Veröffentlichungen
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J. Schmidt, R. Peibst, and R. Brendel Surface passivation of crystalline silicon solar cells: Present and future Artikel Solar Energy Materials and Solar Cells 187 , 39-54 (2018), ISSN: 0927-0248. Abstract | Links | BibTeX | Schlagwörter: Carrier-selective contacts, silicon solar cells, surface passivation @article{Schmidt2018b,
title = {Surface passivation of crystalline silicon solar cells: Present and future}, author = {J Schmidt and R Peibst and R Brendel}, doi = {10.1016/j.solmat.2018.06.047}, issn = {0927-0248}, year = {2018}, date = {2018-12-01}, journal = {Solar Energy Materials and Solar Cells}, volume = {187}, pages = {39-54}, abstract = {In the first part of this paper, we review the developments which led to the present state-of-the-art in the surface passivation of today's industrially predominant dopant-diffused crystalline silicon (c-Si) solar cells, based on dielectric layers such as silicon oxide, silicon nitride, aluminum oxide and stacks thereof. In the second part of this review, we focus on the future developments in the field of c-Si solar cells based on carrier-selective passivation layers. Whereas the dielectric layers are insulating and are hence applied only for passivating the non-contacted areas of the silicon surface, the carrier-selective passivation layers are intended to provide an effective passivation of non-contacted as well as contacted areas of a c-Si solar cell, thereby increasing the efficiency potential of c-Si solar cells significantly. Due to the fact that the carrier-selective layers are implemented in a contact, besides the good passivation properties for minorities, these layers must also provide a good majority carrier transport, i.e. they have to provide a low contact resistance. Both properties, i.e. suppression of minority-carrier recombination as well as good majority-carrier transport, define the selectivity of the carrier-selective contact, which is an important figure of merit for the assessment and comparison of different types of carrier-selective contacts. One very promising type of carrier-selective passivation layer is based on heavily doped polycrystalline silicon layers deposited on a thin silicon oxide layer, the latter providing the excellent passivation while enabling efficient majority-carrier transport via pin-holes and/or tunneling. Moreover, we discuss metal oxides and conductive polymers, which have only recently been applied to c-Si photovoltaics, but seem to have a promising potential as low-cost selective contact materials. We finally compare combinations of the various options of carrier-selective layers concerning their combined selectivities and efficiency potentials.}, keywords = {Carrier-selective contacts, silicon solar cells, surface passivation}, pubstate = {published}, tppubtype = {article} } In the first part of this paper, we review the developments which led to the present state-of-the-art in the surface passivation of today's industrially predominant dopant-diffused crystalline silicon (c-Si) solar cells, based on dielectric layers such as silicon oxide, silicon nitride, aluminum oxide and stacks thereof. In the second part of this review, we focus on the future developments in the field of c-Si solar cells based on carrier-selective passivation layers. Whereas the dielectric layers are insulating and are hence applied only for passivating the non-contacted areas of the silicon surface, the carrier-selective passivation layers are intended to provide an effective passivation of non-contacted as well as contacted areas of a c-Si solar cell, thereby increasing the efficiency potential of c-Si solar cells significantly. Due to the fact that the carrier-selective layers are implemented in a contact, besides the good passivation properties for minorities, these layers must also provide a good majority carrier transport, i.e. they have to provide a low contact resistance. Both properties, i.e. suppression of minority-carrier recombination as well as good majority-carrier transport, define the selectivity of the carrier-selective contact, which is an important figure of merit for the assessment and comparison of different types of carrier-selective contacts. One very promising type of carrier-selective passivation layer is based on heavily doped polycrystalline silicon layers deposited on a thin silicon oxide layer, the latter providing the excellent passivation while enabling efficient majority-carrier transport via pin-holes and/or tunneling. Moreover, we discuss metal oxides and conductive polymers, which have only recently been applied to c-Si photovoltaics, but seem to have a promising potential as low-cost selective contact materials. We finally compare combinations of the various options of carrier-selective layers concerning their combined selectivities and efficiency potentials.
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B. A. Veith-Wolf, S. Schäfer, R. Brendel, and J. Schmidt Solar Energy Materials and Solar Cells 186 , 194-199 (2018), ISSN: 0927-0248. Abstract | Links | BibTeX | Schlagwörter: Aluminum oxide, Auger recombination, charge carrier lifetime, Intrinsic lifetime, silicon, surface passivation @article{Veith-Wolf2018b,
title = {Reassessment of intrinsic lifetime limit in n-type crystalline silicon and implication on maximum solar cell efficiency}, author = {B A Veith-Wolf and S Schäfer and R Brendel and J Schmidt}, doi = {10.1016/j.solmat.2018.06.029}, issn = {0927-0248}, year = {2018}, date = {2018-11-01}, journal = {Solar Energy Materials and Solar Cells}, volume = {186}, pages = {194-199}, abstract = {Unusually high carrier lifetimes are measured by photoconductance decay on n-type Czochralski-grown silicon wafers of different doping concentrations, passivated using plasma-assisted atomic-layer-deposited aluminum oxide (Al2O3) on both wafer surfaces. The measured effective lifetimes significantly exceed the intrinsic lifetime limit previously reported in the literature. Several prerequisites have to be fulfilled to allow the measurement of such high lifetimes on Al2O3-passivated n-type silicon wafers: (i) large-area wafers are required to minimize the impact of edge recombination via the Al2O3-charge-induced inversion layer, (ii) an exceptionally homogeneous Al2O3 surface passivation is required, and (iii) very thick silicon wafers are needed. Based on our lifetime measurements on n-type silicon wafers of different doping concentrations, we introduce a new parameterization of the intrinsic lifetime for n-type crystalline silicon. This new parameterization has implications concerning the maximum reachable efficiency of n-type silicon solar cells, which is larger than assumed before.}, keywords = {Aluminum oxide, Auger recombination, charge carrier lifetime, Intrinsic lifetime, silicon, surface passivation}, pubstate = {published}, tppubtype = {article} } Unusually high carrier lifetimes are measured by photoconductance decay on n-type Czochralski-grown silicon wafers of different doping concentrations, passivated using plasma-assisted atomic-layer-deposited aluminum oxide (Al2O3) on both wafer surfaces. The measured effective lifetimes significantly exceed the intrinsic lifetime limit previously reported in the literature. Several prerequisites have to be fulfilled to allow the measurement of such high lifetimes on Al2O3-passivated n-type silicon wafers: (i) large-area wafers are required to minimize the impact of edge recombination via the Al2O3-charge-induced inversion layer, (ii) an exceptionally homogeneous Al2O3 surface passivation is required, and (iii) very thick silicon wafers are needed. Based on our lifetime measurements on n-type silicon wafers of different doping concentrations, we introduce a new parameterization of the intrinsic lifetime for n-type crystalline silicon. This new parameterization has implications concerning the maximum reachable efficiency of n-type silicon solar cells, which is larger than assumed before.
