Veröffentlichungen
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J. Krügener, M. Rienäcker, S. Schäfer, M. Sanchez, S. Wolter, R. Brendel, S. John, H. J. Osten, and R. Peibst Photonic crystals for highly efficient silicon single junction solar cells Artikel Solar Energy Materials and Solar Cells 233 , 111337, (2021), ISSN: 0927-0248. Abstract | Links | BibTeX | Schlagwörter: Inverted pyramid texture, Photolithography, Photonic crystals, silicon, surface passivation @article{Krügener2021b,
title = {Photonic crystals for highly efficient silicon single junction solar cells}, author = {J Krügener and M Rienäcker and S Schäfer and M Sanchez and S Wolter and R Brendel and S John and H J Osten and R Peibst}, doi = {10.1016/j.solmat.2021.111337}, issn = {0927-0248}, year = {2021}, date = {2021-12-01}, journal = {Solar Energy Materials and Solar Cells}, volume = {233}, pages = {111337}, abstract = {The maximum achievable silicon single junction solar cell efficiency is limited by intrinsic recombination and by its limited capability of absorbing sun light. For Lambertian light trapping the maximum theoretical solar cell efficiency is around 29.5%. Recently a new approach for light trapping has been proposed for silicon photovoltaics. Highly regular structures with a size in the range of the wavelengths of the incident light act as so-called photonic crystals. Such structures allow wave-interference light trapping beyond the Lambertian limit. Applying these photonic crystals to silicon solar cells can help to reduce the absorber thickness and thus to minimizing the unavoidable intrinsic recombination. From a simulation study, we can conclude that 31.6% is the maximum possible single junction solar cell efficiency for a 15 μm-thin substrate. Furthermore, we present a process flow for the preparation of regular inverted pyramid structure, that acts as photonic crystal. Finally, regular inverted pyramid structures are prepared on polished and shiny-etched, i. e. on surfaces with a certain roughness, substrates. Surface passivation of these structured surfaces shows as good lifetimes as on conventional randomly pyramid textured surface. Excellent total saturation current densities on asymmetric samples of 4 ± 2 fA/cm2 for n-type and of 4.5 ± 2.2 fA/cm2 on p-type substrates are obtained.}, keywords = {Inverted pyramid texture, Photolithography, Photonic crystals, silicon, surface passivation}, pubstate = {published}, tppubtype = {article} } The maximum achievable silicon single junction solar cell efficiency is limited by intrinsic recombination and by its limited capability of absorbing sun light. For Lambertian light trapping the maximum theoretical solar cell efficiency is around 29.5%. Recently a new approach for light trapping has been proposed for silicon photovoltaics. Highly regular structures with a size in the range of the wavelengths of the incident light act as so-called photonic crystals. Such structures allow wave-interference light trapping beyond the Lambertian limit. Applying these photonic crystals to silicon solar cells can help to reduce the absorber thickness and thus to minimizing the unavoidable intrinsic recombination. From a simulation study, we can conclude that 31.6% is the maximum possible single junction solar cell efficiency for a 15 μm-thin substrate. Furthermore, we present a process flow for the preparation of regular inverted pyramid structure, that acts as photonic crystal. Finally, regular inverted pyramid structures are prepared on polished and shiny-etched, i. e. on surfaces with a certain roughness, substrates. Surface passivation of these structured surfaces shows as good lifetimes as on conventional randomly pyramid textured surface. Excellent total saturation current densities on asymmetric samples of 4 ± 2 fA/cm2 for n-type and of 4.5 ± 2.2 fA/cm2 on p-type substrates are obtained.
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C. Hollemann, N. Folchert, S. P. Harvey, P. Stradins, D. L. Young, Lima. Salles. C. de Souza, M. Rienäcker, F. Haase, R. Brendel, and R. Peibst Solar Energy Materials and Solar Cells 231 , 111297, (2021), ISSN: 0927-0248. Abstract | Links | BibTeX | Schlagwörter: Firing, Hydrogen, MarcoPOLO, modeling, passivating contacts, POLO @article{Hollemann2021c,
title = {Changes in hydrogen concentration and defect state density at the poly-Si/SiOx/c-Si interface due to firing}, author = {C Hollemann and N Folchert and S P Harvey and P Stradins and D L Young and C Lima Salles de Souza and M Rienäcker and F Haase and R Brendel and R Peibst}, doi = {10.1016/j.solmat.2021.111297}, issn = {0927-0248}, year = {2021}, date = {2021-10-01}, journal = {Solar Energy Materials and Solar Cells}, volume = {231}, pages = {111297}, abstract = {We determined the density of defect states of poly-Si/SiOx/c-Si junctions featuring a wet chemical interfacial oxide from lifetime measurements using the MarcoPOLO model to calculate recombination and contact resistance in poly-Si/SiOx/c-Si-junctions. In samples that did not receive any hydrogen treatment, the Dit,cSi is about 2 × 1012 cm−2 eV⁻1 before firing and rises to 3–7 × 1012 cm⁻2 eV⁻1 during firing at measured peak temperatures between 620 °C and 863 °C. To address the question of why AlOx/SiNy stacks in contrast to pure SiNy layers for hydrogenation during firing provides better passivation quality, we have measured the hydrogen concentrations at the poly-Si/SiOx/c-Si interface as a function of AlOx layer thickness and compared these to J0 and calculated Dit,c-Si values. We observe an increase of the hydrogen concentration at the SiOx/c-Si interface upon firing as a function of the firing temperature that exceeds the defect concentrations at the interface several times. However, the AlOx layer thickness appears to cause an increase in hydrogen concentration at the SiOx/c-Si interface in these samples rather than exhibiting a hydrogen blocking property.}, keywords = {Firing, Hydrogen, MarcoPOLO, modeling, passivating contacts, POLO}, pubstate = {published}, tppubtype = {article} } We determined the density of defect states of poly-Si/SiOx/c-Si junctions featuring a wet chemical interfacial oxide from lifetime measurements using the MarcoPOLO model to calculate recombination and contact resistance in poly-Si/SiOx/c-Si-junctions. In samples that did not receive any hydrogen treatment, the Dit,cSi is about 2 × 1012 cm−2 eV⁻1 before firing and rises to 3–7 × 1012 cm⁻2 eV⁻1 during firing at measured peak temperatures between 620 °C and 863 °C. To address the question of why AlOx/SiNy stacks in contrast to pure SiNy layers for hydrogenation during firing provides better passivation quality, we have measured the hydrogen concentrations at the poly-Si/SiOx/c-Si interface as a function of AlOx layer thickness and compared these to J0 and calculated Dit,c-Si values. We observe an increase of the hydrogen concentration at the SiOx/c-Si interface upon firing as a function of the firing temperature that exceeds the defect concentrations at the interface several times. However, the AlOx layer thickness appears to cause an increase in hydrogen concentration at the SiOx/c-Si interface in these samples rather than exhibiting a hydrogen blocking property.
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L. Helmich, D. C. Walter, R. Falster, V. V. Voronkov, and J. Schmidt Solar Energy Materials and Solar Cells 232 , 111340, (2021), ISSN: 0927-0248. Abstract | Links | BibTeX | Schlagwörter: boron-oxygen defect, Carrier lifetime, Czochralski-grown silicon, Hydrogen, LID, regeneration @article{Helmich2021c,
title = {Impact of hydrogen on the boron-oxygen-related lifetime degradation and regeneration kinetics in crystalline silicon}, author = {L Helmich and D C Walter and R Falster and V V Voronkov and J Schmidt}, doi = {10.1016/j.solmat.2021.111340}, issn = {0927-0248}, year = {2021}, date = {2021-10-01}, journal = {Solar Energy Materials and Solar Cells}, volume = {232}, pages = {111340}, abstract = {We examine the impact of hydrogen on the boron-oxygen-related lifetime degradation and regeneration kinetics in boron-doped p-type Czochralski-grown silicon wafers. We introduce the hydrogen into the silicon bulk by rapid thermal annealing. The hydrogen source are hydrogen-rich silicon nitride (SiNx:H) layers. Aluminum oxide (Al2O3) layers of varying thickness are placed in-between the silicon wafer surfaces and the SiNx:H layers. By varying the Al2O3 thickness, which acts as an effective hydrogen diffusion barrier, the hydrogen bulk content is varied over more than one order of magnitude. The hydrogen content is determined from measured wafer resistivity changes. In order to examine the impact of hydrogen on the degradation kinetics, all samples are illuminated at a light intensity of 0.1 suns near room temperature. We observe no impact of the in-diffused hydrogen content on the degradation rate constant, confirming that hydrogen is not involved in the boron-oxygen degradation mechanism. The regeneration experiments at 160°C and 1 sun, however, show a clear dependence on the hydrogen content with a linear increase of the regeneration rate constant with increasing bulk hydrogen concentration. However, extrapolation of our measurements toward a zero in-diffused hydrogen content shows that the regeneration is still working even without any in-diffused hydrogen. Hence, our measurements demonstrate that there are two distinct regeneration processes taking place. This is in good agreement with a recently proposed defect reaction model and is also in agreement with the finding that the permanent boron-oxygen deactivation also works on non-fired solar cells, though at a lower rate.}, keywords = {boron-oxygen defect, Carrier lifetime, Czochralski-grown silicon, Hydrogen, LID, regeneration}, pubstate = {published}, tppubtype = {article} } We examine the impact of hydrogen on the boron-oxygen-related lifetime degradation and regeneration kinetics in boron-doped p-type Czochralski-grown silicon wafers. We introduce the hydrogen into the silicon bulk by rapid thermal annealing. The hydrogen source are hydrogen-rich silicon nitride (SiNx:H) layers. Aluminum oxide (Al2O3) layers of varying thickness are placed in-between the silicon wafer surfaces and the SiNx:H layers. By varying the Al2O3 thickness, which acts as an effective hydrogen diffusion barrier, the hydrogen bulk content is varied over more than one order of magnitude. The hydrogen content is determined from measured wafer resistivity changes. In order to examine the impact of hydrogen on the degradation kinetics, all samples are illuminated at a light intensity of 0.1 suns near room temperature. We observe no impact of the in-diffused hydrogen content on the degradation rate constant, confirming that hydrogen is not involved in the boron-oxygen degradation mechanism. The regeneration experiments at 160°C and 1 sun, however, show a clear dependence on the hydrogen content with a linear increase of the regeneration rate constant with increasing bulk hydrogen concentration. However, extrapolation of our measurements toward a zero in-diffused hydrogen content shows that the regeneration is still working even without any in-diffused hydrogen. Hence, our measurements demonstrate that there are two distinct regeneration processes taking place. This is in good agreement with a recently proposed defect reaction model and is also in agreement with the finding that the permanent boron-oxygen deactivation also works on non-fired solar cells, though at a lower rate.
