Veröffentlichungen
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E. L. Warren, W. E. McMahon, M. Rienäcker, K. T. VanSant, R. C. Whitehead, R. Peibst, and A. C. Tamboli A Taxonomy for Three-Terminal Tandem Solar Cells Artikel ACS Energy Letters 5 , 1233-1242, (2020). Abstract | Links | BibTeX | Schlagwörter: Doping, Electrochemical cells, Power, Solar Cells, solar energy @article{Warren2020,
title = {A Taxonomy for Three-Terminal Tandem Solar Cells}, author = {E L Warren and W E McMahon and M Rienäcker and K T VanSant and R C Whitehead and R Peibst and A C Tamboli}, doi = {10.1021/acsenergylett.0c00068}, year = {2020}, date = {2020-03-23}, journal = {ACS Energy Letters}, volume = {5}, pages = {1233-1242}, abstract = {Tandem and multijunction solar cells offer the only demonstrated path to terrestrial 1-sun solar cell efficiency over 30%. Three-terminal tandem (3TT) solar cells can overcome some of the limitations of two-terminal and four-terminal tandem solar cell designs. However, the coupled nature of the cells adds a degree of complexity to the devices themselves and the ways that their performance can be measured and reported. While many different configurations of 3TT devices have been proposed, there is no standard taxonomy to discuss the device structure or loading topology. This Perspective proposes a taxonomy for 3TT solar cells to enable a common nomenclature for discussing these devices and their performance. It also provides a brief history of three-terminal devices in the literature and demonstrates that many different 3TT devices can work at efficiencies above 30% if properly designed.}, keywords = {Doping, Electrochemical cells, Power, Solar Cells, solar energy}, pubstate = {published}, tppubtype = {article} } Tandem and multijunction solar cells offer the only demonstrated path to terrestrial 1-sun solar cell efficiency over 30%. Three-terminal tandem (3TT) solar cells can overcome some of the limitations of two-terminal and four-terminal tandem solar cell designs. However, the coupled nature of the cells adds a degree of complexity to the devices themselves and the ways that their performance can be measured and reported. While many different configurations of 3TT devices have been proposed, there is no standard taxonomy to discuss the device structure or loading topology. This Perspective proposes a taxonomy for 3TT solar cells to enable a common nomenclature for discussing these devices and their performance. It also provides a brief history of three-terminal devices in the literature and demonstrates that many different 3TT devices can work at efficiencies above 30% if properly designed.
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S. Gharibzadeh, I. M. Hossain, P. Fassl, Abdollahi. B. Nejand, T. Abzieher, M. Schultes, E. Ahlswede, P. Jackson, M. Powalla, S. Schäfer, M. Rienäcker, T. Wietler, R. Peibst, U. Lemmer, B. S. Richards, and U. W. Paetzold 2D/3D Heterostructure for Semitransparent Perovskite Solar Cells with Engineered Bandgap Enables Efficiencies Exceeding 25% in Four-Terminal Tandems with Silicon and CIGS Artikel Forthcoming Advanced Functional Materials 1909919, Forthcoming. Abstract | Links | BibTeX | Schlagwörter: 2D perovskites, 3D perovskites, copper indium gallium diselenide, tandem solar cells @article{Gharibzadeh2020,
title = {2D/3D Heterostructure for Semitransparent Perovskite Solar Cells with Engineered Bandgap Enables Efficiencies Exceeding 25% in Four-Terminal Tandems with Silicon and CIGS}, author = {S Gharibzadeh and I M Hossain and P Fassl and B Abdollahi Nejand and T Abzieher and M Schultes and E Ahlswede and P Jackson and M Powalla and S Schäfer and M Rienäcker and T Wietler and R Peibst and U Lemmer and B S Richards and U W Paetzold}, doi = {10.1002/adfm.201909919}, year = {2020}, date = {2020-03-11}, journal = {Advanced Functional Materials}, pages = {1909919}, abstract = {Wide-bandgap perovskite solar cells (PSCs) with optimal bandgap (Eg) and high power conversion efficiency (PCE) are key to high-performance perovskite-based tandem photovoltaics. A 2D/3D perovskite heterostructure passivation is employed for double-cation wide-bandgap PSCs with engineered bandgap (1.65 eV ≤ Eg ≤ 1.85 eV), which results in improved stabilized PCEs and a strong enhancement in open-circuit voltages of around 45 mV compared to reference devices for all investigated bandgaps. Making use of this strategy, semitransparent PSCs with engineered bandgap are developed, which show stabilized PCEs of up to 25.7% and 25.0% in four-terminal perovskite/c-Si and perovskite/CIGS tandem solar cells, respectively. Moreover, comparable tandem PCEs are observed for a broad range of perovskite bandgaps. For the first time, the robustness of the four-terminal tandem configuration with respect to variations in the perovskite bandgap for two state-of-the-art bottom solar cells is experimentally validated.}, keywords = {2D perovskites, 3D perovskites, copper indium gallium diselenide, tandem solar cells}, pubstate = {forthcoming}, tppubtype = {article} } Wide-bandgap perovskite solar cells (PSCs) with optimal bandgap (Eg) and high power conversion efficiency (PCE) are key to high-performance perovskite-based tandem photovoltaics. A 2D/3D perovskite heterostructure passivation is employed for double-cation wide-bandgap PSCs with engineered bandgap (1.65 eV ≤ Eg ≤ 1.85 eV), which results in improved stabilized PCEs and a strong enhancement in open-circuit voltages of around 45 mV compared to reference devices for all investigated bandgaps. Making use of this strategy, semitransparent PSCs with engineered bandgap are developed, which show stabilized PCEs of up to 25.7% and 25.0% in four-terminal perovskite/c-Si and perovskite/CIGS tandem solar cells, respectively. Moreover, comparable tandem PCEs are observed for a broad range of perovskite bandgaps. For the first time, the robustness of the four-terminal tandem configuration with respect to variations in the perovskite bandgap for two state-of-the-art bottom solar cells is experimentally validated.
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M. Köntges, A. Morlier, G. Eder, E. Fleiß, B. Kubicek, and J. Lin Review: Ultraviolet Fluorescence as Assessment Tool for Photovoltaic Modules Artikel IEEE Journal of Photovoltaics 10 (2), 616-633, (2020), ISSN: 2156-3403. Abstract | Links | BibTeX | Schlagwörter: fault diagnosis, power system reliability, solar panels, Ultraviolet fluorescence @article{Köntges2020,
title = {Review: Ultraviolet Fluorescence as Assessment Tool for Photovoltaic Modules}, author = {M Köntges and A Morlier and G Eder and E Fleiß and B Kubicek and J Lin}, doi = {10.1109/JPHOTOV.2019.2961781}, issn = {2156-3403}, year = {2020}, date = {2020-03-01}, journal = {IEEE Journal of Photovoltaics}, volume = {10}, number = {2}, pages = {616-633}, abstract = {Since 2010, the ultraviolet fluorescence (UVF) method is used to identify defects in wafer-based crystalline silicon photovoltaic (PV) modules. We summarize all known applications of fluorescence imaging methods on PV modules to identify defects and characteristics. The aim of this review is to present the basic principles for the interpretation of UVF images. The method allows for detection of cell cracks in a chronological order of occurrence, visualizing hot parts in a PV module, and identifying deviating bill of materials of PV modules. The effects of various material combinations on the UVF are reproduced in the lab and explained for the first time. Seasonal effects on the UVF are presented for the first time. In addition, some not yet understood features in the images are shown and discussed. Furthermore, the application of UVF imaging for manual, hood-based, and drone-based inspection is presented. The analysis speed of the three methods has been measured under real conditions. For the manual inspection, we found an evaluation speed of 250 modules/h, for a hood-based system 200 modules/h and the drone-based method allows an imaging speed of up to 720 modules/h.}, keywords = {fault diagnosis, power system reliability, solar panels, Ultraviolet fluorescence}, pubstate = {published}, tppubtype = {article} } Since 2010, the ultraviolet fluorescence (UVF) method is used to identify defects in wafer-based crystalline silicon photovoltaic (PV) modules. We summarize all known applications of fluorescence imaging methods on PV modules to identify defects and characteristics. The aim of this review is to present the basic principles for the interpretation of UVF images. The method allows for detection of cell cracks in a chronological order of occurrence, visualizing hot parts in a PV module, and identifying deviating bill of materials of PV modules. The effects of various material combinations on the UVF are reproduced in the lab and explained for the first time. Seasonal effects on the UVF are presented for the first time. In addition, some not yet understood features in the images are shown and discussed. Furthermore, the application of UVF imaging for manual, hood-based, and drone-based inspection is presented. The analysis speed of the three methods has been measured under real conditions. For the manual inspection, we found an evaluation speed of 250 modules/h, for a hood-based system 200 modules/h and the drone-based method allows an imaging speed of up to 720 modules/h.
