1.
N Folchert; R Brendel
In: Solar Energy Materials and Solar Cells, Bd. 231, S. 111304, 2021, ISSN: 0927-0248.
@article{Folchert2021d,
title = {Extended Cox & Strack analysis for the contact resistance of planar samples with carrier-selective junctions on both sides},
author = {N Folchert and R Brendel},
doi = {10.1016/j.solmat.2021.111304},
issn = {0927-0248},
year = {2021},
date = {2021-10-01},
urldate = {2021-01-01},
journal = {Solar Energy Materials and Solar Cells},
volume = {231},
pages = {111304},
abstract = {We review the famous Cox & Strack equation that is commonly applied in contact resistance measurements of samples with a negligible contact resistance at the sample backside. We apply geometric interpretations to extend the Cox & Strack model a) to samples that have a non-negligible contact resistance not only on the front- but also on the back-side and b) to junctions with a buried contact resistance underneath a conductive layer. Case a) is for example a symmetric sample with a single material junction on both sample surfaces. Case b) could be a poly-Si/SiOx/c-Si or a-Si/c-Si hetero-junction. We compare our analytic treatment with rigorous finite-element simulations and find a relative agreement between 2.5 % and 36 % depending on the sample geometry and resistance values. We apply the method to analyze the contact resistance of lifetime samples with both-sided n+/n-type poly-Si junctions.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We review the famous Cox & Strack equation that is commonly applied in contact resistance measurements of samples with a negligible contact resistance at the sample backside. We apply geometric interpretations to extend the Cox & Strack model a) to samples that have a non-negligible contact resistance not only on the front- but also on the back-side and b) to junctions with a buried contact resistance underneath a conductive layer. Case a) is for example a symmetric sample with a single material junction on both sample surfaces. Case b) could be a poly-Si/SiOx/c-Si or a-Si/c-Si hetero-junction. We compare our analytic treatment with rigorous finite-element simulations and find a relative agreement between 2.5 % and 36 % depending on the sample geometry and resistance values. We apply the method to analyze the contact resistance of lifetime samples with both-sided n+/n-type poly-Si junctions.
2.
N Folchert; M Rienäcker; A A Yeo; B Min; R Peibst; R Brendel
Temperature-dependent contact resistance of carrier selective Poly-Si on oxide junctions Artikel
In: Solar Energy Materials and Solar Cells, Bd. 185, S. 425-430, 2018, ISSN: 0927-0248.
@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 = {},
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.
3.
M Rienäcker; M Bossmeyer; A Merkle; U Römer; F Haase; J Krügener; R Brendel; R Peibst
In: IEEE Journal of Photovoltaics, Bd. 7, Nr. 1, S. 11-18, 2017, ISSN: 2156-3381.
@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 = {},
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 %.
4.
R Brendel; R Peibst
Contact selectivity and efficiency in crystalline silicon photovoltaics Artikel
In: IEEE Journal of Photovoltaics, Bd. 6, Nr. 6, S. 1413-1420, 2016.
@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 = {},
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.