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A. Morlier, S. Blankemeyer, R. Witteck, H. Schulte-Huxel, T. Daschinger, S. Bräunig, M. Köntges, and R. Brendel Photovoltaic Modules with Natural Materials for a Seamless Building Integration Presentation/Poster Online Event, 09.09.2021, (38th European Photovoltaic Solar Energy Conference and Exhibition). Abstract | BibTeX | Schlagwörter: BIPV @misc{Morlier2021b,
title = {Photovoltaic Modules with Natural Materials for a Seamless Building Integration}, author = {A Morlier and S Blankemeyer and R Witteck and H Schulte-Huxel and T Daschinger and S Bräunig and M Köntges and R Brendel}, year = {2021}, date = {2021-09-09}, address = {Online Event}, abstract = {We demonstrate the feasibility of photovoltaic (PV) modules integrating natural materials such as stone or wood veneer in order to hide the solar cells. The aim of this integration is not only to impart a natural material appearance but also to create a similar surface texture and haptic for the modules. To achieve this, we realize sample modules with a natural stone outer layer on the sunny side or with a wood veneer between the front glass and the cell.}, note = {38th European Photovoltaic Solar Energy Conference and Exhibition}, keywords = {BIPV}, pubstate = {published}, tppubtype = {presentation} } We demonstrate the feasibility of photovoltaic (PV) modules integrating natural materials such as stone or wood veneer in order to hide the solar cells. The aim of this integration is not only to impart a natural material appearance but also to create a similar surface texture and haptic for the modules. To achieve this, we realize sample modules with a natural stone outer layer on the sunny side or with a wood veneer between the front glass and the cell.
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M. Stöhr, J. Aprojanz, R. Brendel, and T. Dullweber Firing-Stable PECVD SiOxNy/n-Poly-Si Passivating Contacts for High-Efficiency Silicon Solar Cells Presentation/Poster Online Event, 09.09.2021, (38th European Photovoltaic Solar Energy Conference and Exhibition). Abstract | BibTeX | Schlagwörter: Poly-Si @misc{Stöhr2021b,
title = {Firing-Stable PECVD SiOxNy/n-Poly-Si Passivating Contacts for High-Efficiency Silicon Solar Cells}, author = {M. Stöhr and J Aprojanz and R Brendel and T Dullweber}, year = {2021}, date = {2021-09-09}, address = {Online Event}, abstract = {Passivating contacts based on SiOx / poly-crystalline silicon (SiOx/poly-Si) layer stacks [1-3] are a promising technology for next-generation high-efficiency industrial silicon solar cells potentially succeeding mainstream passivated emitter and rear cells (PERC) and bifacial PERC+ solar cells [4,5]. However, the gain in conversion efficiency is only in the range of 0.5 – 2.0%abs. and therefore a costeffective manufacturing process sequence of SiOx/poly-Si passivating contacts in industrial silicon solar cells is indispensable. LPCVD poly-Si deposition is inherently double-sided requiring a single-sided removal and firing-stable in-situ PECVD SiOx/poly-Si layers are still in development [6]. Hence, improved deposition processes are necessary as well as physical knowledge on the surface passivation mechanism. In this study, we develop a potentially cost-effective PECVD SiOxNy/n-a-Si deposition process which demonstrates an excellent surface passivation quality after annealing to SiOxNy/n-poly-Si, PECVD SiNx deposition and firing. In order to analyze the impact of different hydrogenation processes on the surface passivation, we process samples including a forming gas anneal (FGA) after SiNx deposition and before firing. Also, we compare the PECVD SiOxNy interface to a thermally grown SiOx interface applying identical process steps. We perform photo-conductance lifetime measurements of the symmetrical passivated lifetime samples along the processing sequence and quantify the passivation by the effective carrier lifetime eff, the saturation current density J0 and the implied open circuit voltage iVOC.}, note = {38th European Photovoltaic Solar Energy Conference and Exhibition}, keywords = {Poly-Si}, pubstate = {published}, tppubtype = {presentation} } Passivating contacts based on SiOx / poly-crystalline silicon (SiOx/poly-Si) layer stacks [1-3] are a promising technology for next-generation high-efficiency industrial silicon solar cells potentially succeeding mainstream passivated emitter and rear cells (PERC) and bifacial PERC+ solar cells [4,5]. However, the gain in conversion efficiency is only in the range of 0.5 – 2.0%abs. and therefore a costeffective manufacturing process sequence of SiOx/poly-Si passivating contacts in industrial silicon solar cells is indispensable. LPCVD poly-Si deposition is inherently double-sided requiring a single-sided removal and firing-stable in-situ PECVD SiOx/poly-Si layers are still in development [6]. Hence, improved deposition processes are necessary as well as physical knowledge on the surface passivation mechanism. In this study, we develop a potentially cost-effective PECVD SiOxNy/n-a-Si deposition process which demonstrates an excellent surface passivation quality after annealing to SiOxNy/n-poly-Si, PECVD SiNx deposition and firing. In order to analyze the impact of different hydrogenation processes on the surface passivation, we process samples including a forming gas anneal (FGA) after SiNx deposition and before firing. Also, we compare the PECVD SiOxNy interface to a thermally grown SiOx interface applying identical process steps. We perform photo-conductance lifetime measurements of the symmetrical passivated lifetime samples along the processing sequence and quantify the passivation by the effective carrier lifetime eff, the saturation current density J0 and the implied open circuit voltage iVOC.
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R. Peibst, R. Steib, A. Semmelmann, S. Lutz, M. Brunner, A. Schiessl, S. Wöhe, R. Wecker, F. Haase, H. Schulte-Huxel, S. Blankemeyer, M. Köntges, C. Hollemann, R. Brendel, G. Wetzel, J. Krügener, H-J. Nonnenmacher, H. Mehlich, A. Salavei, K. Ding, A. Lambertz, B. E. Pieters, S. Janke, B. Stannowski, and L. Korte Demonstration of Feeding VIPV-Converted Energy into the High-Voltage On-Board Network of Practical Light Commercial Vehicles for Range Extension Presentation/Poster Online Event, 09.09.2021, (38th European Photovoltaic Solar Energy Conference and Exhibition). Abstract | BibTeX | Schlagwörter: VIPV @misc{Peibst2021d,
title = {Demonstration of Feeding VIPV-Converted Energy into the High-Voltage On-Board Network of Practical Light Commercial Vehicles for Range Extension}, author = {R Peibst and R Steib and A Semmelmann and S Lutz and M Brunner and A Schiessl and S Wöhe and R Wecker and F Haase and H Schulte-Huxel and S Blankemeyer and M Köntges and C Hollemann and R Brendel and G Wetzel and J Krügener and H-J Nonnenmacher and H Mehlich and A Salavei and K Ding and A Lambertz and B E Pieters and S Janke and B Stannowski and L Korte}, year = {2021}, date = {2021-09-09}, address = {Online Event}, abstract = {Vehicle Integrated Photovoltaics (VIPV) can contribute to the reducon of CO2 emissions from the transport sector and reduces peak loads for electric grid [1,2]. So far, it has been applied in “praccal vehicles” mainly for indirect onboard funcons such as cooling or air condioning [3]. In this case, the PV generated electricity is fed into the low voltage (12 V) onboard network with a rather limited baery capacity < 1 kWh. To also ulize PVconverted energy for driving and thus for reducon of charging events from the grid [4], it is required to feed it into the high voltage onboard network. This approach also has the advantage that the large capacity of the high voltage baery can be accessed to store all PVconverted energy, e.g. when charging during parking mes. However, the DC/DC conversion from the typical output voltage of maximum power point trackers (MPPTs) at 12 V to the 400 V level is not trivial and requires a welldesigned buckboost converter with a smart operaon strategy, a high conversion efficiency and low standby power consumpon. Furthermore, safety issues and possible interferences with crical driving funcons are much more severe when interfacing to the high voltage onboard network. In this work, we address these challenges (together with the requirement to develop highly efficient and durable VIPV modules and fast MPPT trackers) by seng up a demonstrator vehicle to experimentally demonstrate a high solar coverage > 20 % for driving a praccal light commercial electrical vehicle.}, note = {38th European Photovoltaic Solar Energy Conference and Exhibition}, keywords = {VIPV}, pubstate = {published}, tppubtype = {presentation} } Vehicle Integrated Photovoltaics (VIPV) can contribute to the reducon of CO2 emissions from the transport sector and reduces peak loads for electric grid [1,2]. So far, it has been applied in “praccal vehicles” mainly for indirect onboard funcons such as cooling or air condioning [3]. In this case, the PV generated electricity is fed into the low voltage (12 V) onboard network with a rather limited baery capacity < 1 kWh. To also ulize PVconverted energy for driving and thus for reducon of charging events from the grid [4], it is required to feed it into the high voltage onboard network. This approach also has the advantage that the large capacity of the high voltage baery can be accessed to store all PVconverted energy, e.g. when charging during parking mes. However, the DC/DC conversion from the typical output voltage of maximum power point trackers (MPPTs) at 12 V to the 400 V level is not trivial and requires a welldesigned buckboost converter with a smart operaon strategy, a high conversion efficiency and low standby power consumpon. Furthermore, safety issues and possible interferences with crical driving funcons are much more severe when interfacing to the high voltage onboard network. In this work, we address these challenges (together with the requirement to develop highly efficient and durable VIPV modules and fast MPPT trackers) by seng up a demonstrator vehicle to experimentally demonstrate a high solar coverage > 20 % for driving a praccal light commercial electrical vehicle.
