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Martin C. Schubert - One of the best experts on this subject based on the ideXlab platform.
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optimized multicrystalline silicon for solar cells enabling conversion efficiencies of 22
Solar Energy Materials and Solar Cells, 2017Co-Authors: Florian Schindler, B Michl, Patricia Krenckel, Stephan Riepe, Jan Benick, Ralph Muller, Armin Richter, S W Glunz, Martin C. SchubertAbstract:Abstract Multicrystalline (mc) n-type silicon has proven to be a suitable substrate for the fabrication of highly efficient mc-Si solar cells. In this paper, we elaborate the impact of base Material parameters on the efficiency potential of n-type mc-Si solar cells featuring a boron-diffused front side emitter and a full-area passivating rear contact (TOPCon). The electrical Material Quality can be significantly improved by replacing the standard crystallization process with a seed-assisted growth for crystallization of high-performance (HP) mc silicon. Using high-purity quartz crucibles or larger crucibles in combination with an optimization of the grain boundary area fraction with an adapted seed structure leads to further improvements of the Material Quality in terms of charge carrier lifetimes. However, not only the charge carrier lifetime, but also the base resistivity is of crucial importance for the efficiency potential depending on the cell concept. Based on experimental data and simulations, we assess the optimal range for the base resistivity and the wafer thickness for n-type mc-Si TOPCon solar cells. With the optimal Material parameters, an “efficiency limiting bulk recombination analysis” (ELBA) reveals an efficiency potential in the range of 22.5% for n-type mc-Si TOPCon solar cells. Finally, we fabricated TOPCon solar cells based on optimized n-type HP mc-Si substrate and demonstrate a certified efficiency of 21.9%, which is the highest efficiency reported for multicrystalline silicon solar cells so far.
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solar cell efficiency losses due to impurities from the crucible in multicrystalline silicon
IEEE Journal of Photovoltaics, 2014Co-Authors: Florian Schindler, B Michl, Jonas Schon, Wilhelm Warta, Wolfram Kwapil, Martin C. SchubertAbstract:The electrical Material Quality of multicrystalline (mc) silicon for photovoltaic applications suffers from crystal defects as well as from impurities that originate from the feedstock, the quartz crucible, and its coating. In this study, we investigate the influence of impurities from the crucible on efficiency losses in mc silicon solar cells, focusing on the limitation due to iron. The applicability of p-type mc silicon, crystallized in G1 sized crucibles of industrial Material Quality and very pure electrically fused silica, for a high-efficiency solar cell process is examined by measuring lifetime and interstitial iron concentration in the wafers after different processing steps and by estimating the cell efficiency potential from injection-dependent bulk lifetime measurements. Interstitial iron concentrations extracted from 2-D simulations of iron precipitation at crystal defects and gettering during processing agree well with Fei measurements at different process stages and explain the observations. Efficiency losses are quantified to losses due to segregated impurities diffused into the silicon melt, losses due to decorated crystal defects and losses due to solid-state diffusion into the crystal. By using a high-purity crucible, losses are reduced significantly and an efficiency gain of 0.5% absolute is estimated to be attainable on wafers with edge region.
