M Winter; D C Walter; J Schmidt
In: IEEE Journal of Photovoltaics, Bd. 11, Nr. 4, S. 866-872, 2021.
@article{Winter2021b,
title = {Carrier Lifetime Degradation and Regeneration in Gallium- and Boron-Doped Monocrystalline Silicon Materials},
author = {M Winter and D C Walter and J Schmidt},
doi = {10.1109/JPHOTOV.2021.3070474},
year = {2021},
date = {2021-07-01},
journal = {IEEE Journal of Photovoltaics},
volume = {11},
number = {4},
pages = {866-872},
abstract = {In this article, carrier lifetime degradation phenomena on fired gallium-doped Czochralski-grown silicon (Cz-Si:Ga) and boron-doped float-zone silicon (FZ-Si:B) are observed. We examine lifetime degradation and regeneration as a function of illumination intensity and temperature and observe qualitatively similar degradation effects in both material classes, which are triggered by a fast-firing high-temperature step. Charge carrier injection, e.g., through illumination, is required to activate the defects responsible for degradation. The extent of degradation increases with increasing temperature, which is untypical for degradation effects reported before. Despite different degradation time constants are measured for Cz-Si:Ga and FZ-Si:B, the activation energies are for both materials in the narrow range (0.58±0.04) eV . The extracted activation energy is quite different compared with other degradation effects in silicon, suggesting a novel defect formation mechanism. Since the lifetime degradation is triggered by the fast-firing of the silicon wafers during the presence of a hydrogen-rich dielectric at the surface, the involvement of hydrogen in the defect reaction is very likely. During prolonged illumination at elevated temperature (135 °C), we observe a permanent regeneration of the lifetime, whereas at temperatures close to room temperature (36 °C), the defect deactivation is only temporary.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
M Winter; L Helmich; D C Walter; J Schmidt
Firing-Triggered LID (FT-LID) of the Carrier Lifetime in Cz-Si Proceedings Article
In: WIP, (Hrsg.): Proceedings of the 37th European Photovoltaic Solar Energy Conference and Exhibition, S. 462–467, Online Event, 2020.
@inproceedings{Winter2020c,
title = {Firing-Triggered LID (FT-LID) of the Carrier Lifetime in Cz-Si},
author = {M Winter and L Helmich and D C Walter and J Schmidt},
editor = {WIP},
doi = {10.4229/EUPVSEC20202020-2DV.2.15},
year = {2020},
date = {2020-10-28},
booktitle = {Proceedings of the 37th European Photovoltaic Solar Energy Conference and Exhibition},
journal = {37th European Photovoltaic Solar Energy Conference and Exhibition},
pages = {462--467},
address = {Online Event},
abstract = {Light-Induced Degradation’ (LID) effects of the carrier lifetime are present in many different silicon materials used in the production of solar cells. In this contribution, we present an approach to separate the boron-oxygen (BO) LID effect observed in boron-doped Czochralski-grown silicon (Cz-Si) from an additional firing-triggered LID (FT-LID) effect. We perform BO degradation/deactivation cycles by alternating illumination and dark annealing (DA) steps at 200 °C, while recording the changes in the carrier lifetime. Our measurements show that – despite some similarities – the observed FT-LID effect in Cz-Si is different to the ‘Light and elevated Temperature Induced Degradation’ (LeTID) effect reported on multicrystalline silicon (mc-Si) materials. In particular, the time constants of the lifetime degradation differs by at least a factor of 10 under the same experimental conditions. In addition, experiments where multiple alternating light degradation, regeneration and DA steps were performed show a different behavior between FTLID in Cz-Si and LeTID in mc-Si. Although FT-LID as well as LeTID are both triggered by fast-firing, which makes it very likely that hydrogen participates in both defect reactions, the detailed defect physics seems to be different.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
M Winter; L Helmich; D C Walter; J Schmidt
Firing-Triggered LID (FT-LID) of the Carrier Lifetime in Cz-Si Wafers Vortrag
Online Event, 10.09.2020, (37th European Photovoltaic Solar Energy Conference and Exhibition).