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C. Barretta, G. Oreski, A. Macher, J. Ascencio-Vásquez, M. Topic, M. Köntges, and K. Resch-Fauster Effects of Climate and Microclimate on EVA Degradation from Field Aged PV Modules Presentation/Poster Online Event, 08.09.2021, (38th European Photovoltaic Solar Energy Conference and Exhibition). Abstract | BibTeX | Schlagwörter: PV Module @misc{Barretta2021,
title = {Effects of Climate and Microclimate on EVA Degradation from Field Aged PV Modules}, author = {C Barretta and G Oreski and A Macher and J Ascencio-Vásquez and M Topic and M Köntges and K Resch-Fauster}, year = {2021}, date = {2021-09-08}, address = {Online Event}, abstract = {The importance of testing materials and modules in different climates has become more and more relevant in recent years. The concept of “one size fits all”, namely one type of module fits all environmental and climatic conditions, showed its limits and new concepts of climate specific module design as well as artificial ageing tests were brought to the attention of the PV community [1]. New models able to predict power degradation in different locations, and therefore able to make lifetime estimations were developed in recent studies [2] and a worldwide mapping of degradation rates have been presented [3]. These studies show how the climatic conditions of tropical climates strongly affect the performances of the PV modules. In these cases, the most relevant power losses were detected and correlated to failure modes such as yellowing of the encapsulant, corrosion of metallic interconnections and silver grids, delamination at different interfaces and backsheet cracks, just to name a few.}, note = {38th European Photovoltaic Solar Energy Conference and Exhibition}, keywords = {PV Module}, pubstate = {published}, tppubtype = {presentation} } The importance of testing materials and modules in different climates has become more and more relevant in recent years. The concept of “one size fits all”, namely one type of module fits all environmental and climatic conditions, showed its limits and new concepts of climate specific module design as well as artificial ageing tests were brought to the attention of the PV community [1]. New models able to predict power degradation in different locations, and therefore able to make lifetime estimations were developed in recent studies [2] and a worldwide mapping of degradation rates have been presented [3]. These studies show how the climatic conditions of tropical climates strongly affect the performances of the PV modules. In these cases, the most relevant power losses were detected and correlated to failure modes such as yellowing of the encapsulant, corrosion of metallic interconnections and silver grids, delamination at different interfaces and backsheet cracks, just to name a few.
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C. Schinke, D. Hinken, M. Wolf, K. Bothe, I. Kröger, S. Nevas, and S. Winter Analysis and Correction of Systematic Deviations in Measurements of the Spectral Irradiance of Solar Simulators Presentation/Poster Online Event, 08.09.2021, (38th European Photovoltaic Solar Energy Conference and Exhibition). Abstract | BibTeX | Schlagwörter: solar simulator @misc{Schinke2021c,
title = {Analysis and Correction of Systematic Deviations in Measurements of the Spectral Irradiance of Solar Simulators}, author = {C Schinke and D Hinken and M Wolf and K Bothe and I Kröger and S Nevas and S Winter}, year = {2021}, date = {2021-09-08}, address = {Online Event}, abstract = {The application of spectral mismatch corrections in solar cell characterization and calibration according to the IEC 60904 standard series [1] requires measuring the spectral irradiance distribution of the solar simulator used for this purpose. Accordingly, many laboratories routinely operate spectroradiometers for the acquisition of spectral irradiance data. Recent intercomparisons of solar spectral irradiance measurements between different laboratories show systematic deviations of up to 10% [2], emphasizing the need for a thorough analysis of the measured data in order to facilitate a correct interpretation. In this contribution, we give an overview of the measuring procedure for determining the spectral irradiance of solar simulators and discuss effects that might require a correction in order to determine the spectral irradiance distribution properly, namely: Internal background of the spectroradiometer (dark signal), external and internal stray light, detector nonlinearity and temperature dependence, spectral bandwidth and effective position of the optical reference plane of the measuring head. Moreover, we show how an uncertainty calculation can be set up based on a Monte-Carlo procedure (as outlined in the Guide to the Expression of Uncertainty in Measurement (GUM), supplement 1 [3, 4]), which allows to assess the accuracy of the measured data. As a specific application example, we discuss the determination of spectral irradiance and the required corrections for ISFH CalTeC’s class AAA solar simulator.}, note = {38th European Photovoltaic Solar Energy Conference and Exhibition}, keywords = {solar simulator}, pubstate = {published}, tppubtype = {presentation} } The application of spectral mismatch corrections in solar cell characterization and calibration according to the IEC 60904 standard series [1] requires measuring the spectral irradiance distribution of the solar simulator used for this purpose. Accordingly, many laboratories routinely operate spectroradiometers for the acquisition of spectral irradiance data. Recent intercomparisons of solar spectral irradiance measurements between different laboratories show systematic deviations of up to 10% [2], emphasizing the need for a thorough analysis of the measured data in order to facilitate a correct interpretation. In this contribution, we give an overview of the measuring procedure for determining the spectral irradiance of solar simulators and discuss effects that might require a correction in order to determine the spectral irradiance distribution properly, namely: Internal background of the spectroradiometer (dark signal), external and internal stray light, detector nonlinearity and temperature dependence, spectral bandwidth and effective position of the optical reference plane of the measuring head. Moreover, we show how an uncertainty calculation can be set up based on a Monte-Carlo procedure (as outlined in the Guide to the Expression of Uncertainty in Measurement (GUM), supplement 1 [3, 4]), which allows to assess the accuracy of the measured data. As a specific application example, we discuss the determination of spectral irradiance and the required corrections for ISFH CalTeC’s class AAA solar simulator.
