Research Centre for Sustainable Solar Cell Technology (SuSolTech) (completed)

• Søndenå, Rune; Aßmann, Nicole; Mosel, Frank & Hansen, Per-Anders (2026). Observation of an Injection Dependent Lifetime Effect in Highly Hydrogenated Boron Doped Wafers. SiliconPV Conference Proceedings. 3. doi: 10.52825/siliconpv.v3i.2669. Full text in Research Archive Show summary

  The correlation between hydrogen content and boron-oxygen related degradation is under debate. In this study surface passivated boron doped silicon wafers with different hydrogen content were illuminated at room temperature with three different light intensities. Their lifetime degradation was monitored with quasi-steady state photoconductance. A characteristic degradation that is separated into a fast and a slow decay characteristic for all light intensities is expected for such wafers. However, with increasing hydrogen content, we observe that the initial lifetime prior to illumination decreases, reducing the fast decay part of the degradation curves. For low intensity illumination the samples with reduced initial lifetimes follow the predicted degradation curve and show only the slow decay. For higher light intensities the degradation curves differ considerably; there is first a temporary lifetime increase before the decay sets in.

• Mubaiwa, Praise Tinotenda; Nzuma, Chiedza Thelma; Kowalczuk, Pshem & Safarian, Jafar (2026). A comparative study on decarburization of silicon kerf through high temperature oxidation and froth flotation techniques. Solar Energy Materials and Solar Cells. ISSN 0927-0248. 298. doi: 10.1016/j.solmat.2026.114171. Full text in Research Archive Show summary

  The need for sustainability and equitable use of resources is ever increasing because of global climate challenges and consequently, there have been increased efforts in the use of renewable energy sources like solar energy. The recycling of silicon kerf (sawdust), a waste material from the manufacture of solar wafers, is an important step in sustainability and circularity within the photovoltaic (PV) industry. The presence of carbon impurities in kerf presents challenges in the performance of the refined product in PV applications and thus it is important that it is reduced to acceptable levels. In this study a thermal oxidative decarburization of silicon kerf was conducted between 400 °C and 700 °C. Reaction mechanisms for the decarburization and simultaneous partial oxidation of silicon kerf particles were proposed based on the obtained results and effective decarburization of more than 90 % was achieved. Froth flotation was also conducted as an alternative low temperature route and under the conditions used was found not to be effective for decarburization of silicon kerf from diamond wire sawing due to limited selectivity at the very fine particle sizes of silicon kerf. The moderate temperature oxidative decarburization was therefore found to be effective for removal of carbon impurities.

• Yuan, Liang; Zheng, Yanxi; Sun, Jiaqi; Ji, Rui; Li, Xiang & Li, Mengkui [Show all 8 contributors for this article] (2025). Metal–Organic Framework-Derived Si@FCN Composite Based on Waste Silicon for High-Performance Lithium Storage. ACS Applied Energy Materials. 8(18). doi: 10.1021/acsaem.5c02276. Full text in Research Archive Show summary

  Nanosizing cheap kerf loss silicon (KL Si) and then compositing it with carbon is one of the effective ways to address the high-cost and low-cycling-life issues of a silicon-based anode for lithium-ion batteries (LIBs). In this work, a unique ZIFs-derived N-doped silicon–carbon structure (Si@FCN) has been prepared by exploiting the modulating effect of Pluronic F127 on metal–organic frameworks (MOFs). When tested as an anode for a CR3032 half-cell, Si@FCN demonstrates an initial Coulombic efficiency (ICE) of 75.4% at 0.1 A g–1, highlighting a stable cycling performance with discharge capacity maintained at 842.6 mAh g–1 (0.1 A g–1 for 200 cycles), 549.3 mAh g–1 (0.5 A g–1 for 300 cycles), and 485.7 mAh g–1 (1.0 A g–1 for 300 cycles). It also reveals good rate performance in the range of 0.2–5.0 A g–1. Such a remarkable electrochemical performance originates from the high surface area and porosity of the composite. The N-doped carbon layer derived from ZIF-8 demonstrated multifunctional enhancements in the electrode. Primarily, it significantly improves electrical conductivity through continuous electron transport pathways. Simultaneously, the mechanically robust carbon matrix effectively accommodates silicon’s substantial volumetric fluctuations during lithiation/delithiation cycles, thereby maintaining structural integrity. Furthermore, the introduced nitrogen heteroatoms create abundant redox sites, which substantially reduce the charge transfer resistance and accelerate redox reaction kinetics. The synthetic strategy for the silicon–carbon composite anode demonstrates enhanced lithium-ion storage capabilities, suggesting strong viability for scalable implementation in next-generation LIBs.

• Li, Xiang; Li, Mengkui; Sun, Jiaqi; Wang, Haoqi; Zheng, Yanxi & Cao, Pei [Show all 10 contributors for this article] (2025). Exploring the impact of ligand variation on MOFs-derived zinc cobaltate for high-performance lithium storage. Journal of The American Ceramic Society. ISSN 0002-7820. 109, p. 1–13. doi: 10.1111/jace.70366. Full text in Research Archive Show summary

  hanks to their excellent capacity, affordability, and eco-friendly character-istics, transition metal oxides (TMOs) hold promise as lithium-ion batteryanodes. Nevertheless, serious challenges, including low electrical conductivityand considerable volume variation during charge–discharge cycles, hinder theircommercial viability. Here, Zn-Co bimetallic metal–organic frameworks (MOFs)precursors with distinct morphologies were fabricated through a solvothermalapproach by employing three different organic ligands (2-aminoterephthalicacid, 2-methylimidazole, and terephthalic acid). After calcination, the obtainedZnCo2 O 4 nanocomposites retained the morphology and porous features of theirMOF precursors. Notably, the ZnCo 2 O 4 derived from terephthalic acid (BDC-ZCO) exhibited an ultrathin lamellar structure, which effectively shortenedion/electron transport paths, facilitated charge transport kinetics and accel-erated ionic migration, and mitigated volume variation. Benefiting from thisunique structure, the BDC-ZCO electrode maintained 695.1 mAh g−1 after 200cycles at 0.1 A g−1 , and 510.9 mAh g−1 after 300 cycles at 0.5 A g−1 , along withexcellent rate performance and cycling stability. This study demonstrates thatstructure-oriented regulation through ligand selection is an effective strategyfor optimizing the anode characteristics of MOFs-derived TMOs for advancedlithium storage.

• Kjeldby, Snorre Braathen; Nielsen, Dina Marie; Cooil, Simon Phillip; Frodason, Ymir Kalmann; Zacharaki, Eirini & Lee, In Hwan [Show all 10 contributors for this article] (2025). Tuning Properties of II-IV-Nitrides for Optoelectronic Applications. Advanced Optical Materials. 13(36). doi: 10.1002/adom.202502634. Full text in Research Archive Show summary

  The earth-abundant II-IV-nitrides ZnSnN2 and ZnGeN2 are direct bandgap semiconductors with a wurtzite-derived crystal structure. Their alloys, ZnSnxGe1 − xN2, have bandgaps tunable across the full visible spectrum, making them interesting for many optoelectronic applications. Here, electrical, structural, and optical properties of near-stoichiometric ZnSnxGe1 − xN2 alloys, i.e., where [Zn]/([Zn]+[Ge]+[Sn]) ≈ 0.5, are reported, for samples synthesized by reactive magnetron sputtering. These results reveal unprecedentedly high electrical mobilities in Ge-rich alloys, with values of 136 and 400 cm2/Vs at room-temperature and ≈100 K, respectively. The bandgaps are determined from optical absorption measurements combined with hybrid density functional calculations and reveal a significant Burstein–Moss shift in the Sn rich alloys. Finally, band alignments are determined in the sputter-grown thin films by combining optical transmission measurements, hybrid density functional calculations, and UV photoelectron spectroscopy measurements, where the bandgap variation is predominantly caused by a shift of the conduction band edge. This work elucidates in unprecedented detail the tuning of optical and electrical properties in ZnSnxGe1 − xN2 by variation of the chemical composition, where bandgap values of alloys with x ∈ [0.5−0.7] are suitable for top cell absorbers in two-terminal tandem solar cells assuming a Si bottom cell.

• Mubaiwa, Praise Tinotenda & Safarian, Jafar (2025). Mechanisms and melting behavior study of Si-kerf agglomerates under inert and vacuum conditions to recover PV silicon. Solar Energy Materials and Solar Cells. ISSN 0927-0248. 295, p. 1–10. doi: 10.1016/j.solmat.2025.113962. Full text in Research Archive Show summary

  The continued increase in usage of solar energy as the world moves towards a greener future means that there is even more PV waste each year than the previous. For every silicon wafer produced, about a third is lost as Si-kerf. Thus, the recovery and recycling of this material is a critical step to maximizing energy and material utilization. A study of the melting behavior of Si-kerf agglomerates under inert and vacuum conditions was carried out. It was found that the size of agglomerates does not play a major role in the melting behavior of kerf pellets within the size range 1 mm–10 mm, while the application of higher temperatures than 1600 °C is necessary. No single melt was produced under inert conditions between 1600 °C and 1700 °C, while a single melt with a shiny metallic luster was produced under vacuum conditions at the same temperature range. It is shown that the melting under inert gas occurs mostly via the joining of tiny silicon droplets surrounded by a thin oxide layer, and the formation of a silicon melt with an oxide layer around it. In the case of vacuum melting, however, the silicon oxide layer is eliminated via deoxidation through SiO gas formation, yielding a silicon melt.

• Honningdalsnes, Erlend Hustad; Marstein, Erik Stensrud; Lindholm, Dag; Bonesmo, Helge & Riise, Heine Nygard (2025). Wind sheltering in vertical agrivoltaics can increase crop yields: A modeling study for Northern Europe. Energy Nexus. 19. doi: 10.1016/j.nexus.2025.100516. Full text in Research Archive Show summary

  Vertical agrivoltaics can help reduce land use competition by integrating food crop cultivation between rows of vertical solar panels. However, its agricultural viability is often questioned due to panel shading. This study demonstrates that wind sheltering from vertical solar panels not only can compensate for the shading losses but lead to net-positive yield changes in Northern Europe. Crops benefit from wind shelter through improved soil moisture retention, higher ambient temperatures, and protection from wind erosion and damage. This study quantified the combined shading and wind sheltering effects on timothy grass (Phleum pratense L.) yields within large-scale vertical agrivoltaics across Norway, Sweden, and Finland. Our modeling framework integrated ERA5 weather data (2010–2023), Computational Fluid Dynamics for wind simulation (OpenFOAM), ray tracing for shading analysis (Honeybee Radiance), and a crop growth simulation model (CATIMO). Additionally, ERA5 temperature data was adjusted to explore shelter-induced warming effects. In the simulation, vertical agrivoltaics decreased ground irradiation by 15–16 % and reduced seasonal mean crop zone wind speeds by up to 40 % (up to 88 % for perpendicular winds), lowering evapotranspiration. When combining shading, wind reduction, and a conservative +0.5 ◦C shelter-induced temperature increase, the model predicted an average regional yield increase of +2.4 % compared to traditional agriculture. Yield improvements were highest in drought-prone soils (+3.7 %) and dry, sunny years (e.g., +9.2 % in 2018). This suggests that vertical agrivoltaics improves agricultural resilience under challenging conditions. These findings demonstrate that agrivoltaic modeling, particularly for vertical systems, should incorporate wind shelter effects to avoid fundamentally underestimating crop yield potential.