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F. Haase, C. Hollemann, S. Schäfer, A. Merkle, M. Rienäcker, J. Krügener, R. Brendel, and R. Peibst Solar Energy Materials and Solar Cells 186 , 184-193 (2018), ISSN: 0927-0248. Abstract | Links | BibTeX | Schlagwörter: Back-contact solar cell, Laser, passivating contacts, POLO @article{Haase2018c,
title = {Laser contact openings for local poly-Si-metal contacts enabling 26.1%-efficient POLO-IBC solar cells}, author = {F Haase and C Hollemann and S Schäfer and A Merkle and M Rienäcker and J Krügener and R Brendel and R Peibst}, doi = {10.1016/j.solmat.2018.06.020}, issn = {0927-0248}, year = {2018}, date = {2018-11-01}, journal = {Solar Energy Materials and Solar Cells}, volume = {186}, pages = {184-193}, abstract = {We demonstrate damage-free laser contact openings in silicon oxide layers on polycrystalline silicon on oxide (POLO) passivating contacts. A pulsed UV-laser evaporates the upper part of the polycrystalline silicon layer, lifting off the silicon oxide layer on top. On n-type POLO (and p-type POLO, respectively) samples a saturation current density of 2 fA cm−2 (6 fA cm−2) and an implied open-circuit voltage of 733 mV (727 mV) are achieved with a laser contact opening area fraction of 12.3% (8.7%). The application of this ablation process in an interdigitated back contact solar cell leads to an independently confirmed power conversion efficiency of 26.1%. The excellent contact quality of the laser contact openings is proven by the low series resistance of 0.1 Ω cm2 on the solar cell with a contact area of only 3%.}, keywords = {Back-contact solar cell, Laser, passivating contacts, POLO}, pubstate = {published}, tppubtype = {article} } We demonstrate damage-free laser contact openings in silicon oxide layers on polycrystalline silicon on oxide (POLO) passivating contacts. A pulsed UV-laser evaporates the upper part of the polycrystalline silicon layer, lifting off the silicon oxide layer on top. On n-type POLO (and p-type POLO, respectively) samples a saturation current density of 2 fA cm−2 (6 fA cm−2) and an implied open-circuit voltage of 733 mV (727 mV) are achieved with a laser contact opening area fraction of 12.3% (8.7%). The application of this ablation process in an interdigitated back contact solar cell leads to an independently confirmed power conversion efficiency of 26.1%. The excellent contact quality of the laser contact openings is proven by the low series resistance of 0.1 Ω cm2 on the solar cell with a contact area of only 3%.
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M. Köntges, H. Schulte-Huxel, S. Blankemeyer, M. R. Vogt, H. Holst, and R. Reineke-Koch Measuring the light recovery factor of backsheets in photovoltaic modules Artikel Solar Energy Materials and Solar Cells 186 , 175-183 (2018), ISSN: 0927-0248. Abstract | Links | BibTeX | Schlagwörter: Backsheet, light harvesting, Light Trapping, Module efficiency, PV Module @article{Köntges2018b,
title = {Measuring the light recovery factor of backsheets in photovoltaic modules}, author = {M Köntges and H Schulte-Huxel and S Blankemeyer and M R Vogt and H Holst and R Reineke-Koch}, doi = {10.1016/j.solmat.2018.06.028}, issn = {0927-0248}, year = {2018}, date = {2018-11-01}, journal = {Solar Energy Materials and Solar Cells}, volume = {186}, pages = {175-183}, abstract = {We measure the short circuit current improvement of various commercial backsheets for passivated emitter and rear solar cells (PERC) in photovoltaic (PV) modules. We quantify this improvement by a light recovery factor k defined as the share of the light reflected by the backsheet around the cell in a PV module laminate, which is converted into electrical current by the solar cells in the module relative to a reference rear surface. The presented measurement method allows measuring the light recovery factor as function of the incident light beam angle, which are important for the calculation of the yield analysis in the field. Simulations of the recovery factor with the optical ray tracing program DIADALOS are performed in order to support the interpretation of the results. For measuring the absolute light recovery probability of a backsheet one should use a reference backsheet with an absorbance of close to 100% to avoid systematic reflection errors especially for high incident light beam angles > 50°. The ranking of various recovery factors are compared to the ranking measured by reflectance measurements defined in standard IEC 62788-2 Ed.1 for backsheets. The standard shows a substantial deviation between the ranking of recovery factor and the reflectance which can be corrected by using an adapted definition for the reflectance measurement method.}, keywords = {Backsheet, light harvesting, Light Trapping, Module efficiency, PV Module}, pubstate = {published}, tppubtype = {article} } We measure the short circuit current improvement of various commercial backsheets for passivated emitter and rear solar cells (PERC) in photovoltaic (PV) modules. We quantify this improvement by a light recovery factor k defined as the share of the light reflected by the backsheet around the cell in a PV module laminate, which is converted into electrical current by the solar cells in the module relative to a reference rear surface. The presented measurement method allows measuring the light recovery factor as function of the incident light beam angle, which are important for the calculation of the yield analysis in the field. Simulations of the recovery factor with the optical ray tracing program DIADALOS are performed in order to support the interpretation of the results. For measuring the absolute light recovery probability of a backsheet one should use a reference backsheet with an absorbance of close to 100% to avoid systematic reflection errors especially for high incident light beam angles > 50°. The ranking of various recovery factors are compared to the ranking measured by reflectance measurements defined in standard IEC 62788-2 Ed.1 for backsheets. The standard shows a substantial deviation between the ranking of recovery factor and the reflectance which can be corrected by using an adapted definition for the reflectance measurement method.
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N. Folchert, M. Rienäcker, A. A. Yeo, B. Min, R. Peibst, and R. Brendel Temperature-dependent contact resistance of carrier selective Poly-Si on oxide junctions Artikel Solar Energy Materials and Solar Cells 185 , 425-430 (2018), ISSN: 0927-0248. Abstract | Links | BibTeX | Schlagwörter: Contact resistance, passivating contacts, Pinhole transport, POLO, Poly-Si, selective contacts, Transfer-length-method, Tunneling @article{Folchert2018b,
title = {Temperature-dependent contact resistance of carrier selective Poly-Si on oxide junctions}, author = {N Folchert and M Rienäcker and A A Yeo and B Min and R Peibst and R Brendel}, doi = {10.1016/j.solmat.2018.05.046}, issn = {0927-0248}, year = {2018}, date = {2018-10-01}, journal = {Solar Energy Materials and Solar Cells}, volume = {185}, pages = {425-430}, abstract = {Abstract Carrier selective junctions using a poly-silicon/ silicon oxide stack on crystalline silicon feature low recombination currents \{J0\} whilst allowing for low contact resistivity ρ C . We describe the limiting current transport mechanism as a combination of homogeneous tunneling through the interfacial silicon oxide layer and transport through pinholes where the interfacial silicon oxide layer is locally disrupted. We present an experimental method and its theoretical basis to discriminate between homogenous tunneling and local pinhole transport mechanisms on n + /n or p + /p junctions by measuring the temperature-dependent contact resistance. Theory predicts opposing trends for the temperature dependencies of tunneling and pinhole transport. This allows identifying the dominant transport path. For the contact resistance of two differently prepared poly-Si/ silicon oxide/ c-Si junctions we either find clear pinhole-type or clear tunneling-type temperature dependence. Pinhole transport contributes more than 94 % to the total current for the sample with a 2.1 nm-thick interfacial silicon oxide that we anneal at a temperature of 1050 °C to achieve highest selectivity. In contrast pinhole transport contributes less than 35 % to the total current for the sample with a 1.7 nm-thick silicon oxide that we annealed at only 700 °C in order to avoid pinholes.}, keywords = {Contact resistance, passivating contacts, Pinhole transport, POLO, Poly-Si, selective contacts, Transfer-length-method, Tunneling}, pubstate = {published}, tppubtype = {article} } Abstract Carrier selective junctions using a poly-silicon/ silicon oxide stack on crystalline silicon feature low recombination currents {J0} whilst allowing for low contact resistivity ρ C . We describe the limiting current transport mechanism as a combination of homogeneous tunneling through the interfacial silicon oxide layer and transport through pinholes where the interfacial silicon oxide layer is locally disrupted. We present an experimental method and its theoretical basis to discriminate between homogenous tunneling and local pinhole transport mechanisms on n + /n or p + /p junctions by measuring the temperature-dependent contact resistance. Theory predicts opposing trends for the temperature dependencies of tunneling and pinhole transport. This allows identifying the dominant transport path. For the contact resistance of two differently prepared poly-Si/ silicon oxide/ c-Si junctions we either find clear pinhole-type or clear tunneling-type temperature dependence. Pinhole transport contributes more than 94 % to the total current for the sample with a 2.1 nm-thick interfacial silicon oxide that we anneal at a temperature of 1050 °C to achieve highest selectivity. In contrast pinhole transport contributes less than 35 % to the total current for the sample with a 1.7 nm-thick silicon oxide that we annealed at only 700 °C in order to avoid pinholes.
