L Helmich; D C Walter; T Pernau; J Schmidt
In: IEEE Journal of Photovoltaics, Bd. 12, Nr. 1, S. 198-203, 2022.
@article{Helmich2022,
title = {Carrier Lifetime Stability of Boron-Doped Czochralski-Grown Silicon Materials for Years After Regeneration in an Industrial Belt Furnace},
author = {L Helmich and D C Walter and T Pernau and J Schmidt},
doi = {10.1109/JPHOTOV.2021.3116019},
year = {2022},
date = {2022-01-01},
urldate = {2021-10-26},
journal = {IEEE Journal of Photovoltaics},
volume = {12},
number = {1},
pages = {198-203},
abstract = {We examine the long-term stability of the carrier lifetime in boron-doped Czochralski-grown silicon materials with different boron and oxygen concentrations, which were regenerated in an industrial belt furnace. After firing and subsequent regeneration in an industrial conveyor-belt furnace, the silicon samples are exposed to long-term illumination at an intensity of 0.1 suns and a sample temperature of about 30 °C for more than two years. After regeneration, we observe a minor re-degradation (30–72% reduced compared to the degradation observed without regeneration step). We attribute this re-degradation to a non-completed regeneration within the belt furnace due to the short regeneration period. Our results show that the industrial process consisting of firing with subsequent regeneration in the same unit is very effective for industrially relevant silicon materials. Typical industrial silicon wafers with a resistivity of (1.75 ± 0.03) Ωcm and an interstitial oxygen concentration of (6.9 ± 0.3) × 1017 cm–3 show lifetimes larger than 2 ms after regeneration and two years of light exposure.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
L Helmich; D C Walter; R Falster; V V Voronkov; J Schmidt
In: Solar Energy Materials and Solar Cells, Bd. 232, S. 111340, 2021, ISSN: 0927-0248.
@article{Helmich2021c,
title = {Impact of hydrogen on the boron-oxygen-related lifetime degradation and regeneration kinetics in crystalline silicon},
author = {L Helmich and D C Walter and R Falster and V V Voronkov and J Schmidt},
doi = {10.1016/j.solmat.2021.111340},
issn = {0927-0248},
year = {2021},
date = {2021-10-01},
journal = {Solar Energy Materials and Solar Cells},
volume = {232},
pages = {111340},
abstract = {We examine the impact of hydrogen on the boron-oxygen-related lifetime degradation and regeneration kinetics in boron-doped p-type Czochralski-grown silicon wafers. We introduce the hydrogen into the silicon bulk by rapid thermal annealing. The hydrogen source are hydrogen-rich silicon nitride (SiNx:H) layers. Aluminum oxide (Al2O3) layers of varying thickness are placed in-between the silicon wafer surfaces and the SiNx:H layers. By varying the Al2O3 thickness, which acts as an effective hydrogen diffusion barrier, the hydrogen bulk content is varied over more than one order of magnitude. The hydrogen content is determined from measured wafer resistivity changes. In order to examine the impact of hydrogen on the degradation kinetics, all samples are illuminated at a light intensity of 0.1 suns near room temperature. We observe no impact of the in-diffused hydrogen content on the degradation rate constant, confirming that hydrogen is not involved in the boron-oxygen degradation mechanism. The regeneration experiments at 160°C and 1 sun, however, show a clear dependence on the hydrogen content with a linear increase of the regeneration rate constant with increasing bulk hydrogen concentration. However, extrapolation of our measurements toward a zero in-diffused hydrogen content shows that the regeneration is still working even without any in-diffused hydrogen. Hence, our measurements demonstrate that there are two distinct regeneration processes taking place. This is in good agreement with a recently proposed defect reaction model and is also in agreement with the finding that the permanent boron-oxygen deactivation also works on non-fired solar cells, though at a lower rate.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
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}
}
N Wehmeier; G Fischer; S Herlufsen; F Wolny; M Wagner; K Bothe; M Müller
In: IEEE Journal of Photovoltaics, Bd. 11, Nr. 4, S. 890-896, 2021, ISSN: 2156-3403.