• Dahlioui, Dounia; Øgaard, Mari & Imenes, Anne Gerd (2025). Snow impact on PV performance: Assessing the zero-output challenge in cold areas. Renewable and Sustainable Energy Reviews. ISSN 1364-0321. 213. doi: 10.1016/j.rser.2025.115468. Full text in Research Archive Show summary

  Solar photovoltaic (PV) technology has a great potential for renewable energy generation. However, in cold climates with heavy snowfall, PV systems performance might be significantly reduced. This review investigates the impact of snow on solar PV in regions with harsh winters. It describes the snow soiling process while determining the main factors leading to snow losses in PV plants. Factors influencing snow losses are classified into four major categories: controllable factors, such as surface properties and PV installation characteristics, and uncontrollable factors, including climatic conditions and snow properties. The literature review reveals significant variations in reported snow losses due to the number of influential factors. One key recommendation is to improve PV system design to better accommodate snowy conditions, rather than relying on configurations optimized for milder conditions. The review also identifies a gap in the literature regarding the implementation of safety devices such as snow guards in the context of PV systems. With the increasing adoption of bifacial technologies, further research is needed to assess the benefits of snow's high albedo. For accurate snow loss modeling and shedding prediction, it is crucial to include additional factors impacting snow accumulation and clearing, such as liquid water content which affects snow adhesion. Additionally, enhancing models through image analysis and integrating drones for precise camera angles can significantly improve snow detection across various PV configurations and locations.

• Aßmann, Nicole; Hammann, Benjamin; Frøland, Mariann Carlsen; Kwapil, Wolfram & Monakhov, Eduard (2025). The differential impact of light soaking and dark annealing on hydrogen species during a LeTID cycle in boron-doped FZ silicon: A quantitative FT-IR study. Solar Energy Materials and Solar Cells. ISSN 0927-0248. 293. doi: 10.1016/j.solmat.2025.113853. Full text in Research Archive Show summary

  Hydrogen is recognized as the key species responsible for light- and elevated- temperature-induced degradation (LeTID) in silicon. The simplest hydrogen species detectable is acceptor-hydrogen, HB in boron-doped material. Many studies track HB trough resistivity measurements and infer the evolution of the hydrogen molecule, H2, often excluding other potentially relevant hydrogen-related species from consideration. This study presents a Fourier transform-infrared analysis of the evolution of the hydrogen species, HB, H2, the hydrogen dimer , and the vacancy-hydrogen complexes VH4 and V2H6, during dark annealing and light soaking. The findings are compared to changes in lifetime-equivalent defect density observed over a LeTID cycle. Before solar cell processing the hydrogen species found are HB, H2, V2H6, and VH4. After processing, is formed, HB and H2 increase in concentration, while VH4 and V2H6 disappear. Light soaking at 75 °C and 1 sun-equivalent and dark annealing at 175 °C both reduce H2 and concentrations, while HB concentration increases with dark annealing but decreases during light soaking. Extended dark annealing results in a re-appearance of VH4. A considerable role of and VH4 in the hydrogen balance in a LeTID cycle is demonstrated. Finally, several unidentified peaks are observed in the wavenumber range of 3000cm−1 to 3300cm−1, showing sensitivity to different treatment conditions. Specifically, peaks at 3029.1cm−1, 3102.1cm−1, and 3238.9cm−1 grow only when light soaking took place as final step. Conversely, a peak at 3025.8cm−1 increases under dark annealing conditions and decreases with prolonged light soaking

• Zainali, Sebastian; Lu, Silvia Ma; Fernández-Solas, Álvaro; Cruz-Escabias, Alejandro; Fernández, Eduardo & Zidane, Tekai Eddine Khalil [Show all 14 contributors for this article] (2025). Modelling, simulation, and optimisation of agrivoltaic systems: a comprehensive review. Applied Energy. ISSN 0306-2619. 386. doi: 10.1016/j.apenergy.2025.125558. Full text in Research Archive Show summary

  Agrivoltaic systems combine food production and solar energy conversion on the same land, offering a dual-use approach to address land use concerns in renewable energy development. One of the main research and market challenges for agrivoltaic systems is the ability to predict food and energy yields prior to installation. The photovoltaic modules reduce solar irradiation on the ground, altering the energy balance at the ground and crop levels, affecting thus evapotranspiration and photosynthesis. The photovoltaic modules also influence local rain distribution and wind patterns, creating a microclimate that impacts both crop production and photovoltaic efficiency. The need to evaluate these effects and their impact on crop growth before installation is underscored by the recent implementation of new standards, guidelines, and regulations governing agrivoltaic systems in various regions. This study provides a critical review of existing research with a focus on the modelling, simulation, and optimisation of agrivoltaic systems. It highlights recent advancements in simulating and optimising the design of agrivoltaic systems through integrated simulations of shading, microclimates, electrical performance, and agricultural productivity. This study highlights the critical role of optimised light distribution in enhancing both crop yields and electricity production within agrivoltaic systems. However, the diversity of modelling approaches from the PV and agricultural sectors, coupled with the absence of standardised benchmarks, complicates the selection of appropriate models for specific systems and conditions. Future research should prioritise the development of standardised benchmarks to enable consistent comparisons across models, facilitating a better understanding of trade-offs between computational efficiency, interpretability, and accuracy. Collaborative efforts, publicly available datasets, and benchmarking initiatives are essential for validating models across diverse agrivoltaic configurations and regions.

• Nygård, Magnus Moe; Wiig, Marie Syre; Roosloot, Nathan Abel; Otnes, Gaute; Øgaard, Mari & Riise, Heine Nygard [Show all 7 contributors for this article] (2025). Elucidating uncertainty in bifacial photovoltaic gain estimation. Solar Energy. ISSN 0038-092X. 292, p. 1–12. doi: 10.1016/j.solener.2025.113469. Full text in Research Archive Show summary

  The bifacial gain of fielded bifacial photovoltaic (PV) systems is commonly estimated by comparing the energy yield of the system with that of a monofacial reference. However, this approach is dependent on the selected reference, and can thus be associated with significant uncertainty, since the two technologies might have very different properties. This study investigates the significance of such differences when the bifacial gain is estimated from energy yield time series data. A series of corrections are applied to account for differences in installed capacity and responses with respect to temperature and irradiance. The analysis is carried out using data collected over two years from a 22.6 kWp ground-mounted fixed-tilt PV system in Norway using four different monofacial technologies as reference systems that all rely on Si as the active material but have different cell architectures. With no corrections applied, the estimated bifacial gain with the monofacial technology that most closely resembles the bifacial is determined to 12.6 % for the two-year period considered. The estimate increases to 13.1 % when correcting for irradiance and 14.4 % when also correcting for temperature. The results demonstrate that the applied corrections reduces the range between the smallest and largest estimate of the bifacial gain from 6.3 to 3.5 percentage points. Although it is possible that the range can be reduced further if differences in spectral response and degradation are accounted for, it should also be expected that some of the remaining variation reflects the measurement uncertainty inherent to this method of estimating the bifacial gain.

• Mehler, Melanie; Weinert, Nicolas; Aßmann, Nicole; Herguth, Axel; Hahn, Giso & Geml, Fabian (2025). Impact of high-temperature processing steps on the long-term stability of charge carrier lifetime in n -type FZ-silicon. EPJ Photovoltaics. 16. doi: 10.1051/epjpv/2025006. Full text in Research Archive Show summary

  In this work, the long-term behavior of excess charge carrier lifetime in n-type FZ-Si wafers without presence of highly doped layers is investigated during illumination at elevated temperatures. Thereby, the influence of high-temperature processing steps such as short high temperature thermal treatment, often referred to as tabula rasa (TR), and phosphorus diffusion gettering is considered. Degradation of effective lifetime is observed as well as a very strong regeneration effect that significantly exceeds the initial effective lifetime value. The phosphorus gettering step appears to have no significant effect on the degradation and regeneration behavior. Samples subjected to a TR treatment show only bulk-related regeneration. Investigations in darkness showed that the bulk-related regeneration is carrier-induced and not necessarily light-induced. FT-IR measurements at 5 K showed that the samples with a TR step have a higher Oi concentration in the Si bulk and that the hydrogen-passivated vacancies (VH4) are dissolved. The regeneration behavior of the samples with a TR step could be correlated with a reduced vacancy concentration. Such a thermal processing step appears to offer a strong mitigation strategy.

• Honningdalsnes, Erlend Hustad; Marstein, Erik Stensrud; Nygård, Magnus Moe; Wiig, Marie Syre & Riise, Heine Nygard (2025). Benchmarking irradiation models for photovoltaic applications: A comparative analysis of radiance-based tools. Solar Energy. ISSN 0038-092X. 296. doi: 10.1016/j.solener.2025.113566. Full text in Research Archive Show summary

  This study compared the accuracy, efficiency, and capabilities of three ray tracing tools—bifacial_radiance, ClimateStudio, and Honeybee Radiance—in modeling irradiance for photovoltaic (PV) systems. Despite similar performance in modeling hourly irradiance and monthly and annual cumulative irradiation levels, the tools exhibited differences in functionalities and computational efficiency. All models estimated cumulative annual front irradiation within 1.3% of measured values, with bifacial_radiance showing the largest error. For rear side irradiance, bifacial_radiance, ClimateStudio, and Honeybee Radiance underestimated irradiance by 2.82%, 5.40% and 8.74%, respectively. bifacial_radiance showed the highest model stochasticity in cumulative simulations due to its reliance on a single cumulative sky model. In contrast, ClimateStudio and Honeybee Radiance employ matrix-based approaches with hourly resolution within the period, averaging out stochasticity and making them more dependable for precise cumulative irradiation values. These matrix-based methods also significantly enhanced time-series analysis efficiency by modeling yearly irradiance with hourly resolution faster than bifacial_radiance analyzes a single point-in-time, while maintaining similar hourly error and bias levels. However, bifacial_radiance exhibited lower model stochasticity in hourly simulations. Enabled by the efficient simulation capabilities of ClimateStudio and Honeybee Radiance, a method for improving rear side irradiance modeling was tested. By combining simulations with different ground albedo values, this approach significantly reduced error and bias in rear side irradiance modeling. Ultimately, the choice of tool depends on study requirements, with bifacial_radiance being advantageous for hourly and sub-hourly resolution in short-term analyzes, while ClimateStudio and Honeybee Radiance are better suited for cumulative and extended time-series analyzes.

• Azarov, Alexander; Radu, Cristian; Galeckas, Augustinas; Mercioniu, Ionel Florinel; Cernescu, Adrian & Venkatachalapathy, Vishnukanthan [Show all 11 contributors for this article] (2025). Self-Assembling of Multilayered Polymorphs with Ion Beams. Nano Letters. ISSN 1530-6984. 25(4), p. 1637–1643. doi: 10.1021/acs.nanolett.4c05727. Full text in Research Archive
• Li, Xiang; Yuan, Liang; Li, Mengkui; Ji, Rui; Han, Zewen & Yu, Shaoxu [Show all 7 contributors for this article] (2025). Ag-doped hollow ZIFs-derived Si@C composite based on waste silicon for lithium-ion battery anodes. Journal of The American Ceramic Society. ISSN 0002-7820. 108(8). doi: 10.1111/jace.20568. Full text in Research Archive Show summary

  Currently, silicon is considered one of the most competitive candidates for the anode materials of lithium-ion batteries (LIBs), mainly benefiting from its extremely superior theoretical capacity. However, their industry application usually suffers from the expensive nano silicon. In the present study, the kerf loss silicon (KL Si) waste generated during the production of silicon wafers in photovoltaic industry is utilized as a low-cost nano silicon after pre-treatment. An Ag-doped hollow zeolitic imidazolate framework-8–derived Si@C composite (Si@HZIF-C/Ag) is synthesized via an in situ tannic acid etching/reduction method. The advanced structure effectively enhances the electrical conductivity and mitigates the volume fluctuation of silicon during charge/discharge process; it also facilitates the transport of Li+ due to the rich pore structure, thus resulting in an excellent electrochemical performance. The tested results indicate that the discharge capacity of Si@HZIF-C/Ag electrodes is up to 900.0 mAh g−1 after 300 cycles under 0.1 A g−1. Moreover, the discharge specific capacity remains at 400.2 mAh g−1 after 500 cycles under 0.25 A g−1, and the electrode exhibits good rate performance with a capacity retention of 99.2% across 0.1–1 A g−1. The presented route for silicon-based anode with promoted lithium storage performance shows huge potential for industry application in new-generation LIBs.