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T. Fellmeth, F. Feldmann, B. Steinhauser, H. Nagel, S. Mack, M. Hermle, F. Torregrosa, A. Ingenito, F-J. Haug, A. Morisset, F. Buchholz, A. Chaudhary, T. Desrues, F. Haase, B. Min, R. Peibst, and L. Tous A Round Robin - HighLiting on the Passivating Contact Technology Presentation/Poster Online Event, 08.09.2021, (38th European Photovoltaic Solar Energy Conference and Exhibition). Abstract | BibTeX | Schlagwörter: passivating contact @misc{Fellmeth2021,
title = {A Round Robin - HighLiting on the Passivating Contact Technology}, author = {T Fellmeth and F Feldmann and B Steinhauser and H Nagel and S Mack and M Hermle and F Torregrosa and A Ingenito and F-J Haug and A Morisset and F Buchholz and A Chaudhary and T Desrues and F Haase and B Min and R Peibst and L Tous}, year = {2021}, date = {2021-09-08}, address = {Online Event}, abstract = {The poly-Si based surface passivation using a thin tunnel oxide also known as “TOPCon” [1] or “POLO” [2] (for simplicity, in the following only the expression “TOPCon” is used) is subjected to an increasing interest from the industry. In the last years, record efficiencies on full sized Si wafers of 24.6 % by Trinasolar [3] and recently of 24.9 % by Jinkosolar have been demonstrated in lab scale production. The aim of this work is to demonstrate the maturity of the TOPCon technology by conducting a round-robin in the leading European PV institutes EPFL, ISC, CEA-INES, ISFH, IMEC and Fraunhofer ISE within the H2020 funded project called HighLite. Deposition tools from various companies using plasma enhanced chemical vapour deposition PECVD and lowpressure chemical vapour deposition LPCVD have been used. Properties of the layers and information of the tools are given in Table 1. N-type Cz-Si wafers were saw damaged etched by ISC Konstanz and distributed to the mentioned institutes to use their best deposition technology to create a n-type TOPCon layer on both sides on the wafer. Despite the differences in the deposition technology, all layers consist of a thin tunnel oxide layer between the c-Si absorber and a phosphorus doped poly-Si layer, which was annealed or POCl3-diffused to transform a- to poly-Si and subsequently capped with a hydrogen- rich dielectric layer. Then, the samples were sent to Fraunhofer ISE for single side screen-printing of a parallel finger pattern and varying finger pitch consisting of nine individual fields (Fig. 1) [4], contact firing and characterization. The dark saturation current-density for a single TOPCon layer J0T as well as the total dark saturation current-density for each field J0 both for metallized and unmetallized areas (Fig. 2) were extracted by the QSSPC [5] J0e analysis from Kimmerle et al. [6] and the modulated photoluminescence Mod-PL [7] method. Finally, transition line method TLM [8] line structures (equidistant lines) were cut off the wafers to obtain the contact resistivity c (Fig. 3).}, note = {38th European Photovoltaic Solar Energy Conference and Exhibition}, keywords = {passivating contact}, pubstate = {published}, tppubtype = {presentation} } The poly-Si based surface passivation using a thin tunnel oxide also known as “TOPCon” [1] or “POLO” [2] (for simplicity, in the following only the expression “TOPCon” is used) is subjected to an increasing interest from the industry. In the last years, record efficiencies on full sized Si wafers of 24.6 % by Trinasolar [3] and recently of 24.9 % by Jinkosolar have been demonstrated in lab scale production. The aim of this work is to demonstrate the maturity of the TOPCon technology by conducting a round-robin in the leading European PV institutes EPFL, ISC, CEA-INES, ISFH, IMEC and Fraunhofer ISE within the H2020 funded project called HighLite. Deposition tools from various companies using plasma enhanced chemical vapour deposition PECVD and lowpressure chemical vapour deposition LPCVD have been used. Properties of the layers and information of the tools are given in Table 1. N-type Cz-Si wafers were saw damaged etched by ISC Konstanz and distributed to the mentioned institutes to use their best deposition technology to create a n-type TOPCon layer on both sides on the wafer. Despite the differences in the deposition technology, all layers consist of a thin tunnel oxide layer between the c-Si absorber and a phosphorus doped poly-Si layer, which was annealed or POCl3-diffused to transform a- to poly-Si and subsequently capped with a hydrogen- rich dielectric layer. Then, the samples were sent to Fraunhofer ISE for single side screen-printing of a parallel finger pattern and varying finger pitch consisting of nine individual fields (Fig. 1) [4], contact firing and characterization. The dark saturation current-density for a single TOPCon layer J0T as well as the total dark saturation current-density for each field J0 both for metallized and unmetallized areas (Fig. 2) were extracted by the QSSPC [5] J0e analysis from Kimmerle et al. [6] and the modulated photoluminescence Mod-PL [7] method. Finally, transition line method TLM [8] line structures (equidistant lines) were cut off the wafers to obtain the contact resistivity c (Fig. 3).
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D. Bredemeier, E. Rott, C. Schinke, T. Gewohn, H. Wagner-Mohnsen, R. Niepelt, and R. Brendel Fast and High-Resolution Calculation of Roof-Top and Façade PV Potentials Using Graphics Processor Accelerated Monte-Carlo Raytracing Presentation/Poster Online Event, 08.09.2021, (38th European Photovoltaic Solar Energy Conference and Exhibition). Abstract | BibTeX | Schlagwörter: PV Potential @misc{Bredemeier2021c,
title = {Fast and High-Resolution Calculation of Roof-Top and Façade PV Potentials Using Graphics Processor Accelerated Monte-Carlo Raytracing}, author = {D Bredemeier and E Rott and C Schinke and T Gewohn and H Wagner-Mohnsen and R Niepelt and R Brendel}, year = {2021}, date = {2021-09-08}, address = {Online Event}, abstract = {Climate change demands a rapid transition of the energy system towards renewable energy sources. Low levelized costs of electricity and a wide range of integration options combined with high modularity makes photovoltaic energy generation a key technology in this transition. Accurate and at the same time fast and scalable methods for estimating the yield of roof-top and façade PV systems are crucial for identifying the overall PV installation potential and the best locations for PV installations with respect to the energy yield. Within this contribution, we implement a graphics processor accelerated monte-carlo raytracing algorithm for the calculation of the energy yield of both roof-top and façade PV systems with high spatial and temporal resolution. Our algorithm works on geodata supplied in the open CityGML format which are widely available from official sources [1, 2]. Since our algorithm is highly parallelized, it can be applied to large scales within reasonable computation time while maintaining the high resolution. Figure 1 shows the calculated irradiance relative to the direct horizontal irradiance for a sample area (≈ 250 × 250 m²) in the city of Hanover (Germany). The calculation of figure 1 takes ≈ 1 hour on a single graphics card with 108 rays while including up to two reflection iterations. We are confident that the computation time can be reduced down to ≈ 20 minutes. Furthermore, by the time of the conference we will have implemented diffuse radiation from the sky. Finally, the PV energy yields are calculated based on the irradiance values using the software package pvlib [3]. Thus, our algorithm is a powerful tool for the evaluation and planning of PV installations on rooftops and façades especially in urban environments.}, note = {38th European Photovoltaic Solar Energy Conference and Exhibition}, keywords = {PV Potential}, pubstate = {published}, tppubtype = {presentation} } Climate change demands a rapid transition of the energy system towards renewable energy sources. Low levelized costs of electricity and a wide range of integration options combined with high modularity makes photovoltaic energy generation a key technology in this transition. Accurate and at the same time fast and scalable methods for estimating the yield of roof-top and façade PV systems are crucial for identifying the overall PV installation potential and the best locations for PV installations with respect to the energy yield. Within this contribution, we implement a graphics processor accelerated monte-carlo raytracing algorithm for the calculation of the energy yield of both roof-top and façade PV systems with high spatial and temporal resolution. Our algorithm works on geodata supplied in the open CityGML format which are widely available from official sources [1, 2]. Since our algorithm is highly parallelized, it can be applied to large scales within reasonable computation time while maintaining the high resolution. Figure 1 shows the calculated irradiance relative to the direct horizontal irradiance for a sample area (≈ 250 × 250 m²) in the city of Hanover (Germany). The calculation of figure 1 takes ≈ 1 hour on a single graphics card with 108 rays while including up to two reflection iterations. We are confident that the computation time can be reduced down to ≈ 20 minutes. Furthermore, by the time of the conference we will have implemented diffuse radiation from the sky. Finally, the PV energy yields are calculated based on the irradiance values using the software package pvlib [3]. Thus, our algorithm is a powerful tool for the evaluation and planning of PV installations on rooftops and façades especially in urban environments.
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V. Mertens, S. Schäfer, M. Stöhr, A. Mercker, A. Köhler, L. Mettner, R. Brendel, N. Ambrosius, T. Pernau, H. Haverkamp, and T. Dullweber Local PECVD SiOxNy/n-Poly-Si Deposition through a Shadow Mask for POLO IBC Solar Cells Presentation/Poster Online Event, 07.09.2021, (38th European Photovoltaic Solar Energy Conference and Exhibition). Abstract | BibTeX | Schlagwörter: IBC @misc{Mertens2021,
