Crystalline Silicon Technology Research Articles

Modelling, analysis and forecasting of photovoltaic waste in Malaysia towards sustainable recycling by 2050

Malaysia is currently pushing for greater solar photovoltaic (PV) penetration through various policies, hence need to assess the consequent PV waste situation in preparation for sustainable End-of-Life (EoL) management of the PV systems. Through incorporation of fixed-loss, early-loss, and regular-loss scenarios into Malaysia's PV roadmap, it is projected that 229,009.17 tons to 481,137.12 tons of PV waste would be generated by 2050. Implementing current achievable PV material recovery rates would result in economic value creation between RM 1.02-2.21 billions (USD 213.78-463.92 millions) and carbon emissions avoidance between 398,858.41 tons CO2-eq to 785,712.93 tons CO2-eq by 2050. With crystalline silicon (c-Si) technology contributing more than 60% of waste share, 2029 to 2039 would be the suitable time period to jumpstart recycling operation due to consistent annual c-Si waste input of 8,000 tons/y for financially sustainable recycling. These findings can help garner support for sustainable EoL management of PV waste in Malaysia.

Annual degradation rates and soiling losses of photovoltaic systems composed of recent crystalline silicon technologies in temperate climate

AbstractThe purpose of this study is to investigate the annual degradation rates of photovoltaic (PV) systems composed of PV modules based on recent crystalline silicon (c‐Si) PV technologies. We investigated the annual degradation rates of four PV systems composed of different c‐Si PV technologies, comprising p‐type multi‐crystalline silicon with a passivated emitter rear cell, n‐type silicon heterojunction, p‐type single‐crystalline silicon (sc‐Si) with an aluminum back surface field, and n‐type (sc‐Si) solar cell technologies. These systems were located in Gunma Prefecture in Japan and were measured over 6 years. Furthermore, the effects of soiling on the annual degradation rates of these PV systems were examined by partially surface cleaning the PV arrays two times. The results obtained indicate that the apparent annual degradation rates of the PV strings before surface cleaning were 0.8, 1.6, 1.4, and 1.2%/year, respectively, because of optical losses due to dust particles. However, the inherent annual degradation rates of the PV strings after surface cleaning were 0.1, 0.6, 0.0, and 0.3%/year, respectively. These low degradation rates indicate that the PV systems composed of the recent c‐Si PV technologies all offered reasonably stable performance that was reduced by 3.6%, 5.5%, 7.3%, and 4.8%, respectively because of the effects of surface soiling, although the surfaces of the PV arrays had been washed by plentiful rainfall under their humid subtropical climatic operating conditions.

Modelling recycling for the life cycle assessment of perovskite/silicon tandem modules

With the massive growth of the global capacity of photovoltaics (PV) over the last decade, the PV waste is expected to increase dramatically in the near future. Having potential to reduce the use of raw materials and preserve natural resources, PV recycling is attracting more and more attention. This being said, the environmental impacts over the life cycle of PV technologies, including the end-of-life (EoL) stage, should be evaluated carefully. Life cycle assessment (LCA) is currently the most common methodology to assess the potential environmental impacts of a product throughout its entire life cycle. However, the modelling of recycling in LCA has always been a challenge and no consensus has yet been reached, since the treatment of recycling does not only involve an EoL management of waste, but also the production of recycled material. Perovskite on silicon tandem is a widely investigated emerging PV technology having the potential to overcome the power conversion efficiency (PCE) limit of the single-junction crystalline silicon technology. The EoL modelling seems more challenging in the case of emerging technologies for which the EoL is more uncertain than for established technologies. In this article, six common and important approaches of EoL modelling in LCA were applied to future perovskite/silicon tandem modules to analyze the effect of the different EoL modelling approaches on the LCA results. The aim was to identify the most suitable methodological approaches to account for recycling, when modelling the life cycle of PV modules. The environmental performance of perovskite/silicon tandem modules was assessed over their life cycle and expressed in terms of impacts per m2 of module. After testing the six EoL modelling approaches and comparing the LCA results, the EoL modelling choice was found to lead to non-negligible differences. For example, in terms of climate change, the impact of the tandem modules ranges from 45 to 59 kg CO2-eq/m2. Among the six EoL modelling options, the approaches of simple cut-off and cut-off with economic allocation are more oriented towards the promotion of high rates of recycled material integrated as an input to the assessed product among industrial actors, while the approach of closed-loop allocation provides incentives to maximize the ratio of recycling at the EoL, regardless the initial ratio of recycled content within the product. Some approaches such as the circular footprint formula (CFF) tend to provide both incentives to increase the content of recycled input material in the manufacturing of the product and the recycling ratio at the EoL of such product. After applying the different alternatives, a set of recommendations to select the relevant EoL modelling approaches are provided: 1) the CFF is recommended as a representative approach due to its wide applicability, tending to provide an intermediate result and reflecting the characteristics of materials; 2) sensitivity analysis should be applied to check the robustness of the results, 3) the cut-off approach and the closed-loop allocation should be used at least for the sensitivity analysis.