• Ji, Hengsong; Han, Zewen; Li, Xiang; Xu, Xiaohua; Yu, Shaoxu & Yuan, Liang [Show all 9 contributors for this article] (2025). Synthesis of MWCNT-Si@Ag@CN composite with improved lithium storage performance from photovoltaic kerf loss Si waste. Ionics (Kiel). ISSN 0947-7047. 31, p. 5465–5477. doi: 10.1007/s11581-025-06323-z. Full text in Research Archive Show summary

  Silicon-based nanomaterials hold great potential as new-generation anodes for lithium-ion batteries (LIBs). While their industrial deployment is often inhibited by the high cost of nano-sized silicon. In this study, cost-effective silicon nanoparticles (Si NPs) were obtained through pretreatment of the kerf loss Si (KL Si) waste originating in photovoltaic industry. These Si NPs, coated with dopamine hydrochloride and doped with silver, were combined with multi-walled carbon nanotubes (MWCNT), which were coated with an N-doped carbon (CN) to effectively mitigate the dramatic variation in volume of Si particles through the reaction process. The MWCNT network connected with silver and carbon layer substantially ameliorates the electrode’s conductivity. The MWCNT-Si@Ag@CN composite material for lithium-ion battery (LIB) anodes was synthesized utilizing this unique structural design. The composite retained 1077.7 mAh g−1 following 100 cycles under 0.1 A g−1 and 580.0 mAh g−1 following 100 cycles under 0.5 A g−1, also demonstrated promoted rate performance across 0.1 to 1 A g−1. The presented route for MWCNT-Si@Ag@CN anode with promoted lithium storage performance shows huge potential for industry application in next-generation LIBs.

• Hammann, Benjamin; Rodrigues, Pedro Vieira; Aßmann, Nicole; Kwapil, Wolfram; Schindler, Florian & Schubert, Martin C. [Show all 7 contributors for this article] (2024). Deciphering the Role of Hydrogen in the Degradation of Silicon Solar Cells under Light and Elevated Temperature. Solar RRL. 8(20). doi: 10.1002/solr.202400457. Full text in Research Archive Show summary

  In recent years, significant attention has been paid to the research of light- and elevated-temperature-induced degradation (LeTID) in silicon solar cells due to the substantial power loss and instability it causes. It has been discovered that the presence of hydrogen is closely linked to the occurrence of LeTID. In this study, a thorough review and re-assessment of previously published results is conducted and connected with newly obtained data. The findings indicate a complex interaction between different hydrogen complexes and the LeTID defect states. The precursor of LeTID is connected to molecular hydrogen (H2), while the LeTID degradation and regeneration are related to the binding of atomic hydrogen to the precursor and defect, respectively. A detailed description of the various reactions that occur under illumination and in the dark is provided. Additionally, explanation is given on how pre-annealing can significantly affect the kinetics of LeTID during subsequent light soaking. Furthermore, a comprehensive hydrogen model that incorporates these various reactions and demonstrates an agreement between simulation and experimental results is developed. Finally, the implications of the findings on strategies for mitigating LeTID are discussed.

• Warden, Gabriela Kazimiera; Ebbinghaus, Petra; Rabe, Martin; Juel, Mari; Gawel, Bartlomiej & Erbe, Andreas [Show all 7 contributors for this article] (2024). Investigation of uniformity in fused quartz crucibles for Czochralski silicon ingots. Journal of Crystal Growth. ISSN 0022-0248. 645. doi: 10.1016/j.jcrysgro.2024.127844. Full text in Research Archive Show summary

  As there is an increased demand for monocrystalline silicon based solar cells, there is an increased interest in stronger and more durable fused quartz crucibles used in the Czochralski process. In this study we focused on the uniformity of hydroxyl impurities in these crucibles, and its potential influence on viscosity of the crucible by combining data from IR-microscopy and a self-made viscosity measurement setup. A half of a fused quartz crucible manufactured from two types of sands was studied, the OH groups content was mapped, and the viscosity at 1500 °C was measured. Local variations in the OH groups content of on average 26.7 ppm difference between the top and the bottom of the crucible were detected. The viscosity measurements further confirmed the crucible’s inhomogeneity as no clear trends or direct correlations to the OH groups content were observed. The correlation between the different sand types used for crucible manufacturing and the OH groups content was also investigated in four samples originating from four different crucibles. Two different trends in the OH groups distribution were found: while two of the studied crucibles showed an increased OH groups content in the boundary between the bubble free and the bubble containing layer, the other two showed an increased and maximum OH groups content in the bubble containing layer, and the link between the sand types and the OH groups content was confirmed. The source of the local inhomogeneities and the two different trends of OH groups distribution can possibly be attributed to the sand quality, the sand particle size, and the difference in the manufacturing process, such as thermal history or distribution of sand.

• Mehler, Melanie; Weinert, Nicolas; Aßmann, Nicole; Herguth, Axel; Hahn, Giso & Geml, Fabian (2024). Long-term carrier lifetime instabilities in n-type FZ- and Cz-silicon under illumination at elevated temperature. Solar Energy Materials and Solar Cells. ISSN 0927-0248. 278. doi: 10.1016/j.solmat.2024.113169. Full text in Research Archive Show summary

  Even though n-type Si wafers show a lower extent of light-induced degradation, similar degradation and regeneration behavior as in p-type Si materials has been observed for various n-type Si monocrystalline materials. In this work, the long-term behavior of minority charge carrier lifetime in non-diffused n-type FZ-Si and Cz-Si wafers during illumination at elevated temperatures is investigated. Thereby, various influencing factors such as peak firing temperature and treatment temperature are considered. Degradation and a very strong regeneration effect, which exceeds the initial effective lifetime value, can be observed in the samples. Since surface-related saturation current density remains almost constant during degradation and regeneration, the effect seems to be bulk related. The extent of degradation and regeneration could be shown to be firing temperature-dependent. It could also be shown for n-type FZ-Si wafers that higher firing temperatures result in an increased H2 content within the silicon bulk. Investigations of the injection-dependent defect density revealed that the defect formed during degradation is not a deep level Shockley-Read-Hall defect. Observations at different treatment temperatures and constant illumination of 0.9(1) sun photon flux equivalent have shown that a higher treatment temperature leads to faster degradation and regeneration kinetics. Similarly, higher injection rates also speed up regeneration kinetics. Since degradation also occurs in darkness, the bulk related degradation effect in n-type FZ-Si is charge carrier-induced and not necessarily light-induced.

• Paudyal, Basant Raj; Somasundaram, Sakthi Guhan; Louwen, Atse; Reinders, Angele H.M.E.; Sark, Wilfried G.J.H.M. van & Stellbogen, Dirk [Show all 8 contributors for this article] (2024). Analysis of spectral irradiance variation in northern Europe using average photon energy distributions. Renewable Energy. ISSN 0960-1481. 224, p. 1–21. doi: 10.1016/j.renene.2024.120057. Full text in Research Archive Show summary

  One major factor affecting the energy yield of photovoltaic modules is the spectral distribution of incident solar radiation. As spectral irradiance data is scarce, this study provides further documentation of recorded spectra at tilt angle 30°– 45°over a period from one to several years, with the resulting distributions of average photon energy (APE) in the 350–1050 nm wavelength range, from five locations in northern Europe. The results show a general trend of higher monthly APE values in summer and lower values in winter, with more pronounced APE variation at increasing latitude. Compared to the reference APE value of 1.88 eV, the largest variation in monthly APE is seen for the northernmost location of Grimstad, Norway, ranging from 1.82 eV to 1.93 eV between January and July with an annual average APE of 1.90 eV. The smallest variation is found for Merklingen, Germany, ranging from 1.86 eV to 1.88 eV between March and July, with an annual average APE of 1.86 eV. Comparing the annual average APE values of the various locations, the study shows a slightly blue-shifted spectrum for Berlin, Enschede and Grimstad, whereas Merklingen experiences a slightly red-shifted spectrum and the APE at Utrecht is similar to the standard reference spectrum. The simulations through SMARTS show air mass, water vapor and aerosols as the major parameters affecting the spectrum. During the winter months, distinct contributions from both clear and cloudy sky conditions result in a bi-modal APE distribution for all locations, which is not observed during the summer months. Analysis of APE demonstrates different site-specific behaviors, even though all sites are categorized in the same Köppen–Geiger (KG) climate class. These differences arise mainly due to atmospheric factors, whereas dissimilarity in albedo conditions, plane of tilt and instrumentation also have some contributions.

• Azarov, Alexander; Galeckas, Augustinas; Wendler, Elke; Monakhov, Eduard & Kuznetsov, Andrej (2024). Inverse dynamic defect annealing in ZnO. Applied Physics Letters. ISSN 0003-6951. 124(4). doi: 10.1063/5.0184669. Full text in Research Archive Show summary

  Radiation tolerance of semiconductors depends on the dynamic defect annealing efficiency during irradiation. Consequently, it matters at what temperature one keeps the sample during irradiation, so that elevated temperatures typically result in lower remaining disorder. In the present work, we observed an opposite trend for the nitrogen ion implants into zinc oxide. Combining ion channeling technique, x-ray diffraction, and photoluminescence spectroscopy, we demonstrate that the interaction of nitrogen with radiation defects promotes an inverse dynamic annealing process, so that the increase in irradiation temperature leads to a more efficient defect formation. As a result, the residual radiation disorder is maximized at 650 °C and this state is characterized by the appearance of prominent optical signatures associated with zinc interstitials and strongly reduced strain accumulation as compared to the samples implanted at lower temperatures. However, for higher implantation temperatures, the impact of the inverse annealing decreases correlating with the surface degradation and loss of nitrogen.

• Azarov, Alexander; Galeckas, Augustinas; Cora, Ildikó; Fogarassy, Zsolt; Venkatachalapathy, Vishnukanthan & Monakhov, Eduard [Show all 7 contributors for this article] (2024). Optical Activity and Phase Transformations in γ/β Ga2O3 Bilayers Under Annealing. Advanced Optical Materials. doi: 10.1002/adom.202401325. Full text in Research Archive Show summary

  Gallium oxide (Ga2O3) can be crystallized in several polymorphs exhibiting different physical properties. In this work, polymorphic structures consisting of the cubic defective spinel (γ) film on the top of the monoclinic (β) substrate are fabricated by disorder-induced ordering, known to be a practical way to stack these polymorphs together. Such bilayer structures are annealed to investigate optical properties and phase transformations. Specifically, photoluminescence and diffuse reflectance spectroscopy are combined with transmission electron microscopy, Rutherford backscattering/channeling spectrometry and X-ray diffraction to monitor the evolutions. As a result, a two-stage annealing kinetics is observed in γ/β Ga2O3 bilayers associated with the epitaxial γ-to-β regrowth at the interface at temperatures below 700 °C and a non-planar γ-to-β phase transformation starting at higher temperatures. Thus, the present data enhance understanding of the polymorphism in Ga2O3, interconnecting the phase transformation kinetics with the evolution of the optical properties.

