@article{Schlemminger.20250115,

title = {Flexibility is the key to decarbonizing heat supply: A case study based on the German energy system},

author = {M Schlemminger and F Peterssen and C Lohr and R Niepelt and A Bensmann and R Brendel and R Hanke-Rauschenbach and M H Breitner},

doi = {10.1016/j.enconman.2024.119300},

issn = {01968904},

year  = {2025},

date = {2025-01-15},

urldate = {2025-01-15},

journal = {Energy Conversion and Management},

volume = {324},

pages = {119300},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Xu2025,

title = {Analytical model for optical permittivity in direct bandgap semiconductors with Gaussian distributed bandgap energies},

author = {C Xu and J Vollbrecht and R Clausing},

doi = {10.1364/OL.542250},

year  = {2025},

date = {2025-01-15},

urldate = {2025-01-01},

journal = {Optics Letters},

volume = {50},

number = {2},

pages = {371–374},

publisher = {Optica Publishing Group},

abstract = {The optical permittivity of monocrystalline direct bandgap semiconductors can be described well by critical point models based on parabolic band approximation (CPPB). However, the optical permittivity of polycrystalline direct bandgap semiconductors like halide perovskite thin films requires a more precise description. Till now, only thermal bandgap fluctuation or exponential decay of density of states is incorporated into the CPPB model. We present an analytical calculation that is based on the CPPB model with only one additional physical assumption, namely, the Gaussian distributed bandgap energies (GCPPB). Furthermore, the GCPPB model satisfies the Kramers–Kronig causality relation.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Green2025,

title = {Solar Cell Efficiency Tables (Version 65)},

author = {M A Green and E D Dunlop and M Yoshita and N Kopidakis and K Bothe and G Siefer and X Hao and J Y Jiang},

doi = {10.1002/pip.3867},

year  = {2025},

date = {2025-01-01},

urldate = {2025-01-01},

journal = {Progress in Photovoltaics: Research and Applications},

volume = {33},

number = {1},

pages = {3-15},

abstract = {Consolidated tables showing an extensive listing of the highest independently confirmed efficiencies for solar cells and modules are presented. Guidelines for inclusion of results into these tables are outlined, and new entries since July 2024 are reviewed.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Min2024b,

title = {24.2% efficient POLO back junction solar cell with an AlOx/SiNy dielectric stack from an industrial-scale direct plasma-enhanced chemical vapor deposition system},

author = {B Min and V Mertens and Y Larionova and T Pernau and H Haverkamp and T Dullweber and R Peibst and R Brendel},

doi = {10.1002/pip.3828},

year  = {2025},

date = {2025-01-01},

urldate = {2025-01-01},

journal = {Progress in Photovoltaics: Research and Applications},

volume = {33},

number = {1},

pages = {236-244},

abstract = {An aluminum oxide (AlOx)/silicon nitride (SiNy) dielectric stack was developed using an industrial plasma-enhanced chemical vapor deposition (PECVD) system with low-frequency (LF) plasma source for the surface passivation of undiffused textured p-type crystalline silicon. The median recombination current density is 4.3 fA cm−2 as determined from photoconductance decay lifetime measurements and numerical device modeling. To the best of our knowledge, this is the first time to present a high-quality LF-PECVD AlOx/SiNy passivation stack on undiffused textured p-type crystalline silicon wafers, which are cleaned with industrial processes using HF, HCl, and O3. The simulation agrees well with the measured effective carrier lifetime if the velocity parameters of 5.6 cm s−1 for holes and 803 cm s−1 for electrons are applied with a fixed negative charge density of −3 × 1012 cm−2. The process integration of developed AlOx/SiNy dielectric stack is successfully demonstrated by fabricating p-type back junction solar cells featuring a poly-Si-based passivating contact at the cell rear side. As the best cell efficiency, we achieve 24.2% with an open-circuit voltage of 725 mV on a M2-sized Ga-doped p-type Czochralski-grown Si wafer as independently confirmed by ISFH CalTeC.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Graf2024,

title = {Domestic hot water systems in well-insulated residential buildings: A comparative simulation study on efficiency and hygiene challenges},

author = {C Graf and P Pärisch and A Marszal-Pomianowska and M Frandsen and B Bendinger and A Cadenbach},

