Veröffentlichungen
2020 |
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T. Dullweber, M. Stöhr, C. Kruse, F. Haase, M. Rudolph, B. Beier, P. Jäger, V. Mertens, R. Peibst, and R. Brendel Solar Energy Materials and Solar Cells 212 , 110586, (2020), ISSN: 0927-0248. Abstract | Links | BibTeX | Schlagwörter: a-Si fingers, Carrier Selective Contacts, PERC, PERC+, POLO, Shadow mask, TOPCon @article{Dullweber2020c,
title = {Evolutionary PERC+ solar cell efficiency projection towards 24% evaluating shadow-mask-deposited poly-Si fingers below the Ag front contact as next improvement step}, author = {T Dullweber and M Stöhr and C Kruse and F Haase and M Rudolph and B Beier and P Jäger and V Mertens and R Peibst and R Brendel}, doi = {10.1016/j.solmat.2020.110586}, issn = {0927-0248}, year = {2020}, date = {2020-08-01}, journal = {Solar Energy Materials and Solar Cells}, volume = {212}, pages = {110586}, abstract = {Monofacial PERC and bifacial PERC + solar cells have become the mainstream solar cell technology exhibiting conversion efficiencies around 22.5% in mass production. We determine a specific saturation current density J0,Ag = 1400 fA/cm2 of the screen-printed Ag front contact. When weighted with the contact area fraction of 3.0% the Ag metal contacts contribute 42 fA/cm2 to the total J0,total = 130 fA/cm2 thereby being a main limitation of the Voc. We investigate carrier selective poly-Si on oxide (POLO) fingers below the screen-printed Ag contacts of PERC + solar cells in order to minimize contact recombination. We name this solar cell PERC + POLO. Numerical simulations reveal that PERC + POLO cells exhibit an efficiency potential up to 24.1% which is 0.3%abs. higher compared to PERC + solar cells. In order to enable low-cost manufacturing of poly-Si fingers, we investigate for the first time the deposition of suitable a-Si fingers by plasma-enhanced chemical vapour deposition (PECVD) through a shadow mask in a vacuum chamber. We demonstrate a-Si fingers as narrow as 70 μm and as high as 250 nm. The parasitic deposition below the mask increases the a-Si finger width by less than 30 μm compared to the mask opening width. First test wafers demonstrate an implied Voc up to 716 mV of PECVD a-Si layers which are crystalized and doped in a subsequent POCl3 diffusion. Applying this process sequence, PERC + POLO cells could be manufactured with the established industrial PERC + process only adding the PECVD deposition of a-Si fingers through a shadow mask.}, keywords = {a-Si fingers, Carrier Selective Contacts, PERC, PERC+, POLO, Shadow mask, TOPCon}, pubstate = {published}, tppubtype = {article} } Monofacial PERC and bifacial PERC + solar cells have become the mainstream solar cell technology exhibiting conversion efficiencies around 22.5% in mass production. We determine a specific saturation current density J0,Ag = 1400 fA/cm2 of the screen-printed Ag front contact. When weighted with the contact area fraction of 3.0% the Ag metal contacts contribute 42 fA/cm2 to the total J0,total = 130 fA/cm2 thereby being a main limitation of the Voc. We investigate carrier selective poly-Si on oxide (POLO) fingers below the screen-printed Ag contacts of PERC + solar cells in order to minimize contact recombination. We name this solar cell PERC + POLO. Numerical simulations reveal that PERC + POLO cells exhibit an efficiency potential up to 24.1% which is 0.3%abs. higher compared to PERC + solar cells. In order to enable low-cost manufacturing of poly-Si fingers, we investigate for the first time the deposition of suitable a-Si fingers by plasma-enhanced chemical vapour deposition (PECVD) through a shadow mask in a vacuum chamber. We demonstrate a-Si fingers as narrow as 70 μm and as high as 250 nm. The parasitic deposition below the mask increases the a-Si finger width by less than 30 μm compared to the mask opening width. First test wafers demonstrate an implied Voc up to 716 mV of PECVD a-Si layers which are crystalized and doped in a subsequent POCl3 diffusion. Applying this process sequence, PERC + POLO cells could be manufactured with the established industrial PERC + process only adding the PECVD deposition of a-Si fingers through a shadow mask.