• Bergsbak, Ingvild; Nordseth, Ørnulf; Saxegaard, Kjetil Karlsen; Olsen, Vegard Skiftestad; Wenckstern, Holger Von & Bergum, Kristin (2024). Device Simulation of 25.9% Efficient ZnOxNy/Si Tandem Solar Cell. Advanced Theory and Simulations. 7(12). doi: 10.1002/adts.202400252. Full text in Research Archive Show summary

  The novel, high electron mobility material ZnOxNy has been investigated theoretically as an absorber in a two-terminal tandem solar cell. In addition to its high mobility, ZnOxNy can attain sufficiently low carrier concentration to enable pn-junctions, and has a tunable bandgap around the 1.7 eV range. It is therefore suitable for pairing with a Si-based bottom cell. In addition to the ZnOxNy layer, the tandem cell consists of a Cu2O emitter and a Si heterojunction bottom cell. A buffer layer is introduced between the emitter and absorber in the top cell to mediate a large valence band offset that resulted in a poor fill factor, FF. A ZnOxNy buffer layer bandgap of 1.5 eV gave the highest power conversion efficiency (PCE). The objective is to estimate the optimal performance of ZnOxNy in a tandem solar cell. The dependence of current–voltage (J–V) characteristics on thickness, mobility and carrier concentration in the ZnOxNy layer is evaluated, and found to yield maximum performance with 0.35 𝛍m, 250 cm2 Vs–1 and 1016 cm−3, respectively. Using these conditions, the J–V parameters of the device under AM1.5 illumination are short circuit current density, JSC = 17.76 mA cm−2, open circuit voltage, VOC = 1.74 V, FF = 83.8% and PCE = 25.9%. With this, it is reported on, to the best of the knowledge, the first device simulation based on ZnOxNy.

• Rasouli, Azam; Kuhn, Raphael; Lai, Samson Yuxiu; Safarian, Jafar & Tranell, Maria Gabriella (2024). Silane Gas Production Through Hydrolysis of Magnesium Silicide by Hydrochloric Acid. Journal of Sustainable Metallurgy. ISSN 2199-3823. 10, p. 687–698. doi: 10.1007/s40831-024-00817-2. Full text in Research Archive Show summary

  Monosilane (SiH4) is a common precursor for the production of high-purity silicon for solar PV applications. As an alternative to carbothermic reduction of silica to produce metallurgical grade silicon with subsequent conversion to silane, an alternative route over magnesiothermic reduction of silica to Mg2Si has been explored in our earlier work. In the current work, silane gas production through hydrolysis of Mg2Si in HCl acid solution was studied. Two sources of Mg2Si were chosen: a commercial Mg2Si source and a Mg2Si source produced through magnesiothermic reduction of high-purity natural quartz. Effects of various parameters on the hydrolysis of Mg2Si, including different experimental setups, temperature of the acid solution, acid concentration, reaction time, and relative amounts of reactants were studied. The evolution of produced gases was determined by two different methods: firstly, by passing the produced gas through a KOH solution to capture Si with subsequent analysis of the Si content in the KOH solution by inductively coupled plasma mass spectrometry and secondly, on-line gas analysis by GC–MS. The silane distribution between different silane species with reaction time was evaluated and the activation energy of silane formation was calculated. The results indicated comparable silane yields obtained from the on-line GC–MS method and KOH solution analysis method, as well as for commercial Mg2Si and the Mg2Si–MgO mixture produced through magnesiothermic reduction. Furthermore, adding HCl acid to Mg2Si in water led to higher SiH4 formation yield than adding Mg2Si to acid. However, the total silane yield for the two methods was similar at approximately 32%.

• Aßmann, Nicole; Søndenå, Rune; Hammann, Benjamin; Kwapil, Wolfram & Monakhov, Eduard (2024). Reducing Time and Costs of FT-IR Studies of the Effect of SiNx, Dopants, and Emitter on Hydrogen Species in Si Wafers and Solar Cell Structures. SiliconPV Conference Proceedings. doi: 10.52825/siliconpv.v1i.840. Full text in Research Archive Show summary

  Accurately measuring the hydrogen content in silicon (Si) solar cells is essential due to its connection to surface degradation and light and elevated temperature induced degradation (LeTID). Fourier Transform-Infrared (FT-IR) spectroscopy provides a quantitative technique for determining the content of various hydrogen species in Si wafers that have undergone various process steps. In this study, we examine both the effect of a silicon nitride (SiNx:H) layer during FT-IR spectroscopic measurements on hydrogen species, as well as the impact of an emitter present during firing on the amount of hydrogen introduced into Si wafers. We find that the presence of SiNx:H during measurements has negligible effects on the measured hydrogen species, potentially simplifying the preparation steps for FT-IR. For the emitter investigation we analyze boron (B)- and gallium (Ga)-doped p-type wafers to detect H-B, H-Ga, Oi-H2, and H2. We observe that hydrogen species initially present in B- and Ga-doped Si wafers differ significantly. Only H-Ga is detected in Ga-doped wafers, while H-B, Oi-H2, and H2 signals are measured in B-doped wafers. Moreover, we cannot confirm an increased release of H through the emitter into the bulk during the firing process. Finally, we conduct measurements at different temperatures and confirm that cryogenic temperatures are more effective for detecting H-B and H2 with concentrations in the 1014 cm-3 range. Nevertheless, useful spectra can still be obtained at liquid nitrogen (N2) temperatures.

• Rodrigues, Rodrigues Vieira; Hammann, B.; Aßmann, Nicole; Schön, J.; Kwapil, W. & Niewelt, T. [Show all 9 contributors for this article] (2024). Doping dependence of boron-hydrogen dynamics in crystalline silicon. Journal of Applied Physics. ISSN 0021-8979. 136(8). doi: 10.1063/5.0215089. Full text in Research Archive Show summary

  In this contribution, we investigate the formation and dissociation of boron–hydrogen (BH) pairs in crystalline silicon under thermal equilibrium conditions. Our samples span doping concentrations of nearly two orders of magnitude and are passivated with a layer stack consisting of thin aluminum oxide and hydrogen-rich silicon nitride (Al 2O 3/SiN x:H). This layer stack acts as a hydrogen source during a following rapid thermal annealing. We characterize the samples using low-temperature Fourier-transform infrared spectroscopy and four-point-probe resistivity measurements. Our findings show that the proportion of hydrogen atoms initially bound to boron (BH pairs) rises with increasing boron concentration. Upon isothermal dark annealing at (163 ± 2) °C, hydrogen present in molecular form, H 2, dissociates at a rate directly proportional to the concentration of boron atoms, ∝ [ B −], leading to the formation of BH pairs. With prolonged annealing, an unknown hydrogen complex is formed at a rate that is inversely proportional to the square of the boron concentration, ∝ 1/[B − ] 2, resulting in the disappearance of BH pairs. Based on experimental observations, we derive a kinetic model in which we describe the formation of the unknown complex through neutral hydrogen H 0 binding to a sink. Additionally, we investigate the temperature dependence of the reaction rates and find that the H 2 dissociation process has an activation energy of (1.11 ± 0.05) eV, which is in close agreement with theoretical predictions.

• Mubaiwa, Praise Tinotenda; Garshol, Askh; Azarov, Alexander & Safarian, Jafar (2024). Silicon Kerf Recovery via Acid Leaching Followed by Melting at Elevated Temperatures. Recycling. ISSN 2313-4321. 9(4). doi: 10.3390/recycling9040066. Full text in Research Archive Show summary

  The aim of this work was to study the purification of silicon kerf loss waste (KLW) by a combination of single-acid leaching followed by inductive melting at high temperatures with an addition of fluidized bed reactor (FBR) silicon granules. The KLW indicated an average particle size (D50) of approximately 1.6 µm, and a BET surface area of 30.4 m2/g. Acid leaching by 1 M HCl indicated significant removal of impurities such as Ni (77%), Fe (91%) and P (75%). The combined two-stage treatment resulted in significant removal of the major impurities: Al (78%), Ni (79%), Ca (85%), P (92%) and Fe (99%). The general material loss during melting decreased with an increasing amount of FBR silicon granules which aided in the melting process and indicated better melting. It was observed that the melting behavior of the samples improved as the temperature increased, with complete melting being observed throughout the crucibles at the highest temperature (1800 °C) used, even without any additives. At lower temperatures (1600 °C–1700 °C) and lower FBR-Si (<30 wt.%) additions, the melting was incomplete, with patches of molten silicon and a lot of surface oxidation as confirmed by both visual observation and electron microscopy. In addition, it was indicated that more reactive and volatile elements (Ga, Mg and P) compared to silicon are partially removed in the melting process (51–87%), while the less reactive elements end up in the final silicon melt. It was concluded that if optimized, the combined treatment of single-acid leaching and inductive melting with the addition of granular FBR silicon has great potential for the recycling of KLW to solar cells and similar applications. Moreover, the application of higher melting temperatures is accompanied by a higher silicon yield of the process, and the involved mechanisms are presented.

• Azarov, Alexander; Galeckas, Augustinas; Mikhaylov, Alexey; Nikolskaya, Alena; Tetelbaum, David & Korolev, Dmitry [Show all 8 contributors for this article] (2024). Defect evolution and nitrogen incorporation in ion-implanted β-Ga2O3. Applied Physics Letters. ISSN 0003-6951. 125(19). doi: 10.1063/5.0239899. Full text in Research Archive Show summary

  Nitrogen plays an important role in the Ga2O3-based device fabrication since it demonstrates a deep acceptor behavior and it can be used as a compensation impurity. In the present work, we introduced N into the monoclinic β-Ga2O3 single crystals by ion implantation using different dose-rates. The thermal evolution of the structural and optical properties of the implanted samples was studied by combining Rutherford backscattering/channeling spectrometry and x-ray diffraction with photoluminescence spectroscopy. We demonstrate that crystal disorder in N-implanted β-Ga2O3 is a strong function of ion flux even for room temperature implantation. Unlike other implanted species, the defect annealing kinetics for N exhibit a distinct two-stage behavior, where the low-temperature stage (<400 °C) is characterized by a rapid defect annealing, whereas the radiation defects exhibit a very slow evolution at the elevated temperatures (>400 °C). These trends are discussed in the framework of the disorder stabilization induced by the incorporation of the implanted N atoms into the Ga2O3 lattice. The obtained results can be used to better understand the interaction between N and intrinsic defects as well as to push forward the development of β-Ga2O3-based electronic devices.

• Vukovic, Marija; Wiig, Marie Syre; Benatto, Gisele Alves dos Reis; Olsen, Espen & Burud, Ingunn (2024). A review of imaging methods for detection of photoluminescence in field-installed photovoltaic modules. Progress in Energy. 6(3). doi: 10.1088/2516-1083/ad4250. Full text in Research Archive
• Zhu, Mengyi; Wu, Guixuan; Tang, Kai; Müller, Michael & Safarian, Jafar (2024). Combined silicon refining for boron removal and Si-Kerf recycling using K2O-CaO-SiO2 slags. Chemical Engineering Journal. ISSN 1385-8947. 488. doi: 10.1016/j.cej.2024.150788. Full text in Research Archive Show summary

  It is crucial for the photovoltaic (PV) industry to establish a circular materials flow for more sustainable solar silicon production. In the present work, a series of K2O-SiO2 and K2O-CaO-SiO2 slags were examined for the combination of silicon purification and Si-kerf waste recycling. The study revealed that the predominant mass transfer mechanism and the variation in slag composition during refining are due to the silicothermic reduction of K2O. The boron removal degree reached levels above 80% in most of tests, with boron gasification as potassium metaborate confirmed as an important mechanism for boron removal, especially in slags with high K2O content. In the case of ternary slags, the results indicated that an increase in CaO enhances boron partitioning in slag phase and a high K2O content also led to boron accumulation in the slag phase due to rapid reaction kinetics in the early stage of refining. The distinct behaviours of calcium and postassium ions in the slag phase were revealed by molecular dynamics simulations. It was found that potassium ions preferentially modify bridging oxygen, while calcium ions contribute more to depolymerizing the tectosilicate network and generating more non-bridging oxygens, which may further aid in the boron stabilization in slag phase. The oxidation layer of Si-kerf was removed successfully and enabled the coalescence of the silicon nanoparticles into the Si melt. Additionally, the presence of SiC clusters in the slag phase was also observed, indicating effective removal of SiC and the feasibility of Si-kerf waste recycling.

