Publications
2020 |
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M. Littwin Using a Dynamic System Model to Characterize a Complex PV System Presentation/Poster Online Event, 10.09.2020, (Performance of New Photovoltaic System Concepts and Designs - Parallel Event at 37th European Photovoltaic Solar Energy Conference and Exhibition). BibTeX | Tags: Dynamic System Model @misc{Littwin2020c,
title = {Using a Dynamic System Model to Characterize a Complex PV System}, author = {M Littwin}, year = {2020}, date = {2020-09-10}, address = {Online Event}, note = {Performance of New Photovoltaic System Concepts and Designs - Parallel Event at 37th European Photovoltaic Solar Energy Conference and Exhibition}, keywords = {Dynamic System Model}, pubstate = {published}, tppubtype = {presentation} } |
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T. Gewohn, M. R. Vogt, B. Lim, C. Schinke, and R. Brendel Customization of BIPV Modules’ Appearance by Colored Textiles (CoTex) and Their Digital Prototypes Presentation/Poster Online Event, 10.09.2020, (37th European Photovoltaic Solar Energy Conference and Exhibition). Abstract | BibTeX | Tags: BIPV, CoTex @misc{Gewohn2020,
title = {Customization of BIPV Modules’ Appearance by Colored Textiles (CoTex) and Their Digital Prototypes}, author = {T Gewohn and M R Vogt and B Lim and C Schinke and R Brendel}, year = {2020}, date = {2020-09-10}, address = {Online Event}, abstract = {Building-integrated photovoltaics (BIPV) gain increasing importance [1],[2] as regulations demand better energy efficiency of buildings, which can only be achieved by using not only the roof but also the building façade for energy generation. Thus, increasing the appearance is important. Simultaneously, a high performance at low cost and a high degree of customization must be achieved in order to be competitive with conventional non-PV building materials. Hence we investigate laminated nonwoven fabrics for these purposes [3]. During the building’s design phase, architects need to know how much energy the PV module with their customized design will produce to calculate the building’s energy balance. Therefore, we present an approach to create a digital prototype that simulates the appearance and calculates the expected yield of the PV module.}, note = {37th European Photovoltaic Solar Energy Conference and Exhibition}, keywords = {BIPV, CoTex}, pubstate = {published}, tppubtype = {presentation} } Building-integrated photovoltaics (BIPV) gain increasing importance [1],[2] as regulations demand better energy efficiency of buildings, which can only be achieved by using not only the roof but also the building façade for energy generation. Thus, increasing the appearance is important. Simultaneously, a high performance at low cost and a high degree of customization must be achieved in order to be competitive with conventional non-PV building materials. Hence we investigate laminated nonwoven fabrics for these purposes [3]. During the building’s design phase, architects need to know how much energy the PV module with their customized design will produce to calculate the building’s energy balance. Therefore, we present an approach to create a digital prototype that simulates the appearance and calculates the expected yield of the PV module.
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M. Winter, L. Helmich, D. C. Walter, and J. Schmidt Firing-Triggered LID (FT-LID) of the Carrier Lifetime in Cz-Si Wafers Presentation/Poster Online Event, 10.09.2020, (37th European Photovoltaic Solar Energy Conference and Exhibition). Abstract | BibTeX | Tags: Degradation @misc{Winter2020b,
title = {Firing-Triggered LID (FT-LID) of the Carrier Lifetime in Cz-Si Wafers}, author = { M Winter and L Helmich and D C Walter and J Schmidt}, year = {2020}, date = {2020-09-10}, address = {Online Event}, abstract = {Light-induced lifetime degradation effects are frequently observed in boron-doped Czochralski-grown silicon (Cz-Si) and in block-cast multicrystalline silicon (mc-Si) wafers as well as in solar cells made thereof. While the respective main degradation effects are the boron-oxygen (BO) defect activation in Cz-Si [1] and the ‘Light and elevated Temperature Induced Degradation’ (LeTID) effect on mc-Si [2–4], recently, there have also been several reports of LeTID-type effects on Cz-Si wafers and solar cells [5–7]. This study presents an experimental approach to separate additional LeTID-type degradation effects in fired Cz-Si wafers from the traditional BO defect activation. In the second part of this study, we compare the observed non-BO-related degradation effect in Cz-Si wafers with the standard LeTID effect, typically observed on mc-Si material and point out the main differences, which lead us to the conclusion that the detailed physics of the two degradation effects are not identical.}, note = {37th European Photovoltaic Solar Energy Conference and Exhibition}, keywords = {Degradation}, pubstate = {published}, tppubtype = {presentation} } Light-induced lifetime degradation effects are frequently observed in boron-doped Czochralski-grown silicon (Cz-Si) and in block-cast multicrystalline silicon (mc-Si) wafers as well as in solar cells made thereof. While the respective main degradation effects are the boron-oxygen (BO) defect activation in Cz-Si [1] and the ‘Light and elevated Temperature Induced Degradation’ (LeTID) effect on mc-Si [2–4], recently, there have also been several reports of LeTID-type effects on Cz-Si wafers and solar cells [5–7]. This study presents an experimental approach to separate additional LeTID-type degradation effects in fired Cz-Si wafers from the traditional BO defect activation. In the second part of this study, we compare the observed non-BO-related degradation effect in Cz-Si wafers with the standard LeTID effect, typically observed on mc-Si material and point out the main differences, which lead us to the conclusion that the detailed physics of the two degradation effects are not identical.
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S. Schäfer, A. Mercker, V. Mertens, T. Neubert, A. Köhler, L. Mettner, R. Brendel, and R. Peibst Laser-Induced Oxidation of Doped Poly-Si at Room Temperature for Si Solar Cells with Structured Passivated Contacts Presentation/Poster Online Event, 10.09.2020, (37th European Photovoltaic Solar Energy Conference and Exhibition). Abstract | BibTeX | Tags: POLO @misc{Schäfer2020,
title = {Laser-Induced Oxidation of Doped Poly-Si at Room Temperature for Si Solar Cells with Structured Passivated Contacts}, author = {S Schäfer and A Mercker and V Mertens and T Neubert and A Köhler and L Mettner and R Brendel and R Peibst}, year = {2020}, date = {2020-09-10}, address = {Online Event}, abstract = {Purpose of the work, scientific approach and innovation: Passivated contacts that use polysilicon on oxide (POLO) show outstanding electrical surface passivation of silicon. However, poly-Si-based junctions have been mainly applied to the rear side of solar cells, either in an IBC architecture [1] or in a front and back side-contacted (FBC) cell [2]. Highly doped poly-Si on the rear side causes less parasitic absorption than on the front side. A possible compromise is to have the POLO contacts only locally under the front metal fingers of an FBC solar cell and spare the interfinger regions. This can be done by localized deposition in the first place, e.g. via shadow masks, or by a three step process with formation of a sacrificial dielectric layer on top of the poly-Si (1), subsequent structuring to form an etching mask (2) and final etching process (3). In this abstract we demonstrate an alternative process where the etching mask is created locally by laser treatment of the poly-Si. Thereby the aforementioned steps (1) and (2) are combined in a single laser process. We show that a local irradiation by UV-ps laser pulses changes the etch resistiveness of the poly-Si in an alkaline solution, which is sufficient to remove the poly- Si in the non-lasered areas. The etch resistiveness increases when additional oxygen gas is introduced to the process chamber. We therefore explain the findings by a laser-induced oxidation of the poly-Si rather than by amorphization of the poly-Si. We demonstrate the process to work on planar as well as textured silicon. The advantage of the lasered etching mask is the reduction of process complexity and process time as compared to ablating the complete interfinger region, which is roughly 98% of the front side.}, note = {37th European Photovoltaic Solar Energy Conference and Exhibition}, keywords = {POLO}, pubstate = {published}, tppubtype = {presentation} } Purpose of the work, scientific approach and innovation: Passivated contacts that use polysilicon on oxide (POLO) show outstanding electrical surface passivation of silicon. However, poly-Si-based junctions have been mainly applied to the rear side of solar cells, either in an IBC architecture [1] or in a front and back side-contacted (FBC) cell [2]. Highly doped poly-Si on the rear side causes less parasitic absorption than on the front side. A possible compromise is to have the POLO contacts only locally under the front metal fingers of an FBC solar cell and spare the interfinger regions. This can be done by localized deposition in the first place, e.g. via shadow masks, or by a three step process with formation of a sacrificial dielectric layer on top of the poly-Si (1), subsequent structuring to form an etching mask (2) and final etching process (3). In this abstract we demonstrate an alternative process where the etching mask is created locally by laser treatment of the poly-Si. Thereby the aforementioned steps (1) and (2) are combined in a single laser process. We show that a local irradiation by UV-ps laser pulses changes the etch resistiveness of the poly-Si in an alkaline solution, which is sufficient to remove the poly- Si in the non-lasered areas. The etch resistiveness increases when additional oxygen gas is introduced to the process chamber. We therefore explain the findings by a laser-induced oxidation of the poly-Si rather than by amorphization of the poly-Si. We demonstrate the process to work on planar as well as textured silicon. The advantage of the lasered etching mask is the reduction of process complexity and process time as compared to ablating the complete interfinger region, which is roughly 98% of the front side.