Potential-induced degradation phenomena in single-encapsulation crystalline Si photovoltaic modules

This paper particularly explains potential-induced degradation (PID) of wafer-based standard p-type crystalline silicon technology. We present a single-encapsulation method that is useful for simulating PID in the laboratory to facilitate microanalyses of module-level solar cells. The PID testing is performed for the module with single-encapsulation and conventional modules. Their current–voltage characteristics and electroluminescence images are investigated before and after the PID tests. As described herein, we infer that the single-encapsulation modules generate PID almost in the same way as conventional modules do, and that the degradation trend is almost identical to that of conventional modules. Results of PID recovery tests indicate that the time necessary for PID recovery is always less than that for PID generation, irrespective of the encapsulation method.

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%.

Improved sustainability of solar panels by improving stability of amorphous silicon solar cells

As the world grapples with global warming, it becomes imperative to carefully examine the sustainable energy technology choices. Solar is the fastest growing clean energy source but today it contributes little to the electricity generated, so future installations will dwarf the existing installed base. There is a factor of 2–4 decrease in the energy payback time from the dominant crystalline silicon technology to thin film technologies. Essential criteria like use of abundant materials and simple but mature production technology point to amorphous silicon (a-Si) technology. Here we delve into the primary issue impeding adoption of a-Si technology—the Staebler Wronski Effect (SWE), that generates metastable, light induced defects which reduce the performance of a-Si based solar cells. We demonstrate that a simple change leads to a significant reduction in SWE power loss and define a clear path to elimination of SWE, allowing the technology to be widely adopted.

Unraveling the passivation mechanisms of c-Si/SiOx/poly-Si contacts

As one of the prospective crystalline silicon (c-Si) technologies, tunnel oxide passivating contact (TOPCon) solar cells have recently attracted much attention in the photovoltaic community. However, the deficit of open-circuit voltage due to the imperfect passivation performance together with the insufficient understanding of the passivation mechanism, especially for the key structures of TOPCon devices ( i.e. , poly-Si/SiO x /c-Si), is a crucial factor to limit the improvement of device efficiency. To unlock the full passivation potential of this type of poly-Si/SiO x /c-Si contact, we report a systematic investigation by combining experiments and simulations. The related results can be summarized: 1) the best passivation can be obtained by optimizing SiO x quality, tailoring the in-diffusion profile, and performing hydrogenation; 2) if SiO x quality is good enough, high-level passivation can be expected even without impurity doping; 3) although the deepened in-diffusion could partially alleviate the degradation of the poor surface passivation, it would also reduce the passivation performance owing to the increased Auger recombination inherent to the high impurity doping; 4) the presence of pinholes would degrade the passivation performance, especially for the cases with the good surface passivation, a shallow in-diffusion and a low doping concentration of poly-Si, where the electric-field effect was minimized. To further confirm these conclusions, recombination distributions and the corresponding current profiles of the minority carriers were reviewed. This work clarifies the passivation mechanism of c-Si/SiO x /poly-Si contact in detail and provides effective guidance for further promoting the passivation level and the efficiencies of TOPCon devices. • An experiment and complementary simulations were designed to confirm the passivation properties of c-Si/SiO x /poly-Si contacts. • Annealing temperature, hydrogenation and SiO x quality were simultaneously regulated to promote passivation quality. • The underlying factors including poly-Si thickness and pinholes to affect the passivation performance were investigated in detail. • Passivation mechanisms were clarified by addressing recombination distributions and current profiles of the minority carriers.