• Søndenå, Rune; Weiser, Philip Michael; Mosel, Frank; Aßmann, Nicole; Hansen, Per-Anders Stensby & Monakhov, Eduard (2023). Controlling the hydrogen concentration in boron- and gallium-doped silicon wafers. AIP Conference Proceedings. ISSN 0094-243X. 2826(1), p. 110008-1–110008-6. doi: 10.1063/5.0141155. Full text in Research Archive Show summary

  The influence of the thickness of the hydrogen-rich silicon nitride layer on the amount of hydrogen introduced into the bulk of silicon wafers, with boron or gallium as the acceptor dopant species, is investigated using cryogenic Fourier Transform-infrared spectroscopy. Nitride layers with comparable refractive indices are deposited on Czochralski wafers and subjected to a simulated contact firing process. Thus, hydrogenation of wafers is performed with different thicknesses of the respective hydrogen sources. Fourier Transform-infrared spectroscopy at 5.0 K show that the hydrogen concentrations can be varied by altering the film thickness. The effect of a subsequent passivation process, i.e. deposition of a second hydrogen rich dielectric film at an elevated temperature, is also investigated. We observe that the passivation may alter the states of hydrogen in the bulk silicon or cause unintentional introduction of hydrogen. This passivation process also revealed considerable differences between boron and gallium doped wafers; The hydrogen-boron concentration grew more than the corresponding hydrogen-gallium concentration during the passivation process.

• Stange, Marit Synnøve Sæverud; Sunde, Tor Olav Løveng; Dahl-Hansen, Runar Plunnecke; Rajput, Kalpna; Graff, Joachim Seland & Belle, Branson Delano [Show all 7 contributors for this article] (2023). High-Rate Epitaxial Growth of Silicon Using Electron Beam Evaporation at High Temperatures. Coatings. 13(12). doi: 10.3390/coatings13122030. Full text in Research Archive Show summary

  This paper describes the high-rate (~1.5 μm/min) growth of Si films on Si supporting substrates with (100) crystallographic orientation at 600 °C, 800 °C, and 1000 °C in a vacuum environment of ~1 × 10−5 mbar using electron beam (e-beam) evaporation. The microstructure, crystallinity, and conductivity of such films were investigated. It was established that fully crystalline (Raman spectroscopy, EBSD) and stress-free epi-Si layers with a thickness of approximately 50 µm can be fabricated at 1000 °C, while at 600 °C and 800 °C, some poly-Si inclusions were observed using Raman spectroscopy. Hall effect measurements showed that epi-Si layers deposited at 1000 °C had resistivity, carrier concentration, and mobility comparable to those obtained for c-Si wafers fabricated through ingot growth and wafering using the same solar grade Si feedstock used for the e-beam depositions. The dislocation densities were determined to be ∼2 × 107 cm−2 and ∼5 × 106 cm−2 at 800 and 1000 °C, respectively, using Secco etch. The results highlight the potential of e-beam evaporation as a promising and cost-effective alternative to conventional CVD for the growth of epi-Si layers and, potentially, epi-Si wafers. Some of the remaining technical challenges of this deposition technology are briefly indicated and discussed.

• Røyset, Arne Karstein; Kolås, Tore; Nordseth, Ørnulf & You, Chang Chuan (2023). Optical interference coatings for coloured building integrated photovoltaic modules: Predicting and optimising visual properties and efficiency. Energy and Buildings. ISSN 0378-7788. 298. doi: 10.1016/j.enbuild.2023.113517. Full text in Research Archive
• Kermani, Arman Hoseinpur; Tang, Kai; Ulyashin, Alexander; Palitzch, Wolfram & Safarian, Jafar (2023). Toward the recovery of solar silicon from end-of-life PVs by vacuum refining. Solar Energy Materials and Solar Cells. ISSN 0927-0248. 251. doi: 10.1016/j.solmat.2023.112181. Full text in Research Archive Show summary

  Considering the boom of Si solar cell installation, it is necessary to establish a process for recycling of Si from End-of-life photovoltaics (PVs). Silicon in the PVs is synthetically doped and coated by various elements and hence dedicated methods will be required for recycling of Si, back to the SoG-Si. In this research, recycling of Si from the shredded solar cells is studied by means of vacuum refining process. In this research the rejected solar cells after the firing step are treated by acid etching techniques to remove the Al back layer and the Ag finger on the front side of the cells, providing a product called de-metallized Si fragments. The vacuum refining experiments were carried out on demetallized Si fragments. Results showed the demetallized Si contained presence of P (11.67 ppmw), B (1 ppmw), Ca with up to 0.28 wt%, Ag (96 ppmw) and Sn (136 ppmw), while other metallic impurities were lower. We have shown that Sn, Ag, O, N, and Mg can be removed from the Si melt via short vacuum refining, while a complete removal of Ca and P required longer times compared to the mentioned impurities. Because vacuum refining process is not limited by thermodynamic equilibrium, a full removal of all the volatile impurities at extended times is expected and then this process has a high chance for returning the recovered Si to the solar grade requirements.

• Hammann, Benjamin; Assmann, Nicole; Weiser, Philip Michael; Kwapil, Wolfram; Niewelt, Tim & Schindler, Florian [Show all 9 contributors for this article] (2023). The Impact of Different Hydrogen Configurations on Light- and Elevated-Temperature- Induced Degradation. IEEE Journal of Photovoltaics. ISSN 2156-3381. 13(2), p. 224–235. doi: 10.1109/JPHOTOV.2023.3236185. Full text in Research Archive Show summary

  In this article, the impact of different hydrogen configurations and their evolution on the extent and kinetics of light- and elevated-temperature-induced degradation (LeTID) is investigated in float-zone silicon via charge carrier lifetime measurements, low-temperature Fourier-transform infrared spectroscopy, and four-point-probe resistance measurements. Degradation conditions were light soaking at 77 °C and 1 sun-equivalent illumination intensity and dark anneal at 175 °C. The initial configuration of hydrogen is manipulated by varying the wafer thickness, the cooling ramp of the fast-firing process, and the dopant type (B- or P-doped). We find lower hydrogen concentrations in thinner samples and samples with a slower cooling ramp. This suggests that hydrogen diffuses out of the sample during the cool-down, which strongly affects the final concentration of hydrogen molecules H 2 , and to a smaller degree the concentration of boron-hydrogen (BH) pairs. A regeneration of potential LeTID defects and a presumed LeTID degradation during dark annealing is found in n-type Si. In p-type Si, the LeTID extent was found to scale with H 2 , suggesting a direct link between both. The temporal evolution of BH pairs, LeTID degradation/regeneration, and surface degradation depends on wafer thickness and the cooling ramp of the fast-firing process. Based upon these findings, we formulate a theory of the hydrogen-related mechanism behind LeTID: Hydrogen originating from H 2 moves between different temporary traps. First, hydrogen binds to LeTID precursors and acceptor atoms in the silicon bulk, later moving toward the surface. This leads first to the LeTID degradation and regeneration and then to the degradation of surface passivation.

• Hammann, Benjamin; Aßmann, Nicole; Schön, Jonas; Kwapil, Wolfram; Schindler, Florian & Roder, Sebastian [Show all 8 contributors for this article] (2023). Understanding the impact of the cooling ramp of the fast-firing process on light- and elevated-temperature-induced degradation. Solar Energy Materials and Solar Cells. ISSN 0927-0248. 259, p. 1–9. doi: 10.1016/j.solmat.2023.112462. Full text in Research Archive
• Hansen, Per-Anders Stensby; Sørensen, Silje Holm; Desbois, Nicolas; Gros, Claude P. & Nilsen, Ola (2023). Perylenes, Porphyrins, and Other Large Dye Molecules for Molecular Layer Deposition. Advanced Materials Interfaces. doi: 10.1002/admi.202300667. Full text in Research Archive Show summary

  Abstract Molecular layer deposition (MLD) is an incredibly powerful and flexible tool for designing completely new materials with novel and unique properties. The low temperature layer‐by‐layer approach and the use of highly reactive reactants allows one to combine vastly different organic and inorganic species and construct nanostructures with subnanometer precision. If not limited by the volatility of the reactants involved, the possibilities will be endless. This is most notable for the organic building blocks where an overall low volatility severely limits the toolbox of large molecules with interesting optical and electrical properties such as red‐ox activity and optical conversion. In this work, different strategies for molecular design of large molecules are investigated that allow vaporization while still having the necessary reactivity for MLD growth. Using these strategies, film growth with perylene and porphyrin derivatives, both molecules well known for their functional and optical properties are successfully achieved. With this knowledge, there is an opening to include much larger and more complex organic molecules into the world of vapor phase chemistry.

• Tang, Kai; Rasouli, Azam; Safarian, Jafar; Ma, Xiang & Tranell, Maria Gabriella (2023). Magnesiothermic Reduction of Silica: A Machine Learning Study. Materials. 16(11). doi: 10.3390/ma16114098. Full text in Research Archive Show summary

  Fundamental studies have been carried out experimentally and theoretically on the magnesiothermic reduction of silica with different Mg/SiO2 molar ratios (1–4) in the temperature range of 1073 to 1373 K with different reaction times (10–240 min). Due to the kinetic barriers occurring in metallothermic reductions, the equilibrium relations calculated by the well-known thermochemical software FactSage (version 8.2) and its databanks are not adequate to describe the experimental observations. The unreacted silica core encapsulated by the reduction products can be found in some parts of laboratory samples. However, other parts of samples show that the metallothermic reduction disappears almost completely. Some quartz particles are broken into fine pieces and form many tiny cracks. Magnesium reactants are able to infiltrate the core of silica particles via tiny fracture pathways, thereby enabling the reaction to occur almost completely. The traditional unreacted core model is thus inadequate to represent such complicated reaction schemes. In the present work, an attempt is made to apply a machine learning approach using hybrid datasets in order to describe complex magnesiothermic reductions. In addition to the experimental laboratory data, equilibrium relations calculated by the thermochemical database are also introduced as boundary conditions for the magnesiothermic reductions, assuming a sufficiently long reaction time. The physics-informed Gaussian process machine (GPM) is then developed and used to describe hybrid data, given its advantages when describing small datasets. A composite kernel for the GPM is specifically developed to mitigate the overfitting problems commonly encountered when using generic kernels. Training the physics-informed Gaussian process machine (GPM) with the hybrid dataset results in a regression score of 0.9665. The trained GPM is thus used to predict the effects of Mg-SiO2 mixtures, temperatures, and reaction times on the products of a magnesiothermic reduction, that have not been covered by experiments. Additional experimental validation indicates that the GPM works well for the interpolates of the observations.

• Warden, Gabriela Kazimiera; Juel, Mari; Gawel, Bartlomiej Adam & Sabatino, Marisa Di (2022). Recent developments on manufacturing and characterization of fused quartz crucibles for monocrystalline silicon for photovoltaic applications. Open Ceramics. 13. doi: 10.1016/j.oceram.2022.100321. Full text in Research Archive Show summary

  The dominating technology of solar cell production today is based on monocrystalline silicon, produced mostly by the Czochralski process. Recently, the solar cell industry, has started to move towards growing larger and better-performing ingots. This triggered a need for crucibles that can withstand longer runtimes with better mechanical properties of high purity to reduce the silicon melt contamination. In this work we present the current state of fused quartz crucibles technology and a summary of the most important literature papers in this field. This review indicates that the characterization of fused quartz crucibles remains a challenge. The existing techniques are often not sufficient for fused quartz glass characterization without optimization. Therefore, further work should be a combination of complementary characterization techniques to be able to assess the properties of the crucible and their interactions, which could result in assessing the best combination of crucible properties.