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M. Stöhr, B. Beier, R. Brendel, and T. Dullweber PECVD Shadow Mask Deposition of a-Si Fingers – a Short Cut to Structured Poly-Si for Local Passivating Contacts Presentation/Poster Online Event, 10.09.2020, (37th European Photovoltaic Solar Energy Conference and Exhibition). Abstract | BibTeX | Tags: Shadow mask @misc{Stöhr2020,
title = {PECVD Shadow Mask Deposition of a-Si Fingers – a Short Cut to Structured Poly-Si for Local Passivating Contacts}, author = {M Stöhr and B Beier and R Brendel and T Dullweber}, year = {2020}, date = {2020-09-10}, address = {Online Event}, abstract = {The solar cell industry has widely introduced the “Passivated Emitter and Rear Cell” (PERC) concept into manufacturing with conversion efficiencies around 22.5% [1]. As a next solar cell technology, passivating contacts based on poly-Si are intensively evaluated for the front and / or rear side with a highest simulated efficiency potential around 25% for two-sided poly-Si contacts [2]. Due to its high light absorption, the poly-Si has to be absent between the metal fingers when applied to the cells front side. So far, the approaches to structure poly-Si involve a full-area poly-Si deposition, annealing, masking and etching which is very expensive and hence has not yet been applied in mass production. In this study, we target a potentially cost-effective manufacturing of structured poly-Si fingers applying only one process step. We deposit amorphous silicon (a-Si) fingers by PECVD through a shadow mask, which is placed between the plasma and the Si wafer. In the past, PECVD shadow masks have been applied for about 200 μm wide a-Si fingers for the rear of IBC heterojunction solar cells [3, 4]. Here we evaluate for the first time, PECVD shadow mask-deposited a-Si fingers as narrow as 70 μm, which are suitable for solar cell front side application. We anneal, crystallize and dope the a-Si to n-type poly-Si in a subsequent POCl3 diffusion, which is anyhow required for several solar cell designs. We analyze the n-poly-Si morphology, crystallinity and passivation quality by optical microscope, Raman and QSSPC measurements.}, note = {37th European Photovoltaic Solar Energy Conference and Exhibition}, keywords = {Shadow mask}, pubstate = {published}, tppubtype = {presentation} } The solar cell industry has widely introduced the “Passivated Emitter and Rear Cell” (PERC) concept into manufacturing with conversion efficiencies around 22.5% [1]. As a next solar cell technology, passivating contacts based on poly-Si are intensively evaluated for the front and / or rear side with a highest simulated efficiency potential around 25% for two-sided poly-Si contacts [2]. Due to its high light absorption, the poly-Si has to be absent between the metal fingers when applied to the cells front side. So far, the approaches to structure poly-Si involve a full-area poly-Si deposition, annealing, masking and etching which is very expensive and hence has not yet been applied in mass production. In this study, we target a potentially cost-effective manufacturing of structured poly-Si fingers applying only one process step. We deposit amorphous silicon (a-Si) fingers by PECVD through a shadow mask, which is placed between the plasma and the Si wafer. In the past, PECVD shadow masks have been applied for about 200 μm wide a-Si fingers for the rear of IBC heterojunction solar cells [3, 4]. Here we evaluate for the first time, PECVD shadow mask-deposited a-Si fingers as narrow as 70 μm, which are suitable for solar cell front side application. We anneal, crystallize and dope the a-Si to n-type poly-Si in a subsequent POCl3 diffusion, which is anyhow required for several solar cell designs. We analyze the n-poly-Si morphology, crystallinity and passivation quality by optical microscope, Raman and QSSPC measurements.
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J. Ulbikas, V. Ulbikaite, J. Denafas, R. Witteck, M. Köntges, M. Topic, F. Frontini, P. Bonomo, E. Saretta, P. Macé, P. J. Bolt, A. G. Ulyashin, T. Haarberg, W. Palitzsch, B. Terheiden, I. Weiss, N. LaPointe, and J. L. Domínguez-García Super PV Progress Report – Developing Innovative High-Quality PV Systems to Regain European Leadership in the Global PV Market Presentation/Poster Online Event, 10.09.2020, (37th European Photovoltaic Solar Energy Conference and Exhibition). Abstract | BibTeX | Tags: SuperPV @misc{Ulbikas2020,
title = {Super PV Progress Report – Developing Innovative High-Quality PV Systems to Regain European Leadership in the Global PV Market}, author = {J Ulbikas and V Ulbikaite and J Denafas and R Witteck and M Köntges and M Topic and F Frontini and P Bonomo and E Saretta and P Macé and P J Bolt and A G Ulyashin and T Haarberg and W Palitzsch and B Terheiden and I Weiss and N LaPointe and J L Domínguez-García}, year = {2020}, date = {2020-09-10}, address = {Online Event}, abstract = {The PV sector is one of the fastest growing industries globally, between 2010 and 2019 global solar installations grew from around 16 gigawatts to over 105 gigawatts in 2019 [1]. This significant rise in photovoltaics has been in large part due to a substantial decrease in the price of PV cells and modules. At the beginning of the decade the average Multi Crystalline Silicon module cost roughly $2 per watt, now (early 2020) the average Multi-Si costs around $0.20 per watt in [1]. This expansion of the PV sector has coincided with a geographical shift in manufacturing capacities. Currently East and Central Asia produce over 80% of the world’s PV modules, while Europe contributes to less than 5% of the global supply [2]. In order to remain competitive and recapture a larger market share of PV manufacturing, European PV companies will need innovate along the PV supply/value chain. SUPER PV project is targeting competitiveness of European produced PV systems integrating 26 partners from all over the Europe delivering innovations from research centers to manufacturing lines. Expected cost reduction will be realized through targeted technological and business innovations which will significantly improve the levelized cost of electricity (LCOE) of European systems. A year and a half into the project these price reductions and innovations have begun to take shape. This abstract will outline the status of this ground-breaking project.}, note = {37th European Photovoltaic Solar Energy Conference and Exhibition}, keywords = {SuperPV}, pubstate = {published}, tppubtype = {presentation} } The PV sector is one of the fastest growing industries globally, between 2010 and 2019 global solar installations grew from around 16 gigawatts to over 105 gigawatts in 2019 [1]. This significant rise in photovoltaics has been in large part due to a substantial decrease in the price of PV cells and modules. At the beginning of the decade the average Multi Crystalline Silicon module cost roughly $2 per watt, now (early 2020) the average Multi-Si costs around $0.20 per watt in [1]. This expansion of the PV sector has coincided with a geographical shift in manufacturing capacities. Currently East and Central Asia produce over 80% of the world’s PV modules, while Europe contributes to less than 5% of the global supply [2]. In order to remain competitive and recapture a larger market share of PV manufacturing, European PV companies will need innovate along the PV supply/value chain. SUPER PV project is targeting competitiveness of European produced PV systems integrating 26 partners from all over the Europe delivering innovations from research centers to manufacturing lines. Expected cost reduction will be realized through targeted technological and business innovations which will significantly improve the levelized cost of electricity (LCOE) of European systems. A year and a half into the project these price reductions and innovations have begun to take shape. This abstract will outline the status of this ground-breaking project.