title = {Local PECVD SiOxNy/n-Poly-Si Deposition through a Shadow Mask for POLO IBC Solar Cells}, author = {V Mertens and S Schäfer and M Stöhr and A Mercker and A Köhler and L Mettner and R Brendel and N Ambrosius and T Pernau and H Haverkamp and T Dullweber}, year = {2021}, date = {2021-09-07}, address = {Online Event}, abstract = {Passivating contacts using polysilicon on oxide (POLO) show excellent electrical surface passivation of silicon enabling highest conversion efficiencies on of lab-type IBC solar cells and front and back side-contacted solar cells [1, 2]. When combing an n-POLO layer with a local p+ Al-BSF contact formed by Al finger screen-printing as applied in PERC+ solar cells in an IBC cell [3], these so-called POLO IBC solar cells exhibit a simulated conversion efficiency potential of 25.5% [4] with first experimental devices yielding 23.0% efficiency [5]. However, for POLO IBC cells the n-POLO layer needs to be structured when starting from a full area deposition which so far requires several separate process steps such as masking and etching. In this paper, we present a lean POLO IBC solar cell process flow using p-type Cz silicon wafers, where a local SiOxNy/n - poly-Si emitter is formed by PECVD-deposition of SiOxNy/n-a-Si through a glass-based shadow mask followed by a subsequent thermal anneal. The glass-based shadow mask enables a confined PECVD deposition and significantly facilitates the local application of polysilicon [3]. We fabricate POLO IBC solar cell precursors using this process flow and demonstrate the feasibility of the local PECVD SiOxNy/n-a-Si deposition through a shadow mask with light microscope images, carrier lifetime data and implied Voc data. We also show, that a PECVD interfacial oxide can be grown in situ just before n+-amorphous silicon deposition also locally through the shadow mask and give some insights into finger broadening by deposition through a shadow mask. We use planar and textured p-type Cz Si wafers to fabricate IBC solar cell precursors with planar and textured front side and in both cases planar rear side. We apply a full-area wet chemical interfacial oxide or a local in-situ grown PECVD interfacial oxide created by an N2O plasma through a shadow mask. Next, we deposit a local n-a-Si layer through the shadow mask, in case of the samples with in situ interfacial oxide without vacuum break. We deposit two different layer thicknesses of 140 nm and 210 nm for the n-a-Si layers. The subsequent thermal anneal in an inert atmosphere at 850°C forms the POLO junctions. Then both wafer surfaces are coated with PECVD AlOx/SiNy stacks passivating all remaining surfaces which did not receive the local SiOxNy/n-a-Si deposition. All samples receive a firing step at 830°C. At the EUPVSEC conference we target to demonstrate first fully-processed POLO IBC solar cells including a complete rear side metallization by LCO, Al finger printing, and Ag finger printing before firing.}, note = {38th European Photovoltaic Solar Energy Conference and Exhibition}, keywords = {IBC}, pubstate = {published}, tppubtype = {presentation} } Passivating contacts using polysilicon on oxide (POLO) show excellent electrical surface passivation of silicon enabling highest conversion efficiencies on of lab-type IBC solar cells and front and back side-contacted solar cells [1, 2]. When combing an n-POLO layer with a local p+ Al-BSF contact formed by Al finger screen-printing as applied in PERC+ solar cells in an IBC cell [3], these so-called POLO IBC solar cells exhibit a simulated conversion efficiency potential of 25.5% [4] with first experimental devices yielding 23.0% efficiency [5]. However, for POLO IBC cells the n-POLO layer needs to be structured when starting from a full area deposition which so far requires several separate process steps such as masking and etching. In this paper, we present a lean POLO IBC solar cell process flow using p-type Cz silicon wafers, where a local SiOxNy/n - poly-Si emitter is formed by PECVD-deposition of SiOxNy/n-a-Si through a glass-based shadow mask followed by a subsequent thermal anneal. The glass-based shadow mask enables a confined PECVD deposition and significantly facilitates the local application of polysilicon [3]. We fabricate POLO IBC solar cell precursors using this process flow and demonstrate the feasibility of the local PECVD SiOxNy/n-a-Si deposition through a shadow mask with light microscope images, carrier lifetime data and implied Voc data. We also show, that a PECVD interfacial oxide can be grown in situ just before n+-amorphous silicon deposition also locally through the shadow mask and give some insights into finger broadening by deposition through a shadow mask. We use planar and textured p-type Cz Si wafers to fabricate IBC solar cell precursors with planar and textured front side and in both cases planar rear side. We apply a full-area wet chemical interfacial oxide or a local in-situ grown PECVD interfacial oxide created by an N2O plasma through a shadow mask. Next, we deposit a local n-a-Si layer through the shadow mask, in case of the samples with in situ interfacial oxide without vacuum break. We deposit two different layer thicknesses of 140 nm and 210 nm for the n-a-Si layers. The subsequent thermal anneal in an inert atmosphere at 850°C forms the POLO junctions. Then both wafer surfaces are coated with PECVD AlOx/SiNy stacks passivating all remaining surfaces which did not receive the local SiOxNy/n-a-Si deposition. All samples receive a firing step at 830°C. At the EUPVSEC conference we target to demonstrate first fully-processed POLO IBC solar cells including a complete rear side metallization by LCO, Al finger printing, and Ag finger printing before firing.
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L. Nasebandt, B. Min, S. Hübner, T. Dippell, P. Wohlfart, R. Peibst, and R. Brendel Controlling Doping Density in DC-Sputtered In-Situ Phosphorous-Doped Polysilicon Layers for Passivating Contacts Presentation/Poster Online Event, 07.09.2021, (38th European Photovoltaic Solar Energy Conference and Exhibition). Abstract | BibTeX | Schlagwörter: Poly-Si @misc{Nasebandt2021,
title = {Controlling Doping Density in DC-Sputtered In-Situ Phosphorous-Doped Polysilicon Layers for Passivating Contacts}, author = {L Nasebandt and B Min and S Hübner and T Dippell and P Wohlfart and R Peibst and R Brendel}, year = {2021}, date = {2021-09-07}, address = {Online Event}, abstract = {The sputtering technology is attractive for fabricating poly-Si based passivating contacts because it allows single-side deposition without using hazardous gases. However, achieving high level in-situ doping is a challenge because sufficiently highly doped sputtering targets are required [1]. Also, phosphorous can effuse from the silicon target material during high-temperature crystallization of the target. We measure the doping density in DC-sputtered poly-Si layers and study their passivation quality using symmetric lifetime samples. We compare in-situ doped and subsequently furnace annealed samples, with samples that are ex-situ doped by a POCl3 diffusion in a tube furnace. The best sputtered and in-situ doped sample shows an implied open circuit voltage iVOC of 734mV and a J0 of 1.8fA/cm² after a hydrogenation step. We separate Auger and surface recombination in our sputtered poly-Si on oxide (POLO) junctions applying EDNA simulations [2]. Surface recombination strongly dominates.}, note = {38th European Photovoltaic Solar Energy Conference and Exhibition}, keywords = {Poly-Si}, pubstate = {published}, tppubtype = {presentation} } The sputtering technology is attractive for fabricating poly-Si based passivating contacts because it allows single-side deposition without using hazardous gases. However, achieving high level in-situ doping is a challenge because sufficiently highly doped sputtering targets are required [1]. Also, phosphorous can effuse from the silicon target material during high-temperature crystallization of the target. We measure the doping density in DC-sputtered poly-Si layers and study their passivation quality using symmetric lifetime samples. We compare in-situ doped and subsequently furnace annealed samples, with samples that are ex-situ doped by a POCl3 diffusion in a tube furnace. The best sputtered and in-situ doped sample shows an implied open circuit voltage iVOC of 734mV and a J0 of 1.8fA/cm² after a hydrogenation step. We separate Auger and surface recombination in our sputtered poly-Si on oxide (POLO) junctions applying EDNA simulations [2]. Surface recombination strongly dominates.
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L. Tous, J. Govaerts, S. Harrison, C. Carrière, F. Buchholz, A. Halm, A. Faes, G. Nogay, A. Ingenito, F-J. Haug, F. Feldmann, D. Raine, M. Mittag, F. Haase, A. Morlier, M. Bokalič, K. Brecl, M. Topic, J. C. P. Kester, S. Wendlandt, M. Galiazzo, A. Voltan, G. Galbiati, L. Theunissen, F. Torregrosa, M. Grimm, J. Denafas, T. Radavicčius, P. Lukinskas, J. Kaakkunen, T. Savisalo, and T. Regrettier Overview of the Latest Results Achieved in the H2020 Funded Project HighLite Aiming for High-Performance, Low-Cost and Sustainable c-Si PV Modules Tailored for Different Applications Presentation/Poster Online Event, 07.09.2021, (38th European Photovoltaic Solar Energy Conference and Exhibition). Abstract | BibTeX | Schlagwörter: VIPV @misc{Tous2021,
title = {Overview of the Latest Results Achieved in the H2020 Funded Project HighLite Aiming for High-Performance, Low-Cost and Sustainable c-Si PV Modules Tailored for Different Applications}, author = {L Tous and J Govaerts and S Harrison and C Carrière and F Buchholz and A Halm and A Faes and G Nogay and A Ingenito and F-J Haug and F Feldmann and D Raine and M Mittag and F Haase and A Morlier and M Bokalič and K Brecl and M Topic and J C P Kester and S Wendlandt and M Galiazzo and A Voltan and G Galbiati and L Theunissen and F Torregrosa and M Grimm and J Denafas and T Radavicčius and P Lukinskas and J Kaakkunen and T Savisalo and T Regrettier}, year = {2021}, date = {2021-09-07}, address = {Online Event}, abstract = {In this work we give an overview of the latest results achieved within the H2020 funded project called HighLite. We report the progress made when implementing novel layers and processes in existing pilot-lines producing high-efficiency silicon heterojunction (SHJ) and interdigitated back-contact (IBC) cells. We present the work done together with several industrial partners to develop innovative production equipment for the module assembly of cut-cells. Finally, we explain key learnings made so far when tailoring modules for various applications including building-applied PV (BAPV), buildingintegrated PV (BIPV) and vehicle-integrated PV (VIPV).}, note = {38th European Photovoltaic Solar Energy Conference and Exhibition}, keywords = {VIPV}, pubstate = {published}, tppubtype = {presentation} } In this work we give an overview of the latest results achieved within the H2020 funded project called HighLite. We report the progress made when implementing novel layers and processes in existing pilot-lines producing high-efficiency silicon heterojunction (SHJ) and interdigitated back-contact (IBC) cells. We present the work done together with several industrial partners to develop innovative production equipment for the module assembly of cut-cells. Finally, we explain key learnings made so far when tailoring modules for various applications including building-applied PV (BAPV), buildingintegrated PV (BIPV) and vehicle-integrated PV (VIPV).