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M. Winter, S. Bordihn, R. Peibst, R. Brendel, and J. Schmidt IEEE Journal of Photovoltaics 10 (2), 423-430, (2020), ISSN: 2156-3403. Abstract | Links | BibTeX | Schlagwörter: Carrier lifetime, Degradation, Poly-Si, Poly-Si on oxide (POLO), silicon, surface passivation @article{Winter2020,
title = {Degradation and Regeneration of n+-Doped Poly-Si Surface Passivation on p-Type and n-Type Cz-Si Under Illumination and Dark Annealing}, author = {M Winter and S Bordihn and R Peibst and R Brendel and J Schmidt}, doi = {10.1109/JPHOTOV.2020.2964987}, issn = {2156-3403}, year = {2020}, date = {2020-03-01}, journal = {IEEE Journal of Photovoltaics}, volume = {10}, number = {2}, pages = {423-430}, abstract = {Degradation and regeneration of recombination parameters can occur in the bulk and at the surfaces of silicon solar cells. This article focuses on the time-resolved analysis of the recombination properties of textured 1.7 Ω cm boron-doped p-type Cz-Si and 5 Ω cm phosphorus-doped n-type Cz-Si wafers, where the surfaces are passivated by n+ poly-Si on interfacial oxide layers exposed to a rapid thermal annealing (RTA) step in a conventional firing furnace. We observe a thermally activated instability in the lifetime over the entire examined injection range. Our experiments show that minority carrier injection (e.g., by illumination) is not required. Degradation in the surface passivation quality of the poly-Si on oxide layer—corresponding to an increase of the saturation current density J0 by up to a factor of five—causes the degradation of the effective lifetime. Interestingly, the surface passivation fully regenerates under prolonged annealing and finally improves even beyond the initial state. Both the extent of the lifetime degradation and the change in J0 depend on the postprocessing treatment temperature which we varied between 80 and 400 °C. Our results indicate that two different processes are responsible for the degradation and the regeneration. Reference samples which did not receive an RTA treatment show no degradation of the surface passivation quality. The RTA treatment applied therefore triggers the degradation effect. A large improvement of the surface passivation quality under prolonged annealing (e.g., at 400 °C) is observed for all samples examined in this study.}, keywords = {Carrier lifetime, Degradation, Poly-Si, Poly-Si on oxide (POLO), silicon, surface passivation}, pubstate = {published}, tppubtype = {article} } Degradation and regeneration of recombination parameters can occur in the bulk and at the surfaces of silicon solar cells. This article focuses on the time-resolved analysis of the recombination properties of textured 1.7 Ω cm boron-doped p-type Cz-Si and 5 Ω cm phosphorus-doped n-type Cz-Si wafers, where the surfaces are passivated by n+ poly-Si on interfacial oxide layers exposed to a rapid thermal annealing (RTA) step in a conventional firing furnace. We observe a thermally activated instability in the lifetime over the entire examined injection range. Our experiments show that minority carrier injection (e.g., by illumination) is not required. Degradation in the surface passivation quality of the poly-Si on oxide layer—corresponding to an increase of the saturation current density J0 by up to a factor of five—causes the degradation of the effective lifetime. Interestingly, the surface passivation fully regenerates under prolonged annealing and finally improves even beyond the initial state. Both the extent of the lifetime degradation and the change in J0 depend on the postprocessing treatment temperature which we varied between 80 and 400 °C. Our results indicate that two different processes are responsible for the degradation and the regeneration. Reference samples which did not receive an RTA treatment show no degradation of the surface passivation quality. The RTA treatment applied therefore triggers the degradation effect. A large improvement of the surface passivation quality under prolonged annealing (e.g., at 400 °C) is observed for all samples examined in this study.
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I. M. Hossain, Y. J. Donie, R. Schmager, M. S. Abdelkhalik, M. Rienäcker, T. F. Wietler, R. Peibst, A. Karabanov, J. A. Schwenzer, S. Moghadamzadeh, U. Lemmer, B. S. Richards, G. Gomard, and U. W. Paetzold Nanostructured front electrodes for perovskite/c-Si tandem photovoltaics Artikel Opt. Express 28 (6), 8878-8897, (2020). Abstract | Links | BibTeX | Schlagwörter: Effective refractive index, Enhanced solar cells, Scanning electron microscopy, Surface light scattering, tandem solar cells, Thin film deposition @article{Hossain2020,
title = {Nanostructured front electrodes for perovskite/c-Si tandem photovoltaics}, author = {I M Hossain and Y J Donie and R Schmager and M S Abdelkhalik and M Rienäcker and T F Wietler and R Peibst and A Karabanov and J A Schwenzer and S Moghadamzadeh and U Lemmer and B S Richards and G Gomard and U W Paetzold}, doi = {10.1364/OE.382253}, year = {2020}, date = {2020-03-01}, journal = {Opt. Express}, volume = {28}, number = {6}, pages = {8878-8897}, publisher = {OSA}, abstract = {The rise in the power conversion efficiency (PCE) of perovskite solar cells has triggered enormous interest in perovskite-based tandem photovoltaics. One key challenge is to achieve high transmission of low energy photons into the bottom cell. Here, nanostructured front electrodes for 4-terminal perovskite/crystalline-silicon (perovskite/c-Si) tandem solar cells are developed by conformal deposition of indium tin oxide (ITO) on self-assembled polystyrene nanopillars. The nanostructured ITO is optimized for reduced reflection and increased transmission with a tradeoff in increased sheet resistance. In the optimum case, the nanostructured ITO electrodes enhance the transmittance by $sim$7% (relative) compared to planar references. Perovskite/c-Si tandem devices with nanostructured ITO exhibit enhanced short-circuit current density (2.9 mA/cm2 absolute) and PCE (1.7% absolute) in the bottom c-Si solar cell compared to the reference. The improved light in-coupling is more pronounced for elevated angle of incidence. Energy yield enhancement up to $sim$10% (relative) is achieved for perovskite/c-Si tandem architecture with the nanostructured ITO electrodes. It is also shown that these nanostructured ITO electrodes are also compatible with various other perovskite-based tandem architectures and bear the potential to improve the PCE up to 27.0%.}, keywords = {Effective refractive index, Enhanced solar cells, Scanning electron microscopy, Surface light scattering, tandem solar cells, Thin film deposition}, pubstate = {published}, tppubtype = {article} } The rise in the power conversion efficiency (PCE) of perovskite solar cells has triggered enormous interest in perovskite-based tandem photovoltaics. One key challenge is to achieve high transmission of low energy photons into the bottom cell. Here, nanostructured front electrodes for 4-terminal perovskite/crystalline-silicon (perovskite/c-Si) tandem solar cells are developed by conformal deposition of indium tin oxide (ITO) on self-assembled polystyrene nanopillars. The nanostructured ITO is optimized for reduced reflection and increased transmission with a tradeoff in increased sheet resistance. In the optimum case, the nanostructured ITO electrodes enhance the transmittance by $sim$7% (relative) compared to planar references. Perovskite/c-Si tandem devices with nanostructured ITO exhibit enhanced short-circuit current density (2.9 mA/cm2 absolute) and PCE (1.7% absolute) in the bottom c-Si solar cell compared to the reference. The improved light in-coupling is more pronounced for elevated angle of incidence. Energy yield enhancement up to $sim$10% (relative) is achieved for perovskite/c-Si tandem architecture with the nanostructured ITO electrodes. It is also shown that these nanostructured ITO electrodes are also compatible with various other perovskite-based tandem architectures and bear the potential to improve the PCE up to 27.0%.