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J. Denafas, P. Lukinskas, T. Radavicčius, L. Petreniene, J. Ulbikas, R. Witteck, M. Köntges, Crespo. J. Gutierrez, J. Cordon, T. Carrère, R. Einhaus, U. Rühle, P. J. Bolt, D. Roosen-Melsen, F. J. van den Bruele, A. G. Ulyashin, T. Haarberg, W. Palitzsch, N. LaPointe, and I. Weiss Super PV Project – Support Cost-Reduction of the PV System through Innovative Technologies on PV Module Level Presentation/Poster Online Event, 10.09.2020, (37th European Photovoltaic Solar Energy Conference and Exhibition). Abstract | BibTeX | Tags: SuperPV @misc{Denafas2020,
title = {Super PV Project – Support Cost-Reduction of the PV System through Innovative Technologies on PV Module Level}, author = {J Denafas and P Lukinskas and T Radavicčius and L Petreniene and J Ulbikas and R Witteck and M Köntges and J Crespo Gutierrez and J Cordon and T Carrère and R Einhaus and U Rühle and P J Bolt and D Roosen-Melsen and F J van den Bruele and A G Ulyashin and T Haarberg and W Palitzsch and N LaPointe and I Weiss}, year = {2020}, date = {2020-09-10}, address = {Online Event}, abstract = { SUPER PV is a collaborative European-funded project initiated in 2018 by 26 partners. It pursues a significant LCOE reduction (up to 37%) for innovative photovoltaic (PV) systems based on a hybrid combination of technological innovations and Data management solutions along the PV value chain from solar module to installed system, including operation of solar plants and possibility to recycle end-of life modules. One of the key elements to achieve the LCOE reduction targets is the cost-reduction of the PV system through innovative technologies on PV module level and recycling of end-of-life modules. Innovations are developed and demonstrated on 3 different module technologies which are used by industrial partners Solitek, Apollon Solar (both c-Si but different encapsulation methods) and Flisom (CIGS flexible module technology). Our project is focusing on the following PV module innovations: • Development and demonstration of low cost and easy to apply multifunctional nano-coatings with antisoiling and antireflective properties in one layer. • Development and demonstration of light management in bifacial c-Si modules to increase the power output up to 7 Wp. • Development and demonstration of laminated diode innovations produced by solar cell production • Development and demonstration of a low-cost encapsulation innovation with a low-cost humidity barrier leading to 45% cost reduction of flexible CIGS modules • Development and demonstration of inline inspection system of encapsulation process for CIGS modules • Development of recycling approaches and their demonstration to all types of modules under consideration in SuperPV project • Cost and performance evaluation (Eur/Wp, Eur/kWh).}, note = {37th European Photovoltaic Solar Energy Conference and Exhibition}, keywords = {SuperPV}, pubstate = {published}, tppubtype = {presentation} } SUPER PV is a collaborative European-funded project initiated in 2018 by 26 partners. It pursues a significant LCOE reduction (up to 37%) for innovative photovoltaic (PV) systems based on a hybrid combination of technological innovations and Data management solutions along the PV value chain from solar module to installed system, including operation of solar plants and possibility to recycle end-of life modules. One of the key elements to achieve the LCOE reduction targets is the cost-reduction of the PV system through innovative technologies on PV module level and recycling of end-of-life modules. Innovations are developed and demonstrated on 3 different module technologies which are used by industrial partners Solitek, Apollon Solar (both c-Si but different encapsulation methods) and Flisom (CIGS flexible module technology). Our project is focusing on the following PV module innovations: • Development and demonstration of low cost and easy to apply multifunctional nano-coatings with antisoiling and antireflective properties in one layer. • Development and demonstration of light management in bifacial c-Si modules to increase the power output up to 7 Wp. • Development and demonstration of laminated diode innovations produced by solar cell production • Development and demonstration of a low-cost encapsulation innovation with a low-cost humidity barrier leading to 45% cost reduction of flexible CIGS modules • Development and demonstration of inline inspection system of encapsulation process for CIGS modules • Development of recycling approaches and their demonstration to all types of modules under consideration in SuperPV project • Cost and performance evaluation (Eur/Wp, Eur/kWh).
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LJ. Koduvelikulathu, J. Lossen, A. Adrian, D. Rudolph, Z-W. Peng, A. Chaudhary, R. Harney, M. Troeller, A. Piechulla, VX. Nguyen, D. Seiffert, T. Pernau, H. Haverkamp, F. Haase, and R. Peibst An Industrial Feasible n+ Poly-Si-IBC Screen Printed Solar Cell with 702 mV Voc on Large Area p-Type Substrates Presentation/Poster Online Event, 10.09.2020, (37th European Photovoltaic Solar Energy Conference and Exhibition). Abstract | BibTeX | Tags: Poly-Si @misc{Koduvelikulathu2020,
title = {An Industrial Feasible n+ Poly-Si-IBC Screen Printed Solar Cell with 702 mV Voc on Large Area p-Type Substrates}, author = {LJ Koduvelikulathu and J Lossen and A Adrian and D Rudolph and Z-W Peng and A Chaudhary and R Harney and M Troeller and A Piechulla and VX Nguyen and D Seiffert and T Pernau and H Haverkamp and F Haase and R Peibst}, year = {2020}, date = {2020-09-10}, address = {Online Event}, abstract = {Motivation, Scientific innovation and relevance The current PV market is mainly driven by cost effective industrial implementation of processes towards high efficiency c-Si solar cell device architecture. These has led to a transformation of production capacities to p-type mono PERC (Passivated Emitter and Rear Contacted) solar cells. Metallisation induced recombination loss is one of the major open circuit voltage (Voc) limiting factor of high efficiency PERC solar cells. Passivating contacts, wherein a thin oxide layer is located between the silicon absorber and a highly doped contact layer, have proven to eliminate or at least strongly reduce the metallization induced recombination losses [1]. Given the enormous installed base of PERC production lines, concepts, which will allow for upgrading these lines with passivated contacts, are of high interest to the industry. The here presented pIBC cell, independently developed by Bende et al. [2] and us [3], combines an n+ passivated poly-emitter contact with AlOx passivation of the base and an Aluminium alloyed p+ base contact from PERC technology. It allows for a high degree of equipment reutilisation while opening the path towards efficiencies beyond the limits of PERC cells.}, note = {37th European Photovoltaic Solar Energy Conference and Exhibition}, keywords = {Poly-Si}, pubstate = {published}, tppubtype = {presentation} } Motivation, Scientific innovation and relevance The current PV market is mainly driven by cost effective industrial implementation of processes towards high efficiency c-Si solar cell device architecture. These has led to a transformation of production capacities to p-type mono PERC (Passivated Emitter and Rear Contacted) solar cells. Metallisation induced recombination loss is one of the major open circuit voltage (Voc) limiting factor of high efficiency PERC solar cells. Passivating contacts, wherein a thin oxide layer is located between the silicon absorber and a highly doped contact layer, have proven to eliminate or at least strongly reduce the metallization induced recombination losses [1]. Given the enormous installed base of PERC production lines, concepts, which will allow for upgrading these lines with passivated contacts, are of high interest to the industry. The here presented pIBC cell, independently developed by Bende et al. [2] and us [3], combines an n+ passivated poly-emitter contact with AlOx passivation of the base and an Aluminium alloyed p+ base contact from PERC technology. It allows for a high degree of equipment reutilisation while opening the path towards efficiencies beyond the limits of PERC cells.
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M. Littwin, F. P. Baumgartner, C. Biba, B. Farnung, R. H. French, D. Gfeller, M. Green, U. Jahn, C. Messner, U. Muntwyler, D. Riley, D. Rivola, T. Schott, J. S. Stein, M. Trommsdorff, W. G. J. H. M. van Sark, M. Köntges, T. Ohrdes, and F. Giovannetti Performance of New Photovoltaic System Designs - IEA PVPS Task 13 Subtask 1.3 Presentation/Poster Online Event, 09.09.2020, (37th European Photovoltaic Solar Energy Conference and Exhibition). Abstract | BibTeX | Tags: IEA PVPS @misc{Littwin2020b,
title = {Performance of New Photovoltaic System Designs - IEA PVPS Task 13 Subtask 1.3}, author = {M Littwin and F P Baumgartner and C Biba and B Farnung and R H French and D Gfeller and M Green and U Jahn and C Messner and U Muntwyler and D Riley and D Rivola and T Schott and J S Stein and M Trommsdorff and W G J H M van Sark and M Köntges and T Ohrdes and F Giovannetti}, year = {2020}, date = {2020-09-09}, address = {Online Event}, abstract = {New PV system designs are being developed to increase the value of the energy produced by either lowering the installation costs, increasing the efficiency or adding functions to the system. Some of these innovations include advanced power electronics to optimize the performance ratio of PV systems. Some new PV systems have additional functions like coupling PV energy with storage and power grid, including storage for electro mobility, agricultural PV, and floating PV systems. For most of the mentioned new system components and dual function systems no standards exist on how to characterize and normalize the system or component performance. In this work we summarize system-level innovations, show how the performance of these new systems can be characterized and demonstrate opportunities for achieving high system level performance in case studies.}, note = {37th European Photovoltaic Solar Energy Conference and Exhibition}, keywords = {IEA PVPS}, pubstate = {published}, tppubtype = {presentation} } New PV system designs are being developed to increase the value of the energy produced by either lowering the installation costs, increasing the efficiency or adding functions to the system. Some of these innovations include advanced power electronics to optimize the performance ratio of PV systems. Some new PV systems have additional functions like coupling PV energy with storage and power grid, including storage for electro mobility, agricultural PV, and floating PV systems. For most of the mentioned new system components and dual function systems no standards exist on how to characterize and normalize the system or component performance. In this work we summarize system-level innovations, show how the performance of these new systems can be characterized and demonstrate opportunities for achieving high system level performance in case studies.