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2018 |
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R. Brendel, C. Kruse, A. Merkle, and R. Peibst Screening Selective Contact Material Combinations for Novel Crystalline Si Cell Structures Inproceedings WIP (Hrsg.): Proceedings of the 35th European Photovoltaic Solar Energy Conference and Exhibition, 39-46, Brussels, Belgium, (2018). Abstract | Links | BibTeX | Schlagwörter: Carrier Selective Contacts, laser processing, loss analysis, poly Si, selective contact, selectivity, Silicon Solar Cell(s) @inproceedings{Brendel2018,
title = {Screening Selective Contact Material Combinations for Novel Crystalline Si Cell Structures}, author = {R Brendel and C Kruse and A Merkle and R Peibst}, editor = {WIP}, doi = {10.4229/35thEUPVSEC20182018-1AO.2.6}, year = {2018}, date = {2018-09-24}, booktitle = {Proceedings of the 35th European Photovoltaic Solar Energy Conference and Exhibition}, pages = {39-46}, address = {Brussels, Belgium}, abstract = {High efficiency crystalline Si solar cells require contacts with high carrier selectivity. This is ensured for contacts having low recombination currents as well as low contact resistances. A large variety of material systems for electron- and hole-selective contacts were measured in the literature. We screen a subset of electron- and hole-selective contacts to find promising combinations in terms of efficiency potential on the one hand and in terms of practical processes on the other hand. We use modelling of ideal Si cells with non-ideal experimental contact properties to determine the maximum efficiency and the optimized areal contact fractions for many contact combinations. Cells using a-Si and/or poly-Si contacts have the highest contact-limited efficiencies. Such cells are, however, quite different from today’s PERC technology. We therefore also look for contact combinations that have one contact type equal to the current PERC technology and identify cell structures that combine a poly-Si(n) contact with a screen-printed Al-doped contacts (PAL cells) as an attractive upgrade for the PERC technology. We also report on experimental work on building blocks for various types of PAL cells.}, keywords = {Carrier Selective Contacts, laser processing, loss analysis, poly Si, selective contact, selectivity, Silicon Solar Cell(s)}, pubstate = {published}, tppubtype = {inproceedings} } High efficiency crystalline Si solar cells require contacts with high carrier selectivity. This is ensured for contacts having low recombination currents as well as low contact resistances. A large variety of material systems for electron- and hole-selective contacts were measured in the literature. We screen a subset of electron- and hole-selective contacts to find promising combinations in terms of efficiency potential on the one hand and in terms of practical processes on the other hand. We use modelling of ideal Si cells with non-ideal experimental contact properties to determine the maximum efficiency and the optimized areal contact fractions for many contact combinations. Cells using a-Si and/or poly-Si contacts have the highest contact-limited efficiencies. Such cells are, however, quite different from today’s PERC technology. We therefore also look for contact combinations that have one contact type equal to the current PERC technology and identify cell structures that combine a poly-Si(n) contact with a screen-printed Al-doped contacts (PAL cells) as an attractive upgrade for the PERC technology. We also report on experimental work on building blocks for various types of PAL cells.