Investigation and recovery of copper from waste silicon solar module

Photovoltaic (PV) technology has seen exponential growth in the last few decades with the total global installation reaching 849 GW by year 2021. With the estimated solar waste of nearly 78 million tonnes by year 2050, its high time to emphasise on the development of the recycling processes for valuable materials contained in end-of-life (EoL) solar panels. Crystalline silicon (c-Si) technology, owing to the largest market share, is forecasted to generate the majority of solar waste flux. A c-Si panel contains metals like Ag, Cu, Al, Pb and Sn. Most of the metallic fraction (Cu, Pb and Sn) by weight is contained in the connecting wires of the panel. In the present study, a process is developed for recovery of metallic Cu along with Pb and Sn without their exposure to the environment. Initially, connecting wires were separate out from panel using toluene solution. These wires were then thermally treated at 800 °C for 7 h in a sealed quartz tube to get impure Cu strips and Pb-Sn powder. A set of chemical reactions was carried out next to first recover CuO powder followed by subsequent treatment with H2SO4 and Zn dust to recover 97.27% pure reddish brown Cu powder. As high purity copper powder with a good recovery rate of around 90% is obtained as the end product, the present study demonstrates a very simple process to recycle connecting wires in an ecological way with trapping toxic Pb and Sn.

New metric for carrier selective contacts for silicon heterojunction solar cells

Heterojunction carrier selective contacts for solar cells have gained great attention because of the ability of these contacts to efficiently collect majority carriers while hindering the recombination of minority carriers, thus resulting in the highest reported voltage among crystalline silicon technologies. The electrode work-function, doping and thickness of the doped layer remain the key parameters for governing the cell performance. Recently, we have studied the requirements for carrier selective contacts under various illumination levels and reported logarithmic dependence of these parameters. In this work, we define a new metric for describing the ability of a contact to collect the carriers and named it as contact strength. We have developed an analytical approach for contact strength of hole selective contacts which represents the requirements on doping, thickness of the contact layer, and electrode work-function for a given illumination. First, the numerical model is calibrated with the experimental data for a wide range of illumination (0.01 Sun – 1.0 Sun) and then simulations have been fitted with analytical model. For the selective contact layer, we observe that only the total charge, rather than thickness and doping individually, matters. The work-function of the top electrode also contributes strongly to contact strength and can in principle substitute doped layer. This insightful metric will guide the solar cell technologists to better understand the carrier selective contacts and to maximize the cell performance not only at standard test conditions (STC), but also at low light illuminations.

A new form of impurity cluster in casting quasi-single crystalline silicon

The casting quasi-single crystalline silicon technology is very promising in the development of high quality and low cost crystals for manufacturing photovoltaic devices. In this study, we find a new type of impurity cluster named as “black spot” in the casting quasi-single crystalline, which is different from the “shadows” caused by SiC/Si3N4 particles discovered in previous research. The “black spot” is systematically studied and characterized using inductively coupled plasma mass spectrometry (ICP-MS), photoluminescence (PL), and infrared (IR) detectors. The test results show that the “black spot” is composed of metal impurities. According to our analysis, the formation mechanism of the “black spot” may be caused by the accumulation of the metal impurities in certain region of the solid/liquid interface. These clustering impurities are not absorbed by enough grain boundaries in the casting quasi-single crystalline after being solidified into the crystal and thus exhibit as “black spot”. An optimization method is proposed in the direction of numerical simulation and verified by experiments to avoid the formation of the “black spot”.