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K. Bothe, C. Kruse, and D. Hinken Contacting of Busbarless Solar Cells for Accurate I-V Measurements Presentation/Poster Online Event, 09.09.2020, (37th European Photovoltaic Solar Energy Conference and Exhibition). Abstract | BibTeX | Tags: busbarless, IV @misc{Bothe2020,
title = {Contacting of Busbarless Solar Cells for Accurate I-V Measurements}, author = {K Bothe and C Kruse and D Hinken}, year = {2020}, date = {2020-09-09}, address = {Online Event}, abstract = {No explicit standard exists for the design of solar cell contacting units. For contacting the solar cell front some authors [1, 2] demand a contacting method which reflects the module integration, while others [3, 4, 5] recommend a contacting scheme with an infinite number of contact points on the busbar, thus neglecting its resistivity. A current-voltage (I-V) characteristic that would be measured with such an ideal contacting would have a fill factor which we call FFinfcp (infcp = infinite number of contact points) in the following. Experimentally, with a finite number of contacts, it was shown [3, 5] that a specific positioning of the voltage measuring contact (sense contact) allows to approximate a busbar-resistance neglecting contacting scheme. In this work, we transfer this principle concept to the measurement of busbarless solar cells by implementing grid-resistance neglecting contacting schemes. By means of analytical modelling, we study the impact of the number of contacting bars/wires on the FF of current voltage curve measurements of busbarless solar cells with different finger resistivity. To verify this experimentally, we compare the measurement results of 30 wires and 12 contact bars configurations.}, note = {37th European Photovoltaic Solar Energy Conference and Exhibition}, keywords = {busbarless, IV}, pubstate = {published}, tppubtype = {presentation} } No explicit standard exists for the design of solar cell contacting units. For contacting the solar cell front some authors [1, 2] demand a contacting method which reflects the module integration, while others [3, 4, 5] recommend a contacting scheme with an infinite number of contact points on the busbar, thus neglecting its resistivity. A current-voltage (I-V) characteristic that would be measured with such an ideal contacting would have a fill factor which we call FFinfcp (infcp = infinite number of contact points) in the following. Experimentally, with a finite number of contacts, it was shown [3, 5] that a specific positioning of the voltage measuring contact (sense contact) allows to approximate a busbar-resistance neglecting contacting scheme. In this work, we transfer this principle concept to the measurement of busbarless solar cells by implementing grid-resistance neglecting contacting schemes. By means of analytical modelling, we study the impact of the number of contacting bars/wires on the FF of current voltage curve measurements of busbarless solar cells with different finger resistivity. To verify this experimentally, we compare the measurement results of 30 wires and 12 contact bars configurations.
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T. Gewohn, M. Koopmeiners, M. R. Vogt, B. Lim, C. Schinke, and R. Brendel Outdoor Testing Facility for an Experimental Validation of Yield Predictions for Building-Integrated Photovoltaic Modules Presentation/Poster Online Event, 09.09.2020, (37th European Photovoltaic Solar Energy Conference and Exhibition). Abstract | BibTeX | Tags: BIPV, Outdoor @misc{Gewohn2020b,
title = {Outdoor Testing Facility for an Experimental Validation of Yield Predictions for Building-Integrated Photovoltaic Modules}, author = {T Gewohn and M Koopmeiners and M R Vogt and B Lim and C Schinke and R Brendel}, year = {2020}, date = {2020-09-09}, address = {Online Event}, abstract = {In the course of the transformation of the energy system towards renewable energy sources, building-integrated photovoltaics (BIPV) become increasingly important. It allows existing building façades to be used for electrical energy generation, thus avoiding the need for additional space. In order to predict the energy efficiency of a building and the payback period of the BIPV system, a reliable energy yield prognosis is essential. Reference irradiance measurement data is required for validation, to develop more accurate methods for predicting the energy yield of modules on the façade. Validation needs both, measuring the PV yield and the weather data to compare the calculation with the experiment. This must also be done at the same location, because especially for BIPV the local irradiation conditions vary heavily (shading, albedo etc.). Climate and irradiation data are hardly available in the vertical plane. Common energy yield prediction tools show deviations of up to 13.2% [1] when deriving insolation in the vertical plane from verified data for the horizontal plane.}, note = {37th European Photovoltaic Solar Energy Conference and Exhibition}, keywords = {BIPV, Outdoor}, pubstate = {published}, tppubtype = {presentation} } In the course of the transformation of the energy system towards renewable energy sources, building-integrated photovoltaics (BIPV) become increasingly important. It allows existing building façades to be used for electrical energy generation, thus avoiding the need for additional space. In order to predict the energy efficiency of a building and the payback period of the BIPV system, a reliable energy yield prognosis is essential. Reference irradiance measurement data is required for validation, to develop more accurate methods for predicting the energy yield of modules on the façade. Validation needs both, measuring the PV yield and the weather data to compare the calculation with the experiment. This must also be done at the same location, because especially for BIPV the local irradiation conditions vary heavily (shading, albedo etc.). Climate and irradiation data are hardly available in the vertical plane. Common energy yield prediction tools show deviations of up to 13.2% [1] when deriving insolation in the vertical plane from verified data for the horizontal plane.
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G. Koutsourakis, M. Rauer, A. Schmid, G. Bellenda, T. R. Betts, J. C. Blakesley, M. Bliss, Bonilla. J. Castro, K. Bothe, S. Dittmann, J. Lopez-Garcia, W. Herrmann, D. Hinken, R. P. Kenny, R. R. Molinero, D. Pavanello, S. Riechelmann, H. Sträter, A. Vegas, and S. Winter Results of the Bifacial PV Cell and PV Module Power Measurement Round Robin Activity of the PV-Enerate Project Presentation/Poster Online Event, 09.09.2020, (37th European Photovoltaic Solar Energy Conference and Exhibition). Abstract | BibTeX | Tags: Bifacial, IV @misc{Koutsourakis2020,
title = {Results of the Bifacial PV Cell and PV Module Power Measurement Round Robin Activity of the PV-Enerate Project}, author = {G Koutsourakis and M Rauer and A Schmid and G Bellenda and T R Betts and J C Blakesley and M Bliss and J Bonilla Castro and K Bothe and S Dittmann and J Lopez-Garcia and W Herrmann and D Hinken and R P Kenny and R R Molinero and D Pavanello and S Riechelmann and H Sträter and A Vegas and S Winter}, year = {2020}, date = {2020-09-09}, address = {Online Event}, abstract = {Bifacial Photovoltaic (PV) technology is expected to acquire an increased market share of the solar PV industry in the future, due to the ability of bifacial PV modules to collect light from both the front and rear side, increasing the energy yield for a specific available area for a PV system. Accurate measurement procedures for bifacial products result in more accurate energy yield estimates, consequently improving the bankability of bifacial PV technology. The aim of this work is to evaluate the procedures for the measurement of electrical power and short circuit current under standard test conditions (STC) of bifacial solar devices with respect to their applicability in calibration laboratories and production line environments. An intercomparison for bifacial PV cells and modules is carried out between nine different test laboratories across Europe, as part of the PV-Enerate project. The measurement procedures as described in IEC technical specification (TS) 60904-1-2:2019 for both single-sided and double-sided illumination systems are followed among the different participants, to evaluate the applicability of these procedures. Three different types of bifacial PV cells and three different types of bifacial PV modules are measured. The intercomparison involves measurements with systems using both single and double-sided illumination methods. The uncertainty budgets and systematic differences that these procedures result in between different laboratories are determined and discussed. Specific common mistakes are reported and improvements for the IEC TS 60904-1-2:2019 are proposed as a result of this intercomparison activity.}, note = {37th European Photovoltaic Solar Energy Conference and Exhibition}, keywords = {Bifacial, IV}, pubstate = {published}, tppubtype = {presentation} } Bifacial Photovoltaic (PV) technology is expected to acquire an increased market share of the solar PV industry in the future, due to the ability of bifacial PV modules to collect light from both the front and rear side, increasing the energy yield for a specific available area for a PV system. Accurate measurement procedures for bifacial products result in more accurate energy yield estimates, consequently improving the bankability of bifacial PV technology. The aim of this work is to evaluate the procedures for the measurement of electrical power and short circuit current under standard test conditions (STC) of bifacial solar devices with respect to their applicability in calibration laboratories and production line environments. An intercomparison for bifacial PV cells and modules is carried out between nine different test laboratories across Europe, as part of the PV-Enerate project. The measurement procedures as described in IEC technical specification (TS) 60904-1-2:2019 for both single-sided and double-sided illumination systems are followed among the different participants, to evaluate the applicability of these procedures. Three different types of bifacial PV cells and three different types of bifacial PV modules are measured. The intercomparison involves measurements with systems using both single and double-sided illumination methods. The uncertainty budgets and systematic differences that these procedures result in between different laboratories are determined and discussed. Specific common mistakes are reported and improvements for the IEC TS 60904-1-2:2019 are proposed as a result of this intercomparison activity.
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G. Oreski, C. Barretta, L. Castillon, P. Christöfl, and M. Köntges Importance of BOM Control and IEC 61215 Scope of Application Presentation/Poster Online Event, 09.09.2020, (37th European Photovoltaic Solar Energy Conference and Exhibition). @misc{Oreski2020,
title = {Importance of BOM Control and IEC 61215 Scope of Application}, author = {G Oreski and C Barretta and L Castillon and P Christöfl and M. Köntges}, year = {2020}, date = {2020-09-09}, address = {Online Event}, abstract = {The area of reliability and durability of PV modules and systems is accepted as crucial and important by industry and policy makers and has the highest priority. Without an understanding of life-time costs, inappropriate materials or components might be used, resulting in pre-mature failure. Currently, also a “one module type fits all” approach is commonly used in PV industry, where one standard module design and unified material quality level composition is used for applications in widely varying climatic conditions and setups around the world.}, note = {37th European Photovoltaic Solar Energy Conference and Exhibition}, keywords = {BOM}, pubstate = {published}, tppubtype = {presentation} } The area of reliability and durability of PV modules and systems is accepted as crucial and important by industry and policy makers and has the highest priority. Without an understanding of life-time costs, inappropriate materials or components might be used, resulting in pre-mature failure. Currently, also a “one module type fits all” approach is commonly used in PV industry, where one standard module design and unified material quality level composition is used for applications in widely varying climatic conditions and setups around the world.
