1.
D C Walter; D Bredemeier; R Falster; V V Voronkov; J Schmidt
Disappearance of Hydrogen-Boron-Pairs in Silicon during Illumination and Its Relevance to Lifetime Degradation and Regeneration Effects in Solar Cells Proceedings Article
In: WIP, (Hrsg.): Proceedings of the 37th European Photovoltaic Solar Energy Conference and Exhibition, S. 140-144, Online Event, 2020.
@inproceedings{Walter2020b,
title = {Disappearance of Hydrogen-Boron-Pairs in Silicon during Illumination and Its Relevance to Lifetime Degradation and Regeneration Effects in Solar Cells},
author = {D C Walter and D Bredemeier and R Falster and V V Voronkov and J Schmidt},
editor = {WIP},
doi = {10.4229/EUPVSEC20202020-2AO.5.1},
year = {2020},
date = {2020-10-28},
booktitle = {Proceedings of the 37th European Photovoltaic Solar Energy Conference and Exhibition},
pages = {140-144},
address = {Online Event},
abstract = {In this contribution, we focus on a well-known complex in hydrogenated silicon, the hydrogen-boron (HB) pair, which allows us to directly determine the absolute hydrogen concentration in the silicon bulk via resistivity measurements. We demonstrate here that HB-pairs, which were formed during dark annealing, disappear under illumination at elevated temperatures. Upon a subsequent dark anneal, HB-pairs form again. Our experimental results suggest a reversible process for the formation of HB-pairs from H2 dimers upon dark annealing and the reformation of H2 dimers upon illuminated annealing. In addition, we show that the time of HB-pairs disappearance depends critically on the temperature and the applied illumination intensity, suggesting a thermally activated electron-enhanced backward formation of hydrogen dimers. Importantly, we observe on our samples made of boron-doped float-zone silicon (FZ-Si), that the loss of HB-pairs is accompanied by a reduction in carrier lifetime, which needs to be accounted for when describing the HB-loss curves, since the excess carrier concentration varies accordingly over time. In addition, our results might point to a connection between light-induced degradation and HB dissociation, which, has however to be examined in more detail in future studies.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
In this contribution, we focus on a well-known complex in hydrogenated silicon, the hydrogen-boron (HB) pair, which allows us to directly determine the absolute hydrogen concentration in the silicon bulk via resistivity measurements. We demonstrate here that HB-pairs, which were formed during dark annealing, disappear under illumination at elevated temperatures. Upon a subsequent dark anneal, HB-pairs form again. Our experimental results suggest a reversible process for the formation of HB-pairs from H2 dimers upon dark annealing and the reformation of H2 dimers upon illuminated annealing. In addition, we show that the time of HB-pairs disappearance depends critically on the temperature and the applied illumination intensity, suggesting a thermally activated electron-enhanced backward formation of hydrogen dimers. Importantly, we observe on our samples made of boron-doped float-zone silicon (FZ-Si), that the loss of HB-pairs is accompanied by a reduction in carrier lifetime, which needs to be accounted for when describing the HB-loss curves, since the excess carrier concentration varies accordingly over time. In addition, our results might point to a connection between light-induced degradation and HB dissociation, which, has however to be examined in more detail in future studies.
2.
M Winter; D Walter; D Bredemeier; J Schmidt
In: Solar Energy Materials and Solar Cells, Bd. 201, S. 110060, 2019, ISSN: 0927-0248.