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O. Mercker, P. Pärisch, and D. Büchner Simulationsstudie zum Potenzial netzdienlicher Betriebsweisen von Biomasse-Einzelraumfeuerstätten in TRNSYS - Methodik, Randbedingungen und Modelle Presentation/Poster 13.02.2020, (3. Regenerative Energietechnik Konferenz (RET.Con)). BibTeX | Schlagwörter: netzdienlich @misc{Mercker2020,
title = {Simulationsstudie zum Potenzial netzdienlicher Betriebsweisen von Biomasse-Einzelraumfeuerstätten in TRNSYS - Methodik, Randbedingungen und Modelle}, author = {O Mercker and P Pärisch and D Büchner}, year = {2020}, date = {2020-02-13}, note = {3. Regenerative Energietechnik Konferenz (RET.Con)}, keywords = {netzdienlich}, pubstate = {published}, tppubtype = {presentation} } |
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T. Ohrdes, M. Knoop, and E. Schneider Energieversorgung mit Wärmepumpen im Quartier Sonstige EnEV Baupraxis Ausgabe Januar / Februar 2020, (2020). Abstract | Links | BibTeX | Schlagwörter: Wärmepumpe @misc{Ohrdes2020,
title = {Energieversorgung mit Wärmepumpen im Quartier}, author = {T Ohrdes and M Knoop and E Schneider}, url = {https://www.enev-baupraxis.de/energieversorgung-mit-waermepumpen-im-quartier/}, year = {2020}, date = {2020-02-01}, abstract = {Der Ausbau von PV- und Windkraftanlagen schreitet immer weiter voran, sodass inzwischen mehr als 45 % des Stroms in Deutschland aus erneuerbaren Energien erzeugt wird [1]. Der Stromverbrauch hat in privaten Haushalten lediglich einen geringen Anteil am Endenergieverbrauch. 83 % der Endenergie entfallen auf Raumwärme und Trinkwarmwassererzeugung [2]. Der Anteil erneuerbarer Wärme am Endenergieverbrauch in privaten Haushalten beträgt derzeit 14 % [3]. Eine Kopplung von Strom- und Wärmeverbrauch über eine effiziente, auf erneuerbar erzeugtem Strom basierende Wärmeversorgung bietet daher Chancen, den Anteil nachhaltig zu erhöhen.}, howpublished = {EnEV Baupraxis Ausgabe Januar / Februar 2020}, keywords = {Wärmepumpe}, pubstate = {published}, tppubtype = {misc} } Der Ausbau von PV- und Windkraftanlagen schreitet immer weiter voran, sodass inzwischen mehr als 45 % des Stroms in Deutschland aus erneuerbaren Energien erzeugt wird [1]. Der Stromverbrauch hat in privaten Haushalten lediglich einen geringen Anteil am Endenergieverbrauch. 83 % der Endenergie entfallen auf Raumwärme und Trinkwarmwassererzeugung [2]. Der Anteil erneuerbarer Wärme am Endenergieverbrauch in privaten Haushalten beträgt derzeit 14 % [3]. Eine Kopplung von Strom- und Wärmeverbrauch über eine effiziente, auf erneuerbar erzeugtem Strom basierende Wärmeversorgung bietet daher Chancen, den Anteil nachhaltig zu erhöhen.
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M. Schnabel, H. Schulte-Huxel, M. Rienäcker, E. L. Warren, P. F. Ndione, B. Nemeth, T. R. Klein, M. F. A. M. van Hest, J. F. Geisz, R. Peibst, P. Stradins, and A. C. Tamboli Three-terminal III–V/Si tandem solar cells enabled by a transparent conductive adhesive Artikel Sustainable Energy Fuels 4 (2), 549-558, (2020). Abstract | Links | BibTeX | Schlagwörter: @article{Schnabel2020,
title = {Three-terminal III–V/Si tandem solar cells enabled by a transparent conductive adhesive}, author = {M Schnabel and H Schulte-Huxel and M Rienäcker and E L Warren and P F Ndione and B Nemeth and T R Klein and M F A M van Hest and J F Geisz and R Peibst and P Stradins and A C Tamboli}, doi = {10.1039/C9SE00893D}, year = {2020}, date = {2020-02-01}, journal = {Sustainable Energy Fuels}, volume = {4}, number = {2}, pages = {549-558}, publisher = {The Royal Society of Chemistry}, abstract = {Tandem or multijunction solar cells are able to convert sunlight to electricity with greater efficiency than single junction solar cells by splitting the solar spectrum across sub-cells with different bandgaps. With the efficiencies of many common single-junction solar cell materials leveling off near their theoretical efficiency limits, there is renewed interest in applying this approach. However, there is ongoing debate as to the best approach for interconnecting sub-cells in series, or whether it is preferable to operate them independently. In this paper, we provide the first experimental demonstration of a tandem cell architecture with three terminals: one on top of the tandem cell, and two beneath it, in interdigitated back contact configuration. The two cells are interconnected with a transparent conductive adhesive, which is compatible with rough surfaces and exhibits negligible series resistance. Combining GaInP and Si sub-cells in this manner allows us to achieve a GaInP/Si tandem cell with a two-terminal efficiency of 26.4 ± 1.0%. We then show that utilizing all three terminals results in an efficiency boost of 0.9 ± 0.2%, to an efficiency of 27.3 ± 1.0%, and discuss the operation of the cell and its two interacting circuits.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Tandem or multijunction solar cells are able to convert sunlight to electricity with greater efficiency than single junction solar cells by splitting the solar spectrum across sub-cells with different bandgaps. With the efficiencies of many common single-junction solar cell materials leveling off near their theoretical efficiency limits, there is renewed interest in applying this approach. However, there is ongoing debate as to the best approach for interconnecting sub-cells in series, or whether it is preferable to operate them independently. In this paper, we provide the first experimental demonstration of a tandem cell architecture with three terminals: one on top of the tandem cell, and two beneath it, in interdigitated back contact configuration. The two cells are interconnected with a transparent conductive adhesive, which is compatible with rough surfaces and exhibits negligible series resistance. Combining GaInP and Si sub-cells in this manner allows us to achieve a GaInP/Si tandem cell with a two-terminal efficiency of 26.4 ± 1.0%. We then show that utilizing all three terminals results in an efficiency boost of 0.9 ± 0.2%, to an efficiency of 27.3 ± 1.0%, and discuss the operation of the cell and its two interacting circuits.
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C. Hollemann, F. Haase, M. Rienäcker, V. Barnscheidt, J. Krügener, N. Folchert, R. Brendel, S. Richter, S. Großer, E. Sauter, J. Hübner, M. Oestreich, and R. Peibst Separating the two polarities of the POLO contacts of an 26.1%-efficient IBC solar cell Artikel Scientific Reports 10 (1), 658, (2020), ISSN: 2045-2322. Abstract | Links | BibTeX | Schlagwörter: @article{Hollemann2020,
title = {Separating the two polarities of the POLO contacts of an 26.1%-efficient IBC solar cell}, author = {C Hollemann and F Haase and M Rienäcker and V Barnscheidt and J Krügener and N Folchert and R Brendel and S Richter and S Großer and E Sauter and J Hübner and M Oestreich and R Peibst}, doi = {10.1038/s41598-019-57310-0}, issn = {2045-2322}, year = {2020}, date = {2020-01-20}, journal = {Scientific Reports}, volume = {10}, number = {1}, pages = {658}, abstract = {By applying an interdigitated back contacted solar cell concept with poly-Si on oxide passivating contacts an efficiency of 26.1% was achieved recently. In this paper the impact of the implemented initially intrinsic poly-Si region between p-type poly-Si and n-type poly-Si regions is investigated. Two recombination paths are identified: The recombination at the interface between the initially intrinsic poly-Si and the wafer as well as the recombination across the resulting p(i)n diode on the rear side which is aimed to be reduced by introducing an initially intrinsic region. By using test structures, it is demonstrated that the width of the initially intrinsic region ((i) poly-Si region) has a strong influence on the recombination current through the p(i)n diode and that this initially intrinsic region needs to be about 30 mm wide to sufficiently reduce the recombination across the p(i)n diode. Lateral and depth-resolved time of flight secondary ion mass spectrometry analysis shows that the high-temperature annealing step causes a strong lateral inter-diffusion of donor and acceptor atoms into the initially intrinsic region. This diffusion has a positive impact on the passivation quality at the c-Si/SiOx/i poly-Si interface and is thus essential for achieving an independently confirmed efficiency of 26.1% with 30 mm-wide initially intrinsic poly-Si regions.}, keywords = {}, pubstate = {published}, tppubtype = {article} } By applying an interdigitated back contacted solar cell concept with poly-Si on oxide passivating contacts an efficiency of 26.1% was achieved recently. In this paper the impact of the implemented initially intrinsic poly-Si region between p-type poly-Si and n-type poly-Si regions is investigated. Two recombination paths are identified: The recombination at the interface between the initially intrinsic poly-Si and the wafer as well as the recombination across the resulting p(i)n diode on the rear side which is aimed to be reduced by introducing an initially intrinsic region. By using test structures, it is demonstrated that the width of the initially intrinsic region ((i) poly-Si region) has a strong influence on the recombination current through the p(i)n diode and that this initially intrinsic region needs to be about 30 mm wide to sufficiently reduce the recombination across the p(i)n diode. Lateral and depth-resolved time of flight secondary ion mass spectrometry analysis shows that the high-temperature annealing step causes a strong lateral inter-diffusion of donor and acceptor atoms into the initially intrinsic region. This diffusion has a positive impact on the passivation quality at the c-Si/SiOx/i poly-Si interface and is thus essential for achieving an independently confirmed efficiency of 26.1% with 30 mm-wide initially intrinsic poly-Si regions.