Monolithic Perovskite-Silicon Tandem Solar Cells: From the Lab to Fab?

This review focuses on monolithic 2-terminal perovskite-silicon tandem solar cells and discusses key scientific and technological challenges to address in view of an industrial implementation of this technology. The authors start by examining the different crystalline silicon (c-Si) technologies suitable for pairing with perovskites, followed by reviewing recent developments in the field of monolithic 2-terminal perovskite-silicon tandems. Factors limiting the power conversion efficiency of these tandem devices are then evaluated, before discussing pathways to achieve an efficiency of >32%, a value that small-scale devices will likely need to achieve to make tandems competitive. Aspects related to the upscaling of these device active areas to industry-relevant ones are reviewed, followed by a short discussion on module integration aspects. The review then focuses on stability issues, likely the most challenging task that will eventually determine the economic viability of this technology. The final part of this review discusses alternative monolithic perovskite-silicon tandem designs. Finally, key areas of research that should be addressed to bring this technology from the lab to the fab are highlighted.

A Note on Limits and Trends in PV Cells and Modules

The key components of photovoltaic (PV) systems are PV modules representing basic devices, which are able to operate in outdoor conditions for a long time. PV modules can be manufactured from different materials using different production technologies. The main criterion supporting or limiting the successful placement of specific technologies on the market is the price of electricity produced by PV systems. The levelized cost of energy (LCOE) method considers investment costs, operating costs, and the total energy produced during a PV system’s service life. The influence of price, efficiency, and service life of PV modules on the LCOE (together with the availability of materials) sets limits for applicable technologies. Increasing the efficiency of the modules from 21% to 23% could lead to a reduction of the area-dependent part of the PV system costs by 8.7%. Extending the service life from 25 to 30 years could reduce the LCOE by about 10%. As shown in the work, wafer-based crystalline silicon technologies best meet these criteria due to their high efficiency, low costs, long service life, and the availability of materials at present. Technological innovations make it possible to increase the efficiency of the modules closer to the physical limits and to extend the service life of the modules.

Quick Diagnostic Tool for Thin-Film Photovoltaic Power Plants Utilizing Dark Current Measurement

There exist many photovoltaic (PV) power plants which are based on thin-film technology. Unlike PV power plant with crystalline silicon technology, the diagnostic possibilities of thin-film PV modules are limited due to seasonal effects and problematic utilization of thermography. The main problem of degradation of these PV plants is the area degradation which affects even PV power plants with transformer inverters. Although there exist measurement methods based on <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I–V</i> curve measurement, these methods require specific climatic conditions (clear sky, sufficient irradiance) and time. Here, we present the novel approach to diagnose thin-film modules affected with degradation which provides quick results with low-cost equipment.

창호용 블라인드 태양광 모듈의 설계

We propose an indoor blind-type solar module that can be applied to the windows of buildings. A comparative study was conducted with solar modules by alternatively assuming crystalline silicon, CIGS, or amorphous silicon thin film solar cell technology. It is self-evident that the output power of the crystalline silicon solar cell module is the largest, but the power gap between modules is smaller than that predicted from the cell efficiency because the module power loss in thin film solar cell modules is comparatively small. In addition, since the temperature coefficient of the thin film solar cell is smaller than that of the crystalline silicon solar cell, the output power gap between the crystalline silicon and thin film solar cell modules is further reduced when operating in a high temperature environment. It is expected that this blind-type solar module would contribute about 10% reduction of the existing fossil energy generation, and about 50% of electricity consumption per household as an urban auxiliary power source.

