Polysilicon Research Articles

Environmental Life Cycle Analysis and Energy Payback Period Evaluation of Solar PV Systems: The Case of Pakistan

This study employs a life cycle assessment (LCA) approach to investigate the environmental burden of photovoltaic power generation systems that use multi-crystalline silicon (multi-Si) modules in Pakistan. This study evaluates the energy payback time (EPBT) of this class of systems, and considers various environmental impacts, including climate change, acidification, and eutrophication. The assessment accounts for upstream, midstream, and downstream processes, including cell as well as module production. The critical stages in the production cycle were identified, including the metallic silicon transformation into solar silicon and the assembly of the panels, which involve energy-intensive materials such as aluminum frames and glass roofing. Despite using the most efficient conversion technology, the former stage consumes a significant amount of electricity. This study reveals that multi-Si PV systems in Pakistan have an EPBT that is considerably less than their lifespan, ranging from 2.5 to 3.5 years. These findings suggest that the development of PV systems in Pakistan is a very interesting option for energy production. Additionally, this study compares solar PV and wind power generation systems in various regions of Pakistan. The study outcomes can facilitate evidence-based decision-making processes in the renewable energy sector and contribute significantly to Pakistan’s endeavor to transition toward a sustainable energy system.

Influence of Temperature of Silicon Dioxide Powder Annealing on the Aluminum-Induced Crystallization of Polycrystalline Silicon

Influence of Temperature of Silicon Dioxide Powder Annealing on the Aluminum-Induced Crystallization of Polycrystalline Silicon

Catalytic recovery of metals from end-of-life polycrystalline silicon photovoltaic cells: Experimental insights into silver recovery

A steady increase in end-of-life (EoL) polycrystalline silicon photovoltaic (c-Si PV) panels is necessitating the development of recycling technologies to guarantee sustainable environmental management and a circular economy. Herein, we propose a comprehensive EoL c-Si PV recycling strategy with an emphasis on selective silver (Ag) recovery. Primarily, a combination of physical and thermal treatment led to the isolation of PV cell fraction from the EoL PV module. Thereafter, a less-toxic, sulphuric acid-hydrogen peroxide (1 M H2SO4- H2O2 1% (v/v %)) lixiviant was used for Ag leaching at 70 °C. A novel catalytic process using platinum-embedded activated carbon (Pt/AC) was used with only hydrogen gas and air to recover selectively and concentrate the Ag+ from the synthetic PV cells leachate. Finally, pure metallic silver (Ag > 99.0 %) was obtained by the conventional electrowinning process. This study also proposes an explicit recovery process for Al, Cu, and Si. In addition, the Pt/AC catalytic process could efficiently recover Cu from the PV cells, similar to Ag. Following the complete recovery of Ag and Cu through Pt/AC, there is sufficient scope to isolate other metals like Al and Pb leaving behind crude Si wafers. Hence, the as-proposed recycling and metal recovery process is a newer approach benefiting industrial implementation.

Outdoor Experimental Investigation of the Temperature Effect on the Performance of Different PV Modules Materials

Desert locations are of great interest for photovoltaic applications due to their high solar availability. However, in these regions, harsh climatic conditions can have a significant impact on the performance and reliability of photovoltaic panels. In the present study, the effect of temperature on the performance of the two PV technologies, Polycrystalline Silicon (pc-Si) and thin film Cadmium Telluride (CdTe), in a hot desert climate was investigated. To accomplish this, one module from each technology was installed in Benguerir city and exposed to outdoor conditions during the hot season of the year (May to October). Results indicate that although pc-Si exhibits higher module efficiency than CdTe, the latter was less temperature-sensitive under high ambient temperature values. In fact, during the monitoring period, CdTe technology demonstrated lower module temperatures than pc-Si, with a daily average temperature deviation of 1.75°C. In addition, the performance ratio and conversion efficiency for pc-Si were reduced by 8.7% and 1.35%, respectively, when the daily average ambient temperature increased from 25°C to 40°C. While with the thin film CdTe technology, the decline in these performance parameters did not exceed 6.8% and 1.05%, respectively.