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wafer thickness optimization for silicon solar cells of heterogeneous Material Quality
Physica Status Solidi-rapid Research Letters, 2013Co-Authors: B Michl, Wilhelm Warta, M Kasemann, Martin C. SchubertAbstract:In this Letter, we introduce a method of calculating the optimal wafer thickness for silicon solar cells with multicrystalline bulk Material. The optimal thickness depends on the relation of bulk recombination to surface recombination and the light trapping. For multicrystalline silicon bulk recombination strongly varies laterally and with injection level, which complicates the calculations. A thickness optimization using the “Efficiency Limiting Bulk Recombination Analysis” (ELBA) takes all these effects correctly into account. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
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excellent average diffusion lengths of 600 μm of n type multicrystalline silicon wafers after the full solar cell process including boron diffusion
Energy Procedia, 2013Co-Authors: B Michl, Martin C. Schubert, Jan Benick, Armin Richter, Martin Bivour, Jeannie Yong, Rob Steeman, S W GlunzAbstract:Abstract In this paper we investigate the Material Quality of n - and p -type multicrystalline silicon wafers after different high- temperature steps, as applied during cell processing. Both Materials start with a high initial bulk diffusion length of around 440 μm (harmonic mean of the whole wafer) which is further improved by the solar cell process. A diffusion length of 510 μm was measured after phosphorus and boron diffusion and firing in the n -type Material. The p -type wafers showed diffusion lengths of 540 μm after phosphorus diffusion and firing. These diffusion lengths were measured at a generation rate of 1/20 sun close to maximum power point injection conditions of a solar cell. At higher injection levels both Materials reach 600 μm diffusion length. The high Material Quality of n -type Material maintained after the high temperature boron diffusion is remarkable. An efficiency analysis shows that these excellent diffusion lengths allow for high efficiency devices exceeding 20% efficiency.
B Michl - One of the best experts on this subject based on the ideXlab platform.
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optimized multicrystalline silicon for solar cells enabling conversion efficiencies of 22
Solar Energy Materials and Solar Cells, 2017Co-Authors: Florian Schindler, B Michl, Patricia Krenckel, Stephan Riepe, Jan Benick, Ralph Muller, Armin Richter, S W Glunz, Martin C. SchubertAbstract:Abstract Multicrystalline (mc) n-type silicon has proven to be a suitable substrate for the fabrication of highly efficient mc-Si solar cells. In this paper, we elaborate the impact of base Material parameters on the efficiency potential of n-type mc-Si solar cells featuring a boron-diffused front side emitter and a full-area passivating rear contact (TOPCon). The electrical Material Quality can be significantly improved by replacing the standard crystallization process with a seed-assisted growth for crystallization of high-performance (HP) mc silicon. Using high-purity quartz crucibles or larger crucibles in combination with an optimization of the grain boundary area fraction with an adapted seed structure leads to further improvements of the Material Quality in terms of charge carrier lifetimes. However, not only the charge carrier lifetime, but also the base resistivity is of crucial importance for the efficiency potential depending on the cell concept. Based on experimental data and simulations, we assess the optimal range for the base resistivity and the wafer thickness for n-type mc-Si TOPCon solar cells. With the optimal Material parameters, an “efficiency limiting bulk recombination analysis” (ELBA) reveals an efficiency potential in the range of 22.5% for n-type mc-Si TOPCon solar cells. Finally, we fabricated TOPCon solar cells based on optimized n-type HP mc-Si substrate and demonstrate a certified efficiency of 21.9%, which is the highest efficiency reported for multicrystalline silicon solar cells so far.
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solar cell efficiency losses due to impurities from the crucible in multicrystalline silicon
IEEE Journal of Photovoltaics, 2014Co-Authors: Florian Schindler, B Michl, Jonas Schon, Wilhelm Warta, Wolfram Kwapil, Martin C. SchubertAbstract:The electrical Material Quality of multicrystalline (mc) silicon for photovoltaic applications suffers from crystal defects as well as from impurities that originate from the feedstock, the quartz crucible, and its coating. In this study, we investigate the influence of impurities from the crucible on efficiency losses in mc silicon solar cells, focusing on the limitation due to iron. The applicability of p-type mc silicon, crystallized in G1 sized crucibles of industrial Material Quality and very pure electrically fused silica, for a high-efficiency solar cell process is examined by measuring lifetime and interstitial iron concentration in the wafers after different processing steps and by estimating the cell efficiency potential from injection-dependent bulk lifetime measurements. Interstitial iron concentrations extracted from 2-D simulations of iron precipitation at crystal defects and gettering during processing agree well with Fei measurements at different process stages and explain the observations. Efficiency losses are quantified to losses due to segregated impurities diffused into the silicon melt, losses due to decorated crystal defects and losses due to solid-state diffusion into the crystal. By using a high-purity crucible, losses are reduced significantly and an efficiency gain of 0.5% absolute is estimated to be attainable on wafers with edge region.