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L. Helmich, D. C. Walter, D. Bredemeier, R. Falster, V. V. Voronkov, and J. Schmidt In-situ characterization of electron-assisted regeneration of Cz-Si solar cells Artikel Solar Energy Materials and Solar Cells 185 , 283-286 (2018), ISSN: 0927-0248. Abstract | Links | BibTeX | Schlagwörter: boron-oxygen defect, Czochralski-grown silicon, LID, regeneration, solar cell @article{Helmich2018b,
title = {In-situ characterization of electron-assisted regeneration of Cz-Si solar cells}, author = {L Helmich and D C Walter and D Bredemeier and R Falster and V V Voronkov and J Schmidt}, doi = {10.1016/j.solmat.2018.05.023}, issn = {0927-0248}, year = {2018}, date = {2018-10-01}, journal = {Solar Energy Materials and Solar Cells}, volume = {185}, pages = {283-286}, abstract = {Abstract We examine the regeneration kinetics of passivated emitter and rear solar cells (PERCs) fabricated on boron-doped p-type Czochralski-grown silicon wafers in darkness by electron injection via application of a forward bias voltage at elevated temperature (140 °C) in order to discriminate between electronic and photonic effects. Based on these dark regeneration experiments, we address the existing inconsistency regarding the measured linear dependence of the regeneration rate constant on the excess carrier density. Using the method of dark regeneration by current injection into the solar cell, we are able to measure the total recombination current of the solar cell at the actual regeneration temperature under applied voltage, i.e., at the physically relevant regeneration conditions. The direct comparison of the regeneration rate constant as a function of electronically injected carrier concentration in the dark and the regeneration rate constant during illumination clearly shows that the regeneration is a purely electronically stimulated effect and that photons are not directly involved.}, keywords = {boron-oxygen defect, Czochralski-grown silicon, LID, regeneration, solar cell}, pubstate = {published}, tppubtype = {article} } Abstract We examine the regeneration kinetics of passivated emitter and rear solar cells (PERCs) fabricated on boron-doped p-type Czochralski-grown silicon wafers in darkness by electron injection via application of a forward bias voltage at elevated temperature (140 °C) in order to discriminate between electronic and photonic effects. Based on these dark regeneration experiments, we address the existing inconsistency regarding the measured linear dependence of the regeneration rate constant on the excess carrier density. Using the method of dark regeneration by current injection into the solar cell, we are able to measure the total recombination current of the solar cell at the actual regeneration temperature under applied voltage, i.e., at the physically relevant regeneration conditions. The direct comparison of the regeneration rate constant as a function of electronically injected carrier concentration in the dark and the regeneration rate constant during illumination clearly shows that the regeneration is a purely electronically stimulated effect and that photons are not directly involved.
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B. Schiebler, S. Jack, H. Dieckmann, and F. Giovannetti Solar Energy 171 , 271-278 (2018), ISSN: 0038-092X. Abstract | Links | BibTeX | Schlagwörter: cost reduction, evacuated tube collector, Flat plate collector, heat pipe, stagnation temperature, Superheated vapour @article{Schiebler2018d,
title = {Experimental and theoretical investigations on temperature limitation in solar thermal collectors with heat pipes: Effect of superheating on the maximum temperature}, author = {B Schiebler and S Jack and H Dieckmann and F Giovannetti}, doi = {10.1016/j.solener.2018.06.036}, issn = {0038-092X}, year = {2018}, date = {2018-09-01}, journal = {Solar Energy}, volume = {171}, pages = {271-278}, abstract = {Heat pipes in solar thermal collectors enable to reduce the temperature loads in the solar circuit during stagnation periods by exploiting their dry-out limit. With this approach vapour formation in the solar circuit can be completely avoided, which is essential to reduce costs of solar thermal systems by simplified and more reliable solar circuits. The design of “deactivating” collector heat pipes with a desired maximum temperature requires a comprehensive understanding of the heat transfer processes in the heat pipe, in particular when dry-out takes place. We developed a model, which allows calculating the maximum fluid temperature in the collector for various working fluids. Compared to existing approaches, the effect of superheated vapour in the heat pipe during stagnation is additionally considered. The paper describes the theoretical model in detail and its extensive experimental validation. The results show that the model is able to predict the maximum fluid temperature with an accuracy better than 5 K. Based on parametric studies with different working fluids, we analyse and discuss the temperature limitation and its effect on the collector performance.}, keywords = {cost reduction, evacuated tube collector, Flat plate collector, heat pipe, stagnation temperature, Superheated vapour}, pubstate = {published}, tppubtype = {article} } Heat pipes in solar thermal collectors enable to reduce the temperature loads in the solar circuit during stagnation periods by exploiting their dry-out limit. With this approach vapour formation in the solar circuit can be completely avoided, which is essential to reduce costs of solar thermal systems by simplified and more reliable solar circuits. The design of “deactivating” collector heat pipes with a desired maximum temperature requires a comprehensive understanding of the heat transfer processes in the heat pipe, in particular when dry-out takes place. We developed a model, which allows calculating the maximum fluid temperature in the collector for various working fluids. Compared to existing approaches, the effect of superheated vapour in the heat pipe during stagnation is additionally considered. The paper describes the theoretical model in detail and its extensive experimental validation. The results show that the model is able to predict the maximum fluid temperature with an accuracy better than 5 K. Based on parametric studies with different working fluids, we analyse and discuss the temperature limitation and its effect on the collector performance.