@article{Winter2019c,
title = {Light-induced lifetime degradation effects at elevated temperature in Czochralski-grown silicon beyond boron-oxygen-related degradation},
author = {M Winter and D Walter and D Bredemeier and J Schmidt},
doi = {10.1016/j.solmat.2019.110060},
issn = {0927-0248},
year = {2019},
date = {2019-10-01},
journal = {Solar Energy Materials and Solar Cells},
volume = {201},
pages = {110060},
abstract = {The effect of ‘Light and elevated Temperature Induced Degradation’ (LeTID) of the carrier lifetime is well known from multicrystalline silicon (mc-Si) wafers and solar cells. In this contribution, we perform a series of carrier lifetime measurements to examine, whether the same effect may also be observable in boron-doped Czochralski-grown silicon (Cz-Si). The Cz-Si samples of our study are illuminated (i) at room temperature, (ii) under standard regeneration conditions eliminating the boron-oxygen (BO) related defect (i.e. at 185 °C) and (iii) at a temperature of 80 °C, typical for the examination of the LeTID effect in mc-Si. We observe the typical decay of the carrier lifetime due to the activation of the BO-related defect. Beyond the BO degradation, applying standard solar cell processes, there is no indication for the activation of a second defect. On samples, whose surfaces are passivated by fired hydrogen-rich silicon nitride layers, an additional bulk lifetime degradation effect on a long timescale is observed in the Cz-Si material. However, defect generation rate and injection dependence of the lifetime suggest another defect type than the mc-Si-specific LeTID defect. We conclude that by applying processing steps that trigger LeTID in mc-Si, the same defect does not occur in the Cz-Si samples examined in this study. On a long timescale, however, a hitherto unknown type of defect is activated, which is different from the mc-Si-specific LeTID defect. A careful differentiation between the various kinds of recombination centres which may form during illumination at elevated temperatures is hence of utmost importance.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The effect of ‘Light and elevated Temperature Induced Degradation’ (LeTID) of the carrier lifetime is well known from multicrystalline silicon (mc-Si) wafers and solar cells. In this contribution, we perform a series of carrier lifetime measurements to examine, whether the same effect may also be observable in boron-doped Czochralski-grown silicon (Cz-Si). The Cz-Si samples of our study are illuminated (i) at room temperature, (ii) under standard regeneration conditions eliminating the boron-oxygen (BO) related defect (i.e. at 185 °C) and (iii) at a temperature of 80 °C, typical for the examination of the LeTID effect in mc-Si. We observe the typical decay of the carrier lifetime due to the activation of the BO-related defect. Beyond the BO degradation, applying standard solar cell processes, there is no indication for the activation of a second defect. On samples, whose surfaces are passivated by fired hydrogen-rich silicon nitride layers, an additional bulk lifetime degradation effect on a long timescale is observed in the Cz-Si material. However, defect generation rate and injection dependence of the lifetime suggest another defect type than the mc-Si-specific LeTID defect. We conclude that by applying processing steps that trigger LeTID in mc-Si, the same defect does not occur in the Cz-Si samples examined in this study. On a long timescale, however, a hitherto unknown type of defect is activated, which is different from the mc-Si-specific LeTID defect. A careful differentiation between the various kinds of recombination centres which may form during illumination at elevated temperatures is hence of utmost importance.
3.
D Bredemeier; D Walter; R Heller; J Schmidt
Impact of SiNx:H Material Properties on Light and Elevated Temperature Induced Degradation (LeTID) in Mc-Si Vortrag
Leuven, Belgium, 08.04.2019, (SiliconPV 2019, 9th International Conference on Silicon Photovoltaics).
@misc{Bredemeier2019,
title = {Impact of SiNx:H Material Properties on Light and Elevated Temperature Induced Degradation (LeTID) in Mc-Si},
author = {D Bredemeier and D Walter and R Heller and J Schmidt},
year = {2019},
date = {2019-04-08},
address = {Leuven, Belgium},
note = {SiliconPV 2019, 9th International Conference on Silicon Photovoltaics},
keywords = {},
pubstate = {published},
tppubtype = {presentation}
}
4.
M Winter; D Walter; D Bredemeier; J Schmidt
Absence of Light and Elevated Temperature Induced Degradation (LeTID) of the Carrier Lifetime in Boron-Doped Cz-Silicon Vortrag
Leuven, Belgium, 08.04.2019, (SiliconPV 2019, 9th International Conference on Silicon Photovoltaics).
@misc{Winter2019,
title = {Absence of Light and Elevated Temperature Induced Degradation (LeTID) of the Carrier Lifetime in Boron-Doped Cz-Silicon},
author = {M Winter and D Walter and D Bredemeier and J Schmidt},
year = {2019},
date = {2019-04-08},
address = {Leuven, Belgium},
note = {SiliconPV 2019, 9th International Conference on Silicon Photovoltaics},
keywords = {},
pubstate = {published},
tppubtype = {presentation}
}
5.
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}
}
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%.