Fatigue crack growth in polysilicon microstructures subjected to multi-axial loading: A Poisson–Voronoi-based finite element analysis

Polycrystalline silicon (polysilicon) is the most commonly used structural material of microscopic electromechanical devices, such as sensors and actuators. Almost all of these miniaturized devices contain mechanical elements experiencing high-frequency loading cycles. Due to the rapidly accumulating loading cycles and very small thicknesses of these microstructures, basic understanding of fatigue crack growth in polysilicon at the microscale is critical to the design of durable microdevices that satisfy application requirements. In this investigation, fatigue crack growth in a typical polysilicon microstructure subjected to multi-axial loading was analyzed with the finite element method. To account for the inherent heterogeneity and anisotropy of polysilicon at the microscale, a Poisson-Voronoi tessellation was incorporated in the highly stressed region of the resonating microdevice to model a polycrystalline microstructure. Simulation results illuminated the effect of local texture on the direction and rate of crack growth. Transgranular or intergranular crack growth were predicted, depending on the angle between the crack-path direction and the grain boundary and the fracture resistance of the grain and the grain boundary. From a fundamental fracture mechanics perspective, the computational approach developed in this study provides a capability for examining the effect of local texture anisotropy on cracking in polycrystalline microstructures.

Passivation of grain boundary electronic activity in polycrystalline silicon thin films by heat treatment and hydrogenation

Passivation of grain boundary electronic activity in polycrystalline silicon thin films by heat treatment and hydrogenation

Temperature profiles of field-aged photovoltaic modules affected by optical degradation

Moisture ingress into PV module in the presence of ultraviolet radiation, high temperature, and other environmental stressors can affect the optical integrity of the PV module. Optical degradation can take the form of delamination, discolouration of encapsulant, metal grids corrosion, and trapped moisture or chemical species. This can influence the photon absorption and current transport properties in the PV module bulk, which can affect the module operating temperature. In the present work, the relationship between optical degradation and temperature sensitivity of 20-year-old multicrystalline silicon field-aged PV modules have been investigated. The selected PV modules were characterized using visual inspection, current-voltage (I–V) characterization, temperature coefficients profiling, current resistivity profiling, infrared (IR) thermal, ultraviolet fluorescence (UV–F), and electroluminescence (EL) imaging. PV modules affected by optical degradation show weak fluorescence and luminescence signal intensities. The average difference in cell temperature (ΔT) between the warmest and coldest cell for the PV modules investigated was found to be around 10 ± 2 °C and the average power degradation rate was approximately 0.8% per year. The underlying factor for the observed degradation is attributed to the degradation in the temperature coefficients of open circuit voltage (βVoc) and maximum power point voltage (βVmpp). The average temperature coefficient of efficiency (βηm) of the modules was found to be around −0.5%/°C. Finally, a temperature dependent resistivity method for extracting temperature coefficients from IR thermal data of PV modules has been proposed.

Electrochemical and Spectroscopic Study on Electrochemical Processing of Silicon in Fluoride Melt

For sustainable space utilization on the Moon and the Mars, it is essential to establish in-situ resources and energy utilization systems in space. Because of the large amount of silica in the regolith which composed of metallic oxides on the Moon and the Mars, the technology development for the covering the silica to silicon and oxygen is indispensable. The silicon can be used as a key material for silicon photovoltaics. Against this background, the authors have studied the electrochemical reduction of silica to silicon in fluoride melt. We propose a one-step process to obtain a silicon film on the cathode by electrolysis using molten salts containing silica. To determine the feasibility of the proposed process, it is necessary to understand the effects of the physicochemical properties such as the coordination structure of Si ions in the fluoride melt since the difference in the melt structure affects the nucleation and growth mechanisms of the silicon electrodeposition. However, there are few reports on the dissolved state of silicon ions in fluoride melt. The author thus clarified the relationship of the electrochemical behavior of coordination structure of Si ions in fluoride melts composed of LiF, KF, and NaF.The coordination structure of Si ions in the fluoride melt was investigated by high-temperature Raman spectroscopy and quantum chemical calculations based on the density functional theory (DFT). The vibrational modes of the Si ions were detected through high-temperature Raman spectroscopy and the Raman bands were simulated by DFT calculations. We clarified the interaction between Si ions and cation and anion species such as Li+, Na+, K+, O2−, and F−. In addition, the electrochemical behavior of Si ions was investigated by electrochemical measurements. The effect of O2− ions on the dissolution of SiO2 and the electrodeposition process of Si in fluoride molten salts revealed a significant increase in the reduction current of Si ions as well as in the film thickness and current efficiency of deposited Si. The molten fluoride system, which can fabricate Si films from SiO2 at low temperatures, has the potential to develop environmentally friendly and sustainable electrolytic systems.

