The SiliconPV Conference Proceedings cover the proceedings of the international SiliconPV conferences taking place annually.
TIB Open Publishing (Technische Informationsbibliothek (TIB))
Impact of AlOx Capping Layer Thickness for Edge Passivation of TOPCon2 Shingle Solar Cell
This work aims at understanding the short circuit current density losses observed on TOPCon² solar cells after AlOx layer deposition and annealing. This process is the most considered for edge passivation of shingle solar cell, who suffer from heavy edge recombination losses after cutting procedures. Our solar cells feature Transparent Conductive Oxide (TCO) layers at the front and rear sides, on top of which the AlOx edge passivation layer is deposited during Atomic Layer Deposition (ALD) process. We focus on the effect of the AlOx layer thickness and the annealing conditions on the optical and electrical properties of the front AlOx/TCO stack. It is found that annealing of thick AlOx layers induce an increase of free carriers’ concentration in the TCO layer, resulting in additional parasitic absorption. Thinner AlOx layer and/or cooler annealing condition would limit this phenomenon, however rising a compromise with the shingle edge passivation goal. Indeed, we see that applicated on the TOPCon² shingle solar cells, less current density loss comes along lower edge passivation level.
Copyright (c) 2024 Franck Dhainaut, Thibaut Desrues, Benoit Martel, Mickael Albaric, Olivier Palais https://creativecommons.org/licenses/by/4.0
Optimization of Poly-Si/SiOx Passivated Contacts for Crystalline Silicon Bottom Cells Applications
In this study we investigate the coupled impacts of poly-Si thickness, dopant activation annealing temperature and hydrogenation on n-TOPCon and p-TOPCon passivated contacts. Their performance is first assessed by Photoconductance Decay (PCD) measurements on symmetrical and asymmetrical cell precursors before being evaluated on cells by I-V characterizations. We show that high-temperature annealing of poly-Si layers is responsible for excessive dopants penetration in the substrate, which can then be limited by the presence of a thicker poly-Si layer. Moreover, these thicker poly-Si layers benefit more from hydrogenation steps, enabling i-Voc of around 720 mV and carrier lifetimes of up to 5 ms on cell precursors. Finally, while increasing the thickness leads to current limitation under AM1.5G (1 Sun) illumination, this limitation is less pronounced under IR illumination. We therefore demonstrate that for tandem applications, the bottom-cell can benefit from a gain in Voc and FF without suffering from a major optical limitation.
Copyright (c) 2024 Julci Ditsougou, Thibaut Desrues, Anne Kaminski, Sébastien Dubois https://creativecommons.org/licenses/by/4.0
Understanding and Minimizing Perimeter Losses of Silicon-Based Monolithic Tandem Solar Cells – A Simulation Study
The vast majority of monolithic perovskite-silicon-based tandem cells to date is manufactured in R&D environments using small scale perovskite top cells (~1-4 cm²), typically placed on a larger silicon bottom cell. The high perimeter-to-area ratio leads to significant perimeter losses, which limit the maximum achievable efficiency and complicates loss analysis for further design optimization. An understanding of perimeter loss mechanisms and design rules for their minimization is therefore important for effectively progressing high efficient tandem solar cells in R&D. In this work we perform a 3D device simulation study of perimeter losses in an exemplary perovskite-silicon tandem solar cell. The impact of structuring the various laterally conducting layers, i.e. at the front and rear side as well as between the sub cells, on the perimeter efficiency loss is systematically investigated. We thereby identify the fundamental mechanisms of carrier transport into the perimeter, and clarify the impact of the silicon and perovskite absorber, the various laterally conducting layers, as well the electrical connection of the sub cells. We find that in each sub cell at least one carrier type must be hindered to be conducted into the perimeter. This is however complicated by the fact that this parasitic lateral transport can also be provided by “bordering” conductive layers connected via the tunnelling or recombination junction. Promising structuring variants and general design rules to achieve low perimeter losses with low structuring effort are then derived from the results. The losses are quantified to range from ~0.2 – 4%abs for a 1 cm2 top cell size, with the lowest values representing an unavoidable loss from the Si wafer conductance which is present also in champion cells with high structuring effort.