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B. Min, T. Wietler, S. Bordihn, R. Peibst, T. Desrues, P. Carroy, J. Jourdan, M. Hermle, F. Feldmann, J. Bartsch, C. Allebé, L. Ding, J. Horzel, A. Lachowicz, A. Ingenito, F-J. Haug, E. Schneiderlöchner, V. Linss, K. Lüdemann, A. Campa, M. Bokalic, M. Topic, M. Zwegers, B. Hartlin, B. Field, B. Bénédicte, Z. Adam, J. Penaud, S. Filonovich, E. Marcon, J. Chupin, and F. Tamini WIP (Hrsg.): Proceedings of the 35th European Photovoltaic Solar Energy Conference and Exhibition, 229-232, Brussels, Belgium, (2018). Abstract | Links | BibTeX | Schlagwörter: Carrier Selective Contacts, Horizon2020, Multi Wire, Passivated Contact, Plating, Transparent Conductive Oxides @inproceedings{Min2018b,
title = {Status of the EU H2020 Disc Project: European Collaboration in Research and Development of High Efficient Double Side Contacted Cells with Innovative Carrier-Selective Contacts}, author = {B Min and T Wietler and S Bordihn and R Peibst and T Desrues and P Carroy and J Jourdan and M Hermle and F Feldmann and J Bartsch and C Allebé and L Ding and J Horzel and A Lachowicz and A Ingenito and F-J Haug and E Schneiderlöchner and V Linss and K Lüdemann and A Campa and M Bokalic and M Topic and M Zwegers and B Hartlin and B Field and B Bénédicte and Z Adam and J Penaud and S Filonovich and E Marcon and J Chupin and F Tamini}, editor = {WIP}, doi = {10.4229/35thEUPVSEC20182018-2BP.1.4}, year = {2018}, date = {2018-09-24}, booktitle = {Proceedings of the 35th European Photovoltaic Solar Energy Conference and Exhibition}, pages = {229-232}, address = {Brussels, Belgium}, abstract = {The DISC project addresses the development of key technologies for the next generation of high-performance photovoltaic solar cells and modules. Our approach is to fully exploit the potential of silicon to its maximum by the use of passivating contacts or carrier selective contacts and junctions. Such contacts allow for simple, non-patterned double-side contacted device architecture and an enhancement of the energy yield, which will be key elements for achieving very low levelized costs of electricity. In this paper, selected highlights are presented concerning the first 18 months in the development of cell and module components such as In-free transparent conductive oxide layers with low sputtering damage. The synergies and results created within DISC will be also interesting for a drop-in combination with other solar cell and module technologies.}, keywords = {Carrier Selective Contacts, Horizon2020, Multi Wire, Passivated Contact, Plating, Transparent Conductive Oxides}, pubstate = {published}, tppubtype = {inproceedings} } The DISC project addresses the development of key technologies for the next generation of high-performance photovoltaic solar cells and modules. Our approach is to fully exploit the potential of silicon to its maximum by the use of passivating contacts or carrier selective contacts and junctions. Such contacts allow for simple, non-patterned double-side contacted device architecture and an enhancement of the energy yield, which will be key elements for achieving very low levelized costs of electricity. In this paper, selected highlights are presented concerning the first 18 months in the development of cell and module components such as In-free transparent conductive oxide layers with low sputtering damage. The synergies and results created within DISC will be also interesting for a drop-in combination with other solar cell and module technologies.
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R. Peibst, Y. Larionova, S. Reiter, T. F. Wietler, N. Orlowski, S. Schäfer, B. Min, M. Stratmann, D. Tetzlaff, J. Krügener, U. Höhne, J. D. Kähler, H. Mehlich, S. Frigge, and R. Brendel IEEE Journal of Photovoltaics 8 (3), 719-725, (2018), ISSN: 2156-3381. Abstract | Links | BibTeX | Schlagwörter: Carrier Selective Contacts, passivation, Polycrystalline silicon, Silicon solar cell, transparent conductive oxide, Zinc oxide @article{Peibst2018,
title = {Building Blocks for Industrial, Screen-Printed Double-Side Contacted POLO Cells With Highly Transparent ZnO:Al Layers}, author = {R Peibst and Y Larionova and S Reiter and T F Wietler and N Orlowski and S Schäfer and B Min and M Stratmann and D Tetzlaff and J Krügener and U Höhne and J D Kähler and H Mehlich and S Frigge and R Brendel}, doi = {10.1109/JPHOTOV.2018.2813427}, issn = {2156-3381}, year = {2018}, date = {2018-05-01}, journal = {IEEE Journal of Photovoltaics}, volume = {8}, number = {3}, pages = {719-725}, abstract = {We report on an industrial large area, screen-printed, double-side contacted cell with polysilicon on oxide (POLO) junctions on both sides and an energy conversion efficiency of 22.3% (A = 244.15 cm 2, Voc = 714 mV, FF = 81.1%, Jsc = 38.5 