• Søndenå, Rune; Weiser, Philip Michael & Monakhov, Eduard (2022). Direct and indirect determination of hydrogen-boron complexes in float-zone silicon wafers. In Brendel, Rolf; Ballif, Christophe; Dubois, Sebastien; Glunz, Stefan; Hahn, Giso; Poortmans, Jeff; Verlinden, Pierre & Weeber, Arthur (Ed.), SiliconPV 2021, The 11th International Conference on Crystalline Silicon Photovoltaics. AIP Publishing (American Institute of Physics). ISSN 9780735443624. doi: 10.1063/5.0089274. Full text in Research Archive
• Vukovic, Marija; Jakovljevic, Marko; Flø, Andreas Svarstad; Olsen, Espen & Burud, Ingunn (2022). Noninvasive photoluminescence imaging of silicon PV modules in daylight. Applied Physics Letters. ISSN 0003-6951. 120(24). doi: 10.1063/5.0097576. Full text in Research Archive
• Hammann, Benjamin; Aßmann, Nicole; Weiser, Philip Michael; Kwapil, Wolfram; Niewelt, Tim & Schindler, Florian [Show all 9 contributors for this article] (2022). Hydrogen complexes present after different firing profiles and their influence on LeTID degradation. Conference record of the Photovoltaic Specialists Conference. ISSN 0160-8371. doi: 10.1109/PVSC48317.2022.9938782. Full text in Research Archive
• Olsen, Vegard Skiftestad; Frodason, Ymir Kalmann; Hommedal, Ylva Knausgård; Nielsen, Dina Marie; Weiser, Philip Michael & Johansen, Klaus Magnus H [Show all 9 contributors for this article] (2022). Li and group-III impurity doping in ZnSnN2: Potential and limitations. PHYSICAL REVIEW MATERIALS. 6(12), p. 1–8. doi: 10.1103/PhysRevMaterials.6.124602. Full text in Research Archive Show summary

  II–IV nitrides and their alloys represent an earth-abundant and potentially cost-efficient alternative to the well-developed AlN-GaN-InN system. A major drawback with the II–IV nitrides is that ZnSnN2, the lowest band gap material, exhibits unfavorably high carrier concentrations for as-grown, stoichiometric material, limiting the material systems potential use in applications such as solar cells and light-emitting diodes. Lithium (Li) has been suggested as a shallow acceptor defect in ZnSnN2 if substituting for Zn, and hence doping with Li has been identified as a possible way to improve the electronic properties. Herein, theoretical calculations by hybrid functional density functional theory have been employed and extended to include defect complexes as well, which to this point remained unexplored. The calculations reveal that even though Li on the Zn site (the LiZn) is an acceptor, the defect may easily complex with the Lii donor, rendering the complex neutral. Our theoretical findings are supported by a Li-doping series of ZnSnN2, where a doping concentration ranging from 2.10×1019cm−3 to 1.85×1020cm−3 was obtained. The n-type carrier concentration was found to be unaffected by the doping concentration, and no systematic change in the absorption onset, probably affected by a Burstein-Moss shift, was observed. Possible group-III dopants, as have been found to yield interesting results for ZnGeN2, such as In, Ga, Al, and B, have also been investigated as an alternative dopant in ZnSnN2.

• Imenes, Anne Gerd (2022). PEARL PV Country Reports 2020 - Norway. In Farkas, Istvan; Atsu, Divine; Raghoebarsing, Amrita; Boddaert, Simon; Moser, David & Reinders, Angele (Ed.), PEARL PV Country Reports 2020. University of Twente. ISSN 9789036553629. p. 187–199. doi: 10.3990/1.9789036553629. Full text in Research Archive
• Langørgen, Amanda; Zimmermann, Christian; Frodason, Ymir Kalmann; Verhoeven, Espen Førdestrøm; Weiser, Philip Michael & Karsthof, Robert Michael [Show all 8 contributors for this article] (2022). Influence of heat treatments in H2 and Ar on the E1 center in β-Ga2O3. Journal of Applied Physics. ISSN 0021-8979. 131(115702). doi: 10.1063/5.0083861. Full text in Research Archive Show summary

  The influence of heat treating [Formula: see text]-type bulk [Formula: see text]-Ga[Formula: see text]O[Formula: see text] in hydrogen (H[Formula: see text]) and argon (Ar) gases on the presence of the defect level commonly labeled as [Formula: see text] was studied. Fourier transform-infrared spectroscopy confirms that hydrogen (H) is incorporated into [Formula: see text]-Ga[Formula: see text]O[Formula: see text] during H[Formula: see text] annealing at 900 °C. Deep-level transient spectroscopy measurements reveal that the concentration of the [Formula: see text] level is promoted by the introduction of H, in contrast to what is observed in samples heat-treated in an Ar flow. We further find the [Formula: see text] level to be stable against heat treatments at 650 K, both with and without an applied reverse-bias voltage. Potential candidates for the defect origin of [Formula: see text] are investigated using hybrid-functional calculations, and three types of defect complexes involving H are found to exhibit charge-state transition levels compatible with [Formula: see text], including substitutional H at one of the threefold coordinated O sites, Ga-substitutional shallow donor impurities passivated by H, and certain configurations of singly hydrogenated Ga–O divacancies. Among these types, only the latter exhibit H binding energies that are consistent with the observed thermal stability of [Formula: see text].

• Karsthof, Robert Michael; Frodason, Ymir Kalmann; Galeckas, Augustinas; Weiser, Philip Michael; Zviagin, Vitaly & Grundmann, Marius (2022). Light Absorption and Emission by Defects in Doped Nickel Oxide. Advanced Photonics Research. ISSN 2699-9293. 3(11). doi: 10.1002/adpr.202200138. Full text in Research Archive
• Lysne, Hogne; Brakstad, Thomas Vågenes; Kildemo, Morten & Reenaas, Turid Dory (2022). Improved methods for design of PLD and combinatorial PLD films. Journal of Applied Physics. ISSN 0021-8979. 132(12). doi: 10.1063/5.0105298. Full text in Research Archive
• Titov, A.I.; Karabeshkin, K.V.; Struchkov, A.I.; Nikolaev, V.I.; Azarov, Alexander & Gogova, D.S. [Show all 7 contributors for this article] (2022). Comparative study of radiation tolerance of GaN and Ga2O3 polymorphs. Vacuum. ISSN 0042-207X. 200. doi: 10.1016/j.vacuum.2022.111005. Full text in Research Archive Show summary

  The mechanisms of ion-induced defect formation and physical characteristics promoting radiation tolerance of wide and ultra-wide bandgap semiconductors are not well-studied and understood. In contrast to gallium nitride (GaN), gallium oxide (Ga2O3) can be crystallized in several polymorphs having different crystal structures and physical properties. In the preset paper, the damage buildup in wurtzite GaN as well as in corundum (α-) and monoclinic (β-) Ga2O3 polymorphs bombarded at room temperature with 40 keV P+ ions is studied by Rutherford backscattering/channeling spectrometry. We demonstrate that ion-beam-induced damage formation in Ga2O3 is different from that observed in GaN and dramatically depends on the polymorph type. Both Ga2O3 polymorphs cannot be rendered amorphous and exhibit considerably higher damage saturation at ∼90% of the full amorphization as compared to that of GaN. Intriguing enough the metastable α-Ga2O3 demonstrates considerably higher radiation resistance as compared to the most thermodynamically stable β-Ga2O3 polymorph. Furthermore, our results indicate that the sample surface and dynamic annealing play a significant role in the ion-induced damage formation processes in all Ga-based compounds studied.

• Azarov, Alexander; Bazioti, Kalliopi; Venkatachalapathy, Vishnukanthan; Ponniah, Vajeeston; Monakhov, Eduard & Kuznetsov, Andrej (2022). Disorder-Induced Ordering in Gallium Oxide Polymorphs. Physical Review Letters. ISSN 0031-9007. 128(1). doi: 10.1103/PhysRevLett.128.015704. Full text in Research Archive Show summary

  olymorphs are common in nature and can be stabilized by applying external pressure in materials. The pressure and strain can also be induced by the gradually accumulated radiation disorder. However, in semiconductors, the radiation disorder accumulation typically results in the amorphization instead of engaging polymorphism. By studying these phenomena in gallium oxide we found that the amorphization may be prominently suppressed by the monoclinic to orthorhombic phase transition. Utilizing this discovery, a highly oriented single-phase orthorhombic film on the top of the monoclinic gallium oxide substrate was fabricated. Exploring this system, a novel mode of the lateral polymorphic regrowth, not previously observed in solids, was detected. In combination, these data envisage a new direction of research on polymorphs in Ga2O3 and, potentially, for similar polymorphic families in other materials.

• Vukovic, Marija; Høiaas, Ingeborg; Jakovljevic, Marko; Flø, Andreas Svarstad; Olsen, Espen & Burud, Ingunn (2022). Outdoor photoluminescence and electroluminescence imaging of photovoltaic silicon modules in a string. AIP Conference Proceedings. ISSN 0094-243X. 2487(1). doi: 10.1063/5.0089308. Full text in Research Archive
• Vukovic, Marija; Høiaas, Ingeborg; Jakovljevic, Marko; Flø, Andreas Svarstad; Olsen, Espen & Burud, Ingunn (2022). Photoluminescence imaging of silicon modules in a string. Progress in Photovoltaics. ISSN 1062-7995. 30(4), p. 436–446. doi: 10.1002/pip.3525. Full text in Research Archive
• Titov, A.I.; Karabeshkin, K.V.; Struchkov, A.I.; Karaseov, P.A. & Azarov, Alexander (2022). Radiation tolerance of GaN: The balance between radiation-stimulated defect annealing and defect stabilization by implanted atoms. Journal of Physics D: Applied Physics. ISSN 0022-3727. 55(17). doi: 10.1088/1361-6463/ac4a38. Full text in Research Archive Show summary

  Abstract Realization of radiation-hard electronic devices that are able to work in harsh environments requires deep understanding of the processes of defect formation/evolution occurring in semiconductors bombarded by energetic particles. In the present work we address such intriguing radiation phenomenon as high radiation tolerance of GaN and analyze structural disorder, employing advanced co-irradiation schemes where low and high energy implants with different ions have been used. Channeling analysis revealed that the interplay between radiation-stimulated defect annealing and defect stabilization by implanted atoms dominates defect formation in the crystal bulk. Furthermore, the balance between these two processes depends on implanted species. In particular, strong damage enhancement leading to the complete GaN bulk amorphization was observed for the samples pre-implanted with fluorine ions, whereas the co-irradiation of the samples pre-implanted with such elements as neon, phosphorus and argon leads to a decrease of the bulk damage.

• Azarov, Alexander; Venkatachalapathy, Vishnukanthan; Vines, Lasse; Monakhov, Eduard; Lee, In-Hwan & Kuznetsov, Andrej (2021). Activation energy of silicon diffusion in gallium oxide: Roles of the mediating defects charge states and phase modification. Applied Physics Letters. ISSN 0003-6951. 119(18). doi: 10.1063/5.0070045. Full text in Research Archive Show summary

  Silicon (Si) is an efficient n-type dopant in gallium oxide (Ga2O3)—an ultra-wide bandgap semiconductor promising in a number of applications. However, in spite of the technological importance for device fabrication, the activation energy for Si diffusion in Ga2O3 is missing in the literature. In the present work, we do such measurements in ion implanted monoclinic β-Ga2O3 samples employing anneals in air ambient, also admitting the influence of potential ion beam induced phase modifications on diffusion. Importantly, we show that Si diffusion in β-Ga2O3 fits with the concentration dependent diffusion model, involving neutral and single negatively charged point defects to mediate the process; so that we assumed gallium vacancies in the corresponding charge states to assist Si diffusion in β-Ga2O3 with activation energies of 3.2 ± 0.3 and 5.4 ± 0.4 eV, respectively. Moreover, we also found that a preexisting phase modified surface layer efficiently suppressed Si diffusion in β-Ga2O3 for temperatures up to 1000 °C.