@misc{Winter2020b,
title = {Firing-Triggered LID (FT-LID) of the Carrier Lifetime in Cz-Si Wafers},
author = {M Winter and L Helmich and D C Walter and J Schmidt},
year = {2020},
date = {2020-09-10},
address = {Online Event},
abstract = {Light-induced lifetime degradation effects are frequently observed in boron-doped Czochralski-grown silicon (Cz-Si) and in block-cast multicrystalline silicon (mc-Si) wafers as well as in solar cells made thereof. While the respective main degradation effects are the boron-oxygen (BO) defect activation in Cz-Si [1] and the ‘Light and elevated Temperature Induced Degradation’ (LeTID) effect on mc-Si [2–4], recently, there have also been several reports of LeTID-type effects on Cz-Si wafers and solar cells [5–7]. This study presents an experimental approach to separate additional LeTID-type degradation effects in fired Cz-Si wafers from the traditional BO defect activation. In the second part of this study, we compare the observed non-BO-related degradation effect in Cz-Si wafers with the standard LeTID effect, typically observed on mc-Si material and point out the main differences, which lead us to the conclusion that the detailed physics of the two degradation effects are not identical.},
note = {37th European Photovoltaic Solar Energy Conference and Exhibition},
keywords = {},
pubstate = {published},
tppubtype = {presentation}
}
M Winter; S Bordihn; R Peibst; R Brendel; J Schmidt
In: IEEE Journal of Photovoltaics, Bd. 10, Nr. 2, S. 423-430, 2020, ISSN: 2156-3403.
@article{Winter2020,
title = {Degradation and Regeneration of n+-Doped Poly-Si Surface Passivation on p-Type and n-Type Cz-Si Under Illumination and Dark Annealing},
author = {M Winter and S Bordihn and R Peibst and R Brendel and J Schmidt},
doi = {10.1109/JPHOTOV.2020.2964987},
issn = {2156-3403},
year = {2020},
date = {2020-03-01},
journal = {IEEE Journal of Photovoltaics},
volume = {10},
number = {2},
pages = {423-430},
abstract = {Degradation and regeneration of recombination parameters can occur in the bulk and at the surfaces of silicon solar cells. This article focuses on the time-resolved analysis of the recombination properties of textured 1.7 Ω cm boron-doped p-type Cz-Si and 5 Ω cm phosphorus-doped n-type Cz-Si wafers, where the surfaces are passivated by n+ poly-Si on interfacial oxide layers exposed to a rapid thermal annealing (RTA) step in a conventional firing furnace. We observe a thermally activated instability in the lifetime over the entire examined injection range. Our experiments show that minority carrier injection (e.g., by illumination) is not required. Degradation in the surface passivation quality of the poly-Si on oxide layer—corresponding to an increase of the saturation current density J0 by up to a factor of five—causes the degradation of the effective lifetime. Interestingly, the surface passivation fully regenerates under prolonged annealing and finally improves even beyond the initial state. Both the extent of the lifetime degradation and the change in J0 depend on the postprocessing treatment temperature which we varied between 80 and 400 °C. Our results indicate that two different processes are responsible for the degradation and the regeneration. Reference samples which did not receive an RTA treatment show no degradation of the surface passivation quality. The RTA treatment applied therefore triggers the degradation effect. A large improvement of the surface passivation quality under prolonged annealing (e.g., at 400 °C) is observed for all samples examined in this study.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
J Schmidt; D Bredemeier; D C Walter
In: IEEE Journal of Photovoltaics, Bd. 9, Nr. 6, S. 1497-1503, 2019.
@article{Schmidt2019d,
title = {On the Defect Physics Behind Light and Elevated Temperature-Induced Degradation (LeTID) of Multicrystalline Silicon Solar Cells},
author = {J Schmidt and D Bredemeier and D C Walter},
doi = {10.1109/JPHOTOV.2019.2937223},
year = {2019},
date = {2019-11-01},
journal = {IEEE Journal of Photovoltaics},
volume = {9},
number = {6},
pages = {1497-1503},
abstract = {State-of-the-art solar cells with passivated surfaces fabricated on block-cast multicrystalline silicon (mc-Si) wafers show a pronounced degradation in efficiency under illumination at elevated temperature, as it typically occurs during operation in a solar module. This effect, frequently named `Light and elevated Temperature-Induced Degradation' (LeTID), has been attributed to the activation of a specific, hitherto unrevealed bulk defect in mc-Si. Recent experimental results of several labs have indicated that hydrogen is somehow involved in the responsible defect physics, without however providing any direct evidence so far. In this article, we present experimental data unambiguously showing a direct positive correlation of the extent of LeTID with the hydrogen content introduced into the silicon bulk during firing of the silicon wafers coated with hydrogen-rich silicon nitride (SiN$_rm x$:H) layers. Additional experiments including the pronounced impact of phosphorus gettering on the LeTID extent and the dependence of the degradation and regeneration on the wafer thickness support the involvement of a second species, with most indications pointing towards a metallic impurity. Several approaches of completely avoiding the instability in mc-Si solar cells are derived from the presented defect model, including 1) tuning of the SiN$_rm x$:H layer properties to minimize the in-diffusion of hydrogen into the wafer and 2) the thinning of the mc-Si wafer, improving the getterability of the metal impurity component toward the surfaces.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
D Bredemeier; D C Walter; J Schmidt
In: Solar RRL, Bd. 2, Nr. 1, S. 1700159, 2018, ISSN: 2367-198X.