mA/cm2, measured in-house). This cell shows an extraordinarily low series resistance below 0.05 Ω cm2. This confirms the low specific junction resistance observed recently for POLO junctions. The present cell suffers from 1) low short-circuit current due to parasitic absorption in the rather thick poly-Si (30 nm), as well as in the indium tin oxide, 2) deterioration of the recombination behavior upon sputter deposition of a transparent conductive oxide (TCO), and 3) shunts near the edge due to nonadapted TCO edge exclusion. We address all of these limitations experimentally. In particular, we developed a plasma-enhanced chemical vapor deposition process for ZnO:Al, which does not compromise the passivation of the POLO junctions underneath. An estimation of the efficiency potential (based on the two-diode model and the assumption that all these building blocks can be successfully combined on a cell level) shows that 25.3% can be achieved with this cell concept. We also look into potential cost advantages of the POLO junction scheme for this cell structure, such as the usage of p-type Cz-Si material and the omission of Ag fingers.}, keywords = {Carrier Selective Contacts, passivation, Polycrystalline silicon, Silicon solar cell, transparent conductive oxide, Zinc oxide}, pubstate = {published}, tppubtype = {article} } We report on an industrial large area, screen-printed, double-side contacted cell with polysilicon on oxide (POLO) junctions on both sides and an energy conversion efficiency of 22.3% (A = 244.15 cm 2, Voc = 714 mV, FF = 81.1%, Jsc = 38.5 mA/cm2, measured in-house). This cell shows an extraordinarily low series resistance below 0.05 Ω cm2. This confirms the low specific junction resistance observed recently for POLO junctions. The present cell suffers from 1) low short-circuit current due to parasitic absorption in the rather thick poly-Si (30 nm), as well as in the indium tin oxide, 2) deterioration of the recombination behavior upon sputter deposition of a transparent conductive oxide (TCO), and 3) shunts near the edge due to nonadapted TCO edge exclusion. We address all of these limitations experimentally. In particular, we developed a plasma-enhanced chemical vapor deposition process for ZnO:Al, which does not compromise the passivation of the POLO junctions underneath. An estimation of the efficiency potential (based on the two-diode model and the assumption that all these building blocks can be successfully combined on a cell level) shows that 25.3% can be achieved with this cell concept. We also look into potential cost advantages of the POLO junction scheme for this cell structure, such as the usage of p-type Cz-Si material and the omission of Ag fingers.
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2017 |
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D. Tetzlaff, J. Krügener, Y. Larionova, S. Reiter, M. Turcu, F. Haase, R. Brendel, R. Peibst, U. Höhne, J. -D. Kähler, and T. F. Wietler Solar Energy Materials and Solar Cells 173 , 106-110, (2017), ISSN: 0927-0248, (Proceedings of the 7th international conference on Crystalline Silicon Photovoltaics). Abstract | Links | BibTeX | Schlagwörter: Carrier Selective Contacts, pinholes, polysilicon, Tetramethylammonium hydroxide (TMAH) @article{Tetzlaff2017c,
title = {A simple method for pinhole detection in carrier selective POLO-junctions for high efficiency silicon solar cells}, author = {D Tetzlaff and J Krügener and Y Larionova and S Reiter and M Turcu and F Haase and R Brendel and R Peibst and U Höhne and J -D Kähler and T F Wietler}, doi = {10.1016/j.solmat.2017.05.041}, issn = {0927-0248}, year = {2017}, date = {2017-12-01}, journal = {Solar Energy Materials and Solar Cells}, volume = {173}, pages = {106-110}, abstract = {Polycrystalline silicon (poly-Si) layers on thin silicon oxide films have received strong research interest as they form excellent carrier selective junctions on crystalline silicon substrates after appropriate thermal processing. Recently, we presented a new method to determine the pinhole density in interfacial oxide films of poly-Si on oxide (POLO)-junctions with excellent electrical properties. The concept of magnification of nanometer-size pinholes in the interfacial oxide by selective etching of the underlying crystalline silicon is used to investigate the influence of annealing temperature on pinhole densities. Eventually, the pinholes are detected by optical microscopy and scanning electron microscopy. We present results on the pinhole density in POLO-junctions with J0 values as low as 1.4 fA/cm2. The stability of this method is demonstrated by proving that no new holes are introduced to the oxide during the etching procedure for a wide range of etching times. Finally, we show the applicability to multiple oxide types and thickness values, differently doped poly-Si layers as well as several types of wafer surface morphologies. For wet chemically grown oxides, we verified the existence of pinholes with an areal density of 2×10^7 cm−2 even already after annealing at a temperature of 750 °C (lower than the optimum annealing temperature for these junctions).