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T. Pernau, C. Derricks, G. Hahn, L. Helmich, A. Herguth, J. Schmidt, and D. Walter Upgrade Technologies for Silicon Photovoltaics – Part I: Industrial Solution to Minimize the Negative Impact of Light Induced Degradation Presentation/Poster Online Event, 09.09.2020, (37th European Photovoltaic Solar Energy Conference and Exhibition). @misc{Pernau2020,
title = {Upgrade Technologies for Silicon Photovoltaics – Part I: Industrial Solution to Minimize the Negative Impact of Light Induced Degradation}, author = {T Pernau and C Derricks and G Hahn and L Helmich and A Herguth and J Schmidt and D Walter}, year = {2020}, date = {2020-09-09}, address = {Online Event}, abstract = {This is Part I of the summary of a joint research project on optimum reduction of boronoxygen related degradation and passivated contacts for PERC-based solar cells. It includes the application of investigated technologies into potential future cell designs such as PERT and bifacial solar cells. The joint project was merged from two individual project suggestions and therefore had two parts. Project part I: industrial solution to minimise the negative impact of light induced degradation (LID) investigate and understand the nature of the degradation effect apply the experimental results and concepts to industrially suppress LID develop an optimized integrated firing-regeneration process for industrial application Project part II: tunnel-oxide passivated contacts (TOPCon) for PERC cells and beyond (not part of this abstract, handed in as a separate abstract to this conference). This project summary is intended to inform the international community about the activity and the results in the project. The detailed project report (in German) will be published with the TIB (Technische Informationsbibliothek Hannover, Germany) soon.}, note = {37th European Photovoltaic Solar Energy Conference and Exhibition}, keywords = {LID}, pubstate = {published}, tppubtype = {presentation} } This is Part I of the summary of a joint research project on optimum reduction of boronoxygen related degradation and passivated contacts for PERC-based solar cells. It includes the application of investigated technologies into potential future cell designs such as PERT and bifacial solar cells. The joint project was merged from two individual project suggestions and therefore had two parts. Project part I: industrial solution to minimise the negative impact of light induced degradation (LID) investigate and understand the nature of the degradation effect apply the experimental results and concepts to industrially suppress LID develop an optimized integrated firing-regeneration process for industrial application Project part II: tunnel-oxide passivated contacts (TOPCon) for PERC cells and beyond (not part of this abstract, handed in as a separate abstract to this conference). This project summary is intended to inform the international community about the activity and the results in the project. The detailed project report (in German) will be published with the TIB (Technische Informationsbibliothek Hannover, Germany) soon.
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L. David, S. Hübner, B. Min, C. Hollemann, T. Dippell, P. Wohlfart, R. Peibst, and R. Brendel Fired-Only Passivating Poly-Si on Oxide Contacts with DC-Sputtered In-Situ Phosphorous-Doped Silicon Layers Presentation/Poster 08.09.2020, (37th European Photovoltaic Solar Energy Conference and Exhibition). Abstract | BibTeX | Tags: POLO @misc{David2020,
title = {Fired-Only Passivating Poly-Si on Oxide Contacts with DC-Sputtered In-Situ Phosphorous-Doped Silicon Layers}, author = {L David and S Hübner and B Min and C Hollemann and T Dippell and P Wohlfart and R Peibst and R Brendel}, year = {2020}, date = {2020-09-08}, abstract = {The PV industry is currently introducing passivating contacts into pilot and mass production lines. A record efficiency of 24.58% was already demonstrated with an n-type industrial solar cell using low pressure vapor deposition (LPCVD) of poly-Si as well as the interfacial oxide [1]. However, the inherent double-sided deposition of LPCVD layers increases process complexity because a subsequent etching step is needed for single-side passivating contacts. Single-side deposition of doped silicon layers using PECVD, APCVD or thermal evaporation is an option for decreasing the complexity. But these CVD techniques use hazardous gases like phosphine for doping and thus require elaborated safety measures. In this work, we report on sputtering with a conventional firing-step as an alternative approach for the fabrication of passivating contacts. It allows single-side deposition at low deposition temperature when compared to LCPVD and PECVD. In addition no hazardous gases are required for doping. We demonstrate contact deposition by direct current (DC) sputtering of a phosphorous-doped silicon target and use a conventional firing step for contact formation used for hightemperature screen-print metallization. We measure an implied open circuit voltage (iVOC) of up to 695 mV with a median of 680 mV for symmetric P-doped poly-Si on oxide (POLO) samples.}, note = {37th European Photovoltaic Solar Energy Conference and Exhibition}, keywords = {POLO}, pubstate = {published}, tppubtype = {presentation} } The PV industry is currently introducing passivating contacts into pilot and mass production lines. A record efficiency of 24.58% was already demonstrated with an n-type industrial solar cell using low pressure vapor deposition (LPCVD) of poly-Si as well as the interfacial oxide [1]. However, the inherent double-sided deposition of LPCVD layers increases process complexity because a subsequent etching step is needed for single-side passivating contacts. Single-side deposition of doped silicon layers using PECVD, APCVD or thermal evaporation is an option for decreasing the complexity. But these CVD techniques use hazardous gases like phosphine for doping and thus require elaborated safety measures. In this work, we report on sputtering with a conventional firing-step as an alternative approach for the fabrication of passivating contacts. It allows single-side deposition at low deposition temperature when compared to LCPVD and PECVD. In addition no hazardous gases are required for doping. We demonstrate contact deposition by direct current (DC) sputtering of a phosphorous-doped silicon target and use a conventional firing step for contact formation used for hightemperature screen-print metallization. We measure an implied open circuit voltage (iVOC) of up to 695 mV with a median of 680 mV for symmetric P-doped poly-Si on oxide (POLO) samples.
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P. Jäger, V. Mertens, U. Baumann, and T. Dullweber Advanced Chemical Model for the Diffusion Mechanism of Phosphorus into the Silicon Wafer during POCl3 Diffusion Presentation/Poster Online Event, 08.09.2020, (37th European Photovoltaic Solar Energy Conference and Exhibition). Abstract | BibTeX | Tags: POCl3 @misc{Jäger2020,
title = {Advanced Chemical Model for the Diffusion Mechanism of Phosphorus into the Silicon Wafer during POCl3 Diffusion}, author = {P Jäger and V Mertens and U Baumann and T Dullweber}, year = {2020}, date = {2020-09-08}, address = {Online Event}, abstract = {Since decades, the POCl3 diffusion is the main process technology to form the pn-junction of industrial silicon solar cells. However, the understanding of the detailed phosphorus (P) diffusion mechanism is still an active research topic. Already in 1964 Kooi et al. [1] proposed that during the drive-in in nitrogen (N2) the P2O5 in the PSG reacts with Si from the wafer to SiO2 (which instantaneously dissolves in the PSG) and P which diffuses into the Si wafer, leading to very high P surface concentrations in the Si wafer. In recent years, new POCl3 diffusion recipes have been developed which apply oxygen (O2) during the drive-in, which limits the diffusion of phosphorus into the Si wafer. Hence significantly lower phosphorus surface concentration can be obtained, enabling very low J0e values close to 20 fA/cm2 [2,3,4] which was a major contributor to increased PERC conversion efficiencies in the past years. To explain the limitation of phosphorus diffusion by O2 atmosphere, two contradicting models have been proposed. Werner et al. [5] showed that the O2 from the atmosphere grows an interfacial SiO2 layer between the PSG and the Si wafer, with increasing SiO2 thickness with longer oxidation time. Hence, they propose that the SiO2 acts as a barrier against the diffusion of phosphorus into the Si wafer. In contrast, Li et al. [6] measured a constant SiO2 thickness of around 5 nm and suggested that free phosphorus in the PSG, which is formed by the reaction of Si with P2O5, is oxidized to P2O5 again by the O2 from the atmosphere. Hence, it remains in the PSG rather than diffusing as P into the Si wafer. One systematic difference between the two studies is that Werner et al. apply the O2 flow throughout the complete drive-in time whereas Li et al. shut down the O2 flow during drive-in. In this contribution, we aim at identifying the exact chemical mechanism for the limitation of the diffusion of phosphorus during drive-in in O2 atmosphere. We systematically vary the drive-in time in O2 atmosphere and additionally investigate the effect of a subsequent drive-in in N2.}, note = {37th European Photovoltaic Solar Energy Conference and Exhibition}, keywords = {POCl3}, pubstate = {published}, tppubtype = {presentation} } Since decades, the POCl3 diffusion is the main process technology to form the pn-junction of industrial silicon solar cells. However, the understanding of the detailed phosphorus (P) diffusion mechanism is still an active research topic. Already in 1964 Kooi et al. [1] proposed that during the drive-in in nitrogen (N2) the P2O5 in the PSG reacts with Si from the wafer to SiO2 (which instantaneously dissolves in the PSG) and P which diffuses into the Si wafer, leading to very high P surface concentrations in the Si wafer. In recent years, new POCl3 diffusion recipes have been developed which apply oxygen (O2) during the drive-in, which limits the diffusion of phosphorus into the Si wafer. Hence significantly lower phosphorus surface concentration can be obtained, enabling very low J0e values close to 20 fA/cm2 [2,3,4] which was a major contributor to increased PERC conversion efficiencies in the past years. To explain the limitation of phosphorus diffusion by O2 atmosphere, two contradicting models have been proposed. Werner et al. [5] showed that the O2 from the atmosphere grows an interfacial SiO2 layer between the PSG and the Si wafer, with increasing SiO2 thickness with longer oxidation time. Hence, they propose that the SiO2 acts as a barrier against the diffusion of phosphorus into the Si wafer. In contrast, Li et al. [6] measured a constant SiO2 thickness of around 5 nm and suggested that free phosphorus in the PSG, which is formed by the reaction of Si with P2O5, is oxidized to P2O5 again by the O2 from the atmosphere. Hence, it remains in the PSG rather than diffusing as P into the Si wafer. One systematic difference between the two studies is that Werner et al. apply the O2 flow throughout the complete drive-in time whereas Li et al. shut down the O2 flow during drive-in. In this contribution, we aim at identifying the exact chemical mechanism for the limitation of the diffusion of phosphorus during drive-in in O2 atmosphere. We systematically vary the drive-in time in O2 atmosphere and additionally investigate the effect of a subsequent drive-in in N2.