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T. Dullweber High-Efficiency Industrial PERC Solar Cells for Monofacial and Bifacial Applications Buchkapitel V. Petrova-Koch, R. Hezel, and A. Goetzberger (Hrsg.): High-Efficient Low-Cost Photovoltaics: Recent Developments, 65-94, Springer International Publishing, Cham, (2020), ISBN: 978-3-030-22864-4. Abstract | Links | BibTeX | Schlagwörter: @inbook{Dullweber2020,
title = {High-Efficiency Industrial PERC Solar Cells for Monofacial and Bifacial Applications}, author = {T Dullweber}, editor = {V Petrova-Koch and R Hezel and A Goetzberger}, doi = {10.1007/978-3-030-22864-4_5}, isbn = {978-3-030-22864-4}, year = {2020}, date = {2020-01-01}, booktitle = {High-Efficient Low-Cost Photovoltaics: Recent Developments}, pages = {65-94}, publisher = {Springer International Publishing}, address = {Cham}, abstract = {The passivated emitter and rear cell (PERC) concept is currently rapidly being introduced into industrial mass production and is expected to be the new silicon waferWafer based solar cellSolar cell technology standard in the photovoltaics industry. In 2018, PERC-type solar cells accounted for approximately 40% of the worldwide produced solar cells and their share is expected to rapidly increase up to 70% within the next few years. Compared to the previous industrial silicon solar cellSilicon solar cell technology which applied a full-area aluminum rear contact, PERC cells passivate the rear silicon wafer surface with a dielectric layer and only locally contact the silicon waferWafer with an aluminum metal contact, which reduces charge carrier recombinationRecombination and hence increases the conversion efficiency. Present record conversion efficienciesEfficiencies up to 22.8% of industrial PERC cells hence exceed the efficiency of conventional Al-BSF silicon solar cells by more than 2%abs. In addition, PERC solar cells can be made bifacialBifacial by substituting the full-area rear aluminum layer with an aluminum finger grid design. This so-called PERC+ solar cell design enables large volume industrial manufacturing of bifacialBifacial silicon solar cellSilicon solar cells which absorb stray light from the rear side and hence increase the energy yield by 5--25% depending on the detailed module installation conditions. This chapter describes the most important research results and technology developments of the past decades as well as the present status of industrial PERC and PERC+ solar cells.}, keywords = {}, pubstate = {published}, tppubtype = {inbook} } The passivated emitter and rear cell (PERC) concept is currently rapidly being introduced into industrial mass production and is expected to be the new silicon waferWafer based solar cellSolar cell technology standard in the photovoltaics industry. In 2018, PERC-type solar cells accounted for approximately 40% of the worldwide produced solar cells and their share is expected to rapidly increase up to 70% within the next few years. Compared to the previous industrial silicon solar cellSilicon solar cell technology which applied a full-area aluminum rear contact, PERC cells passivate the rear silicon wafer surface with a dielectric layer and only locally contact the silicon waferWafer with an aluminum metal contact, which reduces charge carrier recombinationRecombination and hence increases the conversion efficiency. Present record conversion efficienciesEfficiencies up to 22.8% of industrial PERC cells hence exceed the efficiency of conventional Al-BSF silicon solar cells by more than 2%abs. In addition, PERC solar cells can be made bifacialBifacial by substituting the full-area rear aluminum layer with an aluminum finger grid design. This so-called PERC+ solar cell design enables large volume industrial manufacturing of bifacialBifacial silicon solar cellSilicon solar cells which absorb stray light from the rear side and hence increase the energy yield by 5--25% depending on the detailed module installation conditions. This chapter describes the most important research results and technology developments of the past decades as well as the present status of industrial PERC and PERC+ solar cells.
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J. Schmidt, K. Bothe, V. V. Voronkov, and R. Falster Fast and Slow Stages of Lifetime Degradation by Boron–Oxygen Centers in Crystalline Silicon Artikel physica status solidi (b) 257 (1), 1900167, (2020). Abstract | Links | BibTeX | Schlagwörter: defects, Lifetime, light-induced degradation (LID), recombination, silicon @article{Schmidt2020,
title = {Fast and Slow Stages of Lifetime Degradation by Boron–Oxygen Centers in Crystalline Silicon}, author = {J Schmidt and K Bothe and V V Voronkov and R Falster}, doi = {10.1002/pssb.201900167}, year = {2020}, date = {2020-01-01}, journal = {physica status solidi (b)}, volume = {257}, number = {1}, pages = {1900167}, abstract = {A conflict between previous and recently published data on the two-stage light-induced degradation (LID) of carrier lifetime in boron-doped oxygen-containing crystalline silicon is addressed. The previous experiments showed the activation of two boron–oxygen recombination centers with strongly differing recombination properties for the fast and slow stages of LID, whereas more recent studies found only a single center for both stages. To resolve this controversy, the historic silicon samples of these previous examinations are re-examined in this study after more than one decade. It is found that, in the historic samples, the fast stage can be either described by two different centers or a mixture of the two, depending on the duration of previous dark annealing. A possible solution is suggested based on the involvement of different activating impurities in the boron–oxygen defect. In dark-annealed samples, the defect consisting of boron, oxygen, and the activation impurity is present in two latent configurations, which reconfigure during LID at a fast and a slow stage. In the examined historic silicon samples, which did not undergo a gettering pretreatment, a significant concentration of an additional boron–oxygen defect with a different kind of activating impurity attached exists. The historic and modern results are thus reconciled.}, keywords = {defects, Lifetime, light-induced degradation (LID), recombination, silicon}, pubstate = {published}, tppubtype = {article} } A conflict between previous and recently published data on the two-stage light-induced degradation (LID) of carrier lifetime in boron-doped oxygen-containing crystalline silicon is addressed. The previous experiments showed the activation of two boron–oxygen recombination centers with strongly differing recombination properties for the fast and slow stages of LID, whereas more recent studies found only a single center for both stages. To resolve this controversy, the historic silicon samples of these previous examinations are re-examined in this study after more than one decade. It is found that, in the historic samples, the fast stage can be either described by two different centers or a mixture of the two, depending on the duration of previous dark annealing. A possible solution is suggested based on the involvement of different activating impurities in the boron–oxygen defect. In dark-annealed samples, the defect consisting of boron, oxygen, and the activation impurity is present in two latent configurations, which reconfigure during LID at a fast and a slow stage. In the examined historic silicon samples, which did not undergo a gettering pretreatment, a significant concentration of an additional boron–oxygen defect with a different kind of activating impurity attached exists. The historic and modern results are thus reconciled.