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C. Schinke, M. R. Vogt, and K. Bothe Optical Modeling of Photovoltaic Modules with Ray Tracing Simulations Buchkapitel Photovoltaic Modeling Handbook, Kapitel 3, 27-91 Wiley-Blackwell, (2018), ISBN: 9781119364214. Abstract | Links | BibTeX | Schlagwörter: Monte-Carlo ray tracing, multi-domain approach, optical loss analysis, photovoltaic module, power calculation, ray optics @inbook{Schinke2018,
title = {Optical Modeling of Photovoltaic Modules with Ray Tracing Simulations}, author = {C Schinke and M R Vogt and K Bothe}, doi = {10.1002/9781119364214.ch3}, isbn = {9781119364214}, year = {2018}, date = {2018-08-03}, booktitle = {Photovoltaic Modeling Handbook}, pages = {27-91}, publisher = {Wiley-Blackwell}, chapter = {3}, abstract = {Abstract This chapter contains sections titled: Introduction Basics of Optical Ray Tracing Simulations Modeling Illumination Specific Issues for Ray Tracing of Photovoltaic Modules From Optics to Power Output Overview of Optical Simulation Tools for PV Devices Acknowledgments}, keywords = {Monte-Carlo ray tracing, multi-domain approach, optical loss analysis, photovoltaic module, power calculation, ray optics}, pubstate = {published}, tppubtype = {inbook} } Abstract This chapter contains sections titled: Introduction Basics of Optical Ray Tracing Simulations Modeling Illumination Specific Issues for Ray Tracing of Photovoltaic Modules From Optics to Power Output Overview of Optical Simulation Tools for PV Devices Acknowledgments
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T. Dullweber, H. Schulte-Huxel, S. Blankemeyer, H. Hannebauer, S. Schimanke, U. Baumann, R. Witteck, R. Peibst, M. Köntges, R. Brendel, and Y. Yao Present status and future perspectives of bifacial PERC+ solar cells and modules Artikel Japanese Journal of Applied Physics 57 (8S3), 08RA01 (2018). Abstract | Links | BibTeX | Schlagwörter: module, PERC+ @article{Dullweber2018,
title = {Present status and future perspectives of bifacial PERC+ solar cells and modules}, author = {T Dullweber and H Schulte-Huxel and S Blankemeyer and H Hannebauer and S Schimanke and U Baumann and R Witteck and R Peibst and M Köntges and R Brendel and Y Yao}, doi = {10.7567/JJAP.57.08RA01}, year = {2018}, date = {2018-08-01}, journal = {Japanese Journal of Applied Physics}, volume = {57}, number = {8S3}, pages = {08RA01}, abstract = {This paper reviews the main research results related to PERC+ silicon solar cells. Compared to today’s industry typical passivated emitter and rear cell (PERC) silicon solar cells with full-area rear aluminum layer, PERC+ solar cells apply an aluminum finger grid on the rear side and hence are able to absorb diffuse light from the rear side in addition to the direct sunlight which is absorbed from the front side. This bifaciality increases the energy yield of silicon solar modules by up to 25%. Since its first publication in 2015, the PERC+ cell concept has been rapidly adopted by several solar cell manufacturers due to the very similar process technology of bifacial PERC+ cells and main stream monofacial PERC cells. We summarize technological challenges, published PERC+ conversion efficiencies and PERC+ module technologies. First energy yield data of PERC+ field installations demonstrate the high energy yield potential of PERC+ solar cells.}, keywords = {module, PERC+}, pubstate = {published}, tppubtype = {article} } This paper reviews the main research results related to PERC+ silicon solar cells. Compared to today’s industry typical passivated emitter and rear cell (PERC) silicon solar cells with full-area rear aluminum layer, PERC+ solar cells apply an aluminum finger grid on the rear side and hence are able to absorb diffuse light from the rear side in addition to the direct sunlight which is absorbed from the front side. This bifaciality increases the energy yield of silicon solar modules by up to 25%. Since its first publication in 2015, the PERC+ cell concept has been rapidly adopted by several solar cell manufacturers due to the very similar process technology of bifacial PERC+ cells and main stream monofacial PERC cells. We summarize technological challenges, published PERC+ conversion efficiencies and PERC+ module technologies. First energy yield data of PERC+ field installations demonstrate the high energy yield potential of PERC+ solar cells.
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S. Brötje, M. Kirchner, and F. Giovannetti Solar Energy 170 , 406-418 (2018), ISSN: 0038-092X. Abstract | Links | BibTeX | Schlagwörter: Detachable compound, Heat transfer modelling, Photovoltaic-thermal collector, Uncovered collector @article{Brötje2018c,
title = {Performance and heat transfer analysis of uncovered photovoltaic-thermal collectors with detachable compound}, author = {S Brötje and M Kirchner and F Giovannetti}, doi = {10.1016/j.solener.2018.05.030}, issn = {0038-092X}, year = {2018}, date = {2018-08-01}, journal = {Solar Energy}, volume = {170}, pages = {406-418}, abstract = {Concerning the manufacturing of uncovered, liquid-based photovoltaic-thermal (PVT) collectors, design requirements or low expenses have higher priority than the all-out optimization of the thermal efficiency. The specific impact of inevitable thermal resistances caused by wavy surfaces and imperfect contacts between PV modules and heat exchangers has not been comprehensively investigated yet. This paper focuses on the performances of uncovered PVT collectors with detachable mounting of PV modules on heat exchangers and the effect of macroscopic air gaps. Two prototypes with thin film modules were built without using silicon glue, other adhesives or heat conductive paste. Measured in sun simulator in electrical open-circuit mode, the thermal zero-loss efficiencies for the adhesive-free collectors are η0,M = 66.8% (copper pipe meander laser-welded on aluminium sheet) and η0,M = 69.2 % (aluminium roll-bond) based on gross areas. These results are similar or better than the efficiencies of commercially available collectors. Due to the thermal resistance of air gaps, we calculated temperature differences of 12 K and higher between absorbing sheets and heat carrier, which have to be considered while estimating the electrical yield by means of system simulations. For comparison, we built a prototype with a roll-bond heat exchanger and a very thin adhesive layer and thereby an optimized heat transport (η0,M = 76.8 %). Using numerical, two-dimensional models, we can verify the efficiency measurements and determine the influence of design and boundary conditions on heat transfer mechanisms in the collectors. Simulations show good agreement with experimental results and prove to be an effective tool for design optimization.}, keywords = {Detachable compound, Heat transfer modelling, Photovoltaic-thermal collector, Uncovered collector}, pubstate = {published}, tppubtype = {article} } Concerning the manufacturing of uncovered, liquid-based photovoltaic-thermal (PVT) collectors, design requirements or low expenses have higher priority than the all-out optimization of the thermal efficiency. The specific impact of inevitable thermal resistances caused by wavy surfaces and imperfect contacts between PV modules and heat exchangers has not been comprehensively investigated yet. This paper focuses on the performances of uncovered PVT collectors with detachable mounting of PV modules on heat exchangers and the effect of macroscopic air gaps. Two prototypes with thin film modules were built without using silicon glue, other adhesives or heat conductive paste. Measured in sun simulator in electrical open-circuit mode, the thermal zero-loss efficiencies for the adhesive-free collectors are η0,M = 66.8% (copper pipe meander laser-welded on aluminium sheet) and η0,M = 69.2 % (aluminium roll-bond) based on gross areas. These results are similar or better than the efficiencies of commercially available collectors. Due to the thermal resistance of air gaps, we calculated temperature differences of 12 K and higher between absorbing sheets and heat carrier, which have to be considered while estimating the electrical yield by means of system simulations. For comparison, we built a prototype with a roll-bond heat exchanger and a very thin adhesive layer and thereby an optimized heat transport (η0,M = 76.8 %). Using numerical, two-dimensional models, we can verify the efficiency measurements and determine the influence of design and boundary conditions on heat transfer mechanisms in the collectors. Simulations show good agreement with experimental results and prove to be an effective tool for design optimization.