Long-term performance and degradation analysis of different PV modules under temperate climate

The share of solar photovoltaic in the energy mix is achieving significant growth worldwide. Accurate forecasts of return on investment and a good choice of optimal PV technology for different regions require proper PV studies. Long-term performance and degradation analysis, as well as an economic investigation of three based-silicon PV technologies including amorphous silicon (a-Si), polycrystalline silicon (p-Si), and monocrystalline silicon (m-Si) have been performed in this work. This study has been done based on different performance indicators such as AC energy production (EAC), reference yield (Yr), final yield (Yf), performance ratio (PR), temperature corrected performance ratio (PRSTC), degradation rate (Dr), and levelized cost of energy (LCOE). The results of the performance ratio analysis revealed that crystalline silicon technologies are better than amorphous PV system with values of 84.25% for m-Si, 84.32% for p-Si, and 79.14% for a-Si. The degradation analysis was performed using linear regression (LR) and classical seasonal decomposition (CSD) statistical techniques. The results of these latter indicate that a-Si degrades faster than its counterparts with a ratio of 0.9 ± 0.009%/year and 0.75 ± 0.003%/year, followed by m-Si (0.53 ± 0.01%/year and 0.41 ± 0.003%/year), and p-Si (0.36 ± 0.01%/year and 0.28 ± 0.004%/year) using LR and CSD, respectively. However, these degradation rates are comparable to other degradation rates obtained in studies performed in different climates in Morocco. Finally, the LOCE results demonstrate that p-Si technology is the most cost-effective system with a value of 0.09 USD/kWh compared to 0.1 USD/kWh for m-Si, and 0.13 USD/kWh for a-Si. According to the obtained findings, p-Si is the most optimal and suitable technology to be installed in the mountain temperate climate.

Embedded current collectors for efficient large area perovskite solar cells

Perovskite solar cells (PSCs) are an emerging solar cell technology that has shown the fastest growth in power conversion efficiency (PCE). The present power conversion efficiency record of 25.5% is already comparable to crystalline silicon technology, which is attracting the research and industrial community attention. The main challenges in scaling-up PSCs are the limited conductivity of the transparent electrode and the difficulty in depositing an uniform and defect-free perovskite layer over large areas. This work reports the use of engraved gold metal lines in the FTO glass substrate for increasing its electronic conductivity; the prepared 5 cm2 PSC displays a PCE enhancement of 26% over the cells prepared with pristine FTO substrates.

The effect of rain on photovoltaic systems

Photovoltaic technology can be considered a key energy source for the future sustainable development, therefore it's important to carry out a continuous and comprehensive investigation about its actual energy performance in various climatic conditions. More in detail, crystalline silicon technology is currently dominating the market, thus an in-depth assessment on its specific behaviour is essential. In this sense, numerous studies have been performed in the past decades to assess the influence on the energy production of crystalline photovoltaic modules of several factors, such as spectral quality of solar irradiance, temperature, wind speed, soiling, snow etc. but so far the effect of rain appears scarcely investigated. In such a framework, the present work represents a detailed assessment of the rain effect on the performances of crystalline silicon technology, carried out both under a theoretical and experimental viewpoint, with a focus on the temperate climates of European context. Obtained results are promising and confirm that the overall impact of rain can have non-negligible positive influences on the energy productivity of photovoltaic systems, mainly for thermal and optical reasons, paving the way for further studies on the topic.