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K. VanSant, E. Warren, M. Rienäcker, H. Schulte-Huxel, R. Peibst, J. Geisz, P. Stradins, and A. Tamboli Performance Comparison of III-V//Si Tandem Solar Cells in the Three-Terminal Configuration Presentation/Poster Boston, USA, 04.12.2019, (2019 MRS Fall Meeting & Exhibit). Abstract | BibTeX | Schlagwörter: Tandem @misc{VanSant2019b,
title = {Performance Comparison of III-V//Si Tandem Solar Cells in the Three-Terminal Configuration}, author = {K VanSant and E Warren and M Rienäcker and H Schulte-Huxel and R Peibst and J Geisz and P Stradins and A Tamboli}, year = {2019}, date = {2019-12-04}, address = {Boston, USA}, abstract = {Multi-junction solar cells are a key pathway towards achieving higher photovoltaic efficiencies.The theoretical efficiency limit of a single-junction (1J) Si solar cell is 29.6%1, whereas efficiencies >32% have already been achieved for 1J III-V top cells stacked on Si bottom cells in both the two terminal (2T) and four terminal (4T) configurations.2,3 We will present a third path towards achieving efficiencies >32% with mechanically-stacked III-V-on-Si (III-V//Si) tandem solar cells using a three terminal (3T) configuration. The typical tandem device architectures either connect the sub-cells in series in a 2T configuration, or operate the stacked sub-cells independently, which requires four terminals (4T). Both configurations, however, have considerable drawbacks. The 2T configuration requires that the sub-cells are current matched to operate efficiently and so this narrowly constrains the choice of the sub-cell materials. The 4T configuration does not require sub-cell current matching but this design prohibits the possibility of monolithic growth and necessitates the inclusion of gridlines or a lateral conduction layer at the back of the top cell which reduces the transmission of light to the bottom cell.4The 3T configuration is a hybrid approach devised to address the constraints of the other two. The additional contact associated with the interdigitated back contact (IBC) Si bottom cell enables extraction or injection of current which circumvents the need for current matching between the sub-cells. The 3T design does not require an intermediate grid and is potentially compatible with both mechanical stacking, if a transparent conductive adhesive (TCA) is used, or monolithic growth. Moreover, simulations predict that 3T tandem cells could achieve efficiencies over 32%, comparable to record 4T tandem cell efficiencies.3,4We have fabricated and measured 3T mechanically-stacked III-V-on-Si (III-V//Si) tandem solar cells and will present an overview of how a 3T tandem solar cell operates. We will compare the JV and QE characteristics of a GaInP//Si tandem cell to a GaAs//Si tandem cell and analyze how the performance between these two 3T tandem solar cells differ, depending on which sub-cell is current limiting. }, note = {2019 MRS Fall Meeting & Exhibit}, keywords = {Tandem}, pubstate = {published}, tppubtype = {presentation} } Multi-junction solar cells are a key pathway towards achieving higher photovoltaic efficiencies.The theoretical efficiency limit of a single-junction (1J) Si solar cell is 29.6%1, whereas efficiencies >32% have already been achieved for 1J III-V top cells stacked on Si bottom cells in both the two terminal (2T) and four terminal (4T) configurations.2,3 We will present a third path towards achieving efficiencies >32% with mechanically-stacked III-V-on-Si (III-V//Si) tandem solar cells using a three terminal (3T) configuration. The typical tandem device architectures either connect the sub-cells in series in a 2T configuration, or operate the stacked sub-cells independently, which requires four terminals (4T). Both configurations, however, have considerable drawbacks. The 2T configuration requires that the sub-cells are current matched to operate efficiently and so this narrowly constrains the choice of the sub-cell materials. The 4T configuration does not require sub-cell current matching but this design prohibits the possibility of monolithic growth and necessitates the inclusion of gridlines or a lateral conduction layer at the back of the top cell which reduces the transmission of light to the bottom cell.4The 3T configuration is a hybrid approach devised to address the constraints of the other two. The additional contact associated with the interdigitated back contact (IBC) Si bottom cell enables extraction or injection of current which circumvents the need for current matching between the sub-cells. The 3T design does not require an intermediate grid and is potentially compatible with both mechanical stacking, if a transparent conductive adhesive (TCA) is used, or monolithic growth. Moreover, simulations predict that 3T tandem cells could achieve efficiencies over 32%, comparable to record 4T tandem cell efficiencies.3,4We have fabricated and measured 3T mechanically-stacked III-V-on-Si (III-V//Si) tandem solar cells and will present an overview of how a 3T tandem solar cell operates. We will compare the JV and QE characteristics of a GaInP//Si tandem cell to a GaAs//Si tandem cell and analyze how the performance between these two 3T tandem solar cells differ, depending on which sub-cell is current limiting.
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R. Whitehead, K. VanSant, M. Rienäcker, J. Geisz, and A. Tamboli Optimizing the top cell absorbing layer thickness in 4T GaAs on Si tandem solar cells Presentation/Poster Boston, USA, 03.12.2019, (2019 MRS Fall Meeting & Exhibit). Abstract | BibTeX | Schlagwörter: Tandem @misc{Whitehead2019,
title = {Optimizing the top cell absorbing layer thickness in 4T GaAs on Si tandem solar cells}, author = {R Whitehead and K VanSant and M Rienäcker and J Geisz and A Tamboli}, year = {2019}, date = {2019-12-03}, address = {Boston, USA}, abstract = {One method to improve silicon solar cell efficiency is to stack a silicon cell beneath a wide-bandgap top cell. To improve the overall tandem cell efficiency from that of silicon alone, the top cell material should have a higher spectral efficiency than silicon for the wavelengths of light within the top cell’s bandgap. GaAs is currently the material with the highest recorded cell efficiency for a single junction cell, at 29.1% efficiency. GaAs also has a theoretical and realized spectral efficiency higher than that of silicon between the wavelengths of 360-860 nm. Our team was able to exploit these GaAs attributes to obtain a record efficiency of 32.8% for a mechanically-stacked rear heterojunction (RHJ) GaAs-on-Si (GaAs//Si) tandem cell designed to operate in the 4-terminal (4T) (i.e. optically coupled but electrically independent) configuration. The purpose of this study is to further optimize the GaAs emitter layer thickness to maximize the efficiency of the 4T GaAs//Si tandem cells. Our record 4T GaAs//Si tandem solar cell was achieved using a 2 μm GaAs emitter layer but subsequent optical modeling of the 4T GaAs//Si tandem solar cells suggests that a slightly thicker emitter could potentially lead to even better top cell efficiencies. In addition, NREL began a collaboration with ISFH that provides high-efficiency interdigitated back contact (IBC) solar cells that could further improve the tandem cell efficiencies, when used as the Si bottom cell in the 4T GaAs//Si cell. Our un-certified current-voltage (I-V) results show an efficiency increase of 0.43% (absolute) by increasing the emitter thickness from 2.0 μm to 2.8 μm. The tandem cells are currently pending cell certification but the results for the GaAs//Si tandem cell with an emitter thickness of 2.8 μm is expected to be >32% and could potentially exceed the existing record efficiency. We will present the results of modeling the GaAs emitter thickness using modified Hovel equations that estimates the Jsc, based upon light absorption and carrier recombination. We will compare these modeled predictions to the NREL-certified I-V and external quantum efficiency (EQE) results obtained from 4T GaAs//Si tandem cells fabricated with absorber layer thicknesses varying from 1.5 to 3.5 μm. We will also compare the performance of our 4T GaAs//Si tandem cells to the record 4T GaAs//Si tandem cell efficiency of 32.8%.}, note = {2019 MRS Fall Meeting & Exhibit}, keywords = {Tandem}, pubstate = {published}, tppubtype = {presentation} } One method to improve silicon solar cell efficiency is to stack a silicon cell beneath a wide-bandgap top cell. To improve the overall tandem cell efficiency from that of silicon alone, the top cell material should have a higher spectral efficiency than silicon for the wavelengths of light within the top cell’s bandgap. GaAs is currently the material with the highest recorded cell efficiency for a single junction cell, at 29.1% efficiency. GaAs also has a theoretical and realized spectral efficiency higher than that of silicon between the wavelengths of 360-860 nm. Our team was able to exploit these GaAs attributes to obtain a record efficiency of 32.8% for a mechanically-stacked rear heterojunction (RHJ) GaAs-on-Si (GaAs//Si) tandem cell designed to operate in the 4-terminal (4T) (i.e. optically coupled but electrically independent) configuration. The purpose of this study is to further optimize the GaAs emitter layer thickness to maximize the efficiency of the 4T GaAs//Si tandem cells. Our record 4T GaAs//Si tandem solar cell was achieved using a 2 μm GaAs emitter layer but subsequent optical modeling of the 4T GaAs//Si tandem solar cells suggests that a slightly thicker emitter could potentially lead to even better top cell efficiencies. In addition, NREL began a collaboration with ISFH that provides high-efficiency interdigitated back contact (IBC) solar cells that could further improve the tandem cell efficiencies, when used as the Si bottom cell in the 4T GaAs//Si cell. Our un-certified current-voltage (I-V) results show an efficiency increase of 0.43% (absolute) by increasing the emitter thickness from 2.0 μm to 2.8 μm. The tandem cells are currently pending cell certification but the results for the GaAs//Si tandem cell with an emitter thickness of 2.8 μm is expected to be >32% and could potentially exceed the existing record efficiency. We will present the results of modeling the GaAs emitter thickness using modified Hovel equations that estimates the Jsc, based upon light absorption and carrier recombination. We will compare these modeled predictions to the NREL-certified I-V and external quantum efficiency (EQE) results obtained from 4T GaAs//Si tandem cells fabricated with absorber layer thicknesses varying from 1.5 to 3.5 μm. We will also compare the performance of our 4T GaAs//Si tandem cells to the record 4T GaAs//Si tandem cell efficiency of 32.8%.