}, note = {Proceedings of the 7th international conference on Crystalline Silicon Photovoltaics}, keywords = {Carrier Selective Contacts, pinholes, polysilicon, Tetramethylammonium hydroxide (TMAH)}, pubstate = {published}, tppubtype = {article} } Polycrystalline silicon (poly-Si) layers on thin silicon oxide films have received strong research interest as they form excellent carrier selective junctions on crystalline silicon substrates after appropriate thermal processing. Recently, we presented a new method to determine the pinhole density in interfacial oxide films of poly-Si on oxide (POLO)-junctions with excellent electrical properties. The concept of magnification of nanometer-size pinholes in the interfacial oxide by selective etching of the underlying crystalline silicon is used to investigate the influence of annealing temperature on pinhole densities. Eventually, the pinholes are detected by optical microscopy and scanning electron microscopy. We present results on the pinhole density in POLO-junctions with J0 values as low as 1.4 fA/cm2. The stability of this method is demonstrated by proving that no new holes are introduced to the oxide during the etching procedure for a wide range of etching times. Finally, we show the applicability to multiple oxide types and thickness values, differently doped poly-Si layers as well as several types of wafer surface morphologies. For wet chemically grown oxides, we verified the existence of pinholes with an areal density of 2×10^7 cm−2 even already after annealing at a temperature of 750 °C (lower than the optimum annealing temperature for these junctions).
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R. Peibst, Y. Larionova, Reiter. S. N. Orlowski, S. Schäfer, M. Turcu, B. Min, R. Brendel, D. Tetzlaff, J. Krügener, T. Wietler, U. Höhne, J-D. Kähler, H. Mehlich, and S. Frigge Industrial, Screen-Printed Double-Side Contacted Polo Cells Inproceedings WIP (Hrsg.): Proceedings of the 33rd European Photovoltaic Solar Energy Conference and Exhibition, 451-454, Amsterdam, The Netherlands, (2017), ISBN: 3-936338-47-7. Abstract | Links | BibTeX | Schlagwörter: Carrier Selective Contacts, passivation, Polycrystalline Silicon (Si), Silicon Solar Cell(s), Transparent Conductive Oxide Films @inproceedings{Peibst2017,
title = {Industrial, Screen-Printed Double-Side Contacted Polo Cells}, author = {R Peibst and Y Larionova and S Reiter N Orlowski and S Schäfer and M Turcu and B Min and R Brendel and D Tetzlaff and J Krügener and T Wietler and U Höhne and J-D Kähler and H Mehlich and S Frigge }, editor = {WIP}, doi = {10.4229/EUPVSEC20172017-2DO.2.2}, isbn = {3-936338-47-7}, year = {2017}, date = {2017-09-28}, booktitle = {Proceedings of the 33rd European Photovoltaic Solar Energy Conference and Exhibition}, pages = {451-454}, address = {Amsterdam, The Netherlands}, abstract = {We demonstrate an industrial double-side-contacted, screen-printed large area cell with POLO junctions on both sides and an in-house-measured energy conversion efficiency of 22.3 % (A = 244.15 cm2, Voc =714 mV, FF= 81.1 %, Jsc =38.5 mA/cm2). Most remarkably, this cell shows a very low series resistance < 0.05 Ωcm2, which supports previous observations of low specific junction resistance for the POLO scheme. The current limitations of the cell are (i) the low short-circuit current due to parasitic absorption in the rather thick poly-Si (30 nm), as well as in the ITO, (ii) deterioration of the recombination behavior upon TCO sputtering, and (iii) shunts near the edge due to non-adapted TCO edge-exclusion. }, keywords = {Carrier Selective Contacts, passivation, Polycrystalline Silicon (Si), Silicon Solar Cell(s), Transparent Conductive Oxide Films}, pubstate = {published}, tppubtype = {inproceedings} } We demonstrate an industrial double-side-contacted, screen-printed large area cell with POLO junctions on both sides and an in-house-measured energy conversion efficiency of 22.3 % (A = 244.15 cm2, Voc =714 mV, FF= 81.1 %, Jsc =38.5 mA/cm2). Most remarkably, this cell shows a very low series resistance < 0.05 Ωcm2, which supports previous observations of low specific junction resistance for the POLO scheme. The current limitations of the cell are (i) the low short-circuit current due to parasitic absorption in the rather thick poly-Si (30 nm), as well as in the ITO, (ii) deterioration of the recombination behavior upon TCO sputtering, and (iii) shunts near the edge due to non-adapted TCO edge-exclusion.
