Veröffentlichungen
2017 |
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J. Krügener, F. Haase, M. Rienäcker, R. Brendel, H. J. Osten, and R. Peibst Solar Energy Materials and Solar Cells 173 , 85-91, (2017), ISSN: 0927-0248, (Proceedings of the 7th international conference on Crystalline Silicon Photovoltaics). Abstract | Links | BibTeX | Schlagwörter: Carrier lifetime, Gettering, passivating contact, POLO, polysilicon, Silicon solar cell, solar cell @article{Krügener2017b,
title = {Improvement of the SRH bulk lifetime upon formation of n-type POLO junctions for 25% efficient Si solar cells}, author = {J Krügener and F Haase and M Rienäcker and R Brendel and H J Osten and R Peibst}, doi = {10.1016/j.solmat.2017.05.055}, issn = {0927-0248}, year = {2017}, date = {2017-12-01}, journal = {Solar Energy Materials and Solar Cells}, volume = {173}, pages = {85-91}, abstract = {Carrier-selective contact schemes, like polysilicon on oxide (POLO), provide low contact resistivities while preserving an excellent passivation quality. These junctions offer an important additional feature compared to a-Si/c-Si heterojunctions. We find that the formation of n-type POLO junctions lead to a huge increase of the Shockley-Read-Hall (SRH) lifetime of the substrate, a prerequisite for highly efficient solar cells. The SRH lifetime improvement can be observed for both bulk polarities and for a variety of bulk resistivities. Thus we suggest that the highly doped POLO junction getters impurities that have more or less symmetric SRH capture cross sections. We are able to achieve SRH lifetimes of > 50 ms. By applying POLO junctions to interdigitated back contact cells, we achieve cells with an efficiency of 25%.}, note = {Proceedings of the 7th international conference on Crystalline Silicon Photovoltaics}, keywords = {Carrier lifetime, Gettering, passivating contact, POLO, polysilicon, Silicon solar cell, solar cell}, pubstate = {published}, tppubtype = {article} } Carrier-selective contact schemes, like polysilicon on oxide (POLO), provide low contact resistivities while preserving an excellent passivation quality. These junctions offer an important additional feature compared to a-Si/c-Si heterojunctions. We find that the formation of n-type POLO junctions lead to a huge increase of the Shockley-Read-Hall (SRH) lifetime of the substrate, a prerequisite for highly efficient solar cells. The SRH lifetime improvement can be observed for both bulk polarities and for a variety of bulk resistivities. Thus we suggest that the highly doped POLO junction getters impurities that have more or less symmetric SRH capture cross sections. We are able to achieve SRH lifetimes of > 50 ms. By applying POLO junctions to interdigitated back contact cells, we achieve cells with an efficiency of 25%.
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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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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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Y. Larionova, M. Turcu, S. Reiter, R. Brendel, D. Tetzlaff, J. Krügener, T. Wietler, U. Höhne, J-D. Kähler, and R. Peibst physica status solidi (a) 214 (8), 1700058, (2017), ISSN: 1862-6319, (1700058). Abstract | Links | BibTeX | Schlagwörter: passivating contact, passivation, polysilicon, Silicon solar cell @article{Larionova2017,
title = {On the recombination behavior of p+-type polysilicon on oxide junctions deposited by different methods on textured and planar surfaces}, author = {Y Larionova and M Turcu and S Reiter and R Brendel and D Tetzlaff and J Krügener and T Wietler and U Höhne and J-D Kähler and R Peibst}, doi = {10.1002/pssa.201700058}, issn = {1862-6319}, year = {2017}, date = {2017-08-01}, journal = {physica status solidi (a)}, volume = {214}, number = {8}, pages = {1700058}, abstract = {We investigate the passivation quality of hole‐collecting junctions consisting of thermally or wet‐chemically grown interfacial oxides, sandwiched between a monocrystalline‐Si substrate and a p‐type polycrystalline‐silicon (Si) layer. The three different approaches for polycrystalline‐Si preparation are compared: the plasma‐enhanced chemical vapor deposition (PECVD) of in situ p+‐type boron‐doped amorphous Si layers, the low pressure chemical vapor deposition (LPCVD) of in situ p+‐type B‐doped polycrystalline Si layers, and the LPCVD of intrinsic amorphous Si, subsequently ion‐implanted with boron. We observe the lowest J0e values of 3.8 fA cm−2 on thermally grown interfacial oxide on planar surfaces for the case of intrinsic amorphous Si deposited by LPCVD and subsequently implanted with boron. Also, we obtain a similar high passivation of p+‐type poly‐Si junctions on wet‐chemically grown oxides as well as for all