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S. Kajari-Schroder, C. Gemmel, J. Hensen, J. Strey, and R. Brendel High-Quality Kerfless Wafers from the Porous Silicon Layer Transfer Process Presentation/Poster Boston, USA, 02.12.2019, (2019 MRS Fall Meeting & Exhibit). Abstract | BibTeX | Schlagwörter: kerfless @misc{Kajari-Schroder2019b,
title = {High-Quality Kerfless Wafers from the Porous Silicon Layer Transfer Process}, author = {S Kajari-Schroder and C Gemmel and J Hensen and J Strey and R Brendel}, year = {2019}, date = {2019-12-02}, address = {Boston, USA}, abstract = {Silicon wafers constitute a significant cost factor in solar cell and module manufacturing. The porous silicon (PSI) layer transfer process is a kerfless wafering technique that allows for a drastically reduced material and energy consumption per wafer and thus has great potential to reduce the wafer cost. In this process, a thick, highly p-doped substrate is electrochemically porosified, reorganized at high temperature and used as a growth substrate for silicon epitaxy. The epitaxial layer can subsequently be lifted off and the substrate wafer is reused. Key requirements for the realization of this potential in PV industry are, amongst others, a high lift-off yield of the epitaxial wafers from the porosified growth substrate, a robust process sequence, and a high electronic quality at the level of wire-cut Cz wafers. Furthermore, the kerfless wafers should be readily usable in standard solar cell manufacturing equipment, providing drop-in replacement wafers for PV industry. Here, we summarize the recent progress demonstrating several of these key aspects: first, we show that the PSI process is robust with respect to a moderate variation of processing parameters. In high-volume production, it is desirable to use e.g. a typical range of growth substrate resistivities and to use an electrolyte for the porosification process for an extended time. Both conditions would lead to a varying porosity of the growth substrate. We simulate this by a controlled variation of etching parameters, which also results in a variation of porosities in the growth substrate. We find a) that the lifetime of the PSI wafers is independent of the growth substrate separation layer porosities and b) that a reasonable process window in terms of the etching current density can be found. Second, we discuss the statistical evaluation of a large set of epitaxial runs with respect to the process yield: we are able to achieve lift-off of 59 out of 62 PSI wafers, which demonstrates a lift-off yield of the PSI process within our rigorously defined process window of at least 88 % with an error probability of 5 %. Finally, we show that high minority carrier lifetimes of up to 4.3 ms on n-type PSI wafers are achievable right after the epitaxy process, and that these lifetimes can be increased either by phosphorous diffusion gettering or by gettering with a n-type polysilicon on oxide (POLO) junction to up to 8 ms. With this, the PSI wafers are on par with standard PV wafers regarding the electronic quality.}, note = {2019 MRS Fall Meeting & Exhibit}, keywords = {kerfless}, pubstate = {published}, tppubtype = {presentation} } Silicon wafers constitute a significant cost factor in solar cell and module manufacturing. The porous silicon (PSI) layer transfer process is a kerfless wafering technique that allows for a drastically reduced material and energy consumption per wafer and thus has great potential to reduce the wafer cost. In this process, a thick, highly p-doped substrate is electrochemically porosified, reorganized at high temperature and used as a growth substrate for silicon epitaxy. The epitaxial layer can subsequently be lifted off and the substrate wafer is reused. Key requirements for the realization of this potential in PV industry are, amongst others, a high lift-off yield of the epitaxial wafers from the porosified growth substrate, a robust process sequence, and a high electronic quality at the level of wire-cut Cz wafers. Furthermore, the kerfless wafers should be readily usable in standard solar cell manufacturing equipment, providing drop-in replacement wafers for PV industry. Here, we summarize the recent progress demonstrating several of these key aspects: first, we show that the PSI process is robust with respect to a moderate variation of processing parameters. In high-volume production, it is desirable to use e.g. a typical range of growth substrate resistivities and to use an electrolyte for the porosification process for an extended time. Both conditions would lead to a varying porosity of the growth substrate. We simulate this by a controlled variation of etching parameters, which also results in a variation of porosities in the growth substrate. We find a) that the lifetime of the PSI wafers is independent of the growth substrate separation layer porosities and b) that a reasonable process window in terms of the etching current density can be found. Second, we discuss the statistical evaluation of a large set of epitaxial runs with respect to the process yield: we are able to achieve lift-off of 59 out of 62 PSI wafers, which demonstrates a lift-off yield of the PSI process within our rigorously defined process window of at least 88 % with an error probability of 5 %. Finally, we show that high minority carrier lifetimes of up to 4.3 ms on n-type PSI wafers are achievable right after the epitaxy process, and that these lifetimes can be increased either by phosphorous diffusion gettering or by gettering with a n-type polysilicon on oxide (POLO) junction to up to 8 ms. With this, the PSI wafers are on par with standard PV wafers regarding the electronic quality.
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C. Schinke, M. Franke, K. Bothe, and S. Nevas Implementation and uncertainty evaluation of spectral stray light correction by Zong's method Artikel Appl. Opt. 58 (36), 9998-10009, (2019). Abstract | Links | BibTeX | Schlagwörter: Detector arrays, Diode lasers, Light beams, Light wavelength, Optical components, Stray light @article{Schinke2019,
title = {Implementation and uncertainty evaluation of spectral stray light correction by Zong's method}, author = {C Schinke and M Franke and K Bothe and S Nevas}, doi = {10.1364/AO.58.009998}, year = {2019}, date = {2019-12-01}, journal = {Appl. Opt.}, volume = {58}, number = {36}, pages = {9998-10009}, publisher = {OSA}, abstract = {We present a guide to the implementation and uncertainty evaluation for spectral stray light corrections according to the widely used method as proposed by Zong et al. [Appl. Opt.45, 1111 (2006)APOPAI0003-693510.1364/AO.45.001111]. The uncertainty analysis is based on the Monte Carlo approach in accordance with the Guide to the Expression of Uncertainty in Measurement (JCGM, Paris, 2008). We show that significant uncertainty contributions result from drifts of the spectrometer's dark signal and the width of the in-band region selected for shaping stray light distribution functions. Additionally, a simplified method for estimating these uncertainty contributions is presented, which does not require a complex Monte Carlo analysis. We also show that stray light correction may introduce correlations with respect to wavelength.}, keywords = {Detector arrays, Diode lasers, Light beams, Light wavelength, Optical components, Stray light}, pubstate = {published}, tppubtype = {article} } We present a guide to the implementation and uncertainty evaluation for spectral stray light corrections according to the widely used method as proposed by Zong et al. [Appl. Opt.45, 1111 (2006)APOPAI0003-693510.1364/AO.45.001111]. The uncertainty analysis is based on the Monte Carlo approach in accordance with the Guide to the Expression of Uncertainty in Measurement (JCGM, Paris, 2008). We show that significant uncertainty contributions result from drifts of the spectrometer's dark signal and the width of the in-band region selected for shaping stray light distribution functions. Additionally, a simplified method for estimating these uncertainty contributions is presented, which does not require a complex Monte Carlo analysis. We also show that stray light correction may introduce correlations with respect to wavelength.
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D. Hinken, I. Kröger, S. Winter, R. Brendel, and K. Bothe Determining the spectral responsivity of solar cells under standard test conditions Artikel Measurement Science and Technology 30 (12), 125008, (2019). Abstract | Links | BibTeX | Schlagwörter: @article{Hinken2019,
title = {Determining the spectral responsivity of solar cells under standard test conditions}, author = {D Hinken and I Kröger and S Winter and R Brendel and K Bothe}, doi = {10.1088/1361-6501/ab34ef}, year = {2019}, date = {2019-12-01}, journal = {Measurement Science and Technology}, volume = {30}, number = {12}, pages = {125008}, publisher = {IOP Publishing}, abstract = {The spectral responsivity of solar cells is widely used for cell analysis or calibration purposes. According to the IEC60904-8:2014 standard, the reference method for the determination of is the complete differential spectral responsivity approach. For this approach, the differential spectral responsivity is measured as a function of wavelength and bias irradiance. To obtain the spectral responsivity related to standard test conditions the IEC60904-8:2014 standard recommends to integrate via bias current for each wavelength. We show that this integration is wrong. It lacks analytical derivation and provides faulty curves for non-linear solar cells. We prove analytically and by means of simulations that the correct way of calculation is either the integration of via the bias irradiance or the integration of via the bias current , with being the AMx-weighted (e.g. AM1.5G or AM1.5D) differential responsivity. A simulation of the differential spectral responsivity of a strongly non-linear solar cell demonstrates deviations of up to 30% for (the wrong) integration of via at some wavelengths, corresponding to a deviation in the short-circuit current of up to 3.0%.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The spectral responsivity of solar cells is widely used for cell analysis or calibration purposes. According to the IEC60904-8:2014 standard, the reference method for the determination of is the complete differential spectral responsivity approach. For this approach, the differential spectral responsivity is measured as a function of wavelength and bias irradiance. To obtain the spectral responsivity related to standard test conditions the IEC60904-8:2014 standard recommends to integrate via bias current for each wavelength. We show that this integration is wrong. It lacks analytical derivation and provides faulty curves for non-linear solar cells. We prove analytically and by means of simulations that the correct way of calculation is either the integration of via the bias irradiance or the integration of via the bias current , with being the AMx-weighted (e.g. AM1.5G or AM1.5D) differential responsivity. A simulation of the differential spectral responsivity of a strongly non-linear solar cell demonstrates deviations of up to 30% for (the wrong) integration of via at some wavelengths, corresponding to a deviation in the short-circuit current of up to 3.0%.