doi = {10.1016/j.energy.2024.133587},

issn = {0360-5442},

year  = {2024},

date = {2024-12-30},

urldate = {2024-10-29},

journal = {Energy},

volume = {313},

pages = {133587},

abstract = {Domestic hot water (DHW) is essential for daily life, yet the production can be energy intensive. Advances in building insulation reduced space heating demand, while DHW energy demand remained constant or even increased. The need for a higher proportion of renewable heat amplifies the conflict in DHW systems between energy efficiency, hygiene, and comfort, since high temperatures are required for hygienic purposes. Thus, developing DHW systems efficiently utilizing renewable heat without excessive temperature requirements is essential. This paper reviews efficiency and hygiene challenges in DHW systems and assesses proposed solutions through comparative simulations in well-insulated residential buildings. Results show higher efficiencies in decentralised than centralised DHW systems. However, even in decentralised systems the necessity for circulation is a significant limitation. Lowering DHW temperature or transitioning to decentralised systems significantly reduces final energy demand, improves heat pump performance and increases the renewable heat share. Reducing DHW temperature from 60 to 50 °C increases stagnation periods in lower temperature intervals (22–34 °C) in warm water pipes. The study indicates significant potential to increase system efficiency and reduce final energy demand in decentralised or low-temperature DHW systems and introduces a novel method to compare conditions with regard to hygiene of DHW system simulations.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Lohr2024,

title = {Multi-criteria energy system analysis of onshore wind power distribution in climate-neutral Germany},

author = {C. Lohr and F. Peterssen and M. Schlemminger and A. Bensmann and R. Niepelt and R. Brendel and R. Hanke-Rauschenbach},

doi = {10.1016/j.egyr.2024.07.064},

issn = {2352-4847},

year  = {2024},

date = {2024-12-01},

urldate = {2024-01-01},

journal = {Energy Reports},

volume = {12},

pages = {1905-1920},

abstract = {Although onshore wind energy is a key pillar of renewable energy systems, installation targets in Europe have not been met. One contentious issue is its distribution, involving trade-offs between economic costs, environmental impact, public acceptance, and equity considerations. In this study, we evaluate different distribution strategies that meet Germany’s national onshore wind power target of utilizing 2 % land area, breaking it down to subordinate levels such as federal states. Therefore, we define key indicators for energy policy objectives to comprehensively analyze these strategies. We employ an energy system optimization model to address the system integration of spatial onshore wind power distribution, an aspect often overlooked in previous studies. Our results indicate that the impact of different distribution strategies on the overall energy system design is moderate, with the highest sensitivity observed in the allocation of electrolyzers, which closely align with renewable energy surpluses. However, our analysis shows that concentrating onshore wind power in areas with high energy yield can lead to an increase in electricity transport by up to 38 %, whereas more evenly distributed scenarios are preferred for environmental sustainability and distributive justice. In conclusion, we argue that energy system analysis can enhance the accuracy of assessment of onshore wind power distribution, but it must consider non-techno-economic criteria within spatially-distributed energy systems itself to address policymakers.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Veurman2024,

title = {Deciphering hysteresis in perovskite solar cells: Insights from device simulations distinguishing shallow traps from mobile ions},

author = {W Veurman and J Kern and L Pflüger and H Wagner-Mohnsen and M Müller and P P Altermatt and Z Y Lou and M Stolterfoht and F Haase and S Kajari-Schröder and R Peibst},

url = {https://authors.elsevier.com/a/1k1Uj,tRdSPwP},

doi = {10.1016/j.solener.2024.113037},

issn = {0038-092X},

year  = {2024},

date = {2024-12-01},

urldate = {2024-01-01},

journal = {Solar Energy},

volume = {284},

pages = {113037},

abstract = {In perovskite solar cells, a hysteresis of the current–voltage curve is often observed and is usually attributed to moving ions. However, our device modelling forecasts that it can also be explained, at least in part, by the occupation behaviour of slow-shallow trap states in the perovskite material. A difference between the ionic and trap interpretation arises in the illumination dependence of the hysteresis. Under the assumption of slow-shallow trap states, our simulations show that a diffusion capacitive effect should be observed at high scanning rates (> 100 V/s) and low light intensities (< 0.01 sun). This effect does not appear when assuming a device model with moving ion vacancies. This offers an opportunity for experimentally distinguishing between the two explanatory models and to quantify the relative contributions to hysteresis from ion vacancies and traps, respectively.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Schlemminger2024d,