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S. J. Wolter, V. Steckenreiter, M. C. Tatarzyn, T. Wietler, R. Niepelt, and S. Kajari-Schröder Determination and influence evaluation of the acoustic impedance ratio for thermal co-evaporation Artikel Applied Physics Letters 113 (1), 013301 (2018). Abstract | Links | BibTeX | Schlagwörter: Acoustic phenomena, chemical compounds, Crystal structure, Crystalline solids, General atomic properties, Materials @article{Wolter2018,
title = {Determination and influence evaluation of the acoustic impedance ratio for thermal co-evaporation}, author = {S J Wolter and V Steckenreiter and M C Tatarzyn and T Wietler and R Niepelt and S Kajari-Schröder}, doi = {10.1063/1.5037403}, year = {2018}, date = {2018-07-06}, journal = {Applied Physics Letters}, volume = {113}, number = {1}, pages = {013301}, abstract = {Metal-halide perovskites are promising materials for applications like lasers and solar cells. In this work, we show the importance of an accurate determination of the source material parameters (acoustic impedance ratio and density) for thermal co-evaporation of soft materials like perovskites. We use here methylammonium iodide and lead(II)iodide for the exemplary deposition of methylammoniumlead(II)triiodide. We measure the thickness of the deposited layers by scanning electron microscopy cross sections and monitor the frequency change of the quartz crystal microbalances. We use a model with a one-dimensional acoustical composite resonator for the correct determination of the acoustic impedance ratio, resulting in values of 0.025 ± 0.002 for methylammonium iodide and of 0.11 ± 0.01 for lead(II)iodide. We use the resulting material parameters to deposit a layer of crystalline methylammonium lead triiodide with an accurately controlled stoichiometry of MAPbIx with x = 3.2 ± 0.2. We show the impact assuming false acoustic impedance ratios by simulating the actual evaporation rates of the source materials. We show that the ratio of the evaporation rates changes significantly during the deposition process. This results in a strong stoichiometry gradient in the perovskite layer and a mismatch in the average stoichiometry for a typical absorber thickness of 600 nm.}, keywords = {Acoustic phenomena, chemical compounds, Crystal structure, Crystalline solids, General atomic properties, Materials}, pubstate = {published}, tppubtype = {article} } Metal-halide perovskites are promising materials for applications like lasers and solar cells. In this work, we show the importance of an accurate determination of the source material parameters (acoustic impedance ratio and density) for thermal co-evaporation of soft materials like perovskites. We use here methylammonium iodide and lead(II)iodide for the exemplary deposition of methylammoniumlead(II)triiodide. We measure the thickness of the deposited layers by scanning electron microscopy cross sections and monitor the frequency change of the quartz crystal microbalances. We use a model with a one-dimensional acoustical composite resonator for the correct determination of the acoustic impedance ratio, resulting in values of 0.025 ± 0.002 for methylammonium iodide and of 0.11 ± 0.01 for lead(II)iodide. We use the resulting material parameters to deposit a layer of crystalline methylammonium lead triiodide with an accurately controlled stoichiometry of MAPbIx with x = 3.2 ± 0.2. We show the impact assuming false acoustic impedance ratios by simulating the actual evaporation rates of the source materials. We show that the ratio of the evaporation rates changes significantly during the deposition process. This results in a strong stoichiometry gradient in the perovskite layer and a mismatch in the average stoichiometry for a typical absorber thickness of 600 nm.
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S. Schäfer, and R. Brendel IEEE Journal of Photovoltaics 8 (4), 1156-1158 (2018), ISSN: 2156-3381. Abstract | Links | BibTeX | Schlagwörter: Efficiency limit, photon recycling, silicon, solar cell @article{Schäfer2018,
title = {Accurate Calculation of the Absorptance Enhances Efficiency Limit of Crystalline Silicon Solar Cells With Lambertian Light Trapping}, author = {S Schäfer and R Brendel}, doi = {10.1109/JPHOTOV.2018.2824024}, issn = {2156-3381}, year = {2018}, date = {2018-07-01}, journal = {IEEE Journal of Photovoltaics}, volume = {8}, number = {4}, pages = {1156-1158}, abstract = {The widely accepted limiting efficiency for crystalline silicon solar cells with Lambertian light trapping under 1 sun was previously calculated to be 29.43% for a 110-μm-thick device by using the commonly applied weak absorption approximation for light trapping. However, the short-circuit current density increases by 0.17 mA/cm2 when modeling the optical absorptance of an ideal Lambertian light trapping scheme exactly. The resulting new 1-sun efficiency limit is 29.56% and holds for a cell that is 98.1 μm in thickness.}, keywords = {Efficiency limit, photon recycling, silicon, solar cell}, pubstate = {published}, tppubtype = {article} } The widely accepted limiting efficiency for crystalline silicon solar cells with Lambertian light trapping under 1 sun was previously calculated to be 29.43% for a 110-μm-thick device by using the commonly applied weak absorption approximation for light trapping. However, the short-circuit current density increases by 0.17 mA/cm2 when modeling the optical absorptance of an ideal Lambertian light trapping scheme exactly. The resulting new 1-sun efficiency limit is 29.56% and holds for a cell that is 98.1 μm in thickness.
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R. Niepelt, S. J. Wolter, M. Tatarzyn, M. Diederich, V. Steckenreiter, T. Wietler, R. Peibst, and S. Kajari-Schröder Application of Experimentally Determined Acoustic Impedance Ratio for Homogeneous Co-Evaporation of Perovskite Absorbers Inproceedings IEEE (Hrsg.): 7th World Conference on Photovoltaic Energy Conversion (WCPEC-7), Waikoloa, HI, USA, (2018). Abstract | BibTeX | Schlagwörter: Perovskite Solar Cells @inproceedings{Niepelt2018,
title = {Application of Experimentally Determined Acoustic Impedance Ratio for Homogeneous Co-Evaporation of Perovskite Absorbers}, author = {R Niepelt and S J Wolter and M Tatarzyn and M Diederich and V Steckenreiter and T Wietler and R Peibst and S Kajari-Schröder}, editor = {IEEE}, year = {2018}, date = {2018-06-15}, booktitle = {7th World Conference on Photovoltaic Energy Conversion (WCPEC-7)}, address = {Waikoloa, HI, USA}, abstract = {We present the co-evaporation of metal halide perovskite absorbers on wafer scale. We derive the acoustic impedance ratio Z and density ρ of methyl ammonium iodide and lead iodide. We use them for the deposition of perovskite absorbers on 6-inch-diameter silicon wafers. We evaluate the structural and optical conformity of the deposition on wafer scale with x-ray diffraction and spectral photoluminescence. We use a camera-based fluorescence detection system to prove the homogeneity of the luminescence intensity. With our evaporation parameters, we achieve a conformal deposition of a photoluminescent absorber with controllable and homogeneous thickness and stoichiometry.}, keywords = {Perovskite Solar Cells}, pubstate = {published}, tppubtype = {inproceedings} } We present the co-evaporation of metal halide perovskite absorbers on wafer scale. We derive the acoustic impedance ratio Z and density ρ of methyl ammonium iodide and lead iodide. We use them for the deposition of perovskite absorbers on 6-inch-diameter silicon wafers. We evaluate the structural and optical conformity of the deposition on wafer scale with x-ray diffraction and spectral photoluminescence. We use a camera-based fluorescence detection system to prove the homogeneity of the luminescence intensity. With our evaporation parameters, we achieve a conformal deposition of a photoluminescent absorber with controllable and homogeneous thickness and stoichiometry.