@article{Bredemeier2018,
title = {Possible Candidates for Impurities in mc-Si Wafers Responsible for Light-Induced Lifetime Degradation and Regeneration},
author = {D Bredemeier and D C Walter and J Schmidt},
doi = {10.1002/solr.201700159},
issn = {2367-198X},
year = {2018},
date = {2018-01-01},
journal = {Solar RRL},
volume = {2},
number = {1},
pages = {1700159},
abstract = {We examine the light‐induced carrier lifetime degradation and regeneration at elevated temperature in multicrystalline silicon (mc‐Si) wafers of different thicknesses. The experimental results show that the thinner the wafer the less pronounced the degradation is and the faster the regeneration takes place. We interpret this result in the framework of a recently proposed defect model, where the lifetime regeneration is attributed to the diffusion of the recombination‐active impurity to the wafer surfaces, where it is permanently trapped. Modeling the measured thickness‐dependent lifetime evolutions enables us to determine the diffusion coefficient of the impurity to be in the range (5 ± 2) × 10−11 cm2 s−1 at a temperature of 75 °C. Comparing the diffusion coefficient extracted from our measurements with data published in the literature allows us to exclude most impurities. Despite the large uncertainties in the diffusion coefficient data reported in the literature, reasonable agreement is only obtained for nickel, cobalt, and hydrogen. One important practical implication of our study is that mc‐Si wafers thinner than 120 μm do not suffer from pronounced light‐induced lifetime degradation.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
B Veith-Wolf; R Witteck; A Morlier; H Schulte-Huxel; M R Vogt; J Schmidt
Spectra-Dependent Stability of the Passivation Quality of Al2O3/c-Si Interfaces Artikel
In: IEEE Journal of Photovoltaics, Bd. 8, Nr. 1, S. 96-102, 2018, ISSN: 2156-3381.
@article{Veith-Wolf2018,
title = {Spectra-Dependent Stability of the Passivation Quality of Al2O3/c-Si Interfaces},
author = {B Veith-Wolf and R Witteck and A Morlier and H Schulte-Huxel and M R Vogt and J Schmidt},
doi = {10.1109/JPHOTOV.2017.2775147},
issn = {2156-3381},
year = {2018},
date = {2018-01-01},
journal = {IEEE Journal of Photovoltaics},
volume = {8},
number = {1},
pages = {96-102},
abstract = {We examine the stability of the c-Si surface passivation quality by spatial atomic-layer-deposited aluminum oxide (Al2O3), plasma-enhanced chemical vapor deposited silicon nitride (SiNx), and Al2O3/SiNx stacks under illumination with two different spectra. The Al2O3-passivated c-Si surfaces annealed at 350 °C show a weak degradation due to UV illumination, with surface recombination velocities (SRVs) of 122 cm/s after receiving a ultraviolet (UV) dose of 275 kWh/m2. Silicon samples passivated with Al2O3 layers that received a fast-firing step show an improvement due to UV illumination with a reduction of the SRVs initially from 14 to 5 cm/s for single Al2O3 layers. For the fired Al2O3 layers the negative fixed charge density increases from -6×1012 cm-2 up to -1.2×1013 cm-2 during UV illumination. We demonstrate that for the SiNx and the fired Al2O3 single layers, photons with energy greater than 3.4 eV are necessary to reduce the passivation quality. In contrast, low-temperature-annealed Al2O3 single layers and nonfired Al2O3/SiNx stacks showed a degradation already under illumination with a halogen lamp. Importantly, we observe a perfectly stable passivation on boron-diffused p+ emitter for fired Al2O3/SiNx stacks featuring a stable saturation current density of 18 fA/cm2 for a p+ sheet resistance of 90 Ω/sq.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
D Bredemeier; D Walter; J Schmidt
In: Solar Energy Materials and Solar Cells, Bd. 173, S. 2-5, 2017, ISSN: 0927-0248, (Proceedings of the 7th international conference on Crystalline Silicon Photovoltaics).