PV Silicon Recovery for Lithium Ion Battery Anodes

As solar photovoltaic (PV) devices across the globe reach the end of their approximately 30-year lifetimes, an emerging challenge is how to handle the waste from large volumes of end-of-life (EOL) PV modules. It is projected that the cumulative mass of EOL PV modules could be up to 8 million tonnes (Mt) by 2030 so recovery of high value materials from these EOL modules through a cost efficient recycling process would minimize environmental impacts compared to disposing them in landfills[1]. A typical recycling process for EOL PV modules involves mechanical disassembly, separation of the tempered cover glass and silicon wafer followed by purification and recovery of other constituents such as Pb or Ag with the goal of reinstating the recovered materials as a PV module. However, since new module prices continue to decline and the recovered PV modules typically have a shorter lifetime and lower efficiency, the economic value of using the recovered PV materials to manufacture a new PV module is uncertain[2]. Since silicon, particularly boron-doped, is a promising candidate for next-generation anodes for lithium-ion batteries (LIB), recovering the silicon from PV modules for use in LIB anodes could be an attractive alternative. In this study we leverage the National Renewable Energy Laboratory (NREL)’s expertise in PV Si reliability and access to multiple types of EOL PV modules to study the merits of B-doped silicon recovery from silicon PV panels with regard to silicon anode cycling performance and calendar life. A simple ball milling process was developed to prepare recycled Si from EOL PV modules for use as in a LIB anode. In this talk we will be discussing the recovery efficiency, purification requirements and key anode performance metrics of recycled PV silicon materials. IRENA, I.-P., End-of-Life Management: Solar Photovoltaic Panels 2016: International Renewable Energy Agency and International Energy Agency Photovoltaic Power Systems.A. Wade, P.S., K. Drozdiak, E. Brutsch. Beyond Waste – The Fate of End-of-Life Photovoltaic Panels from Large Scale PV Installations in the EU. The Socio-Economic Benefits of High Value Recycling Compared to Re-Use. in 33rd European Photovoltaic Solar Energy Conference and Exhibition. 2017.

Overview of the Current State of Flexible Solar Panels and Photovoltaic Materials.

The rapid growth and evolution of solar panel technology have been driven by continuous advancements in materials science. This review paper provides a comprehensive overview of the diverse range of materials employed in modern solar panels, elucidating their roles, properties, and contributions to overall performance. The discussion encompasses both traditional crystalline silicon-based panels and emerging thin-film technologies. A detailed examination of photovoltaic materials, including monocrystalline and polycrystalline silicon as well as alternative materials such as cadmium telluride (CdTe), copper indium gallium selenide (CIGS), and emerging perovskite solar cells, is presented. Furthermore, the impact of transparent conductive materials, encapsulation polymers, and antireflective coatings on solar panel efficiency and durability is explored. The review delves into the synergistic interplay between material properties, manufacturing processes, and environmental considerations. Through a comprehensive survey of materials utilized in modern solar panels, this paper provides insights into the current state of the field, highlighting avenues for future advancements and sustainable solar energy solutions.

REMOTE MEASUREMENTS OF WATER SURFACE POLLUTION BY THE METHOD OF LASER LOCATION

As it was shown in the nature investigations,the most area of water in the Azerbaijan shore of Caspian Sea is covered by oil film, the square of which depends on direction of wind. The research of pollution's of environment by the mean of optical apparatus of remote sounding, mounted on the board of flying apparatus or space satellites is one of intensely developing directions. The theory of measuring of oil film's thickens by the help of laser location in detail described. The principles of straight¬-line spreading of electromagnetic waves, reflecting of electromagnetic energy by objects and constant speed of their propagation are laid in the basic of location. We have developed lidar for controlling of pollutions of water surface, where helium-neon laser “LGI-102” having power 3mW working in the pulse regime is used as beam radiator. During the experiment the laser was mounted on the plain ground on the distance 1-meter from water surface. The prism was placed in the road of propagation of laser beam and used for direction of radiation under the angle 45 on water surface. Integral photo transducer on the base of local mono-and polycrystalline silicon films with linear output was used in the photo detector device. Photo transducer was made in hybrid form on the base of two crystals: photo sensitive poly-silicon film and unpack operational amplifier 740UD4. Keywords: Pollution, water surface, oil film, laser location, lidar, photo detector.

