@article{Hossain2020,
title = {Nanostructured front electrodes for perovskite/c-Si tandem photovoltaics},
author = {I M Hossain and Y J Donie and R Schmager and M S Abdelkhalik and M Rienäcker and T F Wietler and R Peibst and A Karabanov and J A Schwenzer and S Moghadamzadeh and U Lemmer and B S Richards and G Gomard and U W Paetzold},
doi = {10.1364/OE.382253},
year = {2020},
date = {2020-03-01},
journal = {Opt. Express},
volume = {28},
number = {6},
pages = {8878-8897},
publisher = {OSA},
abstract = {The rise in the power conversion efficiency (PCE) of perovskite solar cells has triggered enormous interest in perovskite-based tandem photovoltaics. One key challenge is to achieve high transmission of low energy photons into the bottom cell. Here, nanostructured front electrodes for 4-terminal perovskite/crystalline-silicon (perovskite/c-Si) tandem solar cells are developed by conformal deposition of indium tin oxide (ITO) on self-assembled polystyrene nanopillars. The nanostructured ITO is optimized for reduced reflection and increased transmission with a tradeoff in increased sheet resistance. In the optimum case, the nanostructured ITO electrodes enhance the transmittance by $sim$7% (relative) compared to planar references. Perovskite/c-Si tandem devices with nanostructured ITO exhibit enhanced short-circuit current density (2.9 mA/cm2 absolute) and PCE (1.7% absolute) in the bottom c-Si solar cell compared to the reference. The improved light in-coupling is more pronounced for elevated angle of incidence. Energy yield enhancement up to $sim$10% (relative) is achieved for perovskite/c-Si tandem architecture with the nanostructured ITO electrodes. It is also shown that these nanostructured ITO electrodes are also compatible with various other perovskite-based tandem architectures and bear the potential to improve the PCE up to 27.0%.},
keywords = {Effective refractive index, Enhanced solar cells, Scanning electron microscopy, Surface light scattering, tandem solar cells, Thin film deposition},
pubstate = {published},
tppubtype = {article}
}

@article{Wietler2017,
title = {Pinhole density and contact resistivity of carrier selective junctions with polycrystalline silicon on oxide},
author = {T F Wietler and D Tetzlaff and J Krügener and M Rienäcker and F Haase and Y Larionova and R Brendel and R Peibst},
doi = {10.1063/1.4986924},
year = {2017},
date = {2017-06-01},
journal = {Applied Physics Letters},
volume = {110},
number = {25},
pages = {253902},
abstract = {In the pursuit of ever higher conversion efficiencies for silicon photovoltaic cells, polycrystalline silicon (poly-Si) layers on thin silicon oxide films were shown to form excellent carrier-selective junctions on crystalline silicon substrates. Investigating the pinhole formation that is induced in the thermal processing of the poly-Si on oxide (POLO) junctions is essential for optimizing their electronic performance. We observe the pinholes in the oxide layer by selective etching of the underlying crystalline silicon. The originally nm-sized pinholes are thus readily detected using simple optical and scanning electron microscopy. The resulting pinhole densities are in the range of 6.6 × 10^6 cm−2 to 1.6 × 10^8 cm−2 for POLO junctions with selectivities close to S10 = 16, i.e., saturation current density J0c below 10 fA/cm2 and contact resistivity ρc below 10 mΩcm2. The measured pinhole densities agree with values deduced by a pinhole-mediated current transport model. Thus, we conclude pinhole-mediated current transport to be the dominating transport mechanism in the POLO junctions investigated here.},
keywords = {electrical resistivity, Etching, optical multistability, Scanning electron microscopy, silicon},
pubstate = {published},
tppubtype = {article}
}