@article{Wehmeier2021,
title = {Kinetics of the Light and Elevated Temperature Induced Degradation and Regeneration of Quasi-Monocrystalline Silicon Solar Cells},
author = {N Wehmeier and G Fischer and S Herlufsen and F Wolny and M Wagner and K Bothe and M Müller},
doi = {10.1109/JPHOTOV.2021.3066239},
issn = {2156-3403},
year = {2021},
date = {2021-07-01},
journal = {IEEE Journal of Photovoltaics},
volume = {11},
number = {4},
pages = {890-896},
abstract = {We investigate the degradation and regeneration behavior of quasi-monocrystalline silicon passivated emitter and rear cells under illumination at elevated temperatures. The decrease and increase of the solar cell efficiencies over time is accelerated under increased temperature or illumination intensity. We examine the defect activation kinetics and determine rate constants both for the degradation and regeneration. We apply temperatures in the range of 37–140 °C and illumination intensities in the range of 0.1–1.4 suns. These conditions typically occur when operating solar modules in the field. The rate constants are strongly increased with increasing temperature and increasing illumination intensity. We perform multiple regressions fits of the degradation and regeneration data with different approaches for the illumination intensity dependence. A linear illumination intensity dependence on the rates of degradation and regeneration is found. Activation energies for the degradation and regeneration of (0.89 ± 0.04) eV and (1.07 ± 0.07) eV, respectively, are extracted that allow for identification of the defect activation and deactivation mechanisms.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
T Pernau; C Derricks; G Hahn; L Helmich; A Herguth; J Schmidt; D Walter
Upgrade Technologies for Silicon Photovoltaics – Part I: Industrial Solution to Minimize the Negative Impact of Light Induced Degradation Proceedings Article
In: WIP, (Hrsg.): Proceedings of the 37th European Photovoltaic Solar Energy Conference and Exhibition, S. 414-417, Online Event, 2020.
@inproceedings{Pernau2020b,
title = {Upgrade Technologies for Silicon Photovoltaics – Part I: Industrial Solution to Minimize the Negative Impact of Light Induced Degradation},
author = {T Pernau and C Derricks and G Hahn and L Helmich and A Herguth and J Schmidt and D Walter},
editor = {WIP},
doi = {10.4229/EUPVSEC20202020-2CV.1.57},
year = {2020},
date = {2020-10-28},
booktitle = {Proceedings of the 37th European Photovoltaic Solar Energy Conference and Exhibition},
pages = {414-417},
address = {Online Event},
abstract = {This paper is to inform about Part I of a joint research project on optimum reduction of boron-oxygen related degradation and passivated contacts for PERC-based solar cells. It includes the application of investigated technologies into potential future cell designs such as PERT and bifacial solar cells. The joint project was merged from two individual project suggestions and therefore had two parts. This paper focuses on an industrial solution to minimize the negative impact of light induced degradation (LID) by: • Investigating and understanding the nature of the degradation effect • Applying the experimental results and concepts to industrially suppress LID • Developing an optimized integrated firing-regeneration process for industrial application The second part of this project is also covered in this conference [1]. The detailed project report (in German) has been published [2].},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
L Helmich; D C Walter; J Schmidt
In: IEEE Journal of Photovoltaics, Bd. 9, Nr. 6, S. 1472-1476, 2019, ISSN: 2156-3381.