Performance assessment of bare and anti‐reflective coated CdTe photovoltaic systems in comparison to multicrystalline Si in Brazil

AbstractThe performance of three ground‐mounted fixed‐tilt photovoltaic (PV) systems installed at the Solar Energy Research Laboratory Fotovoltaica/UFSC in Florianópolis, southern Brazil (27°S, 48°W, Cfa Köppen‐Geiger climate classification), were analyzed in this paper. This study compares the performance of cadmium telluride (CdTe) thin‐film PV modules (both with and without an anti‐reflective coating [ARC]) and multicrystalline silicon (mc‐Si) PV systems over two full years of continuous operation. Furthermore, the paper presents a literature review on previous studies that investigated the main environmental parameters that affect the performance of CdTe and m‐Si PV systems. Results revealed that throughout the period analyzed, the CdTe with ARC PV system presented the best performance, with an overall annual energy yield 5% higher than the reference mc‐Si PV system. In order to evaluate the performance behavior of the three PV systems under study, the main environmental parameters that affect the efficiency of PV systems were analyzed: temperature, spectrum, angle of incidence, weak‐light responsivity, and soiling impact. Irradiation levels for all PV systems were identical, as they are all operating at the same site. Temperature followed by spectral content of sunlight presented the highest impacts on performance, resulting in estimated overall performance gains of 1.9% and 1.5%, respectively, for the CdTe systems. These findings are consistent with our previous research, showing that CdTe has a performance advantage over traditional monofacial crystalline silicon technologies in warm and sunny climates.

In English

We have proposed a new technological solution for the creation of solar energy elements using bilateral structures of macroporous silicon to increase the overall efficiency of converting light energy into electricity. Recently, the research on R&amp;D in solar cell technology has focused mainly on crystalline silicon technologies and photovoltaic systems, including organic ones. The main physical phenomenon that determines the prospects of two-dimensional structures of macroporous silicon with nanocoatings as solar cells is the increase in absorption of electromagnetic radiation and photoconductivity as a result of interaction of optical modes with the developed surface of cylindrical macropores with a barrier on the nanocoating-surface boundary. We fabricated two-sided macroporous silicon structures with nanocoatings for solar cells, including silicon technology, organic nanoformations, and photovoltaic system formation. Silicon is a promising material for the manufacture of structures with a cylindrical geometry of air macropores due to the anisotropy of the cheap process of photoelectrochemical etching. The presence of periodically located cylindrical pores separated by silicon columns provides a large effective surface of the samples and enhanced optical and photophysical characteristics of silicon structures. Polymer composites with nanocoatings with CdS nanocrystals and multilayer carbon nanotubes in polyethyleneimine generate charges of opposite sign on both surfaces of the structures under illumination. The formation of bilateral structures of macroporous silicon with nanocoatings increases the overall energy conversion efficiency in solar cells by up to 60 %. In addition, one can use our proposed solar cells in the upper atmosphere.

Strategy for large‐scale monolithic Perovskite/Silicon tandem solar cell: A review of recent progress

AbstractFor any solar cell technology to reach the final mass‐production/commercialization stage, it must meet all technological, economic, and social criteria such as high efficiency, large‐area scalability, long‐term stability, price competitiveness, and environmental friendliness of constituent materials. Until now, various solar cell technologies have been proposed and investigated, but only crystalline silicon, CdTe, and CIGS technologies have overcome the threshold of mass‐production/commercialization. Recently, a perovskite/silicon (PVK/Si) tandem solar cell technology with high efficiency of 29.1% has been reported, which exceeds the theoretical limit of single‐junction solar cells as well as the efficiency of stand‐alone silicon or perovskite solar cells. The International Technology Roadmap for Photovoltaics (ITRPV) predicts that silicon‐based tandem solar cells will account for about 5% market share in 2029 and among various candidates, the combination of silicon and perovskite is the most likely scenario. Here, we classify and review the PVK/Si tandem solar cell technology in terms of homo‐ and hetero‐junction silicon solar cells, the doping type of the bottom silicon cell, and the corresponding so‐called normal and inverted structure of the top perovskite cell, along with mechanical and monolithic tandemization schemes. In particular, we review and discuss the recent advances in manufacturing top perovskite cells using solution and vacuum deposition technology for large‐area scalability and specific issues of recombination layers and top transparent electrodes for large‐area PVK/Si tandem solar cells, which are indispensable for the final commercialization of tandem solar cells.image