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M. R. Vogt, S. Riechelmann, Gracia. A. M. Amillo, A. Driesse, A. Kokka, P. Kärhä, C. Schinke, K. Bothe, J. C. Blakesley, E. Music, F. Plag, G. Friesen, G. Corbellini, N. Riedel-Lyngskær, R. M. E. Valckenborg, M. Schweiger, and W. Herrmann Interlaboratory Comparison of the PV Module Energy Rating Standard IEC 61853-3 and Reference Parameter Set for the PV Community Presentation/Poster Online Event, 08.09.2020, (37th European Photovoltaic Solar Energy Conference and Exhibition). Abstract | BibTeX | Tags: Energy Rating @misc{Vogt2020,
title = {Interlaboratory Comparison of the PV Module Energy Rating Standard IEC 61853-3 and Reference Parameter Set for the PV Community}, author = {M R Vogt and S Riechelmann and A M Gracia Amillo and A Driesse and A Kokka and P Kärhä and C Schinke and K Bothe and J C Blakesley and E Music and F Plag and G Friesen and G Corbellini and N Riedel-Lyngskær and R M E Valckenborg and M Schweiger and W Herrmann}, year = {2020}, date = {2020-09-08}, address = {Online Event}, abstract = {The IEC 61853 standard series “Photovoltaic (PV) module performance testing and energy rating” was completed in 2018 with the publication of parts (3 and 4) [1, 2]. The series aims to provide a standardized measure for PV module performance, namely the Climate Specific Energy Rating (CSER) in Part 3. For this purpose, reference climate data are specified in Part 4 of the standard. The CSER relates the module efficiency in the reference climates to the module efficiency under Standard Testing Conditions (STC: 25°C, 1 kW/m², AM1.5)[3] and thus aims to be a more realistic measure of a modules outdoor performance. The standard also defines a procedure for the calculation of CSER in Part 3. However, the specific implementation of the calculation is left to the user, and some steps in the procedure leave room for interpretation. This may lead to deviations between different implementations. To date, there is no reference parameter set available to the PV community, which could be used to verify the correct implementation of the CSER calculation. This interlaboratory comparison of CSER calculation, with results from ten different institutions, aims to provide such reference parameter set for the community, removing errors from the individual implementations and establishing best practices for the calculation steps that are not clearly defined in the standard.}, note = {37th European Photovoltaic Solar Energy Conference and Exhibition}, keywords = {Energy Rating}, pubstate = {published}, tppubtype = {presentation} } The IEC 61853 standard series “Photovoltaic (PV) module performance testing and energy rating” was completed in 2018 with the publication of parts (3 and 4) [1, 2]. The series aims to provide a standardized measure for PV module performance, namely the Climate Specific Energy Rating (CSER) in Part 3. For this purpose, reference climate data are specified in Part 4 of the standard. The CSER relates the module efficiency in the reference climates to the module efficiency under Standard Testing Conditions (STC: 25°C, 1 kW/m², AM1.5)[3] and thus aims to be a more realistic measure of a modules outdoor performance. The standard also defines a procedure for the calculation of CSER in Part 3. However, the specific implementation of the calculation is left to the user, and some steps in the procedure leave room for interpretation. This may lead to deviations between different implementations. To date, there is no reference parameter set available to the PV community, which could be used to verify the correct implementation of the CSER calculation. This interlaboratory comparison of CSER calculation, with results from ten different institutions, aims to provide such reference parameter set for the community, removing errors from the individual implementations and establishing best practices for the calculation steps that are not clearly defined in the standard.
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D. C. Walter, D. Bredemeier, V. V. Voronkov, R. Falster, and J. Schmidt Disappearance of Hydrogen-Boron-Pairs in Silicon during Illumination and Its Relevance to Lifetime Degradation and Regeneration Effects in Solar Cells Presentation/Poster Online Event, 07.09.2020, (37th European Photovoltaic Solar Energy Conference and Exhibition). Abstract | BibTeX | Tags: Hydrogen-Boron-Pairs @misc{Walter2020,
title = {Disappearance of Hydrogen-Boron-Pairs in Silicon during Illumination and Its Relevance to Lifetime Degradation and Regeneration Effects in Solar Cells}, author = {D C Walter and D Bredemeier and V V Voronkov and R Falster and J Schmidt}, year = {2020}, date = {2020-09-07}, address = {Online Event}, abstract = {Over the last years, hydrogen has been identified to play a vital role in lifetime degradation and regeneration in multicrystalline silicon (mc-Si), an effect often denoted LeTID1. A similar effect has also been observed on float zone silicon (FZ-Si)2. Moreover, hydrogen is also believed to be the relevant component for the permanent deactivation of boron-oxygen defects (lifetime regeneration) in Czochralski-grown silicon (Cz- Si)3. In all cases, the samples are exposed to comparable physical conditions - illumination and elevated temperatures. Consequently, it appears reasonable that the same physical effects related to hydrogen happen within these different materials. In this contribution, we focus on a well-known complex in hydrogenated silicon, the hydrogen-boron (HB) pair4, which allows us to directly determine the absolute hydrogen concentration in the silicon bulk. We demonstrate here, that HB-pairs disappear under illumination at elevated temperatures –by an electron-enhanced backward formation of hydrogen dimers. In addition, we show that the loss time of HB depends critically on the excess carrier density and proceeds via two stages, a fast initial loss and a slower subsequent loss. Since hydrogen is assumed to be important for several lifetime degradation and regeneration effects, the present study can be regarded as the missing link to fully explain a variety of degradation/regeneration phenomena reported in solar cells over the last couple of years.}, note = {37th European Photovoltaic Solar Energy Conference and Exhibition}, keywords = {Hydrogen-Boron-Pairs}, pubstate = {published}, tppubtype = {presentation} } Over the last years, hydrogen has been identified to play a vital role in lifetime degradation and regeneration in multicrystalline silicon (mc-Si), an effect often denoted LeTID1. A similar effect has also been observed on float zone silicon (FZ-Si)2. Moreover, hydrogen is also believed to be the relevant component for the permanent deactivation of boron-oxygen defects (lifetime regeneration) in Czochralski-grown silicon (Cz- Si)3. In all cases, the samples are exposed to comparable physical conditions - illumination and elevated temperatures. Consequently, it appears reasonable that the same physical effects related to hydrogen happen within these different materials. In this contribution, we focus on a well-known complex in hydrogenated silicon, the hydrogen-boron (HB) pair4, which allows us to directly determine the absolute hydrogen concentration in the silicon bulk. We demonstrate here, that HB-pairs disappear under illumination at elevated temperatures –by an electron-enhanced backward formation of hydrogen dimers. In addition, we show that the loss time of HB depends critically on the excess carrier density and proceeds via two stages, a fast initial loss and a slower subsequent loss. Since hydrogen is assumed to be important for several lifetime degradation and regeneration effects, the present study can be regarded as the missing link to fully explain a variety of degradation/regeneration phenomena reported in solar cells over the last couple of years.