@article{Helmich2019b,
title = {Direct Examination of the Deactivation of the Boron–Oxygen Center in Cz-Si Solar Cells Under Regeneration Conditions via Electroluminescence},
author = {L Helmich and D C Walter and J Schmidt},
doi = {10.1109/JPHOTOV.2019.2926855},
issn = {2156-3381},
year = {2019},
date = {2019-11-01},
journal = {IEEE Journal of Photovoltaics},
volume = {9},
number = {6},
pages = {1472-1476},
abstract = {We examine the regeneration kinetics of the boron–oxygen defect in boron-doped p-type Czochralski-grown silicon (Cz-Si) solar cells as a function of the excess carrier concentration Δn at the regeneration conditions, i.e., at elevated temperature (140 °C). To perform the regeneration, we apply different forward-bias voltages (V$_rm appl$) to solar cells in darkness and measure directly the emitted electroluminescence (EL) signal at different time steps during the regeneration of the cell. Measuring the EL signal emitted by the solar cell during regeneration, we are able to directly determine Δn during regeneration for each applied voltage. In addition to the EL signal, we measure the electric current flowing through the solar cell during the regeneration process. This current is proportional to the overall recombination rate in the cell and, hence, reflects the changing bulk recombination during the regeneration process. From the measured time-dependent cell current, we determine the deactivation rate constant R$_rm de$ of the boron–oxygen defect. Our experimental results unambiguously show that R$_rm de$ increases proportionally with Δn during the regeneration process.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
L Helmich; D C Walter; D Bredemeier; R Falster; V V Voronkov; J Schmidt
In-situ characterization of electron-assisted regeneration of Cz-Si solar cells Artikel
In: Solar Energy Materials and Solar Cells, Bd. 185, S. 283-286, 2018, ISSN: 0927-0248.
@article{Helmich2018b,
title = {In-situ characterization of electron-assisted regeneration of Cz-Si solar cells},
author = {L Helmich and D C Walter and D Bredemeier and R Falster and V V Voronkov and J Schmidt},
doi = {10.1016/j.solmat.2018.05.023},
issn = {0927-0248},
year = {2018},
date = {2018-10-01},
journal = {Solar Energy Materials and Solar Cells},
volume = {185},
pages = {283-286},
abstract = {Abstract We examine the regeneration kinetics of passivated emitter and rear solar cells (PERCs) fabricated on boron-doped p-type Czochralski-grown silicon wafers in darkness by electron injection via application of a forward bias voltage at elevated temperature (140 °C) in order to discriminate between electronic and photonic effects. Based on these dark regeneration experiments, we address the existing inconsistency regarding the measured linear dependence of the regeneration rate constant on the excess carrier density. Using the method of dark regeneration by current injection into the solar cell, we are able to measure the total recombination current of the solar cell at the actual regeneration temperature under applied voltage, i.e., at the physically relevant regeneration conditions. The direct comparison of the regeneration rate constant as a function of electronically injected carrier concentration in the dark and the regeneration rate constant during illumination clearly shows that the regeneration is a purely electronically stimulated effect and that photons are not directly involved.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
D Bredemeier; D C Walter; J Schmidt
Production Compatible Remedy Against LeTID in High-Performance Multicrystalline Silicon Solar Cells Proceedings Article
In: WIP, (Hrsg.): Proceedings of the 35th European Photovoltaic Solar Energy Conference and Exhibition, S. 406-409, Brussels, Belgium, 2018.