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wafer thickness optimization for silicon solar cells of heterogeneous Material Quality
Physica Status Solidi-rapid Research Letters, 2013Co-Authors: B Michl, Wilhelm Warta, M Kasemann, Martin C. SchubertAbstract:In this Letter, we introduce a method of calculating the optimal wafer thickness for silicon solar cells with multicrystalline bulk Material. The optimal thickness depends on the relation of bulk recombination to surface recombination and the light trapping. For multicrystalline silicon bulk recombination strongly varies laterally and with injection level, which complicates the calculations. A thickness optimization using the “Efficiency Limiting Bulk Recombination Analysis” (ELBA) takes all these effects correctly into account. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
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excellent average diffusion lengths of 600 μm of n type multicrystalline silicon wafers after the full solar cell process including boron diffusion
Energy Procedia, 2013Co-Authors: B Michl, Martin C. Schubert, Jan Benick, Armin Richter, Martin Bivour, Jeannie Yong, Rob Steeman, S W GlunzAbstract:Abstract In this paper we investigate the Material Quality of n - and p -type multicrystalline silicon wafers after different high- temperature steps, as applied during cell processing. Both Materials start with a high initial bulk diffusion length of around 440 μm (harmonic mean of the whole wafer) which is further improved by the solar cell process. A diffusion length of 510 μm was measured after phosphorus and boron diffusion and firing in the n -type Material. The p -type wafers showed diffusion lengths of 540 μm after phosphorus diffusion and firing. These diffusion lengths were measured at a generation rate of 1/20 sun close to maximum power point injection conditions of a solar cell. At higher injection levels both Materials reach 600 μm diffusion length. The high Material Quality of n -type Material maintained after the high temperature boron diffusion is remarkable. An efficiency analysis shows that these excellent diffusion lengths allow for high efficiency devices exceeding 20% efficiency.
S W Glunz - One of the best experts on this subject based on the ideXlab platform.
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optimized multicrystalline silicon for solar cells enabling conversion efficiencies of 22
Solar Energy Materials and Solar Cells, 2017Co-Authors: Florian Schindler, B Michl, Patricia Krenckel, Stephan Riepe, Jan Benick, Ralph Muller, Armin Richter, S W Glunz, Martin C. SchubertAbstract:Abstract Multicrystalline (mc) n-type silicon has proven to be a suitable substrate for the fabrication of highly efficient mc-Si solar cells. In this paper, we elaborate the impact of base Material parameters on the efficiency potential of n-type mc-Si solar cells featuring a boron-diffused front side emitter and a full-area passivating rear contact (TOPCon). The electrical Material Quality can be significantly improved by replacing the standard crystallization process with a seed-assisted growth for crystallization of high-performance (HP) mc silicon. Using high-purity quartz crucibles or larger crucibles in combination with an optimization of the grain boundary area fraction with an adapted seed structure leads to further improvements of the Material Quality in terms of charge carrier lifetimes. However, not only the charge carrier lifetime, but also the base resistivity is of crucial importance for the efficiency potential depending on the cell concept. Based on experimental data and simulations, we assess the optimal range for the base resistivity and the wafer thickness for n-type mc-Si TOPCon solar cells. With the optimal Material parameters, an “efficiency limiting bulk recombination analysis” (ELBA) reveals an efficiency potential in the range of 22.5% for n-type mc-Si TOPCon solar cells. Finally, we fabricated TOPCon solar cells based on optimized n-type HP mc-Si substrate and demonstrate a certified efficiency of 21.9%, which is the highest efficiency reported for multicrystalline silicon solar cells so far.
