV product under mixed indoor light with a typical inaccuracy of around 25%, which is sufficient for a design process. Measurements revealed that under mixed indoor lighting of around 20 W/m2, the efficiency of solar cells in 12 commercially available PV products ranges between 5% and 6% for amorphous silicon (a‐Si) cells, 4–6% for multicrystalline silicon (mc‐Si) cells, and 5–7% for the monocrystalline silicon (c‐Si) cells.

Experimental study to separate surface and bulk contributions of light-induced degradation in crystalline silicon solar cells

In this paper, investigations toward understanding the bulk and surface components of light-induced degradation (LID) in low-iron crystalline silicon (Si) solar cells are explored. The bulk effects, arising from boron–oxygen defects, are determined by comparing degradation of cell parameters and their thermal recovery, with that of the minority-carrier lifetime (τ) in sister wafers. It is found that the lifetime of wafer, τ, is recovered fully after annealing, but cell efficiency is recovered partially. It is also shown that cells having SiN:H coating experience a surface degradation (ascribed to surface recombination). The surface LID is seen as an increase in the q/2kT component of the dark saturation current (J02). The surface LID does not recover fully upon annealing and is attributed to degradation linked to the SiN:H–Si interface. This behavior is also exhibited by multi-crystalline silicon cells that have very low oxygen content and do not show any bulk degradation.

Implications for current regulatory waste toxicity characterisation methods from analysing metal and metalloid leaching from photovoltaic modules

The appropriateness of regulatory methods to characterise the toxicity of photovoltaic (PV) modules was investigated to quantify potential environmental impacts for modules disposed of in landfills. Because solar energy is perceived as a green technology, it is important to ensure that end-of-life issues will not be detrimental to solar energy's success. United States Environmental Protection Agency Method 1311, California waste extraction test, and modified versions of both were performed on a multi-crystalline silicon module and cells and a copper indium gallium diselenide (CIGS) module. Variations in metal leachate concentrations were found with changes in testing parameters. Lead concentrations from the multi-crystalline module ranged from 16.2 to 50.2 mg/L. Cadmium concentrations from the CIGS module ranged from 0.1 to 3.52 mg/L. This raises doubt that regulatory methods can adequately characterise PV modules. The results are useful for developing end-of-life procedures, which is a positive step towards avoiding an e-waste problem and continuing trends of increasing installation and cost reduction in the PV market.

Research and Preparation of High Quality Polysilicon Ingots and Multicrystalline Silicon (mc-Si) Cells

Directional solidification is a main method of mc-Si production for solar cells. The main impurities in MS-Si are oxygen and carbon. In this paper, an improved furnace was designed to reduce the carbon and oxygen impurity in MS-Si at unidirectional solidification process. Simulation results showed that the flow pattern of impurity gas at the top of the silicon melt significantly improved under the small cover conditions and the impurity gas eddy currents was also avoided. Experimental results show that the carbon and oxygen content inside the ingot were both significantly reduced when the eddy currents inside the crucible was suppressed and the average minority carrier’s lifetime of silicon block was significantly increased under the conditions of small cover plate. Meantime, the average cell efficiency of ingot was more than 17% under small cover condition which is significantly higher than that of the ordinary ingot.