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R. Reineke-Koch Überhitzungsschutz für Solarkollektoren – neue Lösungswege Presentation/Poster Bern, Switzerland, 29.11.2019. BibTeX | Schlagwörter: Kollektoren @misc{Reineke-Koch2019,
title = {Überhitzungsschutz für Solarkollektoren – neue Lösungswege}, author = {R Reineke-Koch}, year = {2019}, date = {2019-11-29}, address = {Bern, Switzerland}, keywords = {Kollektoren}, pubstate = {published}, tppubtype = {presentation} } |
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F. Weiland, M. Kirchner, V. Rensinghoff, F. Giovannetti, O. Kastner, D. Ridder, Y. Tekinbas, and H. Hachul Journal of Physics: Conference Series 1343 , 012098, (2019). Abstract | Links | BibTeX | Schlagwörter: @article{Weiland2019b,
title = {Performance assessment of solar thermally activated steel sandwich panels with mineral wool core for industrial and commercial buildings}, author = {F Weiland and M Kirchner and V Rensinghoff and F Giovannetti and O Kastner and D Ridder and Y Tekinbas and H Hachul}, doi = {10.1088/1742-6596/1343/1/012098}, year = {2019}, date = {2019-11-20}, journal = {Journal of Physics: Conference Series}, volume = {1343}, pages = {012098}, publisher = {IOP Publishing}, abstract = {Steel sandwich panels are well established, cost effective components for the construction of structural and functional envelopes in buildings. They offer not only design flexibility but also great potential for active solar energy use. This contribution investigates the performance of solar thermal active panels with mineral wool core featuring heat exchangers comprising different designs and materials by means of FEM simulations. The simulation model is validated against measurements of fabricated test specimen. Specific results are reported for a large-sized test specimen with a grey finishing (RAL 7043) where the conversion factor η0 ranges between 0.46 and 0.56. The results imply that higher figures of 0.73 and higher are theoretically achievable with a more efficient use of the panel area and improved manufacturing.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Steel sandwich panels are well established, cost effective components for the construction of structural and functional envelopes in buildings. They offer not only design flexibility but also great potential for active solar energy use. This contribution investigates the performance of solar thermal active panels with mineral wool core featuring heat exchangers comprising different designs and materials by means of FEM simulations. The simulation model is validated against measurements of fabricated test specimen. Specific results are reported for a large-sized test specimen with a grey finishing (RAL 7043) where the conversion factor η0 ranges between 0.46 and 0.56. The results imply that higher figures of 0.73 and higher are theoretically achievable with a more efficient use of the panel area and improved manufacturing.
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H. Schulte-Huxel Interconnect-shingling: Maximizing the active module area to surpass 22% module efficiency with bifacial contacted solar cells Presentation/Poster Xi'an, China, 07.11.2019, (29th International PV Science and Engineering Conference (PVSEC-29)). BibTeX | Schlagwörter: shingling @misc{Schulte-Huxel2019d,
title = {Interconnect-shingling: Maximizing the active module area to surpass 22% module efficiency with bifacial contacted solar cells}, author = {H Schulte-Huxel}, year = {2019}, date = {2019-11-07}, address = {Xi'an, China}, note = {29th International PV Science and Engineering Conference (PVSEC-29)}, keywords = {shingling}, pubstate = {published}, tppubtype = {presentation} } |
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T. Dullweber, M. Stöhr, C. Kruse, F. Haase, M. Rudolph, B. Beier, P. Jaeger, V. Mertens, R. Peibst, and R. Brendel PERC+POLO solar cells minimizing carrier recombination at the Ag front contact with simulated efficiency potential up to 23.8% Presentation/Poster Xi'an, China, 06.11.2019, (29th International PV Science and Engineering Conference (PVSEC-29)). @misc{Dullweber2019,
title = {PERC+POLO solar cells minimizing carrier recombination at the Ag front contact with simulated efficiency potential up to 23.8%}, author = {T Dullweber and M Stöhr and C Kruse and F Haase and M Rudolph and B Beier and P Jaeger and V Mertens and R Peibst and R Brendel}, year = {2019}, date = {2019-11-06}, address = {Xi'an, China}, note = {29th International PV Science and Engineering Conference (PVSEC-29)}, keywords = {PERC}, pubstate = {published}, tppubtype = {presentation} } |
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R. Peibst, C. Kruse, S. Schäfer, V. Mertens, S. Bordihn, T. Dullweber, F. Haase, C. Hollemann, B. Lim, B. Min, R. Niepelt, H. Schulte-Huxel, and R. Brendel For none, one, or two polarities—How do POLO junctions fit best into industrial Si solar cells? Artikel Forthcoming Progress in Photovoltaics: Research and Applications Forthcoming. Abstract | Links | BibTeX | Schlagwörter: efficiency potential, passivating contacts, POLO, Poly-Si, solar cell development @article{Peibst2019f,
title = {For none, one, or two polarities—How do POLO junctions fit best into industrial Si solar cells?}, author = {R Peibst and C Kruse and S Schäfer and V Mertens and S Bordihn and T Dullweber and F Haase and C Hollemann and B Lim and B Min and R Niepelt and H Schulte-Huxel and R Brendel}, doi = {10.1002/pip.3201}, year = {2019}, date = {2019-11-05}, journal = {Progress in Photovoltaics: Research and Applications}, abstract = {Abstract We present a systematic study on the benefit of the implementation of poly-Si on oxide (POLO) or related junctions into p-type industrial Si solar cells as compared with the benchmark of Passivated Emitter and Rear Cell (PERC). We assess three aspects: (a) the simulated efficiency potential of representative structures with POLO junctions for none (=PERC+), one, and for two polarities; (b) possible lean process flows for their fabrication; and (c) experimental results on major building blocks. Synergistic efficiency gain analysis reveals that the exclusive suppression of the contact recombination for one polarity by POLO only yields moderate efficiency improvements between 0.23%abs and 0.41%abs as compared with PERC+ because of the remaining recombination paths. This problem is solved in a structure that includes POLO junctions for both polarities (POLO2), for whose realization we propose a lean process flow, and for which we experimentally demonstrate the most important building blocks. However, two experimental challenges—alignment tolerances and screen-print metallization of p+ poly-Si—are unsolved so far and reduced the efficiency of the “real” POLO2 cell as compared with an idealized scenario. As an intermediate step, we therefore work on a POLO IBC cell with POLO junctions for one polarity. It avoids the abovementioned challenges of the POLO2 structure, can be realized within a lean process flow, and has an efficiency benefit of 1.59%abs as compared with PERC—because not only contact recombination is suppressed but also the entire phosphorus emitter is replaced by an n+ POLO junction.}, keywords = {efficiency potential, passivating contacts, POLO, Poly-Si, solar cell development}, pubstate = {forthcoming}, tppubtype = {article} } Abstract We present a systematic study on the benefit of the implementation of poly-Si on oxide (POLO) or related junctions into p-type industrial Si solar cells as compared with the benchmark of Passivated Emitter and Rear Cell (PERC). We assess three aspects: (a) the simulated efficiency potential of representative structures with POLO junctions for none (=PERC+), one, and for two polarities; (b) possible lean process flows for their fabrication; and (c) experimental results on major building blocks. Synergistic efficiency gain analysis reveals that the exclusive suppression of the contact recombination for one polarity by POLO only yields moderate efficiency improvements between 0.23%abs and 0.41%abs as compared with PERC+ because of the remaining recombination paths. This problem is solved in a structure that includes POLO junctions for both polarities (POLO2), for whose realization we propose a lean process flow, and for which we experimentally demonstrate the most important building blocks. However, two experimental challenges—alignment tolerances and screen-print metallization of p+ poly-Si—are unsolved so far and reduced the efficiency of the “real” POLO2 cell as compared with an idealized scenario. As an intermediate step, we therefore work on a POLO IBC cell with POLO junctions for one polarity. It avoids the abovementioned challenges of the POLO2 structure, can be realized within a lean process flow, and has an efficiency benefit of 1.59%abs as compared with PERC—because not only contact recombination is suppressed but also the entire phosphorus emitter is replaced by an n+ POLO junction.