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D. Tetzlaff, M. Dzinnik, J. Krügener, Y. Larionova, S. Reiter, M. Turcu, R. Peibst, U. Höhne, J-D. Kähler, and T. F. Wietler Energy Procedia 124 (Supplement C), 435-440, (2017), ISSN: 1876-6102, (7th International Conference on Silicon Photovoltaics, SiliconPV 2017, 3-5 April 2017, Freiburg, Germany). Abstract | Links | BibTeX | Schlagwörter: Carrier Selective Contacts, pinholes, polysilicon, Tetramethylammonium hydroxide (TMAH) @article{Tetzlaff2017c,
title = {Introducing pinhole magnification by selective etching: application to poly-Si on ultra-thin silicon oxide films}, author = {D Tetzlaff and M Dzinnik and J Krügener and Y Larionova and S Reiter and M Turcu and R Peibst and U Höhne and J-D Kähler and T F Wietler}, doi = {10.1016/j.egypro.2017.09.270}, issn = {1876-6102}, year = {2017}, date = {2017-09-21}, journal = {Energy Procedia}, volume = {124}, number = {Supplement C}, pages = {435-440}, abstract = {Carrier selective junctions formed by polycrystalline silicon (poly-Si) on ultra-thin silicon oxide films are currently in the spotlight of silicon photovoltaics. We develop a simple method using selective etching and conventional optical microscopy to determine the pinhole density in interfacial oxide films of poly-Si on oxide (POLO)-junctions with excellent electrical properties. We characterize the selective etching of poly-Si versus ultra-thin silicon oxide. We use test structures with deliberately patterned openings and 3 nm thin oxide films to check the feasibility of magnification by undercutting the interfacial oxide. With the successful proof of our concept we introduce a new method to access the density of nanometer-size pinholes in POLO-junctions with excellent passivation properties.}, note = {7th International Conference on Silicon Photovoltaics, SiliconPV 2017, 3-5 April 2017, Freiburg, Germany}, keywords = {Carrier Selective Contacts, pinholes, polysilicon, Tetramethylammonium hydroxide (TMAH)}, pubstate = {published}, tppubtype = {article} } Carrier selective junctions formed by polycrystalline silicon (poly-Si) on ultra-thin silicon oxide films are currently in the spotlight of silicon photovoltaics. We develop a simple method using selective etching and conventional optical microscopy to determine the pinhole density in interfacial oxide films of poly-Si on oxide (POLO)-junctions with excellent electrical properties. We characterize the selective etching of poly-Si versus ultra-thin silicon oxide. We use test structures with deliberately patterned openings and 3 nm thin oxide films to check the feasibility of magnification by undercutting the interfacial oxide. With the successful proof of our concept we introduce a new method to access the density of nanometer-size pinholes in POLO-junctions with excellent passivation properties.