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M. Rienäcker, Y. Larionova, J. Krügener, S. Wolter, R. Brendel, and R. Peibst Rear side dielectrics on interdigitating p+-(i)-n+ back-contact solar cells – hydrogenation vs. charge effects Presentation/Poster Online Event, 07.09.2021, (38th European Photovoltaic Solar Energy Conference and Exhibition). Abstract | BibTeX | Schlagwörter: IBC @misc{Rienäcker2021b,
title = {Rear side dielectrics on interdigitating p+-(i)-n+ back-contact solar cells – hydrogenation vs. charge effects}, author = {M Rienäcker and Y Larionova and J Krügener and S Wolter and R Brendel and R Peibst}, year = {2021}, date = {2021-09-07}, address = {Online Event}, abstract = {The photovoltaic (PV) market demands for ever higher PV module efficiencies, such that polysilicon-on-oxide (POLO) passivating contacts and interdigitated back-contact (IBC) cell technologies have recently attracted a lot of interest as candidates for the implementation in industrial production in the near future. However, the realization of an IBC cell with POLO junctions for both polarities – a POLO²-IBC cell – requires a separation of the highly defective p + and n + poly-Si regions on the rear side of the cell to avoid parasitic recombination. Inserting an initially undoped, intrinsic (i) region between the p + and n + poly-Si regions – as patented by LG [2] and evaluated by several research groups [8, 3, 12] – was demonstrated to successfully prevent the parasitic recombination in the transition region of ISFH’s 26.1%- efficient POLO²-IBC cell [3, 4]. In order to further improve the conversion efficiency towards 27%, we apply hydrogen-donating dielectric layer stacks to the p + -(i)-n + POLO interdigitating rear side to enhance the passivation quality of the POLO junctions of our 26.1%-efficient cell. We show that electric charges, which are induced by applying a particular hydrogen-donating layer stack on the p + -(i)-n + POLO interdigitating rear side, have a large impact on the performance of the POLO²-IBC cell. It is vital to control the induced charge density to avoid the resulting surface effects, which lead to a strong increase of non-ideal recombination at the p + -(i)-n + poly-Si junction. While this effect is highly pronounced for IBC cells with poly-Si, it is of interest to all types of IBC cells with charged dielectric layers on the interdigitated rear side.}, note = {38th European Photovoltaic Solar Energy Conference and Exhibition}, keywords = {IBC}, pubstate = {published}, tppubtype = {presentation} } The photovoltaic (PV) market demands for ever higher PV module efficiencies, such that polysilicon-on-oxide (POLO) passivating contacts and interdigitated back-contact (IBC) cell technologies have recently attracted a lot of interest as candidates for the implementation in industrial production in the near future. However, the realization of an IBC cell with POLO junctions for both polarities – a POLO²-IBC cell – requires a separation of the highly defective p + and n + poly-Si regions on the rear side of the cell to avoid parasitic recombination. Inserting an initially undoped, intrinsic (i) region between the p + and n + poly-Si regions – as patented by LG [2] and evaluated by several research groups [8, 3, 12] – was demonstrated to successfully prevent the parasitic recombination in the transition region of ISFH’s 26.1%- efficient POLO²-IBC cell [3, 4]. In order to further improve the conversion efficiency towards 27%, we apply hydrogen-donating dielectric layer stacks to the p + -(i)-n + POLO interdigitating rear side to enhance the passivation quality of the POLO junctions of our 26.1%-efficient cell. We show that electric charges, which are induced by applying a particular hydrogen-donating layer stack on the p + -(i)-n + POLO interdigitating rear side, have a large impact on the performance of the POLO²-IBC cell. It is vital to control the induced charge density to avoid the resulting surface effects, which lead to a strong increase of non-ideal recombination at the p + -(i)-n + poly-Si junction. While this effect is highly pronounced for IBC cells with poly-Si, it is of interest to all types of IBC cells with charged dielectric layers on the interdigitated rear side.
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B. Min, N. Wehmeier, H. Schulte-Huxel, R. Witteck, T. Brendemühl, T. Daschinger, F. Haase, Y. Larionova, L. Nasebandt, K. Tsuji, M. Dhamrin, R. Peibst, and R. Brendel Approaching 23% with p-Type Back Junction Solar Cells Featuring Screen-Printed Al Front Grid and Passivating Rear Contacts Presentation/Poster Online Event, 07.09.2021, (38th European Photovoltaic Solar Energy Conference and Exhibition). Abstract | BibTeX | Schlagwörter: POLO BJ @misc{Min2021c,
title = {Approaching 23% with p-Type Back Junction Solar Cells Featuring Screen-Printed Al Front Grid and Passivating Rear Contacts}, author = {B Min and N Wehmeier and H Schulte-Huxel and R Witteck and T Brendemühl and T Daschinger and F Haase and Y Larionova and L Nasebandt and K Tsuji and M Dhamrin and R Peibst and R Brendel}, year = {2021}, date = {2021-09-07}, address = {Online Event}, abstract = {This paper reports the recent progress of p-type back junction (BJ) solar cells featuring passivating polysilicon on oxide (POLO) rear contacts with a cell efficiency of 22.74% as independently confirmed by ISFH CalTeC in Germany. The cell area is 244.5 cm². To our knowledge, this is the highest efficiency for a p-type solar cell with screen-printed Al grid on textured front side. Compared to our previous work [1], we improve the passivation quality beneath rear metal fingers by increasing the SiNy capping layer thickness at the rear side. This prevents spiking of poly-Si layers by screen-printed silver during the firing step, resulting in a record Voc of 716 mV for a fully screen-printed large-area p-type solar cell with Al-alloyed local contacts. The Al front grid is improved by upgraded Al paste which enables narrower metal fingers with higher aspect ratio compared to previous experiments. We investigate the morphology of the of p + layers beneath the Al fingers by scanning electron microscopy. In addition, the UV resistance of the AlOx/SiNy passivation stack on undiffused textured front side is investigated by applying UV transparent encapsulant materials.}, note = {38th European Photovoltaic Solar Energy Conference and Exhibition}, keywords = {POLO BJ}, pubstate = {published}, tppubtype = {presentation} } This paper reports the recent progress of p-type back junction (BJ) solar cells featuring passivating polysilicon on oxide (POLO) rear contacts with a cell efficiency of 22.74% as independently confirmed by ISFH CalTeC in Germany. The cell area is 244.5 cm². To our knowledge, this is the highest efficiency for a p-type solar cell with screen-printed Al grid on textured front side. Compared to our previous work [1], we improve the passivation quality beneath rear metal fingers by increasing the SiNy capping layer thickness at the rear side. This prevents spiking of poly-Si layers by screen-printed silver during the firing step, resulting in a record Voc of 716 mV for a fully screen-printed large-area p-type solar cell with Al-alloyed local contacts. The Al front grid is improved by upgraded Al paste which enables narrower metal fingers with higher aspect ratio compared to previous experiments. We investigate the morphology of the of p + layers beneath the Al fingers by scanning electron microscopy. In addition, the UV resistance of the AlOx/SiNy passivation stack on undiffused textured front side is investigated by applying UV transparent encapsulant materials.
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C. Monokroussos, M. Yoshita, K. Yamagoe, H. Müllejans, D. Pavanello, K. Ramspeck, D. Hinken, K. Bothe, Y. Fujita, G. Arnoux, F. Pinto, R. Ambigapathy, Q. Shi, H. Wilterdink, Y. Chen, Y. Ping, and J. Q. Gao Interlaboratory Comparison of Voltage Sweep Methods Used for the Electrical Characterization of Encapsulated High-Efficiency c-Si Solar Cells Presentation/Poster Online Event, 07.09.2021, (38th European Photovoltaic Solar Energy Conference and Exhibition). Abstract | BibTeX | Schlagwörter: Interlaboratory comparison @misc{Monokroussos2021,
title = {Interlaboratory Comparison of Voltage Sweep Methods Used for the Electrical Characterization of Encapsulated High-Efficiency c-Si Solar Cells}, author = {C Monokroussos and M Yoshita and K Yamagoe and H Müllejans and D Pavanello and K Ramspeck and D Hinken and K Bothe and Y Fujita and G Arnoux and F Pinto and R Ambigapathy and Q Shi and H Wilterdink and Y Chen and Y Ping and J Q Gao}, year = {2021}, date = {2021-09-07}, address = {Online Event}, abstract = {The power measurements of high efficiency (HE) c-Si technologies have been a challenge for both production lines and calibration laboratories for over two decades due to their slow response causing hysteresis in IV measurements(in particular on pulsed solar simulators) and their substantial spectral mismatch to reference devices (typical of monocrystalline silicon). Recent developmentsin high efficiency (HE) c-Si technologies(such as p-type PERC, n-type PERT, HJT and IBC) made the accuracy of their calibration increasingly important. In parallel advances in measurement systems have opened new possibilities in characterization. In this context a HE encapsulated solar cellround-robin was initiated.}, note = {38th European Photovoltaic Solar Energy Conference and Exhibition}, keywords = {Interlaboratory comparison}, pubstate = {published}, tppubtype = {presentation} } The power measurements of high efficiency (HE) c-Si technologies have been a challenge for both production lines and calibration laboratories for over two decades due to their slow response causing hysteresis in IV measurements(in particular on pulsed solar simulators) and their substantial spectral mismatch to reference devices (typical of monocrystalline silicon). Recent developmentsin high efficiency (HE) c-Si technologies(such as p-type PERC, n-type PERT, HJT and IBC) made the accuracy of their calibration increasingly important. In parallel advances in measurement systems have opened new possibilities in characterization. In this context a HE encapsulated solar cellround-robin was initiated.