• Nyborg, Martin; Azarov, Alexander; Bergum, Kristin & Monakhov, Eduard (2021). Deposition and characterization of lithium doped direct current magnetron sputtered Cu2O films. Thin Solid Films. ISSN 0040-6090. 722(31), p. 1–5. doi: 10.1016/j.tsf.2021.138573. Full text in Research Archive
• Røyset, Arne Karstein; Kolås, Tore; Ulyashin, Alexsander G. & Rudzikas, Matas (2021). Efficiency Loss in Coloured Photovoltaics: Estimating the Contribution from Reflection Loss and Absorption Loss, EU PVSEC 2021 – 38th European Photovoltaic Solar Energy Conference and Exhibition. EU PVSEC. ISSN 9783936338782. doi: 10.4229/EUPVSEC20212021-4AV.2.10. Full text in Research Archive
• Nyborg, Martin; Kolevatov, Ilia; Vasquez, Geraldo Cristian; Bergum, K. & Monakhov, E. (2021). Dominant defects and carrier transport in single crystalline cuprous oxide: A new attribution of optical transitions. Journal of Applied Physics. ISSN 0021-8979. 130(17). doi: 10.1063/5.0059406. Full text in Research Archive Show summary

  Electronic properties of single crystal (111) Cu2O wafers have been investigated using a number of complementary techniques. Secondary ion mass spectrometry has shown significant presence of hydrogen and nitrogen. Cathodoluminescence measurements reveal strong near-band emission indicating the good electronic quality of the wafers. Two deep emission lines are observed at 1.3 and 1.7 eV. Temperature-dependent Hall effect measurements reveal electronic levels at around EV + 0.16 eV, EV + 0.22 eV, and ∼EV + 0.4 eV, where EV is the valence band edge. The discussion on the identity of the electronic centers calls for a revision of the traditional assignments of the 1.3-eV and 1.7-eV lines in order to take into account independent theoretical predictions. The temperature dependence of carrier mobility shows that the mechanism limiting the mobility can be described by scattering on neutral and ionized defect centers.

• Nyborg, Martin; Karlsen, Kjetil; Bergum, Kristin & Monakhov, Eduard (2021). Dominant acceptors in Li doped, magnetron deposited Cu2O films. Materials Research Express. 8(12), p. 1–8. doi: 10.1088/2053-1591/ac3e24. Full text in Research Archive Show summary

  Cu 2 O films deposited by reactive magnetron sputtering with varying Li concentrations have been investigated by a combination of temperature-dependent Hall effect measurement and thermal admittance spectroscopy. As measured by secondary ion mass spectrometry, Li concentrations up to 5 × 10 20 Li/cm 3 have been achieved. Li doping significantly alters the electrical properties of Cu 2 O and increases hole concentration at room temperature for higher Li concentrations. Moreover, the apparent activation energy for the dominant acceptors decreases from around 0.2 eV for undoped or lightly doped Cu 2 O down to as low as 0.05 eV for higher Li concentrations.

• Zhu, Mengyi; Yue, Shengying; Wu, Guixuan; Tang, Kai; Xu, Yijiang & Safarian, Jafar (2021). P removal from Si by Si-Ca-Al alloying-leaching refining: Effect of Al and the CaAl2Si2 phase. Separation and Purification Technology. ISSN 1383-5866. 271. doi: 10.1016/j.seppur.2021.118675. Full text in Research Archive Show summary

  Phosphorus (P) is a critical impurity in metallurgical-grade Si that needed to be removed for solar-grade Si production. The Si-Ca-Al-P system is one of the most crucial alloy systems for Si refining, where P can be separated by either the Si-Al solvent refining or the Si-Ca alloying-leaching process. In this work, a series of Si-Ca-Al alloys were obtained to investigate the role of alloy composition and the CaAl2Si2 phase in P segregation and separation. The used alumina crucible led to heavy Al contamination and resulted in unexpected Si-Ca-Al alloy compositions. CaAl2Si2 and CaSi2 were found as the main precipitates, and relatively higher P content was detected in the CaAl2Si2 phase. Leaching experiments indicate that P removal degree increases with increasing Ca/Al ratio and increasing total alloying amount (Ca + Al). Effects of alloy composition were further analyzed by statistical methods, which indicates Ca firmly plays a strong, positive, and monotonic role in P removal while no strong attraction between Al and P. Theoretical P removal model for the Si-Ca-Al system was established and in good agreement with measured results. Interaction coefficients of Ca and Al to P were fitted as εP_Ca = 19.2 and εP_Al = 1.8,which further confirms Ca is the essential driving force for P segregation. Finally, the possibility of P solid solution formation was verified by first-principle simulations that both CaAl2Si2 and CaSi2 are able to dissolve P, especially through the Si site, but the CaAl2Si2 phase is more favourable for P dissolution than CaSi2, which explains the reason of the often detected high P content in CaAl2Si2.

• Azarov, Alexander; Venkatachalapathy, Vishnukanthan; Monakhov, Eduard & Kuznetsov, Andrej (2021). Dominating migration barrier for intrinsic defects in gallium oxide: Dose-rate effect measurements. Applied Physics Letters. ISSN 0003-6951. 118(23). doi: 10.1063/5.0051047. Full text in Research Archive Show summary

  Ion bombardment provides an opportunity to study basic properties of intrinsic defects in materials since the radiation-induced disorder accumulation depends on the balance between defect generation and migration rates. In particular, variation of such parameters as irradiation temperature and ion flux, known in the literature as dose-rate effect, interconnects the macroscopically measured lattice disorder with the migration barrier of the dominating defects. In this work, we measured the dose-rate effect in monoclinic gallium oxide (β-Ga2O3) and extracted its activation energy of 0.8 ± 0.1 eV in the range of 25–250 °C. Taking into account that the measurements were performed in the Ga-sublattice and considering 0.8 ± 0.1 eV in the context of theoretical data, we interpreted it as the migration barrier for Ga vacancies in β-Ga2O3, limiting the process. Additionally, we observed and took into account an interesting form of the lattice relaxation due to radiation-induced disorder buildup, interpreted in terms of the compressive strain accumulation, potentially trigging phase transitions in Ga2O3 lattice.

• Olsen, Espen; Mehl, Torbjørn; Stalheim, Helene Eikaas; Juel, Mari; Søndenå, Rune & Burud, Ingunn (2021). The Effect of Pull Speed and Heat Treatment on Thermal Donors in Czhocralski Silicon. Physica Status Solidi (a) applications and materials science. ISSN 1862-6300. 219(1), p. 1–11. doi: 10.1002/pssa.202100655. Full text in Research Archive Show summary

  In silicon crystals manufactured by the Czochralski method, oxygen is incorporated as a contaminant originating primarily from dissolution of the quartz crucible used to contain the molten silicon feedstock. The oxygen can be found either as interstitials, agglomerates, or as oxide particles. Particular kinds of agglomerates are known to lead to the formation of thermal donors—electronic states in the bandgap of the silicon base material. These can act as sites for recombination of excited charge carriers and are called thermal donors due to their ability to inject two electrons into the conduction band of silicon by thermal excitation, leading to enhanced electrical conductivity. Neither of these features are desirable in Cz-Si manufacture. Herein, the behavior of thermal donors as a function of the pull speed, and the position in the ingot, is investigated. Thermal treatment is provided, first for the formation of thermal donors and then for their removal. The aim is to investigate methods for minimalizing their incorporation in the crystal in the first place and then how they can be removed. Hyperspectral imaging and spectroscopy combined with Fourier-transform infrared spectroscopy are used.

• Bonkerud, Julie; Zimmermann, Christian; Weiser, Philip Michael; Vines, Lasse & Monakhov, Eduard (2021). On the permittivity of titanium dioxide. Scientific Reports. 11. doi: 10.1038/s41598-021-92021-5. Full text in Research Archive Show summary

  Abstract Conductive rutile TiO 2 has received considerable attention recently due to multiple applications. However, the permittivity in conductive, reduced or doped TiO 2 appears to cause controversy with reported values in the range 100–10,000. In this work, we propose a method for measurements of the permittivity in conductive, n-type TiO 2 that involves: (i) hydrogen ion-implantation to form a donor concentration peak at a known depth, and (ii) capacitance–voltage measurements for donor profiling. We cannot confirm the claims stating an extremely high permittivity of single crystalline TiO 2 . On the contrary, the permittivity of conductive, reduced single crystalline TiO 2 is similar to that of insulating TiO 2 established previously, with a Curie–Weiss type temperature dependence and the values in the range 160–240 along with the c-axis.

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• Honningdalsnes, Erlend Hustad; Walpita, Harsha Lakmal; Nysted, Vilde Stueland; Marstein, Erik Stensrud; Selj, Josefine Helene Krogh & Riise, Heine Nygard (2025). Satellite Analysis of Floating PV Construction and Extreme Weather Resilience. Full text in Research Archive
• Honningdalsnes, Erlend Hustad; Marstein, Erik Stensrud & Riise, Heine Nygard (2025). Modeling and validation of crop yields in vertical solar parks. Full text in Research Archive
• Hollingsæter, Oliver Heim; Kraugerud, Olav Fjeld; Honningdalsnes, Erlend Hustad & Riise, Heine Nygard (2025). Solkraft på bondens premisser. Full text in Research Archive
• Hollingsæter, Oliver Heim; Kraugerud, Olav Fjeld; Honningdalsnes, Erlend Hustad & Riise, Heine Nygard (2025). Solkraft på bondens premisser. Full text in Research Archive
• Hollingsæter, Oliver Heim; Kraugerud, Olav Fjeld; Honningdalsnes, Erlend Hustad & Riise, Heine Nygard (2025). Slik kan solkraft øke bondens inntekter. Full text in Research Archive
• Øgaard, Mari; Eriksen, Erling Ween; Dahlioui, Dounia; Rønneberg, Sigrid & Riise, Heine Nygard (2025). Analyzing and modeling snow loss in ground-mounted PV systems. Full text in Research Archive
• Honningdalsnes, Erlend Hustad; Riise, Heine Nygard; Kjeldstad, Torunn; Marstein, Erik Stensrud; Stokkan, Gaute & Randle-Boggis, Richard [Show all 10 contributors for this article] (2024). Fordeler med solkraftverk på jord- og skogbruksarealer. Bondebladet. ISSN 0332-8414. Full text in Research Archive
• Tang, Kai; Ma, Xiang & Roman, Dumitru (2024). Enhancing Ferroalloy Processing through Machine Learning: Bridging Theory and Practice. Full text in Research Archive
• Orobengoa, Joseba Miren Ormaetxea; Stokkeland, Astrid & Reenaas, Turid Dory (2024). Bandgap optimization for colored multi-bandgap solar cells. Full text in Research Archive
• Rønneberg, Sigrid; Kjeldstad, Torunn; Riise, Heine Nygard; Breen, Anneline Malling & Tollisen, Stian (2024). Alle nye bygg bør få integrerte solceller i bygningskroppen. Full text in Research Archive
• Honningdalsnes, Erlend Hustad (2024). Solar Fields: Where Energy Meets Agriculture. Full text in Research Archive
• Honningdalsnes, Erlend Hustad; Marstein, Erik Stensrud & Riise, Heine Nygard (2024). Microclimatic Changes in Norwegian Solar Power Systems. Full text in Research Archive
• Kringlebotten, Erlend; Blom, Youri; Øgaard, Mari; Olsen, Espen; Santbergen, Rudi & Otnes, Gaute (2024). Comparing measured to modelled spectral irradiance for energy yield assessments of tandem PV modules. Full text in Research Archive
• Milani, Simone; Marstein, Erik Stensrud; Honningdalsnes, Erlend Hustad & Riise, Heine Nygard (2024). Water Reduction Potential for Olive Orchards within AgriPV Systems in Southern Italy. Full text in Research Archive
• Øgaard, Mari (2024). Snow losses and snow loss prediction. Full text in Research Archive
• Honningdalsnes, Erlend Hustad & Karlsen, Tia (2024). Vil unngå nytt vindkraft-bråk: Erlend (28) forsker på hvordan solparker påvirker norsk natur. [Journal]. Teknisk Ukeblad. Full text in Research Archive
• Dahlioui, Dounia & Imenes, Anne Gerd (2024). Snow Impact on PV Performance: Review and Investigation Towards Optimum System Design. Full text in Research Archive Show summary