Copyright (c) 2024 Andreas Fell, Martin Bivour, Mario Hanser, Martin Schubert https://creativecommons.org/licenses/by/4.0
Characterization of Ultrathin Layers in Perovskite/TOPCon Tandem Cells With Photoelectron Spectroscopy Utilizing Advanced Data Evaluation Methods
Next generation solar cells like tunnel oxide passivated contacts (TOPCon) or perovskite/TOPCon tandem solar cells require efficient interface passivation by ultrathin organic or inorganic layers to uncover their true efficiency potential. Especially the microstructure and the Si suboxide content of the tunnel oxide in poly-Si(Ox)/SiO2/c-Si TOPCon stacks have been shown to have a tremendous influence on macroscopic device properties. Similarly, perovskite/ITO interface modification by a self-assembled monolayer (SAM) molecule is necessary to achieve high power conversion efficiencies of the perovskite sub cell. However, the characterization of such thin film structures and the interfacial composition is challenging. In this contribution, we present characterization results of ultrathin passivation layers using angle-resolved X-ray photoelectron spectroscopy (XPS) and advanced data evaluation routines, including maximum entropy methods and analyses of inelastically-scattered electron background data. In particular, the interfaces in the stacks (1) partially oxidized a-Si/SiO2/c-Si and (2) 2PACz/ITO after different thermal treatment were investigated. It could be shown that already a ~5 nm thin SiNx layer prevents unwanted oxidation from ambient during cooldown of TOPCon-like stacks and that annealing above 100 °C can convert a 2PACz multilayer to a 2PACz monolayer on an ITO substrate.
Copyright (c) 2024 Stefan Lange, Carl Eric Hartwig, Oussama Er-Raji, Patricia S. C. Schulze, Marko Turek, Juliane Borchert https://creativecommons.org/licenses/by/4.0
Investigation of Contact Properties and Device Performance for Bifacial Double-Side Textured Silicon Solar Cells With Polysilicon Based Passivating Contacts
We investigate the impact of the surface morphology on the contact properties of phosphorus doped poly-Si layers. If the poly-Si layer on a textured surface remains intact after high-temperature metallization using a fire-through (FT) silver (Ag) paste, the J0,metal is not expected to increase significantly while the specific contact resistivity can improve with a textured surface. The contact properties of the FT Ag contacts to n+ poly-Si deposited on both textured and planar surfaces are investigated by measuring and evaluating ρc and J0,metal. The reasons for differences in contact resistance and recombination are further investigated with SEM imaging. Solar cells with n-type polysilicon based passivating contacts on the rear side are fabricated and characterized. The scientific approach used, and the insights presented in this work, help to understand the mechanisms and behavior of screen-printed and fired-through contacts to polysilicon layers deposited onto textured silicon surfaces.
Copyright (c) 2024 Pradeep Padhamnath, John Derek D. Arcebal, Sagnik Dasgupta, Gabby De Luna, Ajeet Rohatgi, Armin G. Aberle https://creativecommons.org/licenses/by/4.0
Investigation of the Impact of the Wafer Resistivities on Double-Side Passivated Contact Silicon Solar Cells
In this work, we investigate the impact of substrate resistivities on the performance of poly-Si based double-side passivated contact solar cells, featuring high-temperature fire-through contacts to both n-type and p-type poly-Si, where the contacts are co-fired at the same firing temperatures. Large-area double-side passivated contact solar cells are fabricated on n-type wafers and thoroughly characterized to understand the impact of the change in Si wafer resistivity on the performance of the solar cells. The solar cells are fabricated on n-type substrates, with p+ poly-Si deposited on the planar rear side and n+ poly-Si on the textured front. The n+ poly-Si on the front side is selectively patterned to constrain it to the regions below the metal contacts. The fabricated solar cells achieve ≈ 22% efficiency on large area using high-temperature fire-through metallization. With the help of detailed characterization, we identify the losses that limit the device efficiency.