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2016 |
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R. Brendel, M. Rienaecker, and R. Peibst A quantitative measure for the carrier selectivity of contacts to solar cells Inproceedings WIP (Hrsg.): Proceedings of the 32nd European Photovoltaic Solar Energy Conference, 447-451, Munich, Germany, (2016), ISBN: 3-936338-41-8. Abstract | Links | BibTeX | Schlagwörter: Carrier Selective Contacts, loss analysis, selectivity, Silicon Solar Cell(s) @inproceedings{Brendel2016,
title = {A quantitative measure for the carrier selectivity of contacts to solar cells}, author = {R Brendel and M Rienaecker and R Peibst}, editor = {WIP}, doi = {10.4229/EUPVSEC20162016-2CO.4.1}, isbn = {3-936338-41-8}, year = {2016}, date = {2016-09-01}, booktitle = {Proceedings of the 32nd European Photovoltaic Solar Energy Conference}, journal = {Proceedings of the 32nd European Photovoltaic Solar Energy Conference}, pages = {447-451}, address = {Munich, Germany}, abstract = {We discuss a physically motivated definition for a quantitative measure of the selectivity of electron and hole contacts. We define the selectivity S10 = log10(Vth /(c ×Jc)) to depend on the contact resistance c, the recombination current density Jc of the contact, and the thermal voltage Vth. A high selectivity relies on a highly asymmetric equilibrium carrier concentration of majority and minority carriers in the contact. The maximum efficiency max increases with the selectivity S10. This increase is linear until the efficiency starts to be limited by radiative recombination. We give analytic equations for calculating the maximum efficiency max(S10) of a crystalline Si cell that is ideal except for either one or two contacts. Achieving the maximum efficiency max requires optimized areal fractions fe,max and fh,max for the electron and the hole contacts, respectively . We give analytic equations for these contact fractions. }, keywords = {Carrier Selective Contacts, loss analysis, selectivity, Silicon Solar Cell(s)}, pubstate = {published}, tppubtype = {inproceedings} } We discuss a physically motivated definition for a quantitative measure of the selectivity of electron and hole contacts. We define the selectivity S10 = log10(Vth /(c ×Jc)) to depend on the contact resistance c, the recombination current density Jc of the contact, and the thermal voltage Vth. A high selectivity relies on a highly asymmetric equilibrium carrier concentration of majority and minority carriers in the contact. The maximum efficiency max increases with the selectivity S10. This increase is linear until the efficiency starts to be limited by radiative recombination. We give analytic equations for calculating the maximum efficiency max(S10) of a crystalline Si cell that is ideal except for either one or two contacts. Achieving the maximum efficiency max requires optimized areal fractions fe,max and fh,max for the electron and the hole contacts, respectively . We give analytic equations for these contact fractions.
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R. Peibst, Y. Larionova, S. Reiter, M. Turcu, R. Brendel, D. Tetzlaff, J. Krügener, T. Wietler, U. Höhne, J. -D. Kähler, H. Mehlich, and S. Frigge Implementation of n+ and p+ poly junctions on front and rear side of double-side-contacted industrial silicon solar cells Inproceedings WIP (Hrsg.): Proceedings of the 32nd European Photovoltaic Solar Energy Conference, 323-327, Munich, Germany, (2016), ISBN: 3-936338-41-8. Abstract | Links | BibTeX | Schlagwörter: Carrier Selective Contacts, passivation, Polycrystalline Silicon (Si), Silicon Solar Cell(s) @inproceedings{Peibst2016,
title = {Implementation of n+ and p+ poly junctions on front and rear side of double-side-contacted industrial silicon solar cells}, author = {R Peibst and Y Larionova and S Reiter and M Turcu and R Brendel and D Tetzlaff and J Krügener and T Wietler and U Höhne and J -D Kähler and H Mehlich and S Frigge}, editor = {WIP}, doi = {10.4229/EUPVSEC20162016-2BO.3.2}, isbn = {3-936338-41-8}, year = {2016}, date = {2016-09-01}, booktitle = {Proceedings of the 32nd European Photovoltaic Solar Energy Conference}, journal = {Proceedings of the 32nd European Photovoltaic Solar Energy Conference}, pages = {323-327}, address = {Munich, Germany}, abstract = {We present building blocks for double-side contacted cells with poly-Si on passivating interfacial oxides (POLO) junctions for both polarities, fabricated by a lean process flow. For this purpose, we evaluate p+ and n+ POLO junctions utilizing ~1.7 nm thin wet chemically grown (ozone diluted in di-ionized water) and ozone grown interfacial oxides on different surface morphologies. We achieve excellent passivation quality on damaged etched (100) surfaces with record low J0 values of 0.6 fA/cm2 (implied open