Evidence of twin mediated growth in the CVD of polycrystalline silicon carbide

The origin of the 〈110〉 texture in polycrystalline 3C-SiC grown by chemical vapor deposition at different temperatures is investigated by thorough EBSD, SEM and XRD characterizations. Regarding the 〈110〉 orientation, although XRD suggests a fiber texture, closer inspection of isolated clusters of grains by EBSD reveals a high symmetrical order in-plane. The pole figures associated with these clusters are in good agreement with cross-twinned pentagonal structures in which each grain shares a common 〈110〉 axis. These structures form via twin-mediated growth involving the formation of twin plane reentrant edges that act as a preferential site for the incorporation of adatoms. A deviation from a perfect cross-twinned structure is observed and is attributed to the presence of additional parallel twins. In this study, the transition to the 〈110〉 orientation occurs when the temperature increases and the partial pressure of reactive species decreases. This can be explained by the enhancement of surface mobility that promotes surface diffusion to the twin plane reentrant edges, thus activating the twin mediated growth mechanism.

Regionalizing Nitrogen Doping of Polysilicon Films Enabling High-Efficiency Tunnel Oxide Passivating Contact Silicon Solar Cells.

Tunnel oxide passivating contact (TOPCon) solar cells (SCs) as one of the most competitive crystalline silicon (c-Si) technologies for the TW-scaled photovoltaic (PV) market require higher passivation performance to further improve their device efficiencies. Here, the successful construction of a double-layered polycrystalline silicon (poly-Si) TOPCon structure is reported using an in situ nitrogen (N)-doped poly-Si covered by a normal poly-Si, which achieves excellent passivation and contact properties simultaneously. The new design exhibits the highest implied open-circuit voltage of 755mV and the lowest single-sided recombination current density (J0 ) of ≈0.7 fAcm⁻2 for a TOPCon structure and a low contact resistivity of less than 5 mΩ·cm2 , resulting in a high selectivity factor of ≈16. The mechanisms of passivation improvement are disclosed, which suggest that the introduction of N atoms into poly-Si restrains H overflow by forming stronger Si-N and N-H bonds, reduces interfacial defects, and induces favorable energy bending. Proof-of-concept TOPCon SCs with such a design receive a remarkable certified efficiency of 25.53%.

Effect of the diamond saw wires capillary adhesion on the thickness variation of ultra-thin photovoltaic silicon wafers during slicing

In order to improve the performance of solar cells and reduce their manufacturing costs, monocrystalline silicon wafers used for manufacturing solar cells are developing towards larger sizes and ultra-thin thickness, and the diameter of diamond saw wires used to cut silicon wafers is also continuously decreasing. These aspects cause uneven thickness and lager thickness variation (TV) of the as-cut wafer during slicing process. The reason of uneven thickness was analyzed from the point of liquid bridge with capillary force between the saw wires in this paper. The mechanical equilibrium equation between the liquid bridge and the saw wires was established based on the Young-Laplace equation, and the theoretical model of the as-cut wafer thickness was derived during the sawing process. The effect of the saw wire tensioning force, span, the diameter of the core wire and the wetting angle of coolant on the as-cut wafer thickness variation was analyzed based on the model. The results show that the increase in the saw wire tensioning force, the core wire diameter and the wetting angle of coolant improved the thickness accuracy and reduced the thickness variation of the as-cut wafer. And the increase in the saw wire span reduced the thickness accuracy and increased the thickness variation. The research results of this paper provide the mechanism analysis for the thickness variation of the ultra-thin wafer during the slicing process. It is of great significance to produce the ultra-thin photovoltaic silicon wafers with the fine saw wire in the future.