title = {Rooftop PV Potential Determined by Backward Ray Tracing: A Case Study for the German Regions of Berlin, Cologne, and Hanover},

author = {M Schlemminger and D Bredemeier and A Mahner and R Niepelt and M H Breitner and R Brendel},

doi = {10.1002/pip.3844},

year  = {2024},

date = {2024-12-01},

urldate = {2024-09-18},

journal = {Progress in Photovoltaics: Research and Applications},

volume = {32},

number = {12},

pages = {912-929},

abstract = {Photovoltaics (PV) on building rooftops is a major contributor to the decarbonization of energy systems. We simulate the PV energy yield potential for 2.5 million individual roofs in three German regions. We cumulate the results for each single roof to calculate the cost-potential curves for the three cities Berlin, Cologne, and Hanover. These curves give the amount of electricity that can be generated at less than a given cost per kWh. We find that these curves have the shape of a hockey stick. Neglecting the dependence of PV investment on building size and thus on the system sizes causes largely different cost-potential curves that differ by 11%–18% for flat roofs due to their heterogeneous building size distribution. The cost-potential curves of the three cities are very similar when appropriately normalized, for example, by the local solar irradiation and the settlement area of the city, despite substantial variations in population density. This allows for an extrapolation of our results. For Germany, we reveal an upper limit for the total electricity generation from rooftop PV of 762 TWh/a with cost as low as 6.9 ct/kWh without accounting for area losses due to chimneys, air conditioning systems, and so forth. We estimate the actual potential to be at least half of that figure.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Jensen2024,

title = {Modeling of solar thermal heat pipe collectors with overheating prevention in system simulations},

author = {J Jensen and B Schiebler and S Kabelac and F Giovannetti},

doi = {10.1016/j.solener.2024.112861},

issn = {0038-092X},

year  = {2024},

date = {2024-11-01},

urldate = {2024-01-01},

journal = {Solar Energy},

volume = {282},

pages = {112861},

abstract = {Solar thermal collectors can provide renewable heat in an efficient way. They face however issues of overheating under certain circumstances, which can lead to thermal stress and steam formation. One solution to this issue consists in using solar thermal collectors with overheating prevention based on heat pipes. This paper presents the new TRNSYS type 839 that accurately reproduces the heat pipe overheating prevention effect. The model is validated using data from high accuracy solar tracker measurements as well as real solar thermal systems. A mean absolute deviation in the validation of less than 2% shows the functionality and accuracy of type 839. The results were compared with simulations using the existing Type 832 (without heat pipe limitation) and the simpler 2-part efficiency curve approach adapted from practice-oriented planning tools. By comparison, type 832 shows a mean absolute deviation of 44.8% using the same data. The use of the 2-part efficiency curve approach results in a mean absolute deviation of 49 %. With type 839 it is possible to design and evaluate solar thermal collectors with heat pipe limitation in TRNSYS and assess their use in a wide variety of systems. The new model is particularly recommended for applications with a relatively high and constant temperature level (e.g. process or district heating), for gross heat yield simulations or for the design of systems in order to correctly analyze the influence of the heat pipe limitation.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Katkus2024,

title = {Bessel-Beam Direct Write of the Etch Mask in a Nano-Film of Alumina for High-Efficiency Si Solar Cells},

author = {T Katkus and S H Ng and H Mu and N H An Le and D Stonytė and Z Khajehsaeidimahabadi and G Seniutinas and J Baltrukonis and O Ulčinas and M Mikutis and V Sabonis and Y Nishijima and M Rienäcker and U Römer and J Krügener and R Peibst and S John and S Juodkazis},

