1.
S Schäfer; F Haase; R Peibst; R Brendel
Silicon nanopowder as diffuse rear reflector for silicon solar cells Artikel
In: Journal of Applied Physics, Bd. 122, Nr. 5, S. 053102, 2017.
@article{Schäfer2017,
title = {Silicon nanopowder as diffuse rear reflector for silicon solar cells},
author = {S Schäfer and F Haase and R Peibst and R Brendel},
doi = {10.1063/1.4997183},
year = {2017},
date = {2017-08-03},
journal = {Journal of Applied Physics},
volume = {122},
number = {5},
pages = {053102},
abstract = {Highly efficient solar cells require minimized recombination and maximized optical absorption. We apply Si nanopowder with a median particle size of 500 nm to the rear side of poly-Si on oxide (POLO) passivated Si wafers that have a planar front side. The enhanced optical absorption consists of a useful component from the wafer and useless absorption by the Si pigments and the poly-Si layer. We derive and successfully apply an analytical model that accounts for both contributions and for the light trapping that is caused by light scattering at the nanopowder layer. We measure and model that this rear side increases the photogenerated current density by 1.3 mA/cm2 for a 140 μm-thick planar cell. We compare the performance of the Si-pigmented diffuse rear side reflectors (PDR) with reflectors using random pyramids (RPs) and POLO junctions. We find that for full surface coverage by Si nanopowder, the better surface passivation compensates for an inferior optical performance of a PDR when compared to RP.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Highly efficient solar cells require minimized recombination and maximized optical absorption. We apply Si nanopowder with a median particle size of 500 nm to the rear side of poly-Si on oxide (POLO) passivated Si wafers that have a planar front side. The enhanced optical absorption consists of a useful component from the wafer and useless absorption by the Si pigments and the poly-Si layer. We derive and successfully apply an analytical model that accounts for both contributions and for the light trapping that is caused by light scattering at the nanopowder layer. We measure and model that this rear side increases the photogenerated current density by 1.3 mA/cm2 for a 140 μm-thick planar cell. We compare the performance of the Si-pigmented diffuse rear side reflectors (PDR) with reflectors using random pyramids (RPs) and POLO junctions. We find that for full surface coverage by Si nanopowder, the better surface passivation compensates for an inferior optical performance of a PDR when compared to RP.
2.
V Steckenreiter; D C Walter; J Schmidt
In: AIP Advances, Bd. 7, Nr. 3, S. 035305, 2017.
@article{Steckenreiter2017b,
title = {Kinetics of the permanent deactivation of the boron-oxygen complex in crystalline silicon as a function of illumination intensity},
author = {V Steckenreiter and D C Walter and J Schmidt},
doi = {10.1063/1.4978266},
year = {2017},
date = {2017-03-01},
journal = {AIP Advances},
volume = {7},
number = {3},
pages = {035305},
abstract = {Based on contactless carrier lifetime measurements performed on p-type boron-doped Czochralski-grown silicon (Cz-Si) wafers, we examine the rate constant Rde of the permanent deactivation process of the boron-oxygen-related defect center as a function of the illumination intensity I at 170°C. While at low illumination intensities, a linear increase of Rde on I is measured, at high illumination intensities, Rde seems to saturate. We are able to explain the saturation by assuming that Rde increases proportionally with the excess carrier concentration Δn and take the fact into account that at sufficiently high illumination intensities, the carrier lifetime decreases with increasing Δn and hence the slope of Δn(I) decreases, leading to an apparent saturation. Importantly, on low-lifetime Cz-Si samples no saturation of the deactivation rate constant is observed for the same illumination intensities, proving that the deactivation is stimulated by the presence of excess electrons and not directly by the photons.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Based on contactless carrier lifetime measurements performed on p-type boron-doped Czochralski-grown silicon (Cz-Si) wafers, we examine the rate constant Rde of the permanent deactivation process of the boron-oxygen-related defect center as a function of the illumination intensity I at 170°C. While at low illumination intensities, a linear increase of Rde on I is measured, at high illumination intensities, Rde seems to saturate. We are able to explain the saturation by assuming that Rde increases proportionally with the excess carrier concentration Δn and take the fact into account that at sufficiently high illumination intensities, the carrier lifetime decreases with increasing Δn and hence the slope of Δn(I) decreases, leading to an apparent saturation. Importantly, on low-lifetime Cz-Si samples no saturation of the deactivation rate constant is observed for the same illumination intensities, proving that the deactivation is stimulated by the presence of excess electrons and not directly by the photons.
3.
D Bredemeier; D Walter; S Herlufsen; J Schmidt
In: AIP Advances, Bd. 6, S. 035119, 2016.
@article{Bredemeier2016c,
title = {Lifetime degradation and regeneration in multicrystalline silicon under illumination at elevated temperature},
author = {D Bredemeier and D Walter and S Herlufsen and J Schmidt},
doi = {10.1063/1.4944839},
year = {2016},
date = {2016-03-22},
journal = {AIP Advances},
volume = {6},
pages = {035119},
abstract = {We examine the carrier lifetime evolution of block-cast multicrystalline silicon (mc-Si) wafers under illumination (100 mW/cm2) at elevated temperature (75°C). Samples are treated with different 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. After completion of the degradation, the lifetime is observed to recover and finally reaches carrier lifetimes comparable to the initial state. To explain the observed lifetime evolution, we suggest a defect model, where metal precipitates in the mc-Si bulk dissolve during the RTA treatment.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We examine the carrier lifetime evolution of block-cast multicrystalline silicon (mc-Si) wafers under illumination (100 mW/cm2) at elevated temperature (75°C). Samples are treated with different 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. After completion of the degradation, the lifetime is observed to recover and finally reaches carrier lifetimes comparable to the initial state. To explain the observed lifetime evolution, we suggest a defect model, where metal precipitates in the mc-Si bulk dissolve during the RTA treatment.
4.
D C Walter; B Lim; K Bothe; V V Voronkov; R Falster; J Schmidt
Effect of rapid thermal annealing on recombination centres in boron-doped Czochralski-grown silicon Artikel
In: Applied Physics Letters, Bd. 104, Nr. 4, S. 042111, 2014.
@article{Walter2014b,
title = {Effect of rapid thermal annealing on recombination centres in boron-doped Czochralski-grown silicon},
author = {D C Walter and B Lim and K Bothe and V V Voronkov and R Falster and J Schmidt},
doi = {10.1063/1.4863674},
year = {2014},
date = {2014-01-01},
journal = {Applied Physics Letters},
volume = {104},
number = {4},
pages = {042111},
keywords = {},
pubstate = {published},
tppubtype = {article}
}