@article{Bredemeier2017b,
title = {Light-induced lifetime degradation in high-performance multicrystalline silicon: Detailed kinetics of the defect activation},
author = {D Bredemeier and D Walter and J Schmidt},
doi = {10.1016/j.solmat.2017.08.007},
issn = {0927-0248},
year = {2017},
date = {2017-12-01},
journal = {Solar Energy Materials and Solar Cells},
volume = {173},
pages = {2-5},
abstract = {We examine the defect activation kinetics in block-cast high-performance multicrystalline silicon (HP mc-Si) under illumination at elevated temperature. Our lifetime analysis shows that the observed light-induced lifetime degradation consists of two separate stages: a fast stage followed by a slow stage. Our experiments reveal that both degradation stages can be fitted using a sum of two exponential decay functions. The resulting degradation rate constants depend both on the temperature and the light intensity applied during degradation. For the fast component, we determine an activation energy of (0.89 ± 0.04) eV from an Arrhenius plot of the degradation rate and for the slow component we determine a value of (0.94 ± 0.06) eV. The activation energies are relatively large, leading to a very pronounced dependence of the degradation rates on temperature. We also observe that both degradation rates show a linear dependence on the applied light intensity during degradation in the examined intensity range between 0.25 and 1.5 suns.},
note = {Proceedings of the 7th international conference on Crystalline Silicon Photovoltaics},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
B Veith-Wolf; R Witteck; A Morlier; H Schulte-Huxel; J Schmidt
Effect of UV illumination on the passivation quality of AlOx/c-Si interfaces Proceedings Article
In: IEEE, (Hrsg.): 2016 IEEE 43rd Photovoltaic Specialists Conference (PVSC), S. 1173-1178, Portland, OR, USA, 2016, ISBN: 978-1-5090-2725-5.
@inproceedings{Veith-Wolf2016,
title = {Effect of UV illumination on the passivation quality of AlOx/c-Si interfaces},
author = {B Veith-Wolf and R Witteck and A Morlier and H Schulte-Huxel and J Schmidt},
editor = {IEEE},
doi = {10.1109/PVSC.2016.7749799},
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 = {1173-1178},
address = {Portland, OR, USA},
abstract = {We report on the stability of the c-Si surface passivation quality by aluminum oxide (AlOx), silicon nitride (SiNp), and AlOx/SiNy stacks under UV illumination. Low-temperature annealed AlOx shows a weak degradation during UV illumination, with surface recombination velocities (SRVs) of 25 cm/s after a UV dose of 275 kWh/m2. This degradation is less pronounced compared to that of fired SiNy layers with an SRV of 117 cm/s. After a firing step, the AlOx layer show even an improvement during UV illumination, resulting in stabilized SRVs of down to 1 cm/s. The improvement is mainly due to an increase of the negative fixed charge density in the AlOx layer up to a large value of -1.2×10^13 cm-2.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
A Morlier; S Klotz; S Sczuka; I Kunze; I Schaumann; S Blankemeyer; M Siegert; T Döring; T Alshuth; U Giese; M Denz; M Köntges
Influence of the curing state of ethylene-vinyl acetate on photovoltaic modules aging Proceedings Article
In: WIP, (Hrsg.): Proceedings of the 28th European Photovoltaic Solar Energy Conference, S. 2832-2837, Paris, France, 2013, ISBN: 3-936338-33-7.
@inproceedings{Morlier2013,
title = {Influence of the curing state of ethylene-vinyl acetate on photovoltaic modules aging},
author = {A Morlier and S Klotz and S Sczuka and I Kunze and I Schaumann and S Blankemeyer and M Siegert and T Döring and T Alshuth and U Giese and M Denz and M Köntges},
editor = {WIP},
doi = {10.4229/28thEUPVSEC2013-4CO.9.5},
isbn = {3-936338-33-7},
year = {2013},
date = {2013-09-01},
booktitle = {Proceedings of the 28th European Photovoltaic Solar Energy Conference},
journal = {Proceedings of the 28th European Photovoltaic Solar Energy Conference},
pages = {2832-2837},
address = {Paris, France},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
T Dullweber; C Kranz; U Baumann; R Hesse; D Walter; J Schmidt; P Altermatt; R Brendel
Silicon wafer material options for highly efficient p-type PERC solar cells Proceedings Article
In: IEEE, (Hrsg.): 2013 IEEE 39th Photovoltaic Specialists Conference (PVSC), S. 3074-3078, Tampa, FL, USA, 2013, ISBN: 978-1-4799-3299-3.