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F. Giovannetti Experimental Investigations on Photovoltaic-Thermal Arrays Designed for the Use as Heat Pump Source Presentation/Poster Santiago, Chile, 04.11.2019, (ISES Solar World Congress and IEA Solar Heating and Cooling (SHC) Conference). @misc{Giovannetti2019c,
title = {Experimental Investigations on Photovoltaic-Thermal Arrays Designed for the Use as Heat Pump Source}, author = {F Giovannetti}, year = {2019}, date = {2019-11-04}, address = {Santiago, Chile}, note = {ISES Solar World Congress and IEA Solar Heating and Cooling (SHC) Conference}, keywords = {PVT}, pubstate = {published}, tppubtype = {presentation} } |
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F. Giovannetti Improved flat plate collector with heat pipes for overheating prevention in solar thermal systems Presentation/Poster Santiago, Chile, 04.11.2019, (ISES Solar World Congress and IEA Solar Heating and Cooling (SHC) Conference). BibTeX | Schlagwörter: Solar thermal @misc{Giovannetti2019d,
title = {Improved flat plate collector with heat pipes for overheating prevention in solar thermal systems}, author = {F Giovannetti}, year = {2019}, date = {2019-11-04}, address = {Santiago, Chile}, note = {ISES Solar World Congress and IEA Solar Heating and Cooling (SHC) Conference}, keywords = {Solar thermal}, pubstate = {published}, tppubtype = {presentation} } |
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C. Hollemann, F. Haase, S. Schäfer, J. Krügener, R. Brendel, and R. Peibst 26.1%-efficient POLO-IBC cells: Quantification of electrical and optical loss mechanisms Artikel Progress in Photovoltaics: Research and Applications 27 (11), 950-958, (2019). Abstract | Links | BibTeX | Schlagwörter: efficiency potential, IBC solar cells, lifetime monitoring, passivating contacts, POLO @article{Hollemann2019,
title = {26.1%-efficient POLO-IBC cells: Quantification of electrical and optical loss mechanisms}, author = {C Hollemann and F Haase and S Schäfer and J Krügener and R Brendel and R Peibst}, doi = {10.1002/pip.3098}, year = {2019}, date = {2019-11-01}, journal = {Progress in Photovoltaics: Research and Applications}, volume = {27}, number = {11}, pages = {950-958}, abstract = {Abstract We present experimental results for interdigitated back contacted (IBC) solar cells with passivating POLO contacts for both polarities with a nominal intrinsic poly-Si region between them. We reach efficiencies of 26.1% and 24.9% on a 1.3 Ω cm and 80 Ω cm p-type FZ wafer and 24.6% on a 2 Ω cm n-type Cz wafer, respectively. The initially measured implied efficiency potentials of the cells after passivating the surfaces are very similar, namely, 26.8%, 26.8%, and 26.4%, respectively. We attribute the difference between the efficiency potential and the final current-voltage measurement to degradation, perimeter, and series and shunt resistance losses, which we quantify by lifetime measurements. With these measurements in combination with a finite element simulation, we determine the surface recombination velocity in the nominal intrinsic poly-Si region to be in the range from 13 to 21 cm s−1. Using the same approach, we analyze the increase of the front surface recombination velocity during cell processing from 2 to 10 cm s−1 for the 1.3 Ω cm and from 0.5 to 2.3 cm s−1 for the 80 Ω cm. This leads to the fact that cells fabricated on lowly doped bulk material are more vulnerable to a process-induced degradation of the surface passivation quality. We further determine the theoretical limits of the cells by firstly idealizing the recombination (28% for 1.3 Ω cm and 28.2% for 80 Ω cm) and secondly also idealizing the optics of the solar cells (29.4% and 29.5%).}, keywords = {efficiency potential, IBC solar cells, lifetime monitoring, passivating contacts, POLO}, pubstate = {published}, tppubtype = {article} } Abstract We present experimental results for interdigitated back contacted (IBC) solar cells with passivating POLO contacts for both polarities with a nominal intrinsic poly-Si region between them. We reach efficiencies of 26.1% and 24.9% on a 1.3 Ω cm and 80 Ω cm p-type FZ wafer and 24.6% on a 2 Ω cm n-type Cz wafer, respectively. The initially measured implied efficiency potentials of the cells after passivating the surfaces are very similar, namely, 26.8%, 26.8%, and 26.4%, respectively. We attribute the difference between the efficiency potential and the final current-voltage measurement to degradation, perimeter, and series and shunt resistance losses, which we quantify by lifetime measurements. With these measurements in combination with a finite element simulation, we determine the surface recombination velocity in the nominal intrinsic poly-Si region to be in the range from 13 to 21 cm s−1. Using the same approach, we analyze the increase of the front surface recombination velocity during cell processing from 2 to 10 cm s−1 for the 1.3 Ω cm and from 0.5 to 2.3 cm s−1 for the 80 Ω cm. This leads to the fact that cells fabricated on lowly doped bulk material are more vulnerable to a process-induced degradation of the surface passivation quality. We further determine the theoretical limits of the cells by firstly idealizing the recombination (28% for 1.3 Ω cm and 28.2% for 80 Ω cm) and secondly also idealizing the optics of the solar cells (29.4% and 29.5%).
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C. Gemmel, J. Hensen, S. Kajari-Schröder, and R. Brendel Detachment yield statistics for kerfless wafering using the porous silicon process Artikel Solar Energy Materials and Solar Cells 202 , 110061, (2019), ISSN: 0927-0248. Abstract | Links | BibTeX | Schlagwörter: Detachment probability, Porous silicon process, Statistical evaluation, Yield @article{Gemmel2019c,
title = {Detachment yield statistics for kerfless wafering using the porous silicon process}, author = {C Gemmel and J Hensen and S Kajari-Schröder and R Brendel}, doi = {10.1016/j.solmat.2019.110061}, issn = {0927-0248}, year = {2019}, date = {2019-11-01}, journal = {Solar Energy Materials and Solar Cells}, volume = {202}, pages = {110061}, abstract = {The porous silicon (PSI) process is a wafering method to fabricate high quality kerfless crystalline Si wafers by epitaxial wafer growth on porous Si and subsequent detachment from a reusable substrate wafer. The process yield is a key parameter for the economic viability of the PSI process. We experimentally demonstrate the detachment of 59 out of 62 PSI wafers with a size of 10 × 10 cm2, and separation layer etch current densities of 105–120 mA/cm2 for electrochemically etching the porous Si, and for substrate wafers with a resistivity of 15.7–16.9 mΩcm. We discuss the statistics of how to deduce a detachment probability from this. From our experiments, we determine a detachment yield of at least 88% with an error probability of 5%. The demonstration of a 99% detachment yield with an error probability of 5% would require at least 300 successfully detached wafers with no failed detachment. Samples have a minority carrier density ranging from 1 to 1.7 ms before any external gettering, which demonstrates the high electric quality of the PSI wafers.}, keywords = {Detachment probability, Porous silicon process, Statistical evaluation, Yield}, pubstate = {published}, tppubtype = {article} } The porous silicon (PSI) process is a wafering method to fabricate high quality kerfless crystalline Si wafers by epitaxial wafer growth on porous Si and subsequent detachment from a reusable substrate wafer. The process yield is a key parameter for the economic viability of the PSI process. We experimentally demonstrate the detachment of 59 out of 62 PSI wafers with a size of 10 × 10 cm2, and separation layer etch current densities of 105–120 mA/cm2 for electrochemically etching the porous Si, and for substrate wafers with a resistivity of 15.7–16.9 mΩcm. We discuss the statistics of how to deduce a detachment probability from this. From our experiments, we determine a detachment yield of at least 88% with an error probability of 5%. The demonstration of a 99% detachment yield with an error probability of 5% would require at least 300 successfully detached wafers with no failed detachment. Samples have a minority carrier density ranging from 1 to 1.7 ms before any external gettering, which demonstrates the high electric quality of the PSI wafers.
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