  PV technology faces certain challenges in cold climates such as snow and ice acting as barriers, obstructing light from reaching the cells, but also opportunities for increased albedo during snowy winters. This work presents two sections highlighting : ▪ A review of the impact of snow on PV performance focusing on the challenges and opportunities posed by snow accumulation. ▪ Distribution of snow losses across various PV technologies and climate zones, as reported in literature. ▪ Analysis and classification of factors influencing snow losses. ▪ Description of snow soiling process. ▪ Parametric analysis of energy yield and snow losses to tilt angle and ground coverage ratio through production modelling using Solar Advisor Model (SAM) for a case study in Grimstad

• Honningdalsnes, Erlend Hustad; Marstein, Erik Stensrud; Lindholm, Dag; Bonesmo, Helge & Riise, Heine Nygard (2024). Reducing Wind Speeds and Boosting Agricultural Productivity with Vertical Bifacial Solar Panels. Full text in Research Archive
• Lysne, Hogne; Brakstad, Thomas Vågenes; Kildemo, Morten & Reenaas, Turid Dory (2023). pyPLD: Phyton library for tailoring thickness and composition of PLD thin films. Full text in Research Archive
• Honningdalsnes, Erlend Hustad; Bonesmo, Helge; Marstein, Erik Stensrud; Völler, Steve & Riise, Heine Nygard (2023). Autonomous Optimization of Agrivoltaic Systems - A Case Study on Grass and Vertical Bifacial PV. Full text in Research Archive
• Aßmann, Nicole; Sondenå, Rune; Hammann, Benjamin; Kwapil, Wolfram & Monakhov, Eduard (2023). Reducing Time and Costs of FT-IR Studies of the Ef-fect of SiNx, Dopants, and Emitter on Hydrogen Spe-cies in Si Wafers and Solar Cell Structures. Full text in Research Archive
• Kolås, Tore; Røyset, Arne Karstein; Nordseth, Ørnulf & You, Chang Chuan (2023). Predicting and optimising the performance of coloured solar cell modules based on interference coatings. Full text in Research Archive
• Kolås, Tore (2023). Coloured PV modules based on optical interference coatings. Full text in Research Archive
• Nilsen, Ola (2023). MLD as a Sandbox for Photoactive Hybrid Materials. Full text in Research Archive
• Imenes, Anne Gerd (2022). The Terawatt challenge: Why do we need PV monitoring? Full text in Research Archive
• Rosnes, Andreas; Lysne, Hogne; Christiansen, Emil; Reenaas, Turid Dory & Holmestad, Randi (2022). Differentiating Polyamorphous SiO2 by SPED, PDF and Blind Source Separation Algorithm. Full text in Research Archive
• Sund, Steinar Steinkopf & Kolås, Tore (2022). Store fordeler med med solceller på fasaden. Fremtidens Byggenæring (internett). 3, p. 159–162. Full text in Research Archive
• Imenes, Anne Gerd (2022). The Terawatt challenge: The key role of PV monitoring. Full text in Research Archive Show summary

  As the installation of new PV capacity continues to grow at a rapid rate worldwide, expected to rise from today’s 4% of the global electricity production to almost 15% by 2030, the value of and need for PV monitoring will arguably increase in a corresponding manner. Monitoring data represent the main source of information for the evaluation of economic profitability, system operation strategies, and environmental sustainability of PV power systems. This work will discuss the need for PV monitoring towards the Terawatt transition, including important international work on PV monitoring and databases, standards and guidelines for methods and equipment, data requirements of different user groups, challenges of data access and data quality, further work needed, and consideration of trends for future data collection from various sources of PV monitoring data and as it crosses borderlines with health inspection and diagnostic tools. Examples of the collection and sharing of data as part of collaborative work in the COST Action PEARL PV on Performance and Reliability of PV Systems will be given.

• Strandberg, Rune & Imenes, Anne Gerd (2022). Production estimates for tandem cells using high resolution spectral data. Full text in Research Archive
• Kolås, Tore (2022). Hva er fremtiden i bygningsintegrerte solceller? Full text in Research Archive
• Røyset, Arne Karstein; Kolås, Tore; Ulyashin, Alexsander G. & Rudzikas, Matas (2021). Efficiency Loss in Coloured Photovoltaics: Estimating the Contribution from Reflection Loss and Absorption Loss. Full text in Research Archive Show summary

  Building integrated photovoltaics (BIPV) offers efficient utilisation of land area and local renewable energy generation. Attractive aesthetic aspects and efficient energy generation are important drivers for market acceptance of solar panels as building elements. Coloured modules improve aesthetic aspects at the expense of efficiency loss and increased cost. For a given lightness and colour, a minimum energy loss due to reflected photons is unavoidable. Additional efficiency loss may come from parasitic absorption in the colour providing layers and from unwanted reflection and absorption in the nonvisible near infrared wavelength range. In this paper we present a novel method to identify the different loss contributions: visible reflection loss, near infrared reflection loss, and parasitic absorption loss. The methodology is applied to silicon solar cells where colouration is introduced by interference from a thin indium tin oxide layer on top of the SiNx:H antireflection coating. The method presented here will be a useful tool to optimize efficient colouring of solar cells.

• Selj, Josefine Helene Krogh (2021). Strømprisen til værs. [TV]. NRK. Full text in Research Archive
• Selj, Josefine Helene Krogh (2021). Dette er solenergi. [Internet]. Solklyngen Podcast. Full text in Research Archive
• Selj, Josefine Helene Krogh (2021). Solenergi i Norge. [Internet]. Norsk Klimastilftelse, Klimakvarter. Full text in Research Archive
• Lysne, Hogne; Brakstad, Thomas Vågenes; Lundberg, Marisa Di Sabatino; Inzani, Katherine; Kildemo, Morten & Selbach, Sverre Magnus [Show all 8 contributors for this article] (2021). Pulsed laser deposition of doped TiO2 thin films with lateral composition gradients. Full text in Research Archive
• Honningdalsnes, Erlend Hustad; Riise, Heine Nygard & Marstein, Erik Stensrud (2026). Vertical agrivoltaic systems: Modeling, optimization, and monitoring - With special emphasis on northern climates. Universitetet i Oslo. Full text in Research Archive Show summary

  Agricultural activities occupy nearly half of the world’s habitable land, an area larger than the Americas and the European Union combined. This has largely come at the expense of natural habitats, and today, new land uses such as utility-scale photovoltaic (PV) electricity production add further pressure. Agrivoltaic systems, in which PV modules and agricultural crops coexist on the same land, offer a pathway to greater land-use efficiency without claiming additional territory from nature. Although both PV modules and food crops rely on sunlight as their primary energy source, synergistic effects between the two have been demonstrated worldwide. PV modules can, for instance, harvest irradiance that exceeds a crop’s biological saturation point, or provide shade and shelter under harsh environmental conditions. The efficacy of these synergies, however, depends strongly on the specific crops and climates involved. In Northern Europe, short growing seasons and, in some places, strong regulatory protection of scarce agricultural land may require that crop yields are maintained or improved. In this context, vertical bifacial agrivoltaic systems have attracted particular interest due to their low physical footprint and limited crop shading. In these systems, vertically mounted PV modules arranged in rows leave the inter-row space accessible for agricultural machinery while simultaneously functioning as windbreaks that improve the local microclimate in ways that most other agrivoltaic designs do not. This thesis develops computational frameworks for the design and evaluation of agrivoltaic systems, with particular emphasis on vertical bifacial systems in northern climates. The research is structured around methodological gaps identified in the literature. Paper I reviews the state of the art of agrivoltaic modeling, identifying weaknesses that several subsequent papers help address. Among these is the need for accurate optical modeling without the high computational cost of ray tracing tools commonly used for PV production modeling. Paper II addresses this bottleneck by identifying and benchmarking efficient matrix-based ray-tracing tools against industry-standard approaches, demonstrating that they deliver both the accuracy and speed required for autonomous optimization of agrivoltaic system design. Paper III then utilizes one of the identified ray-tracing tools within an autonomous optimization framework. The framework identifies system designs that maximize the Land Equivalent Ratio through optimal light sharing between food crops and PV modules. Optical modeling alone, however, neglects thermodynamic and aerodynamic changes that are especially relevant where vertical systems act as windbreaks. Paper IV therefore integrates computational fluid dynamics to analyze this windbreak effect. The results demonstrate how vertical photovoltaic rows create sheltered zones with significantly reduced wind speeds, which leads to reduced evapotranspiration and increased temperatures. The subsequent crop yield analysis shows that these beneficial mechanisms can compensate for shading, resulting in net-positive crop yields in high-latitude climates, particularly during years of drought. Finally, Paper V uses satellite remote sensing to monitor operating vertical systems across the world, offering a scalable way to independently verify agricultural productivity in commercial systems. The analysis finds no reduction in vegetation indices after installation, indicating that commercial systems maintain agricultural performance.

• Lysne, Hogne; Reenaas, Turid Dory; Sabatino, Marisa Di & Holmestad, Randi (2023). Design and fabrication of (Cr + N) co-doped TiO2 films with a continuous compositional spread. Norges teknisk-naturvitenskapelige universitet. ISSN 9788232671557. Full text in Research Archive Show summary

  Intermediate band solar cells (IBSCs) have a theoretically conversion efficiency that is approximately 50 % higher than for the solar cell technologies dominating today. IBSCs are based on a new type of materials, where an additional, intermediate, energy band is present between the valence band and conduction band. Chromium and nitrogen (Cr + N) co-doped titanium dioxide (TiO2) have been proposed in literature as a candidate for such an intermediate band material. However, the ideal amount of doping for use in an IBSC is unknown. The aim of this PhD project has therefore been to utilize combinatorial pulsed laser deposition (PLD) to deposit (Cr + N) co-doped TiO2 with a continuous compositional spread (CCS). The films were deposited on 50.8 mm diameter silicon substrates, and the amount of doping was controlled by separate ablation of a TiO2 target and a CrN target. An improved method for the design of films made using combinatorial PLD was developed. Both CCS films and films with a uniform composition and thickness were designed and deposited. A high agreement between the designed/simulated and measured thickness, of both uniform (undoped) TiO2 films and (Cr + N) co-doped TiO2 CCS films was obtained. For the CCS films, it was challenging to obtain the desired equal amounts of Cr and N doping. Initially, the CCS films were grown in an oxygen background gas, and we found that these films had a considerably lower nitrogen content than intended. Consequently, we developed a deposition routine to improve nitrogen incorporation by ablating the CrN target in nitrogen background gas and capping the deposited material with TiO2 also ablated in nitrogen background gas. We found that the films with the capping contained both chromium and nitrogen at much higher concentration levels, than for the films deposited in oxygen. The characterization of the optical properties of the CCS films showed a sub-bandgap optical absorption at energies relevant for a TiO2 based intermediate band material, and in good agreement with what has been reported in literature, from density functional theory calculations. The characterization of the micro-structure of the films revealed that the sub-bandgap absorption correlated with the local crystal quality of the film and could be associated with a crystalline phase present for high Cr and N doping concentrations. At the same time the capping deposition routine had negative effects on the general crystalline quality. Further optimization of the nc-PLD process is needed to obtain higher crystalline quality.

• Hanson, Jens; Chasanidou, Dimitra & Normann, Håkon Endresen (2021). The Norwegian solar energy innovation system. NTRANS - Norwegian Centre for Energy Transition Strategies. ISSN 9788293863038. Full text in Research Archive
• Larsen, Sigrid Langholm & Imenes, Anne Gerd (2021). Investigation of Outdoor Performance of Silicon Photovoltaic Modules at Different Installation Angles. Universitetet i Agder. Full text in Research Archive Show summary

  The objective of this master thesis is to analyse and compare the performance of two different PV technologies mounted at different tilt angles and orientations. The PV modules are installed on the roof of the J5 building in the University of Agder, located in Grimstad, Norway. The analysis was carried out by comparing 13 months of measured data (from March 2020 to March 2021).The technologies assessed are mono crystalline silicon and poly crystalline silicon, mounted at atilt angle of 10◦East/West, 45◦South and 90◦South.

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