@article{Wang2022,

title = {Diode Factor in Solar Cells with Metastable Defects and Back Contact Recombination},

author = {T Wang and F Ehre and T P Weiss and B Veith-Wolf and V Titova and N Valle and M Melchiorre and O Ramírez and J Schmidt and S Siebentritt},

doi = {10.1002/aenm.202202076},

year  = {2022},

date = {2022-09-22},

journal = {Advanced Energy Materials},

pages = {2202076},

abstract = {To achieve a high fill factor, a small diode factor close to 1 is essential. The optical diode factor determined by photoluminescence is the diode factor from the neutral zone of the solar cell and thus a lower bound for the diode factor. Due to metastable defects transitions, the optical diode factor is higher than 1 even at low excitation. Here, the influence of the backside recombination and the doping level on the optical diode factor are studied. First, photoluminescence and solar cell capacitance simulator (SCAPS) simulations are used to determine the back surface recombination velocity of Cu(In, Ga)Se2 with various back contacts and different doping levels. Then, experimental results and simulations show that both back surface recombination and high doping density reduce the optical diode factor. The back surface recombination reduces the optical diode factor with undesirable extra nonradiative recombination. The smaller value achieved by higher doping can increase quasi-Fermi level splitting at the same time. The simulations show that the back surface recombination reduces the optical diode factor due to an illumination-dependent recombination rate. In addition, a higher majority carrier doping reduces the influence of majority carrier gain from metastable defect transitions, thus reducing the optical diode factor.},

keywords = {},

pubstate = {forthcoming},

tppubtype = {article}

}

@article{VanSant2022b,

title = {A performance comparison between GaInP-on-Si and GaAs-on-Si 3-terminal tandem solar cells},

author = {K T VanSant and E L Warren and J F Geisz and T R Klein and S Johnston and W E McMahon and H Schulte-Huxel and M Rienäcker and R Peibst and A C Tamboli},

doi = {10.1016/j.isci.2022.104950},

issn = {2589-0042},

year  = {2022},

date = {2022-09-16},

urldate = {2022-09-16},

journal = {iScience},

volume = {25},

number = {9},

publisher = {Elsevier},

abstract = {The pursuit of ever-higher solar cell efficiencies has focused heavily on multijunction technologies. In tandem cells, subcells are typically either contacted via two terminals (2T) or four terminals (4T). Simulations show that the less-common three-terminal (3T) design may be comparable to 4T tandem cells in its compatibility with a range of materials, operating conditions, and methods for subcell integration, yet the 3T design circumvents shading losses of the 4T intermediate conductive layers. This study analyzes the performance of two superstrate 3T III-V-on-Si (III-V//Si) tandem cells: One has slightly greater current contribution from the Si bottom cell (GaInP//Si) and the other has substantially greater current contribution from the GaAs top cell (GaAs//Si). Our results show that both tandem cells exhibit the same efficiency (21.3%), thereby demonstrating that the third terminal allows for flexibility in the selection of the top cell material, similar to the 4T design.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Folchert2022b,

title = {Modelling the annealing of poly-Si/SiOx/c-Si junctions},

author = {N Folchert and S Bordihn and R Peibst and R Brendel},

doi = {10.1063/5.0089597},

issn = {0094-243X},

year  = {2022},

date = {2022-08-24},

urldate = {2022-08-24},

journal = {AIP Conference Proceedings},

volume = {2487},

number = {1},

pages = {020006},

publisher = {American Institute of Physics},

abstract = {We use the MarcoPOLO model for the calculation of recombination and contact resistances of poly-Si-based junctions (such as POLO or TOPCon) to quantify the density of states Dit,cSi at the SiOx/c-Si interface of n+/n-type poly-Si based junctions during annealing. We compare the calculations to measurements of the recombination parameter, contact resistance and temperature-dependent contact resistance measurements and describe these measurements with the same set of parameters. We find that a constant Dit,cSi can explain the change of the recombination parameter J0 with increasing annealing temperature. The MarcoPOLO model allows the structural analysis and hence paths for the optimization of poly- Si junctions by e.g. a shallow diffusion below the interfacial oxide.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Min2022,

title = {Impact of dielectric capping layer thickness on the contact formation between n+-type passivating contacts and screen-printed fire-through silver pastes},

author = {B Min and N Wehmeier and T Brendemuehl and F Haase and Y Larionova and L Nasebandt and H Schulte-Huxel and R Peibst and R Brendel},

doi = {10.1063/5.0089239},

issn = {0094-243X},

year  = {2022},

date = {2022-08-24},

urldate = {2022-08-24},

journal = {AIP Conference Proceedings},

volume = {2487},

number = {1},

pages = {020014},

publisher = {American Institute of Physics},

abstract = {This paper presents the approach to reduce the deterioration of poly-Si based passivating contacts through screen- printed silver pastes by modifying the SiNx capping layer thickness and firing temperature. Its impact is investigated by fabricating p-type back junction solar cells featuring the passivating contacts at the cell rear side. We demonstrate that the improved contact formation without compromising of the quality of passivating contacts is possible if the firing temperature is optimized for the chosen SiNx layer thickness. On the full area of M2-sized industrial p-type Cz wafers, we achieve an open-circuit voltage of 716 mV and an efficiency of 22.6%, both independently. A median contact resistivity of 2 Ohm cm2 is measured with transfer length method for the optimized SiNx layer thickness and firing temperature. The investigation with scanning electron microcopy shows that certain amount of small etch pits are necessary to form the contact between screen-printed silver and phosphorus-doped poly-Si properly. The best efficiency that we achieved so far with this cell concept is 22.9 %, independently confirmed.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Wetzel2022,