Polycrystalline silicon 2 × 2 Mach-Zehnder interferometer optical switch.

In this paper, we demonstrate a broadband Mach-Zehnder interferometer optical switch based on polycrystalline silicon (poly-Si), which enables the development of multilayer photonics integrated circuits. The poly-Si is deposited under a low temperature of 620 °C to avoid unexpected thermal stress and influence on optoelectronic performance. By introducing a π/2 phase shifter and a push-pull configuration, the switch achieved low power consumption and loss caused by carrier plasma absorption (CPA). The switch operates effectively in both "Bar" and "Cross" states at voltages of -3.35 V and 3.85 V. The power consumptions are 7.98 mW and 9.39 mW, respectively. The on-chip loss is 5.9 ± 0.4 dB at 1550 nm, and the crosstalk is below -20 dB within the C-band. The switch exhibits a 10%-90% rise time of 7.7 µs and a 90%-10% fall time of 3.4 µs at 1550 nm. As far as we know, it is the first demonstration of a poly-Si switch on an 8-inch wafer pilot-line. The low-temperature deposited poly-Si switch is promising for multilayer active photonic devices and photonic-electronic applications.

Visual and IR Inspection Analysis of PV Modules Installed at the Desert Climate of Qatar

This study presents the results of visual and infrared (IR) inspection of photovoltaics (PV) technologies installed at the Qatar environment and energy research institute (QEERI) outdoor test facility (OTF) at Qatar Foundation (Doha, Qatar). Silicon based PV technologies which have been operational in the field since 2014, have been investigated for various failure modes. The visual inspections were carried out for all the PV modules from the backside however, the inspection from the front side was not possible for some modules due to heavy soiling. The visual defects which were identified during this study include, cracking of the back glass, yellowing of the encapsulant material, cracks formation in the back sheet, and pits formation in the back sheet. The visual inspection revealed that around 19 % of the total modules have back sheet cracking and discoloration, 8 % have yellowing of the encapsulant, and around 4 % were having pits in the back sheet. Moreover, one module was detected with back glass cracking. The IR inspection was also done both from front and backside for all the silicon PV modules to detect hot spots. The IR inspection has revealed that hot spots were generated at different locations of the PV modules. 39 % of the modules have hot spots at the location of junction boxes, around 6 % of the modules have hot spots in junction boxes and around 1 % have hot spots at the locations away from junction boxes. The visual and IR inspection has revealed that the dominant failure modes which have been observed for silicon-based technologies at OTF are the hot spots generation at junction boxes and the back sheet cracking, and its yellowing.

Multiscale CFD Simulation of Multiphase Erosion Process in a Connecting Pipe of Industrial Polycrystalline Silicon Unit

Severe erosion phenomena often occur in industrial polycrystalline silicon units, leading to hydrogen leakage accidents and affecting long-term operation. It is favorable to use a computational fluid dynamics (CFD) simulation with the dense discrete phase model (DDPM) and the sub-grid energy-minimization multi-scale (EMMS) drag model to improve the prediction accuracy of complex multiphase erosion phenomena in a connecting pipe of an industrial polycrystalline silicon unit. Furthermore, the effect of droplet the specularity coefficient on boundary conditions is thoroughly considered. The predicted erosion behaviors are consistent with industrial data. The effects of operations parameters were discussed with three-dimensional CFD simulation, including droplet size and hydrogen volume fraction on erosion behaviors. The results indicated that the non-uniform multiphase erosion flow behavior near the wall can be simulated accurately with the EMMS drag model in a coarse mesh. A suitable droplet specularity coefficient such as 0.5 can also improve the accuracy of erosion position. Small liquid droplets, such as those of 30 μm size, will follow the gas phase better and have a lower erosion rate. The inertia effect of large droplets, such as those of 150 μm size, plays a dominant role, resulting in obvious erosion on the elbow walls. The erosion range and thinning rate enlarge with the increase in hydrogen volume fraction. A few silicon solid particles, such as 0.01% volume fraction, change local flow behaviors and probably cause the variation of local erosion positions. The process of erosion deformation first circumferentially extended and then accelerated at the local center position deeper.