the investigated polycrystalline‐Si deposition approaches. Conversely, on alkaline‐textured surfaces, J0e is at least 4 times higher compared to planar surfaces. This finding holds for all the junction preparation methods investigated. We show that the higher J0e on textured surfaces can be attributed to a poorer passivation of the p+ poly/c‐Si stacks on (111) when compared to (100) surfaces. }, note = {1700058}, keywords = {passivating contact, passivation, polysilicon, Silicon solar cell}, pubstate = {published}, tppubtype = {article} } We investigate the passivation quality of hole‐collecting junctions consisting of thermally or wet‐chemically grown interfacial oxides, sandwiched between a monocrystalline‐Si substrate and a p‐type polycrystalline‐silicon (Si) layer. The three different approaches for polycrystalline‐Si preparation are compared: the plasma‐enhanced chemical vapor deposition (PECVD) of in situ p+‐type boron‐doped amorphous Si layers, the low pressure chemical vapor deposition (LPCVD) of in situ p+‐type B‐doped polycrystalline Si layers, and the LPCVD of intrinsic amorphous Si, subsequently ion‐implanted with boron. We observe the lowest J0e values of 3.8 fA cm−2 on thermally grown interfacial oxide on planar surfaces for the case of intrinsic amorphous Si deposited by LPCVD and subsequently implanted with boron. Also, we obtain a similar high passivation of p+‐type poly‐Si junctions on wet‐chemically grown oxides as well as for all the investigated polycrystalline‐Si deposition approaches. Conversely, on alkaline‐textured surfaces, J0e is at least 4 times higher compared to planar surfaces. This finding holds for all the junction preparation methods investigated. We show that the higher J0e on textured surfaces can be attributed to a poorer passivation of the p+ poly/c‐Si stacks on (111) when compared to (100) surfaces.
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M. Rienäcker, M. Bossmeyer, A. Merkle, U. Römer, F. Haase, J. Krügener, R. Brendel, and R. Peibst IEEE Journal of Photovoltaics 7 (1), 11-18, (2017), ISSN: 2156-3381. Abstract | Links | BibTeX | Schlagwörter: Aluminum, Back-junction back-contact (BJBC) cells, boron, Conductivity, contact resistivity, Current density, Junctions, Photovoltaic cells, polysilicon, polysilicon on oxide (POLO) junctions, recombination, selective contacts, selectivity @article{Rienäcker2017b,
title = {Junction resistivity of carrier-selective polysilicon on oxide junctions and its impact on solar cell performance}, author = {M Rienäcker and M Bossmeyer and A Merkle and U Römer and F Haase and J Krügener and R Brendel and R Peibst}, doi = {10.1109/JPHOTOV.2016.2614123}, issn = {2156-3381}, year = {2017}, date = {2017-01-01}, journal = {IEEE Journal of Photovoltaics}, volume = {7}, number = {1}, pages = {11-18}, abstract = {We investigate the junction resistivity of high-quality carrier-selective polysilicon on oxide (POLO) junctions with the transfer length method. We demonstrate n+ POLO junctions with a saturation current density JC,poly of 6.2 fA/cm2 and a junction resistivity ρc of 0.6 mΩcm2, counterdoped n+ POLO junctions with 2.7 fA/cm2 and 1.3 mΩcm2, and p+ POLO junctions with 6.7 fA/cm2 and 0.2 mΩcm2. Such low junction resistivities and saturation current densities correspond to excellent selectivities S10 of up to 16.2. The efficiency potential for back-junction back-contact solar cells with these POLO junctions was determined to be larger than 25 % by numerical device simulations. We demonstrate experimentally a back-junction back-contact solar cell with p-type and n-type POLO junctions with an independently confirmed efficiency of 24.25 %.}, keywords = {Aluminum, Back-junction back-contact (BJBC) cells, boron, Conductivity, contact resistivity, Current density, Junctions, Photovoltaic cells, polysilicon, polysilicon on oxide (POLO) junctions, recombination, selective contacts, selectivity}, pubstate = {published}, tppubtype = {article} } We investigate the junction resistivity of high-quality carrier-selective polysilicon on oxide (POLO) junctions with the transfer length method. We demonstrate n+ POLO junctions with a saturation current density JC,poly of 6.2 fA/cm2 and a junction resistivity ρc of 0.6 mΩcm2, counterdoped n+ POLO junctions with 2.7 fA/cm2 and 1.3 mΩcm2, and p+ POLO junctions with 6.7 fA/cm2 and 0.2 mΩcm2. Such low junction resistivities and saturation current densities correspond to excellent selectivities S10 of up to 16.2. The efficiency potential for back-junction back-contact solar cells with these POLO junctions was determined to be larger than 25 % by numerical device simulations. We demonstrate experimentally a back-junction back-contact solar cell with p-type and n-type POLO junctions with an independently confirmed efficiency of 24.25 %.