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R. Peibst, M. Rienäcker, B. Min, C. Klamt, R. Niepelt, T. Wietler, T. Dullweber, E. Sauter, J. Hübner, M. Oestreich, and R. Brendel p+/n+ polysilicon-on-oxide tunneling junctions as an interface of p-type PERC cells for tandem applications Inproceedings IEEE (Hrsg.): 7th World Conference on Photovoltaic Energy Conversion (WCPEC-7), Waikoloa, HI, USA, (2018). Abstract | BibTeX | Schlagwörter: POLO, Tandem @inproceedings{Peibst2018b,
title = {p+/n+ polysilicon-on-oxide tunneling junctions as an interface of p-type PERC cells for tandem applications}, author = {R Peibst and M Rienäcker and B Min and C Klamt and R Niepelt and T Wietler and T Dullweber and E Sauter and J Hübner and M Oestreich and R Brendel}, editor = {IEEE}, year = {2018}, date = {2018-06-15}, booktitle = {7th World Conference on Photovoltaic Energy Conversion (WCPEC-7)}, address = {Waikoloa, HI, USA}, abstract = {We present a novel cell concept that combines the tandem cell approach with the PERC mainstream technology. As an interface between Si bottom and top cell, we utilize passivating n+-type polysilicon on oxide (POLO) contacts and a p+ poly-Si / n+ poly-Si tunneling junction. Our full area POLO-PERC+ Si bottom cells are fabricated within a typical industrial process sequence where the POCl3-diffusion and SiNx deposition are replaced by the POLO junction formation processes. The implied open circuit voltage iVoc measured on these devices reaches up to 708 mV (684 mV) under 1 sun (under filtered spectrum), respectively. On sister cells with planar front-side, the respective iVoc values are 718 mV (696 mV). In order to understand the device physics of our abrupt p+ poly-Si / n+ poly-Si tunneling junction, we determined the carrier lifetime in the poly-Si by time-resolved photoluminescence. The extracted lifetimes of 42-54 ps enter as input parameter for numerical Sentaurus Device simulations. These simulations reveal the importance of band-to-band and trap-assisted tunneling for a low tunneling junction resistivity of 2.95 mΩcm2.}, keywords = {POLO, Tandem}, pubstate = {published}, tppubtype = {inproceedings} } We present a novel cell concept that combines the tandem cell approach with the PERC mainstream technology. As an interface between Si bottom and top cell, we utilize passivating n+-type polysilicon on oxide (POLO) contacts and a p+ poly-Si / n+ poly-Si tunneling junction. Our full area POLO-PERC+ Si bottom cells are fabricated within a typical industrial process sequence where the POCl3-diffusion and SiNx deposition are replaced by the POLO junction formation processes. The implied open circuit voltage iVoc measured on these devices reaches up to 708 mV (684 mV) under 1 sun (under filtered spectrum), respectively. On sister cells with planar front-side, the respective iVoc values are 718 mV (696 mV). In order to understand the device physics of our abrupt p+ poly-Si / n+ poly-Si tunneling junction, we determined the carrier lifetime in the poly-Si by time-resolved photoluminescence. The extracted lifetimes of 42-54 ps enter as input parameter for numerical Sentaurus Device simulations. These simulations reveal the importance of band-to-band and trap-assisted tunneling for a low tunneling junction resistivity of 2.95 mΩcm2.
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E. L. Warren, M. Rienaecker, M. G. Deceglie, M. Schnabel, R. Peibst, A. C. Tamboli, and P. Stradins Operating principles of three-terminal solar cells Inproceedings IEEE (Hrsg.): 7th World Conference on Photovoltaic Energy Conversion (WCPEC-7), Waikoloa, HI, USA, (2018). Abstract | BibTeX | Schlagwörter: 3T, Tandem @inproceedings{Warren2018b,
title = {Operating principles of three-terminal solar cells}, author = {E L Warren and M Rienaecker and M G Deceglie and M Schnabel and R Peibst and A C Tamboli and P Stradins}, editor = {IEEE}, year = {2018}, date = {2018-06-15}, booktitle = {7th World Conference on Photovoltaic Energy Conversion (WCPEC-7)}, address = {Waikoloa, HI, USA}, abstract = {Most tandem solar cells are either two-terminal devices where the subcells are electrically connected in series or four terminal devices where each subcell is operated independently. There are trade-offs between the two integration schemes in terms of ease of fabrication, overall efficiency, and spectral sensitivity. Three-terminal (3T) tandem cells can combine the best aspects of both integration schemes if designed properly. Using a 3T design based on an interdigitated back contact (IBC) Si device with conductive front surface, combined with a wider bandgap III-V top cell, we discuss the operation of three terminal tandems in detail. We present both technology computer aided design (TCAD) device physics simulations and a simplified analytical model to describe trends in performance. We show that this type of 3T device can provide a robust operating mechanism to efficiently capture the solar spectrum without the need to current match sub-cells or fabricate complicated metal interconnects between cells.}, keywords = {3T, Tandem}, pubstate = {published}, tppubtype = {inproceedings} } Most tandem solar cells are either two-terminal devices where the subcells are electrically connected in series or four terminal devices where each subcell is operated independently. There are trade-offs between the two integration schemes in terms of ease of fabrication, overall efficiency, and spectral sensitivity. Three-terminal (3T) tandem cells can combine the best aspects of both integration schemes if designed properly. Using a 3T design based on an interdigitated back contact (IBC) Si device with conductive front surface, combined with a wider bandgap III-V top cell, we discuss the operation of three terminal tandems in detail. We present both technology computer aided design (TCAD) device physics simulations and a simplified analytical model to describe trends in performance. We show that this type of 3T device can provide a robust operating mechanism to efficiently capture the solar spectrum without the need to current match sub-cells or fabricate complicated metal interconnects between cells.
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K. VanSant, M. Schnabel, J. Simon, J. Geisz, A. Ptak, M. Young, D. Guiling, W. Olavarria, M. Rienaecker, H. Schulte-Huxel, R. Niepelt, Kajari-. S. Schroeder, R. Brendel, R. Peibst, and A. Tamboli HVPE vs. MOCVD: A Comparison of GaAs//Si Tandem Device Performance Inproceedings IEEE (Hrsg.): 7th World Conference on Photovoltaic Energy Conversion (WCPEC-7), Waikoloa, HI, USA, (2018). Abstract | BibTeX | Schlagwörter: III/V, silicon, Tandem @inproceedings{VanSant2018,
title = { HVPE vs. MOCVD: A Comparison of GaAs//Si Tandem Device Performance}, author = {K VanSant and M Schnabel and J Simon and J Geisz and A Ptak and M Young and D Guiling and W Olavarria and M Rienaecker and H Schulte-Huxel and R Niepelt and S Kajari- Schroeder and R Brendel and R Peibst and A Tamboli}, editor = {IEEE}, year = {2018}, date = {2018-06-15}, booktitle = {7th World Conference on Photovoltaic Energy Conversion (WCPEC-7)}, address = {Waikoloa, HI, USA}, abstract = {The performance of III-V//Si tandem devices has successfully exceeded the theoretical efficiency limit of single junction Si devices (29.4%) yet the costs associated with these high-efficiency tandem devices are still too high to compete with today’s conventional Si solar cells. Recent cost modeling efforts suggest that hydride vapor phase epitaxy (HVPE) could be adopted as an alternative growth technique to metal-organic chemical vapor deposition (MOCVD) because the costs of HVPE are substantially lower and the performance of devices fabricated from HVPE materials are continuously improving. This study will directly compare the performance of mechanically stacked GaAs//Si tandem solar cells fabricated from both HVPE and MOCVD materials and analyze observed discrepancies in device performance. We will also investigate and quantify the effects of potential near-term device optimizations and analyze whether these efficiencies are comparable to those assumed in the near- and mid-term cost model scenarios. }, keywords = {III/V, silicon, Tandem}, pubstate = {published}, tppubtype = {inproceedings} } The performance of III-V//Si tandem devices has successfully exceeded the theoretical efficiency limit of single junction Si devices (29.4%) yet the costs associated with these high-efficiency tandem devices are still too high to compete with today’s conventional Si solar cells. Recent cost modeling efforts suggest that hydride vapor phase epitaxy (HVPE) could be adopted as an alternative growth technique to metal-organic chemical vapor deposition (MOCVD) because the costs of HVPE are substantially lower and the performance of devices fabricated from HVPE materials are continuously improving. This study will directly compare the performance of mechanically stacked GaAs//Si tandem solar cells fabricated from both HVPE and MOCVD materials and analyze observed discrepancies in device performance. We will also investigate and quantify the effects of potential near-term device optimizations and analyze whether these efficiencies are comparable to those assumed in the near- and mid-term cost model scenarios.