Thermal interdiffusion, microstructure and contact resistivity of NiOx/Ni/p+ poly-Si layer systems for perovskite/TOPCon tandem solar cells during annealing processes

In a recently published article (Lange et al., 2023) [1], we envisioned and discussed a tandem solar cell concept based on a perovskite/TOPCon architecture in p-i-n configuration, that utilizes a p+/n+ polycrystalline silicon (poly-Si) tunnel junction and NiOx as hole transport material of the perovskite top cell. A direct contact of NiOx to p+ poly-Si is inevitable in such a device. We investigated that junction and reported how the contact resistivity of the NiOx/p+ poly-Si junction can be improved by orders of magnitudes by intentionally inserting a nm-thin metallic Ni interlayer at that interface through the formation of nickel silicide.In this contribution, we present comprehensive data on layer stack morphology, composition and interdiffusion and the impact on the measured contact resistivity based on (scanning) transmission electron microscopy (STEM) coupled with energy-dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) of model samples as well as the real contact structures. Diffusion and reaction processes in the NiOx/Ni/p+ poly-Si layer stack are investigated during the annealing in the temperature range between 100 °C and 500 °C for varying Ni interlayer thicknesses of 0, 1.0 and 2.0 nm. Furthermore, two NiOx syntheses routes are investigated: sputter deposition (s-NiOx) and a wet-chemical approach (wc-NiOx). We correlate the improvement of contact resistivity for both systems and temperatures <300 °C in regard to contacts without metallic Ni interlayer with the observation of pinhole formation within the SiOz. We have observed that annealing the Ag/s-NiOx junctions above 300 °C under ambient air leads to rectifying contacts and high contact resistivities due to excessive interdiffusion of Ni, O and Ag.

Comparative analysis of outdoor energy harvest of organic and silicon solar modules for applications in BIPV systems

Organic photovoltaics (OPV) have the potential to fill niches that traditional silicon photovoltaics (Si-PV) have left open so far. Building-integrated photovoltaics (BIPV) is one key area where OPV modules can play a vital role due to their functional attributes of semitransparency, flexibility, and lightweight. However, the architectural constraints and physical layout of buildings often do not allow the installation of photovoltaic (PV) modules at their optimal angles. Herein, we report the outdoor energy harvest of commercial OPV, and monocrystalline silicon (m-Si) modules mounted at inclinations of 45° and 90°, using the ISOS-O2 protocol as a test standard. The semitransparent OPV modules incorporating a P3HT:PCBM bulk heterojunction absorbing layer were found to offer daily specific energy yields (YF) that are 10–15% higher than those of the m-Si modules at 45° inclination. For vertical (90°) mounting, the YF of the OPV modules is even 24–30% higher than that of their inorganic counterparts, thus making them ideally suited for façade integrated BIPV. Laboratory investigations reveal that the superior performance of OPV modules in the vertical position is mainly due to a strongly enhanced fill factor (FF) at reduced in-plane irradiance. At a 45° inclination, the positive temperature coefficient of the OPV modules also plays an important role during high-irradiance hours.

Evaluation of the degradation of a PV panel in an arid zone; case study Biskra (Algeria)

Even for a limited period of time, weather conditions including solar radiation, temperature, wind, UV intensity, humidity, and precipitation have an effect on the degradation and efficiency of PV panels. As a result, these are the primary variables that impact the lifetime and durability of a photovoltaic system. Thus, increasing the efficiency of PV modules requires overcoming the critical problem of degradation. The current study aims to examine the deterioration of a poly-crystalline silicon photovoltaic panel that was exposed to outside conditions for four years in Biskra’s arid climate (Algerian town). To assess the performance of the tested PV module, two characterization techniques—I-V and P-V characterization as well as visual inspection—have been applied.Under normal conditions, a new model for determining the five criteria (a, Rs, Rp, I0, and Iph) has been developed using curve-fitting method. It was adapted for panels with and without degradation. By estimating how those parameters degrade, a new technique for identifying damaged panels has been created. The results highlight the dominance of the EVA degradation mode, which has a significant effect on the degradation rates of Rs (54.27%), Rp (−62.68%), and Iph (77.45%), as well as the evolution of the I-V and P-V curves.