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2016 |
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R. Peibst, U. Römer, Y. Larionova, M. Rienäcker, A. Merkle, N. Folchert, S. Reiter, M. Turcu, B. Min, J. Krügener, D. Tetzlaff, E. Bugiel, T. Wietler, and R. Brendel Working principle of carrier selective poly-Si/c-Si junctions: Is tunnelling the whole story? Artikel Solar Energy Materials and Solar Cells 158 , 60-67, (2016). Abstract | Links | BibTeX | Schlagwörter: Modelling, passivating contact, passivation, polysilicon, Silicon solar cell @article{Peibst2016b,
title = {Working principle of carrier selective poly-Si/c-Si junctions: Is tunnelling the whole story?}, author = {R Peibst and U Römer and Y Larionova and M Rienäcker and A Merkle and N Folchert and S Reiter and M Turcu and B Min and J Krügener and D Tetzlaff and E Bugiel and T Wietler and R Brendel}, doi = {10.1016/j.solmat.2016.05.045}, year = {2016}, date = {2016-12-01}, journal = {Solar Energy Materials and Solar Cells}, volume = {158}, pages = {60-67}, abstract = {We present arguments that additional effects besides laterally homogenous tunnelling might occur in carrier-selective poly-Si/c-Si junctions: (i) the symmetrical electrical behaviour of n+ and p+ poly-Si/c-Si junctions, (ii) direct observation of structural modifications of the interfacial oxide upon thermal treatment by transmission electron microscopy, even for poly-Si/c-Si junctions with good passivation quality, and (iii) the achievement of low junction resistances even for interfacial oxide thicknesses >2 nm after thermal treatment. We present an alternative picture, essentially based on a localized current flow through the interfacial oxide, mediated either by local reduction of the oxide layer thickness or by pinholes. In consequence, the local current flow implies transport limitations for both minority and majority carriers in the c-Si absorber, and thus a correlation between recombination current and series resistance. Thus, a poly-Si/c-Si junction can also be explained within the framework of a classical pn junction picture for a passivated, locally contacted emitter, e.g. by the model of Fischer. Both electron selective contacts (n+ poly-Si) and hole selective contacts (p+ poly-Si) can be described consistently when using reasonable input parameters. Especially for p+ poly-Si/c-Si junctions, our model could guideline further improvement.}, keywords = {Modelling, passivating contact, passivation, polysilicon, Silicon solar cell}, pubstate = {published}, tppubtype = {article} } We present arguments that additional effects besides laterally homogenous tunnelling might occur in carrier-selective poly-Si/c-Si junctions: (i) the symmetrical electrical behaviour of n+ and p+ poly-Si/c-Si junctions, (ii) direct observation of structural modifications of the interfacial oxide upon thermal treatment by transmission electron microscopy, even for poly-Si/c-Si junctions with good passivation quality, and (iii) the achievement of low junction resistances even for interfacial oxide thicknesses >2 nm after thermal treatment. We present an alternative picture, essentially based on a localized current flow through the interfacial oxide, mediated either by local reduction of the oxide layer thickness or by pinholes. In consequence, the local current flow implies transport limitations for both minority and majority carriers in the c-Si absorber, and thus a correlation between recombination current and series resistance. Thus, a poly-Si/c-Si junction can also be explained within the framework of a classical pn junction picture for a passivated, locally contacted emitter, e.g. by the model of Fischer. Both electron selective contacts (n+ poly-Si) and hole selective contacts (p+ poly-Si) can be described consistently when using reasonable input parameters. Especially for p+ poly-Si/c-Si junctions, our model could guideline further improvement.