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M. Schnabel, H. Schulte-Huxel, T. R. Klein, M. Rienaecker, J. F. Giesz, B. G. Lee, R. Niepelt, S. Kajari-Schroeder, M. F. A. M. van Hest, E. L. Warren, R. Brendel, R. Peibst, P. Stradins, and A. C. Tamboli Three-Terminal III-V/Si Tandem Solar Cells Fabricated Using a Transparent, Conductive Adhesive Inproceedings IEEE (Hrsg.): 7th World Conference on Photovoltaic Energy Conversion (WCPEC-7), Waikoloa, HI, USA, (2018). Abstract | BibTeX | Schlagwörter: 3T, Tandem @inproceedings{Schnabel2018,
title = {Three-Terminal III-V/Si Tandem Solar Cells Fabricated Using a Transparent, Conductive Adhesive}, author = {M Schnabel and H Schulte-Huxel and T R Klein and M Rienaecker and J F Giesz and B G Lee and R Niepelt and S Kajari-Schroeder and M.F.A.M. van Hest and E L Warren and R Brendel and R Peibst and P Stradins and A C Tamboli}, editor = {IEEE}, year = {2018}, date = {2018-06-15}, booktitle = {7th World Conference on Photovoltaic Energy Conversion (WCPEC-7)}, address = {Waikoloa, HI, USA}, abstract = {Multijunction architectures provide a crosscutting solution for increasing solar cell efficiency for a variety of material types and combinations. We discuss a three-terminal tandem cell demonstrated using a III-V/Si platform. High efficiencies have been achieved in two and four terminal designs, but two-terminal cells require current matching, and four-terminal cells require intermediate grids to transport current laterally from in between the cells to the edges, which can lead to optical and resistive losses. Our three-terminal architecture utilizes a modified interdigitated back contact Si bottom cell, enabling maximized power extraction for any band gap combination, without intermediate grids. We demonstrate a >25% efficient GaInP/Si 3T cell which is bonded using a transparent, conductive adhesive material to enable optical and electrical coupling between the subcells.}, keywords = {3T, Tandem}, pubstate = {published}, tppubtype = {inproceedings} } Multijunction architectures provide a crosscutting solution for increasing solar cell efficiency for a variety of material types and combinations. We discuss a three-terminal tandem cell demonstrated using a III-V/Si platform. High efficiencies have been achieved in two and four terminal designs, but two-terminal cells require current matching, and four-terminal cells require intermediate grids to transport current laterally from in between the cells to the edges, which can lead to optical and resistive losses. Our three-terminal architecture utilizes a modified interdigitated back contact Si bottom cell, enabling maximized power extraction for any band gap combination, without intermediate grids. We demonstrate a >25% efficient GaInP/Si 3T cell which is bonded using a transparent, conductive adhesive material to enable optical and electrical coupling between the subcells.
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K. Bothe, D. Hinken, T. Gandy, I. Ahrens, and C. Schinke Approximating the determination of the spectral responsivity of solar cells Inproceedings IEEE (Hrsg.): 7th World Conference on Photovoltaic Energy Conversion (WCPEC-7), Waikoloa, HI, USA, (2018). Abstract | BibTeX | Schlagwörter: spectral responsivity @inproceedings{Bothe2018b,
title = {Approximating the determination of the spectral responsivity of solar cells}, author = {K Bothe and D Hinken and T Gandy and I Ahrens and C Schinke}, editor = {IEEE}, year = {2018}, date = {2018-06-15}, booktitle = {7th World Conference on Photovoltaic Energy Conversion (WCPEC-7)}, address = {Waikoloa, HI, USA}, abstract = {The determination of the spectral responsivity is an essential part of solar cell calibration. Apart from the complete differential spectral responsivity procedure, which yields the most accurate results, the IEC 60904-8 defines four simplifications. We provide detailed information on the expected variations in the calculated spectral responsivity curves for the different simplifications compared to the complete procedure. For non-linear crystalline silicon front junction solar cells, we show that deviations mainly occur at wavelengths above 700 nm and become largest between 1000 to 1200 nm. Even though we found a maximum deviation in spectral responsivity of 7% for the simplification with lowest requirements in bias irradiance, all other simplifications yield deviations well below 3%. This transforms into a deviation of 0.01 in the spectral mismatch factor for an industrial PERC solar cell when using a typical world photovoltaic scale (WPVS) reference solar cell and a class A two-lamp solar simulator. If you are reliant on the use of a simplification, we recommend using the multicolour approach. Even though the singlecolour approach might yield lower deviations in specific cases, it requires knowledge about the maximum in the spectral responsivity, which is not generally known in advance of the measurement. Accepting a slightly higher deviation, the white bias approach is a recommendable alternative.}, keywords = {spectral responsivity}, pubstate = {published}, tppubtype = {inproceedings} } The determination of the spectral responsivity is an essential part of solar cell calibration. Apart from the complete differential spectral responsivity procedure, which yields the most accurate results, the IEC 60904-8 defines four simplifications. We provide detailed information on the expected variations in the calculated spectral responsivity curves for the different simplifications compared to the complete procedure. For non-linear crystalline silicon front junction solar cells, we show that deviations mainly occur at wavelengths above 700 nm and become largest between 1000 to 1200 nm. Even though we found a maximum deviation in spectral responsivity of 7% for the simplification with lowest requirements in bias irradiance, all other simplifications yield deviations well below 3%. This transforms into a deviation of 0.01 in the spectral mismatch factor for an industrial PERC solar cell when using a typical world photovoltaic scale (WPVS) reference solar cell and a class A two-lamp solar simulator. If you are reliant on the use of a simplification, we recommend using the multicolour approach. Even though the singlecolour approach might yield lower deviations in specific cases, it requires knowledge about the maximum in the spectral responsivity, which is not generally known in advance of the measurement. Accepting a slightly higher deviation, the white bias approach is a recommendable alternative.
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A. Morlier, M. Siebert, I. Kunze, S. Blankemeyer, and M. Köntges Influence of environmental conditions on UV fluorescence imaging in the field Inproceedings IEEE (Hrsg.): 7th World Conference on Photovoltaic Energy Conversion (WCPEC-7), Waikoloa, HI, USA, (2018). Abstract | BibTeX | Schlagwörter: Fluorescence, UV @inproceedings{Morlier2018,
title = { Influence of environmental conditions on UV fluorescence imaging in the field}, author = {A Morlier and M Siebert and I Kunze and S Blankemeyer and M Köntges}, editor = {IEEE}, year = {2018}, date = {2018-06-15}, booktitle = {7th World Conference on Photovoltaic Energy Conversion (WCPEC-7)}, address = {Waikoloa, HI, USA}, abstract = {The potential of ultraviolet (UV) fluorescence as a field technique for photovoltaic module defect detection has been demonstrated recently. In the field during daytime, environmental parameters are not controllable. We assess in this work the influence of environmental temperature on the quality and reproducibility of UV fluorescence measurements. The kind of lamination material and its aging history very much influences the fluorescence intensity. During the measurement, the temperature of the module influences the fluorescence emission. A module at NOCT can show from 3% up to 30% less fluorescence intensity than when observed at 25°C. The temperature dependence of the excitation UV light source itself has also some effect on the imaging quality but the influence of the camera temperature is negligible.}, keywords = {Fluorescence, UV}, pubstate = {published}, tppubtype = {inproceedings} } The potential of ultraviolet (UV) fluorescence as a field technique for photovoltaic module defect detection has been demonstrated recently. In the field during daytime, environmental parameters are not controllable. We assess in this work the influence of environmental temperature on the quality and reproducibility of UV fluorescence measurements. The kind of lamination material and its aging history very much influences the fluorescence intensity. During the measurement, the temperature of the module influences the fluorescence emission. A module at NOCT can show from 3% up to 30% less fluorescence intensity than when observed at 25°C. The temperature dependence of the excitation UV light source itself has also some effect on the imaging quality but the influence of the camera temperature is negligible.