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excellent average diffusion lengths of 600 μm of n type multicrystalline silicon wafers after the full solar cell process including boron diffusion
Energy Procedia, 2013Co-Authors: B Michl, Martin C. Schubert, Jan Benick, Armin Richter, Martin Bivour, Jeannie Yong, Rob Steeman, S W GlunzAbstract:Abstract In this paper we investigate the Material Quality of n - and p -type multicrystalline silicon wafers after different high- temperature steps, as applied during cell processing. Both Materials start with a high initial bulk diffusion length of around 440 μm (harmonic mean of the whole wafer) which is further improved by the solar cell process. A diffusion length of 510 μm was measured after phosphorus and boron diffusion and firing in the n -type Material. The p -type wafers showed diffusion lengths of 540 μm after phosphorus diffusion and firing. These diffusion lengths were measured at a generation rate of 1/20 sun close to maximum power point injection conditions of a solar cell. At higher injection levels both Materials reach 600 μm diffusion length. The high Material Quality of n -type Material maintained after the high temperature boron diffusion is remarkable. An efficiency analysis shows that these excellent diffusion lengths allow for high efficiency devices exceeding 20% efficiency.
Paul Plocica - One of the best experts on this subject based on the ideXlab platform.
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polycrystalline silicon thin film solar cells status and perspectives
Solar Energy Materials and Solar Cells, 2013Co-Authors: Christiane Becker, Daniel Amkreutz, Tobias Sontheimer, Veit Preidel, Daniel Lockau, Jan Haschke, Lisa Jogschies, Carola Klimm, Janis Merkel, Paul PlocicaAbstract:Abstract The present article gives a summary of recent technological and scientific developments in the field of polycrystalline silicon (poly-Si) thin-film solar cells on foreign substrates. Cost-effective fabrication methods and cheap substrate Materials make poly-Si thin-film solar cells promising candidates for photovoltaics. However, it is still the challenge for research and development to achieve the necessary high electrical Material Quality known from crystalline Si wafers on glass as a prerequisite to harvest the advantages of thin-film technologies. A wide variety of poly-Si thin-film solar cell approaches has been investigated in the past years, such as thermal solid phase crystallization – the only technology that had already been matured to industrial production so far – the seed layer concept where a large-grained seed layer is epitaxially thickened, direct growth of fine grained Material, and liquid phase crystallization methods by laser or electron beam. In the first part of this paper, the status of these four different poly-Si thin-film solar cell concepts is summarized, by comparing the technological fabrication methods, as well as the structural and electrical properties and solar cell performances of the respective Materials. In the second part, three promising technologies are described in more detail due to their highly auspicious properties regarding Material Quality and throughput aspects during fabrication: (1) High-rate electron–beam evaporation of silicon for the low-cost deposition of high-Quality Material, (2) large-area periodic nano- and micro-structuring of poly-Si by the use of imprinted substrates providing a large absorption enhancement by a factor of six at a wavelength of 900 nm, (3) liquid-phase crystallization of silicon thin-film solar cells by electron–beam, yielding an excellent poly-Si Material Quality reflected by an open-circuit voltage of 582 mV which has been achieved only very recently. A successful combination of these three complementary technologies is envisaged to be the basis for a prospective low-cost and highly efficient poly-Si solar cell device.
Daniel Amkreutz - One of the best experts on this subject based on the ideXlab platform.