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F. Haase, B. Min, C. Hollemann, J. Krügener, R. Brendel, and R. Peibst Fully Screen-Printed Silicon Solar Cells with Local Al-BSF Base Contact and a Voc of 711 mV Presentation/Poster Online Event, 07.09.2020, (37th European Photovoltaic Solar Energy Conference and Exhibition). Abstract | BibTeX | Tags: POLO @misc{Haase2020b,
title = {Fully Screen-Printed Silicon Solar Cells with Local Al-BSF Base Contact and a Voc of 711 mV}, author = {F Haase and B Min and C Hollemann and J Krügener and R Brendel and R Peibst}, year = {2020}, date = {2020-09-07}, address = {Online Event}, abstract = {We investigate the open circuit voltage potential of local aluminum-back surface fields (Al-BSF) on cell level. We implement these contacts in a cell process, which uses almost the same process equipment as PERC cells [1,2]. The most limiting factor in PERC cells is the emitter and emitter contact recombination that typically limits the open circuit voltage to values below 700 mV. We eliminate this losses channel by substituting the P-diffused emitter by a passivating n-type poly-Silicon on Oxide (POLO) contact. We place this contact on the rear side because of its strong free carrier absorption. The Al-BSF contacts are also located at the rear side to avoid front-side shading. Figure 1 shows the resulting POLO-IBC cell structure with interdigitated back contacts that uses Al-BSF for the hole selective contact and n-type POLO for the electron selective contact.}, note = {37th European Photovoltaic Solar Energy Conference and Exhibition}, keywords = {POLO}, pubstate = {published}, tppubtype = {presentation} } We investigate the open circuit voltage potential of local aluminum-back surface fields (Al-BSF) on cell level. We implement these contacts in a cell process, which uses almost the same process equipment as PERC cells [1,2]. The most limiting factor in PERC cells is the emitter and emitter contact recombination that typically limits the open circuit voltage to values below 700 mV. We eliminate this losses channel by substituting the P-diffused emitter by a passivating n-type poly-Silicon on Oxide (POLO) contact. We place this contact on the rear side because of its strong free carrier absorption. The Al-BSF contacts are also located at the rear side to avoid front-side shading. Figure 1 shows the resulting POLO-IBC cell structure with interdigitated back contacts that uses Al-BSF for the hole selective contact and n-type POLO for the electron selective contact.
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B. Min, A. Merkle, T. Brendemühl, N. Wehmeier, Y. Larionova, B. Beier, L. David, H. Schulte-Huxel, T. Dullweber, R. Peibst, and R. Brendel POLO Back Junction: An Elegant Way to Implement Electron-Collecting Passivating Contacts in p-Type Industrial Silicon Solar Cells Presentation/Poster Online Event, 07.09.2020, (37th European Photovoltaic Solar Energy Conference and Exhibition). Abstract | BibTeX | Tags: POLO @misc{Min2020,
title = {POLO Back Junction: An Elegant Way to Implement Electron-Collecting Passivating Contacts in p-Type Industrial Silicon Solar Cells}, author = {B Min and A Merkle and T Brendemühl and N Wehmeier and Y Larionova and B Beier and L David and H Schulte-Huxel and T Dullweber and R Peibst and R Brendel}, year = {2020}, date = {2020-09-07}, address = {Online Event}, abstract = {any manufacturers select passivating contacts as the key technology to boost the cell efficiency level of industrial silicon solar cells. For its implementation in mass production, most of them choose n-type solar cells featuring boron emitter at the front side and electron-collecting passivating contacts at the rear side, which is also known as TOPCon structure. However, it is a huge leap for current cell manufacturers to implement this structure in mainstream production, since it requires multiple pieces of new equipment and the change from p-type to n-type wafers. Hence, there is still a need for an alternative concept for the industrialization of passivating contacts which needs only few pieces of equipment to be added to current PERC production lines. In this paper, we present recent progress of our alternative cell concept to implement electroncollecting passivating contacts in mass production of p-type solar cells. Based on the bifacial PERC+ structure, we only replace the POCl3-diffused emitter by an electron-collecting poly-Si on oxide (POLO) contact while all other components are maintained. It is not necessary to pattern the poly-Si layers since the electron-collecting POLO contacts are located at the cell rear side, resulting in a POLO back junction solar cell [1]. Compared to our previous work [2] we improve, among other things, the front side of POLO back junction cells with 5 busbars achieving an efficiency up to 20.5 % and an open-circuit voltage up to 693 mV.}, note = {37th European Photovoltaic Solar Energy Conference and Exhibition}, keywords = {POLO}, pubstate = {published}, tppubtype = {presentation} } any manufacturers select passivating contacts as the key technology to boost the cell efficiency level of industrial silicon solar cells. For its implementation in mass production, most of them choose n-type solar cells featuring boron emitter at the front side and electron-collecting passivating contacts at the rear side, which is also known as TOPCon structure. However, it is a huge leap for current cell manufacturers to implement this structure in mainstream production, since it requires multiple pieces of new equipment and the change from p-type to n-type wafers. Hence, there is still a need for an alternative concept for the industrialization of passivating contacts which needs only few pieces of equipment to be added to current PERC production lines. In this paper, we present recent progress of our alternative cell concept to implement electroncollecting passivating contacts in mass production of p-type solar cells. Based on the bifacial PERC+ structure, we only replace the POCl3-diffused emitter by an electron-collecting poly-Si on oxide (POLO) contact while all other components are maintained. It is not necessary to pattern the poly-Si layers since the electron-collecting POLO contacts are located at the cell rear side, resulting in a POLO back junction solar cell [1]. Compared to our previous work [2] we improve, among other things, the front side of POLO back junction cells with 5 busbars achieving an efficiency up to 20.5 % and an open-circuit voltage up to 693 mV.
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I. M. Hossain, S. Gharibzadeh, P. Fassl, A. Mertens, S. Schäfer, M. Rienäcker, T. Wietler, R. Peibst, U. Lemmer, B. S. Richards, and U. W. Paetzold 2D Surface Passivation for Semi-Transparent Perovskite Solar Cells with Engineered Bandgap for 4T Tandem Photovoltaics Presentation/Poster Online Event, 07.09.2020, (37th European Photovoltaic Solar Energy Conference and Exhibition). Abstract | BibTeX | Tags: Tandem @misc{Hossain2020b,
title = {2D Surface Passivation for Semi-Transparent Perovskite Solar Cells with Engineered Bandgap for 4T Tandem Photovoltaics}, author = {I M Hossain and S Gharibzadeh and P Fassl and A Mertens and S Schäfer and M Rienäcker and T Wietler and R Peibst and U Lemmer and B S Richards and U W Paetzold}, year = {2020}, date = {2020-09-07}, address = {Online Event}, abstract = {Wide-bandgap organometal halide perovskite solar cells (PSCs) are key for high performance perovskite-based tandem photovoltaics (PV). In this work, semi-transparent perovskite solar cells (PSCs) with engineered bandgap are passivated by employing a 2D/3D perovskite heterostructure. Irrespective of the perovskite absorber bandgap, devices with 2D/3D heterostructure exhibit a strong enhancement in VOC of around 45 mV compared to reference PSCs without the heterostructure. This is attributed to reduced non-radiative recombination losses at the perovskite/hole transport layer interface. Using this strategy, efficient four-terminal (4T) perovskite/c-Si tandem solar cells with a stabilized power conversion efficiency (PCE) of 25.7% are demonstrated. For the first time, it is shown experimentally that a broad range of bandgaps of the top PSCs is suitable for attaining high-efficiencies in a 4T tandem configuration. In order to further improve the PCE, we developed an indium zinc oxide (IZO) electrode as an alternative rear transparent conductive oxide, which reduces parasitic absorption losses and potentially allows further improvement in the tandem PCEs.}, note = {37th European Photovoltaic Solar Energy Conference and Exhibition}, keywords = {Tandem}, pubstate = {published}, tppubtype = {presentation} } Wide-bandgap organometal halide perovskite solar cells (PSCs) are key for high performance perovskite-based tandem photovoltaics (PV). In this work, semi-transparent perovskite solar cells (PSCs) with engineered bandgap are passivated by employing a 2D/3D perovskite heterostructure. Irrespective of the perovskite absorber bandgap, devices with 2D/3D heterostructure exhibit a strong enhancement in VOC of around 45 mV compared to reference PSCs without the heterostructure. This is attributed to reduced non-radiative recombination losses at the perovskite/hole transport layer interface. Using this strategy, efficient four-terminal (4T) perovskite/c-Si tandem solar cells with a stabilized power conversion efficiency (PCE) of 25.7% are demonstrated. For the first time, it is shown experimentally that a broad range of bandgaps of the top PSCs is suitable for attaining high-efficiencies in a 4T tandem configuration. In order to further improve the PCE, we developed an indium zinc oxide (IZO) electrode as an alternative rear transparent conductive oxide, which reduces parasitic absorption losses and potentially allows further improvement in the tandem PCEs.