@inproceedings{Dullweber2013,
title = {Silicon wafer material options for highly efficient p-type PERC solar cells},
author = {T Dullweber and C Kranz and U Baumann and R Hesse and D Walter and J Schmidt and P Altermatt and R Brendel},
editor = {IEEE},
doi = {10.1109/PVSC.2013.6745110},
isbn = {978-1-4799-3299-3},
year = {2013},
date = {2013-06-16},
booktitle = {2013 IEEE 39th Photovoltaic Specialists Conference (PVSC)},
journal = {Proceedings of the 39th IEEE Photovoltaic Specialists Conference},
pages = {3074-3078},
address = {Tampa, FL, USA},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
F E Rougieux; M Forster; D Macdonald; A Cuevas; B Lim; J Schmidt
Recombination Activity and Impact of the Boron-Oxygen-Related Defect in Compensated N-Type Silicon Artikel
In: IEEE Journal of Photovoltaics, Bd. 1, Nr. 1, S. 54-58, 2011, ISSN: 2156-3381.
@article{Rougieux2011,
title = {Recombination Activity and Impact of the Boron-Oxygen-Related Defect in Compensated N-Type Silicon},
author = {F E Rougieux and M Forster and D Macdonald and A Cuevas and B Lim and J Schmidt},
doi = {10.1109/JPHOTOV.2011.2165698},
issn = {2156-3381},
year = {2011},
date = {2011-07-01},
journal = {IEEE Journal of Photovoltaics},
volume = {1},
number = {1},
pages = {54-58},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Y Larionova; N P Harder; R Brendel
Effect of SiO2 thicknesses in thermal-SiO2/PECVD-SiN stacks on surface passivation of n-type Cz silicon substrates Proceedings Article
In: IEEE, (Hrsg.): 2010 35th IEEE Photovoltaic Specialists Conference, S. 001207-001209, Honolulu, HI, USA, 2010, ISSN: 0160-8371.
@inproceedings{Larionova2010,
title = {Effect of SiO2 thicknesses in thermal-SiO2/PECVD-SiN stacks on surface passivation of n-type Cz silicon substrates},
author = {Y Larionova and N P Harder and R Brendel},
editor = {IEEE},
doi = {10.1109/PVSC.2010.5614072},
issn = {0160-8371},
year = {2010},
date = {2010-06-01},
booktitle = {2010 35th IEEE Photovoltaic Specialists Conference},
pages = {001207-001209},
address = {Honolulu, HI, USA},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
M A Kessler; T Ohrdes; B Wolpensinger; R Bock; N P Harder
Characterisation and implications of the boron rich layer resulting from open-tube liquid source BBR3 boron diffusion processes Proceedings Article
In: IEEE, (Hrsg.): 2009 34th IEEE Photovoltaic Specialists Conference (PVSC), S. 001556-001561, Philadelphia, PA, USA, 2009, ISSN: 0160-8371.
@inproceedings{Kessler2009,
title = {Characterisation and implications of the boron rich layer resulting from open-tube liquid source BBR3 boron diffusion processes},
author = {M A Kessler and T Ohrdes and B Wolpensinger and R Bock and N P Harder},
editor = {IEEE},
doi = {10.1109/PVSC.2009.5411365},
issn = {0160-8371},
year = {2009},
date = {2009-06-01},
booktitle = {2009 34th IEEE Photovoltaic Specialists Conference (PVSC)},
pages = {001556-001561},
address = {Philadelphia, PA, USA},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
B Lim; K Bothe; J Schmidt
Modeling the generation and dissociation of the boron-oxygen complex in B-Doped Cz-Si Proceedings Article
In: IEEE, (Hrsg.): 2008 33rd IEEE Photovoltaic Specialists Conference, S. 1-4, San Diego, CA, USA, 2008, ISSN: 0160-8371.
@inproceedings{Lim2008d,
title = {Modeling the generation and dissociation of the boron-oxygen complex in B-Doped Cz-Si},
author = {B Lim and K Bothe and J Schmidt},
editor = {IEEE},
doi = {10.1109/PVSC.2008.4922482},
issn = {0160-8371},
year = {2008},
date = {2008-05-01},
booktitle = {2008 33rd IEEE Photovoltaic Specialists Conference},
pages = {1-4},
address = {San Diego, CA, USA},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}