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R. Peibst Beyond Single Junction Efficiencies Presentation/Poster Online Event, 06.09.2021, (38th European Photovoltaic Solar Energy Conference and Exhibition). @misc{Peibst2021c,
title = {Beyond Single Junction Efficiencies}, author = {R Peibst}, year = {2021}, date = {2021-09-06}, address = {Online Event}, note = {38th European Photovoltaic Solar Energy Conference and Exhibition}, keywords = {solar}, pubstate = {published}, tppubtype = {presentation} } |
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R. Witteck, M. Siebert, I. Kunze, and M. Köntges Hot Cells in High-Power PV Modules with Solar Cells from Larger Silicon Wafer Formats Presentation/Poster Online Event, 06.09.2021, (38th European Photovoltaic Solar Energy Conference and Exhibition). Abstract | BibTeX | Schlagwörter: hot cells @misc{Witteck2021bb,
title = {Hot Cells in High-Power PV Modules with Solar Cells from Larger Silicon Wafer Formats}, author = {R Witteck and M Siebert and I Kunze and M Köntges}, year = {2021}, date = {2021-09-06}, address = {Online Event}, abstract = {We demonstrate that partial shading of a single solar cell in a state-of-the-art high-power photovoltaic (PV) module with three bypass diodes can result in hot cells with critical module peak temperatures of 196°C. The PV module under test features 144 bifacial PERC+ half-cells of M6 silicon wafer format with a cell area of (166 x 83) mm2 . The module’s measured maximum power output is 437 WP. We test three cells of the PV module in an extended IEC 61215-2 MQT09 hot-spot endurance test for 5 h in a steady-state sun simulator. All shaded cells reach steady-state temperatures above 175°C. Our results are essential for improving the long-term stability of new high-power modules with M10- or M12-sized cells and power outputs over 500 WP against partial shading.}, note = {38th European Photovoltaic Solar Energy Conference and Exhibition}, keywords = {hot cells}, pubstate = {published}, tppubtype = {presentation} } We demonstrate that partial shading of a single solar cell in a state-of-the-art high-power photovoltaic (PV) module with three bypass diodes can result in hot cells with critical module peak temperatures of 196°C. The PV module under test features 144 bifacial PERC+ half-cells of M6 silicon wafer format with a cell area of (166 x 83) mm2 . The module’s measured maximum power output is 437 WP. We test three cells of the PV module in an extended IEC 61215-2 MQT09 hot-spot endurance test for 5 h in a steady-state sun simulator. All shaded cells reach steady-state temperatures above 175°C. Our results are essential for improving the long-term stability of new high-power modules with M10- or M12-sized cells and power outputs over 500 WP against partial shading.
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J. Govaerts, K. Moliya, B. Luo, T. Borgers, Van. R. Dyck, A. S. H. van der Heide, L. Tous, A. Morlier, F. Lisco, L. Cerasti, M. Galiazzo, and J. Poortmans The Potential of Glass-Fibre-Reinforcement: (Thermo-)Mechanical Testing of Light-Weight PV Modules Presentation/Poster Online Event, 06.09.2021, (38th European Photovoltaic Solar Energy Conference and Exhibition). Abstract | BibTeX | Schlagwörter: PV Module @misc{Govaerts2021,
title = {The Potential of Glass-Fibre-Reinforcement: (Thermo-)Mechanical Testing of Light-Weight PV Modules}, author = {J Govaerts and K Moliya and B Luo and T Borgers and R Van Dyck and A S H van der Heide and L Tous and A Morlier and F Lisco and L Cerasti and M Galiazzo and J Poortmans}, year = {2021}, date = {2021-09-06}, address = {Online Event}, abstract = {In this work we report on our approach on integrating c-Si PV into lightweight structures, in particular towards vehicle integration. To this end we want to get rid of the (bulk weight of the) glass but seek a suitable replacement in terms of mechanical stability. First we elaborate on the most basic standards and norms that VIPV products should relate to in terms of (thermo-)mechanical testing. Then, for the experimental part, 2 concepts are investigated. In a first approach, we reinforced the encapsulant with glass fibre material, while in a second one we applied a dedicated glass-fibre-reinforced sheet as a replacement of the backsheet. In both cases we stay as close as possible to using commercially available material. Extending our previously reported work, we then elaborate for each approach the testing that has been carried out so far, and what is still ongoing and being planned in the short-term future (before the conference): indicating the promising results so far on thermal cycling and vibration testing, the hail impact testing is a challenge to be tackled still.}, note = {38th European Photovoltaic Solar Energy Conference and Exhibition}, keywords = {PV Module}, pubstate = {published}, tppubtype = {presentation} } In this work we report on our approach on integrating c-Si PV into lightweight structures, in particular towards vehicle integration. To this end we want to get rid of the (bulk weight of the) glass but seek a suitable replacement in terms of mechanical stability. First we elaborate on the most basic standards and norms that VIPV products should relate to in terms of (thermo-)mechanical testing. Then, for the experimental part, 2 concepts are investigated. In a first approach, we reinforced the encapsulant with glass fibre material, while in a second one we applied a dedicated glass-fibre-reinforced sheet as a replacement of the backsheet. In both cases we stay as close as possible to using commercially available material. Extending our previously reported work, we then elaborate for each approach the testing that has been carried out so far, and what is still ongoing and being planned in the short-term future (before the conference): indicating the promising results so far on thermal cycling and vibration testing, the hail impact testing is a challenge to be tackled still.
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S. Wendlandt, J. Govaerts, A. S. H. van der Heide, J. Kaakkunen, T. Savisalo, A. Morlier, D. Raine, and D. Röder Angle of Incidence Study at Photovoltaic Modules with Polymer Front Sheet Presentation/Poster Online Event, 06.09.2021, (38th European Photovoltaic Solar Energy Conference and Exhibition). Abstract | BibTeX | Schlagwörter: PV Module @misc{Wendlandt2021,
title = {Angle of Incidence Study at Photovoltaic Modules with Polymer Front Sheet}, author = {S Wendlandt and J Govaerts and A S H van der Heide and J Kaakkunen and T Savisalo and A Morlier and D Raine and D Röder}, year = {2021}, date = {2021-09-06}, address = {Online Event}, abstract = {For years, photovoltaic systems have been successfully installed on a large scale on open spaces as well as on (BAPV) and on buildings (BIPV). For the applications, PV modules in the classic glass-backsheet or glass-glass design are mostly used because their properties are well known. For BIPV and further on for automotive applications it makes sense to reduce the weight of the modules in order not to overload the building’s loadbearing capacity statics as well as for vehicles to minimize their energy consumption. One approach for weight reduction is by replacing glass with polymer materials. The light coupling on typical PV modules is largely optimized by means of an anti-reflective coating (ARC) on the front glass. This has not yet been done for polymer front sheets, but this paper will take the first step and characterize different lightweight approaches based on polymer front sheets with different solar cell types (SHJ, IBC) for their skewing behavior and then give an evaluation of the electrical yield for angle-dependent installation as well as for different locations.}, note = {38th European Photovoltaic Solar Energy Conference and Exhibition}, keywords = {PV Module}, pubstate = {published}, tppubtype = {presentation} } For years, photovoltaic systems have been successfully installed on a large scale on open spaces as well as on (BAPV) and on buildings (BIPV). For the applications, PV modules in the classic glass-backsheet or glass-glass design are mostly used because their properties are well known. For BIPV and further on for automotive applications it makes sense to reduce the weight of the modules in order not to overload the building’s loadbearing capacity statics as well as for vehicles to minimize their energy consumption. One approach for weight reduction is by replacing glass with polymer materials. The light coupling on typical PV modules is largely optimized by means of an anti-reflective coating (ARC) on the front glass. This has not yet been done for polymer front sheets, but this paper will take the first step and characterize different lightweight approaches based on polymer front sheets with different solar cell types (SHJ, IBC) for their skewing behavior and then give an evaluation of the electrical yield for angle-dependent installation as well as for different locations.
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N. Wehmeier, F. Kiefer, T. Brendemühl, L. Mettner, S. J. Wolter, F. Haase, R. Peibst, M. Holthausen, D. Mispelkamp, C. Mader, C. Daeschlein, O. Wunnicke, and S. Kajari-Schröder Inkjet-Printed In Situ Structured and Doped Polysilicon on Oxide Junctions Artikel IEEE Journal of Photovoltaics 1-9, (2021). Abstract | Links | BibTeX | Schlagwörter: Inkjet printing, interdigitated back contact (IBC) structure, liquid silicon (LiSi) ink, passivating contacts, silicon solar cells @article{Wehmeier2021b,
title = {Inkjet-Printed In Situ Structured and Doped Polysilicon on Oxide Junctions}, author = {N Wehmeier and F Kiefer and T Brendemühl and L Mettner and S J Wolter and F Haase and R Peibst and M Holthausen and D Mispelkamp and C Mader and C Daeschlein and O Wunnicke and S Kajari-Schröder}, doi = {10.1109/JPHOTOV.2021.3094131}, year = {2021}, date = {2021-09-01}, journal = {IEEE Journal of Photovoltaics}, pages = {1-9}, abstract = {We investigate the inkjet printing of liquid silicon ink to form in situ doped and structured passivating contacts. The ink consists of neopentasilane oligomers in solvents and decomposes into amorphous silicon with a short anneal. By printing boron- and phosphorus-doped ink on silicon oxide, polycrystalline silicon on oxide (POLO) junctions for both p-type and n-type polarities (POLO²) are formed and the saturation current densities as low as 5 fA/cm2 are achieved for n+-POLO junctions. We perform a structured printing in interdigitated back contact (IBC) geometry achieving emitter and base fingers with an average finger height of up to 103 nm. The application of inkjet printing allows for a simplification of POLO and POLO2 solar cell processing. In particular, for POLO2-IBC cells, a lean process flow is facilitated.}, keywords = {Inkjet printing, interdigitated back contact (IBC) structure, liquid silicon (LiSi) ink, passivating contacts, silicon solar cells}, pubstate = {published}, tppubtype = {article} } We investigate the inkjet printing of liquid silicon ink to form in situ doped and structured passivating contacts. The ink consists of neopentasilane oligomers in solvents and decomposes into amorphous silicon with a short anneal. By printing boron- and phosphorus-doped ink on silicon oxide, polycrystalline silicon on oxide (POLO) junctions for both p-type and n-type polarities (POLO²) are formed and the saturation current densities as low as 5 fA/cm2 are achieved for n+-POLO junctions. We perform a structured printing in interdigitated back contact (IBC) geometry achieving emitter and base fingers with an average finger height of up to 103 nm. The application of inkjet printing allows for a simplification of POLO and POLO2 solar cell processing. In particular, for POLO2-IBC cells, a lean process flow is facilitated.
