Veröffentlichungen
2018 |
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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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2017 |
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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. Brendel, and R. Peibst Contact selectivity and efficiency in crystalline silicon photovoltaics Artikel IEEE Journal of Photovoltaics 6 (6), 1413-1420, (2016). Abstract | Links | BibTeX | Schlagwörter: Contact resistance, Junctions, passivated emitter and rear cell (PERC), Photovoltaic cells, Photovoltaic systems, principle of solar cells, Resistance, selective contacts, silicon @article{Brendel2016b,
title = {Contact selectivity and efficiency in crystalline silicon photovoltaics}, author = {R Brendel and R Peibst}, doi = {10.1109/JPHOTOV.2016.2598267}, year = {2016}, date = {2016-11-01}, journal = {IEEE Journal of Photovoltaics}, volume = {6}, number = {6}, pages = {1413-1420}, abstract = {Highly doped junctions of a Si solar cell function as membranes that block minority carriers and, at the same time, provide a high conductivity for transporting majority carriers to the contacts. They are thus said to be selective contacts. We propose a quantitative definition for the selectivity of contacts. The selectivity provides a figure of merit for electron and hole contacts that is helpful in designing solar cells and in identifying the efficiency limiting components. Applying the definition of selectivity to poly-Si junctions reveals that the root cause of their high selectivity is the highly asymmetric carrier concentration rather than a specific contact geometry.}, keywords = {Contact resistance, Junctions, passivated emitter and rear cell (PERC), Photovoltaic cells, Photovoltaic systems, principle of solar cells, Resistance, selective contacts, silicon}, pubstate = {published}, tppubtype = {article} } Highly doped junctions of a Si solar cell function as membranes that block minority carriers and, at the same time, provide a high conductivity for transporting majority carriers to the contacts. They are thus said to be selective contacts. We propose a quantitative definition for the selectivity of contacts. The selectivity provides a figure of merit for electron and hole contacts that is helpful in designing solar cells and in identifying the efficiency limiting components. Applying the definition of selectivity to poly-Si junctions reveals that the root cause of their high selectivity is the highly asymmetric carrier concentration rather than a specific contact geometry.
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