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crystalline silicon on glass interface passivation and absorber Material Quality
Progress in Photovoltaics, 2016Co-Authors: Onno Gabriel, Daniel Amkreutz, Bernd Rech, Tim Frijnts, Natalie Preissler, Sonya Calnan, Sven Ring, Bernd Stannowski, Rutger SchlatmannAbstract:Thin crystalline silicon solar cells prepared directly on glass substrates by means of liquid-phase crystallization of the absorber utilize only a small fraction of the silicon Material used by standard wafer-based silicon solar cells. The Material consists of large crystal grains of up to square centimeter area and results in solar cells with open-circuit voltages of 650 mV, which is comparable with results achieved with multi-crystalline silicon wafers. We give a brief status update and present new results on the electronic interface and bulk properties. The interrelation between surface passivation and additional hydrogen plasma passivation is investigated for p-type and n-type absorbers with different doping concentrations. Internal quantum efficiency measurements from both sides on bifacial solar cells are used to extract the bulk-diffusion length and surface-recombination velocity. Finally, we compare various types of solar cell devices based on 10 µm thin crystalline silicon, where conversion efficiencies of 11–12% were achieved with p–type and n-type liquid-phase crystallized absorbers on glass. Copyright © 2015 John Wiley & Sons, Ltd.
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liquid phase crystallized silicon on glass technology Material Quality and back contacted heterojunction solar cells
Japanese Journal of Applied Physics, 2016Co-Authors: Jan Haschke, Daniel Amkreutz, Bernd RechAbstract:Liquid phase crystallization has emerged as a novel approach to grow large grained polycrystalline silicon films on glass with high electronic Quality. In recent years a lot of effort was conducted by different groups to determine and optimize suitable interlayer Materials, enhance the crystallographic Quality or to improve post crystallization treatments. In this paper, we give an overview on liquid phase crystallization and describe the necessary process steps and discuss their influence on the absorber properties. Available line sources are compared and different interlayer configurations are presented. Furthermore, we present one-dimensional numerical simulations of a rear junction device, considering silicon absorber thicknesses between 1 and 500 mu m. We vary the front surface recombination velocity as well as doping density and minority carrier lifetime in the absorber. The simulations suggest that a higher absorber doping density is beneficial for layer thicknesses below 20 mu m or when the minority carrier lifetime is short. Finally, we discuss possible routes for device optimization and propose a hybride cell structure to circumvent current limitations in device design. (C) 2016 The Japan Society of Applied Physics
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polycrystalline silicon thin film solar cells status and perspectives
Solar Energy Materials and Solar Cells, 2013Co-Authors: Christiane Becker, Daniel Amkreutz, Tobias Sontheimer, Veit Preidel, Daniel Lockau, Jan Haschke, Lisa Jogschies, Carola Klimm, Janis Merkel, Paul PlocicaAbstract:Abstract The present article gives a summary of recent technological and scientific developments in the field of polycrystalline silicon (poly-Si) thin-film solar cells on foreign substrates. Cost-effective fabrication methods and cheap substrate Materials make poly-Si thin-film solar cells promising candidates for photovoltaics. However, it is still the challenge for research and development to achieve the necessary high electrical Material Quality known from crystalline Si wafers on glass as a prerequisite to harvest the advantages of thin-film technologies. A wide variety of poly-Si thin-film solar cell approaches has been investigated in the past years, such as thermal solid phase crystallization – the only technology that had already been matured to industrial production so far – the seed layer concept where a large-grained seed layer is epitaxially thickened, direct growth of fine grained Material, and liquid phase crystallization methods by laser or electron beam. In the first part of this paper, the status of these four different poly-Si thin-film solar cell concepts is summarized, by comparing the technological fabrication methods, as well as the structural and electrical properties and solar cell performances of the respective Materials. In the second part, three promising technologies are described in more detail due to their highly auspicious properties regarding Material Quality and throughput aspects during fabrication: (1) High-rate electron–beam evaporation of silicon for the low-cost deposition of high-Quality Material, (2) large-area periodic nano- and micro-structuring of poly-Si by the use of imprinted substrates providing a large absorption enhancement by a factor of six at a wavelength of 900 nm, (3) liquid-phase crystallization of silicon thin-film solar cells by electron–beam, yielding an excellent poly-Si Material Quality reflected by an open-circuit voltage of 582 mV which has been achieved only very recently. A successful combination of these three complementary technologies is envisaged to be the basis for a prospective low-cost and highly efficient poly-Si solar cell device.