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T. Gewohn, C. Schinke, B. Lim, and R. Brendel Predicting color and short-circuit current of colored BIPV modules Artikel AIP Advances 11 (9), 095104, (2021). Links | BibTeX | Schlagwörter: Colorimetry, MATLAB, optical properties, photovoltaics, quantum efficiency, Reflection spectroscopy, Solar Cells @article{Gewohn2021b,
title = {Predicting color and short-circuit current of colored BIPV modules}, author = {T Gewohn and C Schinke and B Lim and R Brendel}, doi = {10.1063/5.0063140}, year = {2021}, date = {2021-09-01}, journal = {AIP Advances}, volume = {11}, number = {9}, pages = {095104}, keywords = {Colorimetry, MATLAB, optical properties, photovoltaics, quantum efficiency, Reflection spectroscopy, Solar Cells}, pubstate = {published}, tppubtype = {article} } |
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C. Hollemann, M. Rienäcker, A. Soeriyadi, C. Madumelu, F. Haase, J. Krügener, B. Hallam, R. Brendel, and R. Peibst Firing stability of tube furnace-annealed n-type poly-Si on oxide junctions Artikel Forthcoming Progress in Photovoltaics: Research and Applications Forthcoming. Abstract | Links | BibTeX | Schlagwörter: blistering, Firing, passivating contacts, passivation, POLO @article{Hollemann2021c,
title = {Firing stability of tube furnace-annealed n-type poly-Si on oxide junctions}, author = {C Hollemann and M Rienäcker and A Soeriyadi and C Madumelu and F Haase and J Krügener and B Hallam and R Brendel and R Peibst}, doi = {10.1002/pip.3459}, year = {2021}, date = {2021-08-22}, journal = {Progress in Photovoltaics: Research and Applications}, abstract = {Stability of the passivation quality of poly-Si on oxide junctions against the conventional mainstream high-temperature screen-print firing processes is highly desirable and also expected since the poly-Si on oxide preparation occurs at higher temperatures and for longer durations than firing. We measure recombination current densities (J0) and interface state densities (Dit) of symmetrical samples with n-type poly-Si contacts before and after firing. Samples without a capping dielectric layer show a significant deterioration of the passivation quality during firing. The Dit values are (3 ± 0.2) × 1011 and (8 ± 2) × 1011 eV/cm2 when fired at 620°C and 900°C, respectively. The activation energy in an Arrhenius fit of Dit versus the firing temperature is 0.30 ± 0.03 eV. This indicates that thermally induced desorption of hydrogen from SiH bonds at the poly-Si/SiOx interface is not the root cause of depassivation. Postfiring annealing at 425°C can improve the passivation again. Samples with SiNx capping layers show an increase in J0 up to about 100 fA/cm2 by firing, which can be attributed to blistering and is not reversed by annealing at 425°C. On the other hand, blistering does not occur in poly-Si samples capped with AlOx layers or AlOx/SiNy stacks, and J0 values of 2–5 fA/cm2 can be achieved after firing. Those findings suggest that a combination of two effects might be the root cause of the increase in J0 and Dit: thermal stress at the SiOz interface during firing and blistering. Blistering is presumed to occur when the hydrogen concentration in the capping layers exceeds a certain level.}, keywords = {blistering, Firing, passivating contacts, passivation, POLO}, pubstate = {forthcoming}, tppubtype = {article} } Stability of the passivation quality of poly-Si on oxide junctions against the conventional mainstream high-temperature screen-print firing processes is highly desirable and also expected since the poly-Si on oxide preparation occurs at higher temperatures and for longer durations than firing. We measure recombination current densities (J0) and interface state densities (Dit) of symmetrical samples with n-type poly-Si contacts before and after firing. Samples without a capping dielectric layer show a significant deterioration of the passivation quality during firing. The Dit values are (3 ± 0.2) × 1011 and (8 ± 2) × 1011 eV/cm2 when fired at 620°C and 900°C, respectively. The activation energy in an Arrhenius fit of Dit versus the firing temperature is 0.30 ± 0.03 eV. This indicates that thermally induced desorption of hydrogen from SiH bonds at the poly-Si/SiOx interface is not the root cause of depassivation. Postfiring annealing at 425°C can improve the passivation again. Samples with SiNx capping layers show an increase in J0 up to about 100 fA/cm2 by firing, which can be attributed to blistering and is not reversed by annealing at 425°C. On the other hand, blistering does not occur in poly-Si samples capped with AlOx layers or AlOx/SiNy stacks, and J0 values of 2–5 fA/cm2 can be achieved after firing. Those findings suggest that a combination of two effects might be the root cause of the increase in J0 and Dit: thermal stress at the SiOz interface during firing and blistering. Blistering is presumed to occur when the hydrogen concentration in the capping layers exceeds a certain level.
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P. Bayerl, N. Folchert, J. Bayer, M. Dzinnik, C. Hollemann, R. Brendel, R. Peibst, and R. J. Haug Progress in Photovoltaics: Research and Applications 29 (8), 936-942, (2021). Abstract | Links | BibTeX | Schlagwörter: Pinhole transport, POLO junction, record energy conversion efficiency, Silicon solar cell @article{Bayerl2021,
title = {Contacting a single nanometer-sized pinhole in the interfacial oxide of a poly-silicon on oxide (POLO) solar cell junction}, author = {P Bayerl and N Folchert and J Bayer and M Dzinnik and C Hollemann and R Brendel and R Peibst and R J Haug}, doi = {10.1002/pip.3417}, year = {2021}, date = {2021-08-01}, journal = {Progress in Photovoltaics: Research and Applications}, volume = {29}, number = {8}, pages = {936-942}, abstract = {The electrical current through poly-Si on oxide (POLO) solar cells is mediated by tunneling and by nanometer-sized pinholes in the interfacial oxide. To distinguish the two processes, a POLO junction with a measured pinhole density of 1 × 107 cm−2 is contacted by different contact areas ranging from 1 μm2 to 2.5 × 105 μm2, and the temperature-dependent current–voltage curves are measured for the different devices. Model regressions to the measured curves, their temperature dependence, and the quantized value of contact resistances indicate average numbers of pinholes per device corresponding to the expected pinhole density. For the small contacts, the different transport processes can be studied separately, which facilitates further improvements in respect to the present-day POLO junctions. Single-pinhole transport is found for one of the contacts with an area of 1 μm2. Random telegraph noise observed for this device in the current–voltage characteristics shows a high sensitivity to single charges.}, keywords = {Pinhole transport, POLO junction, record energy conversion efficiency, Silicon solar cell}, pubstate = {published}, tppubtype = {article} } The electrical current through poly-Si on oxide (POLO) solar cells is mediated by tunneling and by nanometer-sized pinholes in the interfacial oxide. To distinguish the two processes, a POLO junction with a measured pinhole density of 1 × 107 cm−2 is contacted by different contact areas ranging from 1 μm2 to 2.5 × 105 μm2, and the temperature-dependent current–voltage curves are measured for the different devices. Model regressions to the measured curves, their temperature dependence, and the quantized value of contact resistances indicate average numbers of pinholes per device corresponding to the expected pinhole density. For the small contacts, the different transport processes can be studied separately, which facilitates further improvements in respect to the present-day POLO junctions. Single-pinhole transport is found for one of the contacts with an area of 1 μm2. Random telegraph noise observed for this device in the current–voltage characteristics shows a high sensitivity to single charges.
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M. Schmidt, F. Müller-Langer, J. Kretschmar, C. Agert, J. Bard, C. Hebling, H. Heinrichs, M. Robinius, R. Niebelt, R. Dittmeyer, and F. Graf Grüner Wasserstoff als Schlüsseltechnologie für die europäische Energiewende Inproceedings ForschungsVerbund. Erneuerbare. Energien. (FVEE) (Hrsg.): Forschung für den European Green Deal (Themen 2020), 10-14, Online Event, (2021). BibTeX | Schlagwörter: Wasserstoff @inproceedings{Schmidt2021,
title = {Grüner Wasserstoff als Schlüsseltechnologie für die europäische Energiewende}, author = {M Schmidt and F Müller-Langer and J Kretschmar and C Agert and J Bard and C Hebling and H Heinrichs and M Robinius and R Niebelt and R Dittmeyer and F Graf}, editor = {ForschungsVerbund Erneuerbare Energien (FVEE)}, year = {2021}, date = {2021-07-09}, booktitle = {Forschung für den European Green Deal (Themen 2020)}, pages = {10-14}, address = {Online Event}, keywords = {Wasserstoff}, pubstate = {published}, tppubtype = {inproceedings} } |