@article{Kranz2016b,
title = {Analysis of local aluminum rear contacts of bifacial PERC+ solar cells},
author = {C Kranz and B Wolpensinger and R Brendel and T Dullweber},
doi = {10.1109/JPHOTOV.2016.2551465},
year = {2016},
date = {2016-07-01},
journal = {IEEE Journal of Photovoltaics},
volume = {6},
number = {4},
pages = {830},
abstract = {A recently published industrial passivated emitter rear contact (PERC) solar cell concept called PERC+ enables bifacial applications by printing an aluminum (Al) finger grid instead of the full-area Al layer aligned to the laser contact openings on the rear side. We demonstrate that the rear contacts of these PERC+ solar cells exhibit back-surface field (BSF) depths of around 6 μm over a large range of contact linewidths, whereas PERC cells with full-area Al rear layer show a reduction of the Al-BSF depths for narrower contact lines. Using an existing analytical model for the local contact formation, we show that the measured Al-BSF depths are well described solely by the different volume of Al paste printed on the rear side. Consequently, the open-circuit voltage of PERC+ solar cells improves by up to 5 mV when reducing the contact linewidth only. In contrast, for PERC cells with full-area Al layer, the Voc slightly decreases with narrower contact linewidths due to the thinner Al-BSF depths. We observe a strongly reduced number of voids in the Al-Si eutectic layer for PERC+ cells, compared with PERC. As physical root cause for void formation, we propose the minimization of surface energy of the Al-Si melt.},
keywords = {Aluminum, Analytical models, Bifacial passivated emitter rear contact (PERC) solar cells, contact formation, Photovoltaic cells, Printing, Scanning electron microscopy, screen-printing, silicon, Solids},
pubstate = {published},
tppubtype = {article}
}

@inproceedings{Krügener2016b,
title = {Dopant diffusion from p+-poly-Si into c-Si during thermal annealing},
author = {J Krügener and Y Larionova and B Wolpensinger and D Tetzlaff and S Reiter and M Turcu and R Peibst and J -D Kähler and T Wietler},
editor = {IEEE},
doi = {10.1109/PVSC.2016.7750083},
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 = {2451-2454},
address = {Portland, OR, USA},
abstract = {Passivating junctions, like hole-collecting p-polycrystalline silicon/SiOx/crystalline silicon junctions, need a thermal activation to activate their excellent passivation and contact properties. Here, the diffusion of boron from the highly doped poly-Si layer into the Si is often considered to compromise the passivation quality. In contrast we show that at least a slight diffusion of boron into the crystalline silicon is present for optimized annealing conditions. We achieve low emitter saturation current densities of 11 fA/cm2 for in situ p+ doped polysilicon deposited by low pressure chemical vapor deposition. Furthermore, we show that the polysilicon layer and the in-diffused region within the substrate are electrically connected.},
keywords = {Annealing, boron, diffusion, junction formation, Junctions, low pressure chemical vapor deposition, passivating contacts, Resistance, Scanning electron microscopy, silicon, Substrates, Temperature measurement},
pubstate = {published},
tppubtype = {inproceedings}
}

@article{Muller2011,
title = {Contact Formation and Recombination at Screen-Printed Local Aluminum-Alloyed Silicon Solar Cell Base Contacts},
author = {J Muller and K Bothe and S Gatz and H Plagwitz and G Schubert and R Brendel},
doi = {10.1109/TED.2011.2161089},
issn = {0018-9383},
year = {2011},
date = {2011-10-01},
journal = {IEEE Transactions on Electron Devices},
volume = {58},
number = {10},
pages = {3239-3245},
keywords = {Carrier lifetime, Conductivity, Geometry, Laser ablation, local back surface field (LBSF), metallization, Scanning electron microscopy, silicon, silicon solar cells, Spontaneous emission},
pubstate = {published},
tppubtype = {article}
}

@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 = {boron, charge carrier lifetime, Degradation, Diffusion processes, Furnaces, Glass, oxygen, Scanning electron microscopy, silicon, Temperature},
pubstate = {published},
tppubtype = {inproceedings}
}

@inproceedings{Bock2008d,
title = {Electron microscopy analysis of silicon islands and line structures formed on screen-printed Al-doped p+-surfaces},
author = {R Bock and J Schmidt and R Brendel and H Schuhmann and M Seibt},
editor = {IEEE},
doi = {10.1109/PVSC.2008.4922485},
issn = {0160-8371},
year = {2008},
date = {2008-05-01},
booktitle = {2008 33rd IEEE Photovoltaic Specialists Conference},
pages = {1-5},
address = {San Diego, CA, USA},
keywords = {Aluminum, Crystallization, Dispersion, Electron microscopy, nanostructures, Photovoltaic cells, Scanning electron microscopy, silicon, Transmission electron microscopy},
pubstate = {published},
tppubtype = {inproceedings}
}