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A. Morlier, M. Siebert, I. Kunze, S. Blankemeyer, and M. Köntges Ultraviolet fluorescence of ethylene-vinyl acetate in photovoltaic modules as estimation tool for yellowing and power loss Inproceedings IEEE (Hrsg.): 7th World Conference on Photovoltaic Energy Conversion (WCPEC-7), Waikoloa, HI, USA, (2018). Abstract | BibTeX | Schlagwörter: Fluorescence, UV @inproceedings{Morlier2018b,
title = {Ultraviolet fluorescence of ethylene-vinyl acetate in photovoltaic modules as estimation tool for yellowing and power loss}, author = {A Morlier and M Siebert and I Kunze and S Blankemeyer and M Köntges}, editor = {IEEE}, year = {2018}, date = {2018-06-15}, booktitle = {7th World Conference on Photovoltaic Energy Conversion (WCPEC-7)}, address = {Waikoloa, HI, USA}, abstract = {The potential of ultraviolet (UV) fluorescence as a field technique for photovoltaic module defect detection was demonstrated recently. Here we study the formation rate of the fluorophores in module encapsulating material under UV illumination. We observe a correlation between the decrease in visible light transmission of the encapsulant and UV fluorescence intensity. This correlation allows estimating the yellowing-induced power loss via fluorescence measurements}, keywords = {Fluorescence, UV}, pubstate = {published}, tppubtype = {inproceedings} } The potential of ultraviolet (UV) fluorescence as a field technique for photovoltaic module defect detection was demonstrated recently. Here we study the formation rate of the fluorophores in module encapsulating material under UV illumination. We observe a correlation between the decrease in visible light transmission of the encapsulant and UV fluorescence intensity. This correlation allows estimating the yellowing-induced power loss via fluorescence measurements
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B. Schiebler, F. Weiland, F. Giovannetti, and S. Jack Entwicklung und Bewertung von Flachkollektoren mit Wärmerohren zur Begrenzung der Stagnationstemperatur in Solarkreisen Inproceedings Symposium Solarthermie 2018, 50-69 Bad Staffelstein, Germany, (2018). BibTeX | Schlagwörter: Flachkollektor @inproceedings{Schiebler2018,
title = {Entwicklung und Bewertung von Flachkollektoren mit Wärmerohren zur Begrenzung der Stagnationstemperatur in Solarkreisen}, author = {B Schiebler and F Weiland and F Giovannetti and S Jack}, year = {2018}, date = {2018-06-15}, booktitle = {Symposium Solarthermie 2018}, pages = {50-69}, address = {Bad Staffelstein, Germany}, keywords = {Flachkollektor}, pubstate = {published}, tppubtype = {inproceedings} } |
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S. Brötje, L. Busche, Z. Grodtke, N. Tränkel, M. Kirchner, I. Kunze, R. Witteck, T. Schabbach, and F. Giovannetti Optimierung und Evaluation eines nicht abgedeckten, modularen photovoltaisch-thermischen Kollektors basierend auf einem Montagesystem mit Integralbauweise Inproceedings Symposium Solarthermie 2018, 234-252 Bad Staffelstein, Germany, (2018). @inproceedings{Brötje2018,
title = {Optimierung und Evaluation eines nicht abgedeckten, modularen photovoltaisch-thermischen Kollektors basierend auf einem Montagesystem mit Integralbauweise}, author = {S Brötje and L Busche and Z Grodtke and N Tränkel and M Kirchner and I Kunze and R Witteck and T Schabbach and F Giovannetti}, year = {2018}, date = {2018-06-15}, booktitle = {Symposium Solarthermie 2018}, pages = {234-252}, address = {Bad Staffelstein, Germany}, keywords = {PVT}, pubstate = {published}, tppubtype = {inproceedings} } |
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S. Müller, R. Reineke-Koch, F. Giovannetti, and B. Hafner Experimentelle Untersuchung der Stagnationsbelastungen in einer Trinkwarmwasseranlage mit thermochromen Flachkollektoren Inproceedings Symposium Solarthermie 2018, 281-296 Bad Staffelstein, Germany, (2018). BibTeX | Schlagwörter: Flachkollektor @inproceedings{Mueller2018,
title = {Experimentelle Untersuchung der Stagnationsbelastungen in einer Trinkwarmwasseranlage mit thermochromen Flachkollektoren}, author = {S Müller and R Reineke-Koch and F Giovannetti and B Hafner}, year = {2018}, date = {2018-06-15}, booktitle = {Symposium Solarthermie 2018}, pages = {281-296}, address = {Bad Staffelstein, Germany}, keywords = {Flachkollektor}, pubstate = {published}, tppubtype = {inproceedings} } |
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B. Schiebler, F. Weiland, and F. Giovannetti Experimentelle Bewertung von stagnationssicheren Sonnenkollektoren mit Wärmerohren zur solaren Trinkwarmwasserbereitung in Thermosiphonsystemen Inproceedings Symposium Solarthermie 2018, 306-322 Bad Staffelstein, Germany, (2018). BibTeX | Schlagwörter: Flachkollektor @inproceedings{Schiebler2018b,
title = {Experimentelle Bewertung von stagnationssicheren Sonnenkollektoren mit Wärmerohren zur solaren Trinkwarmwasserbereitung in Thermosiphonsystemen}, author = {B Schiebler and F Weiland and F Giovannetti}, year = {2018}, date = {2018-06-15}, booktitle = {Symposium Solarthermie 2018}, pages = {306-322}, address = {Bad Staffelstein, Germany}, keywords = {Flachkollektor}, pubstate = {published}, tppubtype = {inproceedings} } |
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S. Helbig, M. Kirchner, F. Giovannetti, C. Lampe, M. Littwin, and O. Kastner PVT-Kollektoren als bisolare Wärmepumpenquelle Ein Simulationsvergleich zwischen Polysun und TRNSYS Inproceedings Symposium Solarthermie 2018, 376-388 Bad Staffelstein, Germany, (2018). @inproceedings{Helbig2018,
title = {PVT-Kollektoren als bisolare Wärmepumpenquelle Ein Simulationsvergleich zwischen Polysun und TRNSYS}, author = {S Helbig and M Kirchner and F Giovannetti and C Lampe and M Littwin and O Kastner}, year = {2018}, date = {2018-06-15}, booktitle = {Symposium Solarthermie 2018}, pages = {376-388}, address = {Bad Staffelstein, Germany}, keywords = {PVT}, pubstate = {published}, tppubtype = {inproceedings} } |