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D. Tetzlaff, J. Krügener, Y. Larionova, S. Reiter, M. Turcu, R. Peibst, U. Höhne, J. -D. Kähler, and T. Wietler Evolution of oxide disruptions: The (w)hole story about passivating contacts Inproceedings IEEE (Hrsg.): 2016 IEEE 43rd Photovoltaic Specialists Conference (PVSC), 0221-0224, Portland, OR, USA, (2016), ISBN: 978-1-5090-2725-5. Abstract | Links | BibTeX | Schlagwörter: Annealing, junction formation, Junctions, Microscopy, passivating contacts, Photovoltaic cells, Photovoltaic systems, pinholes, polysilicon, silicon, silicon oxide @inproceedings{Tetzlaff2016,
title = {Evolution of oxide disruptions: The (w)hole story about passivating contacts}, author = {D Tetzlaff and J Krügener and Y Larionova and S Reiter and M Turcu and R Peibst and U Höhne and J -D Kähler and T Wietler}, editor = {IEEE}, doi = {10.1109/PVSC.2016.7749582}, isbn = {978-1-5090-2725-5}, year = {2016}, date = {2016-06-01}, booktitle = {2016 IEEE 43rd Photovoltaic Specialists Conference (PVSC)}, journal = {Proceedings of the 43rd IEEE Photovoltaic Specialists Conference}, pages = {0221-0224}, address = {Portland, OR, USA}, abstract = {Different models exist describing the current transport in polycrystalline Si/SiOx/crystalline Si junctions. Besides tunneling through thin oxides, transport through pinholes is discussed. We investigate the influence of annealing temperature on the structural properties of polycrystalline Si/SiOx/crystalline Si interfaces and analyze the formation and evolution of holes by high resolution transmission electron microscopy in comparison to electrical results. We prove the existence of pinholes in samples with good electrical properties in agreement with the pinhole model.}, keywords = {Annealing, junction formation, Junctions, Microscopy, passivating contacts, Photovoltaic cells, Photovoltaic systems, pinholes, polysilicon, silicon, silicon oxide}, pubstate = {published}, tppubtype = {inproceedings} } Different models exist describing the current transport in polycrystalline Si/SiOx/crystalline Si junctions. Besides tunneling through thin oxides, transport through pinholes is discussed. We investigate the influence of annealing temperature on the structural properties of polycrystalline Si/SiOx/crystalline Si interfaces and analyze the formation and evolution of holes by high resolution transmission electron microscopy in comparison to electrical results. We prove the existence of pinholes in samples with good electrical properties in agreement with the pinhole model.
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2014 |
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U. Römer, R. Peibst, B. Lim, J. Krügener, E. Bugiel, T. Wietler, and R. Brendel Solar Energy Materials and Solar Cells 131 , 85-91, (2014), (SiliconPV 2014). Links | BibTeX | Schlagwörter: Passivated Contact, passivation, polysilicon, Silicon solar cell, Tunnel oxide @article{Römer2014b,
title = {Recombination behaviour and contact resistance of n+ and p+ polycrystalline Si/monocrystalline Si junctions*}, author = {U Römer and R Peibst and B Lim and J Krügener and E Bugiel and T Wietler and R Brendel}, doi = {10.1016/j.solmat.2014.06.003}, year = {2014}, date = {2014-12-01}, journal = {Solar Energy Materials and Solar Cells}, volume = {131}, pages = {85-91}, note = {SiliconPV 2014}, keywords = {Passivated Contact, passivation, polysilicon, Silicon solar cell, Tunnel oxide}, pubstate = {published}, tppubtype = {article} } |