circuit voltage Voc,impl 748 mV) for n+ POLO junctions and of 5 fA/cm2 (Voc,impl 729 mV) for p+ POLO junctions. However, on alkaline textured surfaces, ~6 times higher J0 values are obtained. We compare ex-situ-doped poly-Si (intrinsically deposited and subsequently ion implanted) with in-situ-doped poly-Si layers. For POLO junctions formed on textured surfaces by utilizing wet chemical oxides and low-pressure chemical vapor deposition (LP-CVD) of 20 nm in-situ n+-doped poly-Si, we obtain J0 values down to 2.4 fA/cm2. Also with plasma-enhanced chemical vapor deposition (PE-CVD) of in-situ-doped amorphous Si and subsequent crystallization, we obtain comparable results. A transparent conductive oxide (TCO), preferably temperature stable, seems to be required to support the limited lateral conductivity of POLO junctions with poly-Si layer thicknesses ≤ 20 nm. We find that the conductivity of indium tin oxide (ITO) strongly decreases upon firing, while the initial conductivity can be maintained even for firing temperatures of 800°C when capping the ITO with a thin SiNx layer. Our recent cell precursors (156 mm 156 mm Cz n-type wafers with an n+ POLO junction on an alkaline textured front-side and a p+ POLO junction on a damage-etched rear-side) exhibit a promising Voc,impl value of 732 mV, and a total J0 value of the doped surfaces of 12 fA/cm2. In combination with the high pseudo fill factor of 85.3 % and with a short-circuit current density of 40 mA/cm2 as calculated by ray tracing simulations, the corresponding pseudo efficiency is 25.0 %. }, keywords = {Carrier Selective Contacts, passivation, Polycrystalline Silicon (Si), Silicon Solar Cell(s)}, pubstate = {published}, tppubtype = {inproceedings} } We present building blocks for double-side contacted cells with poly-Si on passivating interfacial oxides (POLO) junctions for both polarities, fabricated by a lean process flow. For this purpose, we evaluate p+ and n+ POLO junctions utilizing ~1.7 nm thin wet chemically grown (ozone diluted in di-ionized water) and ozone grown interfacial oxides on different surface morphologies. We achieve excellent passivation quality on damaged etched (100) surfaces with record low J0 values of 0.6 fA/cm2 (implied open circuit voltage Voc,impl 748 mV) for n+ POLO junctions and of 5 fA/cm2 (Voc,impl 729 mV) for p+ POLO junctions. However, on alkaline textured surfaces, ~6 times higher J0 values are obtained. We compare ex-situ-doped poly-Si (intrinsically deposited and subsequently ion implanted) with in-situ-doped poly-Si layers. For POLO junctions formed on textured surfaces by utilizing wet chemical oxides and low-pressure chemical vapor deposition (LP-CVD) of 20 nm in-situ n+-doped poly-Si, we obtain J0 values down to 2.4 fA/cm2. Also with plasma-enhanced chemical vapor deposition (PE-CVD) of in-situ-doped amorphous Si and subsequent crystallization, we obtain comparable results. A transparent conductive oxide (TCO), preferably temperature stable, seems to be required to support the limited lateral conductivity of POLO junctions with poly-Si layer thicknesses ≤ 20 nm. We find that the conductivity of indium tin oxide (ITO) strongly decreases upon firing, while the initial conductivity can be maintained even for firing temperatures of 800°C when capping the ITO with a thin SiNx layer. Our recent cell precursors (156 mm 156 mm Cz n-type wafers with an n+ POLO junction on an alkaline textured front-side and a p+ POLO junction on a damage-etched rear-side) exhibit a promising Voc,impl value of 732 mV, and a total J0 value of the doped surfaces of 12 fA/cm2. In combination with the high pseudo fill factor of 85.3 % and with a short-circuit current density of 40 mA/cm2 as calculated by ray tracing simulations, the corresponding pseudo efficiency is 25.0 %.
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U. Römer, R. Peibst, T. Ohrdes, B. Lim, J. Krügener, T. Wietler, and R. Brendel Ion implantation for poly-Si passivated back-junction back-contacted solar cells Artikel IEEE Journal of Photovoltaics 5 (2), 507-514, (2015). Links | BibTeX | Schlagwörter: Back contact solar cells, boron, Carrier Selective Contacts, Doping, Implants, Ion implantation, Junctions, Photovoltaic cells, silicon, solar energy @article{Römer2015,
title = {Ion implantation for poly-Si passivated back-junction back-contacted solar cells}, author = {U Römer and R Peibst and T Ohrdes and B Lim and J Krügener and T Wietler and R Brendel}, doi = {10.1109/JPHOTOV.2014.2382975}, year = {2015}, date = {2015-03-01}, journal = {IEEE Journal of Photovoltaics}, volume = {5}, number = {2}, pages = {507-514}, keywords = {Back contact solar cells, boron, Carrier Selective Contacts, Doping, Implants, Ion implantation, Junctions, Photovoltaic cells, silicon, solar energy}, pubstate = {published}, tppubtype = {article} } |