title = {Transient electrical characteristics of silicon heterojunction solar cells under fast transient illumination},

author = {G Wetzel and J Krügener and B Stannowski and S Janke and R Peibst},

doi = {10.1063/5.0090104},

issn = {0094-243X},

year  = {2022},

date = {2022-08-24},

urldate = {2022-08-24},

journal = {AIP Conference Proceedings},

volume = {2487},

number = {1},

pages = {030014},

publisher = {American Institute of Physics},

abstract = {For vehicle integrated photovoltaics (VIPV) there are possibly specific requirements on the speed of maximum power point tracking. However, a certain delay in the response of solar cells to fast irradiance changes might impact those requirements on the MPPT. The subject of this work is therefore the investigation of the transient electrical behaviour of state-of-the-art silicon heterojunction solar cells. We use a fast switchable LED-array and an oscilloscope to investigate the cell voltage of silicon heterojunction solar cells under transient illumination. We find that these cells have a switch-off delay that is smaller than one millisecond when operated at or close to the maximum power point. This can be assumed to be faster than the time scale on that irradiances change typically occur on a car body while driving. We also find that, after switching off the light source, the transient cell voltage does not show a simple capacitive behaviour, but a more complex characteristic. A theoretical analysis shows that this behaviour can be explained by the nonlinear dependency of the diffusion and depletion capacitance and the minority carrier lifetime on the cell voltage.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Baumann2022b,

title = {Influence of encapsulation process temperature on the performance of perovskite mini modules},

author = {S Baumann and L Brockmann and S Blankemeyer and V Steckenreiter and V Barnscheidt and M Köntges and S Kajari-Schröder and S J Wolter and H Schulte-Huxel and T Wietler},

doi = {10.1063/5.0090632},

issn = {0094-243X},

year  = {2022},

date = {2022-08-24},

urldate = {2022-08-24},

journal = {AIP Conference Proceedings},

volume = {2487},

number = {1},

pages = {120001},

publisher = {American Institute of Physics},

abstract = {Perovskite-on-silicon tandem solar cells are a promising candidate to significantly increase the efficiency of PV modules. Despite the fast research progress on material and solar cells aspects, there is still a lack of processes for an industrial module integration of these devices. One aspect hereby is the adaption of encapsulation materials and processes to the requirements of perovskite materials. Process temperatures of about 150 °C are necessary to use well proven, in silicon PV commonly applied encapsulation materials with a high reliability. However, perovskites start to decompose into their components at high temperatures. This limits the encapsulation process temperature, which in turn constraints the choice of encapsulation materials. This work presents an encapsulation process for methylammonium lead iodide (MAPbl3) single junction perovskite solar cells (PSCs) with conventional production tools in glass-glass modules that serves as a model system for perovskite tandem applications. We evaluate the influence of the encapsulation process temperature between 120 °C and 160 °C on the performance of mini modules. The UV-absorbing encapsulation material is processable over the whole investigated temperature regime. We observe a difference in the IV-characteristics between the PSCs encapsulated in the temperature range of 120 °C - 140 °C to those processed at 160 °C. At lower encapsulation temperatures the IV curves taken 1 h after encapsulation show a pronounced S-shape and no degradation of VOC. ln contrast, the PSCs encapsulated at 160 °C exhibit a VOC decrease of up to 29% compared to the initial measurement shortly after PSC fabrication and no significant S-shape. Both, the S-shape that occurs at low encapsulation temperatures and the VOC loss after encapsulation at 160 °C, are no longer significant after one week of module storage under dark conditions. The presented encapsulation process therefore does not permanently damage the MAPbl3 PSCs even at a standard encapsulation temperature of 160 °C. To ensure long-term operation, we test the fabricated mini modules in a damp heat test at 85 °C and a relative humidity of 85%. We find no significant additional degradation caused by damp heat in 1250 h test duration compared to a reference module stored in ambient air.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Nasebandt2022,

title = {Sputtered Phosphorus-Doped poly-Si on Oxide Contacts for Screen-Printed Si Solar Cells},

author = {L Nasebandt and B Min and C Hollemann and S Hübner and T Dippell and R Peibst and R Brendel},

doi = {10.1002/solr.202200409},

year  = {2022},

date = {2022-06-16},

journal = {Solar RRL},

pages = {2200409},

abstract = {The impact of the phosphorus doping density in direct current-sputtered polysilicon layers on surface passivation and contact resistance by fabricating polysilicon on oxide (POLO) contacts is studied, when applying doping densities ranging from 3 × 1019 to 4 × 1020 cm−3. Hydrogenation is performed either via a hydrogen-releasing AlO x layer and postdeposition anneals in forming gas using a tube furnace at 400 °C, or by rapid firing of an AlO x /SiN y stack in a conveyor belt furnace at 810 °C. The study shows that the forming gas anneal of the weakly in situ phosphorus-doped poly-Si layers with AlO x enables a passivation quality with an implied open-circuit voltage of up to 734 mV and a recombination current density down to 1.8 fA cm− 2. For fast firing, a high phosphorus concentration of 4 × 1020 cm−3 is required for comparably high passivation quality with a recombination current density down to 1.3 fA cm− 2. A p-type POLO back-junction solar cell featuring such ex situ doped sputtered POLO contacts with a cell efficiency of 22.4% and an open-circuit voltage of 714 mV is fabricated. To our knowledge, this is the highest open-circuit voltage published so far with sputtered POLO contacts.},

keywords = {},

pubstate = {forthcoming},

tppubtype = {article}

}