@inproceedings{Bredemeier2018c,
title = {Production Compatible Remedy Against LeTID in High-Performance Multicrystalline Silicon Solar Cells},
author = {D Bredemeier and D C Walter and J Schmidt},
editor = {WIP},
doi = {10.4229/35thEUPVSEC20182018-2CO.9.4},
year = {2018},
date = {2018-09-24},
booktitle = {Proceedings of the 35th European Photovoltaic Solar Energy Conference and Exhibition},
pages = {406-409},
address = {Brussels, Belgium},
abstract = {We examine the ‘LeTID’ (Light and elevated Temperature Induced Degradation) effect and the subsequent regeneration in high-performance multicrystalline silicon (mc-Si). We treat lifetime samples and PERC solar cells with a production-compatible inline regeneration furnace (c.REG) from centrotherm international AG and demonstrate that this industrial-type regeneration treatment is capable of effectively suppressing LeTID. On lifetime samples, we observe an increase in the lifetime by one order of magnitude compared to the untreated and fully degraded samples. On finished industrial-type PERC solar cells, the c.REG treatment results in a gain of 6 to 14 mV in the open-circuit voltage at the point of maximum degradation compared to untreated reference solar cells. This compares to a relative gain in conversion efficiency of up to 6.8%.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
D C Walter; L Helmich; D Bredemeier; J Schmidt; R Falster; V V Voronkov
Lifetime Evolution during Regeneration in Boron-Doped Czochralski-Silicon Proceedings Article
In: WIP, (Hrsg.): Proceedings of the 35th European Photovoltaic Solar Energy Conference and Exhibition, S. 522-526, Brussels, Belgium, 2018.
@inproceedings{Walter2018,
title = {Lifetime Evolution during Regeneration in Boron-Doped Czochralski-Silicon},
author = {D C Walter and L Helmich and D Bredemeier and J Schmidt and R Falster and V V Voronkov},
editor = {WIP},
doi = {10.4229/35thEUPVSEC20182018-2AV.1.29},
year = {2018},
date = {2018-09-24},
booktitle = {Proceedings of the 35th European Photovoltaic Solar Energy Conference and Exhibition},
pages = {522-526},
address = {Brussels, Belgium},
abstract = {We measure the evolution of the carrier lifetime in boron-doped Czochralski-grown silicon wafers for the first time in-situ during permanent deactivation of the boron-oxygen defect under the applied conditions, i.e. illumination with a halogen lamp at elevated temperatures. Applying illumination intensities ≥1 sun on standard 1.5 Ωcm p-type Cz-Si, the lifetime (measured at the regeneration temperature) changes only negligibly during this regeneration process. As expected, in this case, the time dependence of the defect concentration (measured at room temperature) follows a single-exponential decay function during regeneration. For light intensities << 1 sun on the same material, the lifetime shows a significant change during the regeneration conditions and the evolution of the defect concentration does no longer follow a single-exponential decay curve. In addition, on 0.5 Ωcm p-type Cz-Si we observe a non-exponential decay of the defect concentration for a regeneration treatment performed at 1 sun illumination intensity and a single-exponential decay for a higher illumination intensity of 2.9 suns. These observations are well compatible with a deactivation rate increasing proportionally with the excess carrier concentration.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
D C Walter; T Pernau; J Schmidt
Ultrafast lifetime regeneration of boron-doped Czochralski-silicon in an industrial belt-line furnace Sonstige
Photovoltaics International Volume 34, 2016.
@misc{Walter2016d,
title = {Ultrafast lifetime regeneration of boron-doped Czochralski-silicon in an industrial belt-line furnace},
author = {D C Walter and T Pernau and J Schmidt},
year = {2016},
date = {2016-12-01},
abstract = {Solar cells made of boron-doped, oxygen-rich Czochralski-grown silicon (Cz-Si) wafers suffer degraded efficiency when illuminated, an effect sometimes labelled light-induced degradation (LID). This is caused by a specific defect centre within the silicon bulk, often referred to as a BO defect, which activates its recombination properties under illumination, leading to a degradation in carrier lifetime. However, the BO defect centre can be permanently deactivated, and the lifetime permanently recovered, by illumination at an elevated temperature. In this paper the focus is on transferring ISFH’s lab-type BO deactivation process to an ultrafast high-throughput process, employing an industrial-type belt furnace especially designed by centrotherm photovoltaics AG for this very purpose. By using this industrial furnace, inline regeneration in a solar cell production line becomes feasible. The investigations clearly demonstrate that the industrial belt furnace is well suited to permanently deactivating the BO complex; in addition, excellent stability of the lifetimes after regeneration is demonstrated.},
howpublished = {Photovoltaics International Volume 34},
keywords = {},
pubstate = {published},
tppubtype = {misc}
}
F Hüsing; H Hirsch; G Rockendorf
Combination of Solar Thermal Collectors and Horizontal Ground Heat Exchangers as Optimized Source for Heat Pumps Proceedings Article
In: ISES, (Hrsg.): Conference Proceedings EuroSun 2016, Palma de Mallorca, Spain, 2016.