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P. Pärisch Status quo Solarthermie – Ertragskontrolle und neueste Entwicklungen Presentation/Poster Cottbus, Germany, 28.08.2020, (Workshop „Klimaneutraler Gebäudebestand durch Pauschalmiete?“). BibTeX | Tags: Ertragskontrolle, Kollektorentwicklungen zur Stagnationsvermeidung @misc{Pärisch2020e,
title = {Status quo Solarthermie – Ertragskontrolle und neueste Entwicklungen}, author = {P Pärisch}, year = {2020}, date = {2020-08-28}, address = {Cottbus, Germany}, note = {Workshop „Klimaneutraler Gebäudebestand durch Pauschalmiete?“}, keywords = {Ertragskontrolle, Kollektorentwicklungen zur Stagnationsvermeidung}, pubstate = {published}, tppubtype = {presentation} } |
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Y. Larionova, H. Schulte-Huxel, B. Min, S. Schäfer, T. Kluge, H. Mehlich, R. Brendel, and R. Peibst Ultra-Thin Poly-Si Layers: Passivation Quality, Utilization of Charge Carriers Generated in the Poly-Si and Application on Screen-Printed Double-Side Contacted Polycrystalline Si on Oxide Cells Journal Article Forthcoming Solar RRL 2000177, Forthcoming. Abstract | Links | BibTeX | Tags: passivating contacts, Polycrystalline silicon, silicon solar cells, Transparent conducting oxides @article{Larionova2020,
title = {Ultra-Thin Poly-Si Layers: Passivation Quality, Utilization of Charge Carriers Generated in the Poly-Si and Application on Screen-Printed Double-Side Contacted Polycrystalline Si on Oxide Cells}, author = {Y Larionova and H Schulte-Huxel and B Min and S Schäfer and T Kluge and H Mehlich and R Brendel and R Peibst}, doi = {10.1002/solr.202000177}, year = {2020}, date = {2020-08-07}, journal = {Solar RRL}, pages = {2000177}, abstract = {Herein, the various measures to improve the efficiency of large-area screen-printed double-side contacted polycrystalline Si on oxide (POLO)-cells are experimentally demonstrated. The short-circuit current density Jsc increases by 0.6 mA cm−2 upon reducing the thickness of poly-Si from 25 to 10 nm due to the reduction of the parasitic absorption in the poly-Si layer at the textured front side of the cell. Additionally, it is shown for the first time that the minority carriers generated by light absorbed in the poly-Si layer can at least partially be transferred into the crystalline Si base. Remarkably high implied open-circuit voltage Voc,impl values are achieved with n-type cell precursors by introducing an hydrogenation step by AlxOy after reducing the poly-Si thickness, and by an additional annealing step after sputtering of transparent conductive oxides (TCOs). All cell precursors show Voc,impl values of up to 740 mV independent of the poly-Si thickness. A reduction in the open-circuit voltage Voc is observed during back-end processing to 728 mV as measured on the final cells. A certified cell energy conversion efficiency of 22.3% is reported.}, keywords = {passivating contacts, Polycrystalline silicon, silicon solar cells, Transparent conducting oxides}, pubstate = {forthcoming}, tppubtype = {article} } Herein, the various measures to improve the efficiency of large-area screen-printed double-side contacted polycrystalline Si on oxide (POLO)-cells are experimentally demonstrated. The short-circuit current density Jsc increases by 0.6 mA cm−2 upon reducing the thickness of poly-Si from 25 to 10 nm due to the reduction of the parasitic absorption in the poly-Si layer at the textured front side of the cell. Additionally, it is shown for the first time that the minority carriers generated by light absorbed in the poly-Si layer can at least partially be transferred into the crystalline Si base. Remarkably high implied open-circuit voltage Voc,impl values are achieved with n-type cell precursors by introducing an hydrogenation step by AlxOy after reducing the poly-Si thickness, and by an additional annealing step after sputtering of transparent conductive oxides (TCOs). All cell precursors show Voc,impl values of up to 740 mV independent of the poly-Si thickness. A reduction in the open-circuit voltage Voc is observed during back-end processing to 728 mV as measured on the final cells. A certified cell energy conversion efficiency of 22.3% is reported.
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T. Dullweber, M. Stöhr, C. Kruse, F. Haase, M. Rudolph, B. Beier, P. Jäger, V. Mertens, R. Peibst, and R. Brendel Solar Energy Materials and Solar Cells 212 , 110586, (2020), ISSN: 0927-0248. Abstract | Links | BibTeX | Tags: a-Si fingers, Carrier Selective Contacts, PERC, PERC+, POLO, Shadow mask, TOPCon @article{Dullweber2020c,
title = {Evolutionary PERC+ solar cell efficiency projection towards 24% evaluating shadow-mask-deposited poly-Si fingers below the Ag front contact as next improvement step}, author = {T Dullweber and M Stöhr and C Kruse and F Haase and M Rudolph and B Beier and P Jäger and V Mertens and R Peibst and R Brendel}, doi = {10.1016/j.solmat.2020.110586}, issn = {0927-0248}, year = {2020}, date = {2020-08-01}, journal = {Solar Energy Materials and Solar Cells}, volume = {212}, pages = {110586}, abstract = {Monofacial PERC and bifacial PERC + solar cells have become the mainstream solar cell technology exhibiting conversion efficiencies around 22.5% in mass production. We determine a specific saturation current density J0,Ag = 1400 fA/cm2 of the screen-printed Ag front contact. When weighted with the contact area fraction of 3.0% the Ag metal contacts contribute 42 fA/cm2 to the total J0,total = 130 fA/cm2 thereby being a main limitation of the Voc. We investigate carrier selective poly-Si on oxide (POLO) fingers below the screen-printed Ag contacts of PERC + solar cells in order to minimize contact recombination. We name this solar cell PERC + POLO. Numerical simulations reveal that PERC + POLO cells exhibit an efficiency potential up to 24.1% which is 0.3%abs. higher compared to PERC + solar cells. In order to enable low-cost manufacturing of poly-Si fingers, we investigate for the first time the deposition of suitable a-Si fingers by plasma-enhanced chemical vapour deposition (PECVD) through a shadow mask in a vacuum chamber. We demonstrate a-Si fingers as narrow as 70 μm and as high as 250 nm. The parasitic deposition below the mask increases the a-Si finger width by less than 30 μm compared to the mask opening width. First test wafers demonstrate an implied Voc up to 716 mV of PECVD a-Si layers which are crystalized and doped in a subsequent POCl3 diffusion. Applying this process sequence, PERC + POLO cells could be manufactured with the established industrial PERC + process only adding the PECVD deposition of a-Si fingers through a shadow mask.}, keywords = {a-Si fingers, Carrier Selective Contacts, PERC, PERC+, POLO, Shadow mask, TOPCon}, pubstate = {published}, tppubtype = {article} } Monofacial PERC and bifacial PERC + solar cells have become the mainstream solar cell technology exhibiting conversion efficiencies around 22.5% in mass production. We determine a specific saturation current density J0,Ag = 1400 fA/cm2 of the screen-printed Ag front contact. When weighted with the contact area fraction of 3.0% the Ag metal contacts contribute 42 fA/cm2 to the total J0,total = 130 fA/cm2 thereby being a main limitation of the Voc. We investigate carrier selective poly-Si on oxide (POLO) fingers below the screen-printed Ag contacts of PERC + solar cells in order to minimize contact recombination. We name this solar cell PERC + POLO. Numerical simulations reveal that PERC + POLO cells exhibit an efficiency potential up to 24.1% which is 0.3%abs. higher compared to PERC + solar cells. In order to enable low-cost manufacturing of poly-Si fingers, we investigate for the first time the deposition of suitable a-Si fingers by plasma-enhanced chemical vapour deposition (PECVD) through a shadow mask in a vacuum chamber. We demonstrate a-Si fingers as narrow as 70 μm and as high as 250 nm. The parasitic deposition below the mask increases the a-Si finger width by less than 30 μm compared to the mask opening width. First test wafers demonstrate an implied Voc up to 716 mV of PECVD a-Si layers which are crystalized and doped in a subsequent POCl3 diffusion. Applying this process sequence, PERC + POLO cells could be manufactured with the established industrial PERC + process only adding the PECVD deposition of a-Si fingers through a shadow mask.
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R. Brendel, R. Niepelt, D. Bredemeier, and P. Pärisch Niedersachsen in die Sonne: Die Solarenergie in der Energiewende Presentation/Poster Online, 23.06.2020, (3. Niedersächsisches Forum Solarenergie). BibTeX | Tags: Energiewende @misc{Brendel2020,
title = {Niedersachsen in die Sonne: Die Solarenergie in der Energiewende}, author = {R Brendel and R Niepelt and D Bredemeier and P Pärisch}, year = {2020}, date = {2020-06-23}, address = {Online}, note = {3. Niedersächsisches Forum Solarenergie}, keywords = {Energiewende}, pubstate = {published}, tppubtype = {presentation} } |