doi = {10.1002/adem.202400711},

year  = {2024},

date = {2024-11-01},

urldate = {2024-08-29},

journal = {Advanced Engineering Materials},

volume = {26},

number = {21},

pages = {2400711},

abstract = {Large surface area applications such as high efficiency >26% solar cells require surface patterning with 1–10 μm periodic patterns at high fidelity over 1–10 cm2$1 - łeft(textcmright)^2$ areas (before up scaling to 1 m2$ łeft(textmright)^2$) to perform at, or exceed, the Lambertian (ray optics) limit of light trapping. Herein, a pathway is shown to high-resolution sub-1 μm etch mask patterning by ablation using direct femtosecond laser writing performed at room conditions (without the need for a vacuum-based lithography approach). A Bessel beam is used to alleviate the required high surface tracking tolerance for ablation of 0.3–0.8 μm diameter holes in 40 nm alumina Al2O3$łeft(textAlright)_2 łeft(textOright)_3$–mask at high writing speed, 7.5 cm s−1; a patterning rate 1 cm2 per 20 min. Plasma etching protocol was optimized for a zero-mesa formation of photonic-crystal-trapping structures and smooth surfaces at the nanoscale level. The maximum of minority carrier recombination time of 2.9 ms was achieved after the standard wafer passivation etch; resistivity of the wafer was 3.5 Ω cm. Scaling up in area and throughput of the demonstrated approach is outlined.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Baumann2024,

title = {Stability and reliability of perovskite containing solar cells and modules: degradation mechanisms and mitigation strategies},

author = {S Baumann and G E Eperon and A Virtuani and Q Jeangros and D B Sulas-Kern and D Barrit and J Schall and W Nie and G Oreski and M Khenkin and C Ulbrich and R Peibst and J S Stein and M Köntges},

doi = {10.1039/D4EE01898B},

year  = {2024},

date = {2024-10-21},

urldate = {2024-08-02},

journal = {Energy Environ. Sci.},

volume = {17},

pages = {7566-7599},

publisher = {The Royal Society of Chemistry},

abstract = {Perovskite solar cells have shown a strong increase in efficiency over the last 15 years. With a record power conversion efficiency on small area above 34%, perovskite/silicon tandem solar cells already exceed the efficiency limit of silicon solar cells and their efficiency is expected to increase further. While predicted to take large markets shares in a few years thanks to their high efficiency and low manufacturing cost potential, perovskite/silicon tandem devices are not yet sufficiently reliable, which brings into question the commercial viability of this new technology. This review provides an extensive summary of degradation mechanisms occurring in perovskite solar cells and modules. In particular, instabilities triggered by the presence and generation of mobile ions in the perovskite absorber and/or by extrinsic stress factors are discussed in detail. In addition, mitigation strategies developed so far to improve the reliability of the technology are also presented.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Schmidt2024,

title = {Electronic Passivation of Crystalline Silicon Surfaces Using Spatial-Atomic-Layer-Deposited HfO2 Films and HfO2/SiN Stacks},

author = {J Schmidt and M Winter and F Souren and J Bolding and H Vries},

doi = {10.1002/pssr.202400255},

year  = {2024},

date = {2024-10-07},

urldate = {2024-10-07},

journal = {physica status solidi (RRL) – Rapid Research Letters},

pages = {2400255},

abstract = {Spatial atomic layer deposition (SALD) is applied to the electronic passivation of moderately doped (≈1016 cm−3) p-type crystalline silicon surfaces by thin layers of hafnium oxide (HfO2). For 10 nm thick HfO2 layers annealed at 400 °C, an effective surface recombination velocity Seff of 4 cm s−1 is achieved, which is below what has been reported before on moderately doped p-type silicon. The one-sun implied open-circuit voltage amounts to iVoc = 727 mV. After firing at 700 °C peak temperature in a conveyor-belt furnace, as applied in the production of solar cells, still a good level of surface passivation with an Seff of 21 cm s−1 is attained. Reducing the HfO2 thickness to 1 nm, the passivation virtually vanishes after firing (i.e., Seff > 1000 cm s−1). However, by adding a capping layer of plasma-enhanced-chemical-vapor-deposited hydrogen-rich silicon nitride (SiNx) onto the 1 nm HfO2, a substantially improved firing stability is attained, as demonstrated by Seff values as low as 30 cm s−1 after firing, which is attributed to the hydrogenation of interface states. The presented study demonstrates that SALD-deposited HfO2 layers and HfO2/SiNx stacks have the potential to evolve into an attractive surface passivation scheme for future solar cells.},

keywords = {},

pubstate = {forthcoming},

tppubtype = {article}

}