@inproceedings{Hüsing2016,
title = {Combination of Solar Thermal Collectors and Horizontal Ground Heat Exchangers as Optimized Source for Heat Pumps},
author = {F Hüsing and H Hirsch and G Rockendorf},
editor = {ISES},
doi = {10.18086/eurosun.2016.04.18},
year = {2016},
date = {2016-10-14},
booktitle = {Conference Proceedings EuroSun 2016},
address = {Palma de Mallorca, Spain},
abstract = {Heat pumps coupled to thermal ground sources, such as Horizontal Ground Heat Exchangers (HGHX), represent an efficient option to supply heating demands of single- and multi-family houses. However, the high land-use yet often prevents HGHXs from installation. The combination with solar thermal energy promises reduction of the HGHX area while retaining high system efficiencies. Our contribution studies the combination of HGHXs and solar thermal collectors, focusing on solar thermal regeneration of the soil. This is analyzed through both numerical modelling and experimental investigations. Modelling rests on a novel TRNSYS type for the HGHX, developed at ISFH. A test facility, installed on the premises of ISFH in Lower Saxony / Germany is used to validate the model. System simulations extrapolate the perceptions on differently configured heating systems.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
D Bredemeier; D Walter; S Herlufsen; J Schmidt
Measures for eliminating light-induced lifetime degradation in multicrystalline silicon Proceedings Article
In: WIP, (Hrsg.): Proceedings of the 32nd European Photovoltaic Solar Energy Conference, S. 504-506, Munich, Germany, 2016, ISBN: 3-936338-41-8.
@inproceedings{Bredemeier2016,
title = {Measures for eliminating light-induced lifetime degradation in multicrystalline silicon},
author = {D Bredemeier and D Walter and S Herlufsen and J Schmidt},
editor = {WIP},
doi = {10.4229/EUPVSEC20162016-2DO.2.5},
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 = {504-506},
address = {Munich, Germany},
abstract = {We examine the light-induced degradation and regeneration in multicrystalline silicon (mc-Si) under illumination at elevated temperature. Samples are treated with process steps typically applied in industrial solar cell production. We observe a pronounced degradation in lifetime after rapid thermal annealing (RTA) at 900°C. However, we detect only a weak lifetime instability in mc-Si wafers which are RTA-treated at 650°C. We pay particular attention to the regeneration of the lifetime which takes place under prolonged illumination at elevated temperature. It is found that this regeneration can be significantly accelerated by increasing the temperature. Additionally we have tested the stability of the regenerated state under illumination and elevated temperature. We show that the regeneration cannot be further accelerated by increasing the applied light intensity, as the regeneration rate does not depend on the illumination intensity for intensities exceeding 1 sun. We hence propose three measures for elimating the lightinduced degradation: (i) the adaption of the firing profile, (ii) the growth of metal-reduced mc-Si blocks, and (iii) by regeneration at illumination at increased temperature.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
D Walter; T Pernau; J Schmidt
Ultrafast lifetime regeneration in an industrial belt-line furnace applying intense illumination at elevated temperature Proceedings Article
In: WIP, (Hrsg.): Proceedings of the 32nd European Photovoltaic Solar Energy Conference, S. 469-473, Munich, Germany, 2016, ISBN: 3-936338-41-8.
@inproceedings{Walter2016,
title = {Ultrafast lifetime regeneration in an industrial belt-line furnace applying intense illumination at elevated temperature},
author = {D Walter and T Pernau and J Schmidt},
editor = {WIP},
doi = {10.4229/EUPVSEC20162016-2DO.1.1},
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 = {469-473},
address = {Munich, Germany},
abstract = {Solar cells made of boron-doped, oxygen-rich Czochralski-grown silicon (Cz-Si) wafers suffer from a degradation in conversion efficiency upon illumination. This effect, sometimes labeled “light-induced degradation” (LID), is caused by a defect center within the silicon bulk, often referred to as BO defect, which activates its recombination properties under illumination leading to a degradation of the carrier lifetime. However, the BO defect center can be permanently deactivated, i.e. the lifetime can be permanently recovered, under illumination at elevated temperature. Within this contribution, we focus on transferring our lab-type BO deactivation process, using a hotplate and a halogen lamp, into an ultrafast high-throughput process, applying an industrial-type belt-furnace especially designed for this very purpose by centrotherm photovoltaics AG. Using this industrial furnace, inline processing in a solar cell production line is feasible. Our investigation clearly shows that a permanent recovery of the lifetime with an industrial belt-furnace can be achieved. In addition, we prove this result also for a shorter lab-type version of the longer industrial belt-furnace. The lifetimes reached after processing can be comparable to the lifetimes obtained on the same Cz-Si materials after applying our lab-type approach. Excellent stability of the lifetime is verified for up to 1000 hours of illumination at room temperature.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
D Bredemeier; D Walter; S Herlufsen; J Schmidt
Understanding the light-induced lifetime degradation and regeneration in multicrystalline silicon Artikel
In: Energy Procedia, Bd. 92, S. 773-778, 2016, ISSN: 1876-6102, (Proceedings of the 6th International Conference on Crystalline Silicon Photovoltaics (SiliconPV 2016)).
@article{Bredemeier2016d,
title = {Understanding the light-induced lifetime degradation and regeneration in multicrystalline silicon},
author = {D Bredemeier and D Walter and S Herlufsen and J Schmidt},
doi = {10.1016/j.egypro.2016.07.060},
issn = {1876-6102},
year = {2016},
date = {2016-08-01},
journal = {Energy Procedia},
volume = {92},
pages = {773-778},
abstract = {In this contribution, we focus on improving the fundamental understanding of the carrier lifetime degradation and regeneration observed in block-cast multicrystalline silicon (mc-Si) wafers under illumination at elevated temperature. We observe a pronounced degradation in lifetime at 1 sun light intensity and 75̊C after rapid thermal annealing (RTA) in a belt-firing furnace at a set peak temperature of 900̊C. However, almost no lifetime instability is detected in mc-Si wafers which are fired at a peak temperature of only 650̊C, clearly showing that the firing step is triggering the degradation effect. Lifetime spectroscopy reveals that the light-induced recombination centre is a deep-level centre with an asymmetric electron-to-hole capture cross section ratio of 20±7. After completion of the degradation, the lifetime is observed to recover and finally reaches even higher carrier lifetimes compared to the initial state. While the lifetime degradation is found to be homogeneous, the regeneration shows an inhomogeneous behaviour, which starts locally and spreads later laterally throughout the sample. Furthermore, the regeneration process is extremely slow with time constants of several hundred hours. We demonstrate, however, that by increasing the regeneration temperature, it is possible to significantly speed up the regeneration process so that it might become compatible with industrial solar cell production. To explain the observed lifetime evolution, we propose a defect model, where metal precipitates in the mc-Si bulk dissolve during the RTA treatment and the mobile metal atoms bind to a homogeneously distributed impurity. Restructuring and subsequent dissociation of this defect complex is assumed to cause the lifetime degradation, whereas a subsequent diffusion of the mobile species to the sample surfaces and crystallographic defects explains the regeneration.},
note = {Proceedings of the 6th International Conference on Crystalline Silicon Photovoltaics (SiliconPV 2016)},
keywords = {},
pubstate = {published},
tppubtype = {article}
}