Copyright (c) 2024 Pradeep Padhamnath, Gabby De Luna, Ruohan Zhong, John Derek Arcebal, Ajeet Rohatgi, Armin G. Aberle https://creativecommons.org/licenses/by/4.0
Evaluation of Cells Cracks Impact on PV Module’s Performance
This work aims to perform an assessment of cell cracks impact on PV module’s performances. Cracks can occur during transportation, severe weather conditions such as hailstorms [1], poor installation practices and manufacturing [2]. Even with multiwire interconnection technologies, the impact of such defects can affect PV module’s performances as well as the energy yield and lifetime of a photovoltaic installation [3]. Moreover, cracks will leave the silicon edge unpassivated with a risk of being more sensitive to external stresses, especially on highly efficient technologies like TOPCon. The main objective of this work is studying the cracks impact on new module’s technology performance to quantify its impact on the production yield and forecast power plant performance. A laboratory testing sequence was performed on two different Glass/backsheet PV technologies: PERC and TOPCon. First, a cracking procedure was conducted to generate several cracks patterns on two batches of PV modules similar to the patterns observed on powerplants sites. An electrical characterization was then performed to carry out a first evaluation of power losses after the cracks. Moreover, several accelerated aging sequences were conducted on the cracked and reference modules to quantify the average losses after each accelerated aging test.
Copyright (c) 2024 Christine Abdel Nour, Julien Dupuis, Paul Lefillastre, Axel Becker https://creativecommons.org/licenses/by/4.0
Recovery of Silicon Kerf Through Oxidative Cleaning and Drying Process
High quantity of slurries, kerf, are generated during ingot wafering and represent up to 40% of the silicon in weight. The highly pure silicon contained in kerf is contaminated with organics, metal impurities, water and an oxide layer. The recovery of the silicon could be an efficient way to reduce costs in the production of solar panels through material and energy savings. At high temperatures, organic contamination causes the formation of silicon carbide species that are difficult to segregate during kerf remelting into a pure silicon ingot. Also, during the fusion of silicon, temperatures up to 1500°C are reached and the mixture of silicon and water forms oxides and gases that reduce production yields and affect melting conditions. For these reason, purification and drying steps are required to ensure proper silicon raw material for remelting into ingots. So far, approaches using strong acidic or organic solvent are used to reduce contamination by organic compounds. In this study, more environmentally friendly processes were applied on authentic kerf waste to purify and dry silicon, to make it suitable as raw material for silicon ingot preparation. The amount of water and organic compounds were monitored along the process steps. Using aqueous oxidative processes in combination with filtration, kerf was cleaned and a total carbon reduction of at least 30% was observed. The control of humidity enables the convenient conditioning of purified kerf and effective drying reduced the moisture content to less than 5% wt.
Copyright (c) 2024 Marion Chevallier, Jean-Baptiste Antoine, Francis Marchitto, Yoann Doré, Yun Luo, Yohan Parsa https://creativecommons.org/licenses/by/4.0
Recycling of Photovoltaic Modules – A Strategy for Silicon and Metal Contact Recovery
As the installed capacity of photovoltaic (PV) systems continues to grow, also does the necessity to address the accumulating waste from decommissioned PV modules. Millions of modules will need to be retired in the next few decades, and this poses a challenge that requires the development of cost-effective and efficient recycling strategies, with a focus on essential components such as solar cells, which are known for their significant environmental impact and energy budget. This study explores strategies to recover metal from front and rear contacts, as well as the potentiality of silicon substrate recrystallization. Alkaline-organic solutions allow for complete metal detachment with small-to-minimal silicon loss, and recrystallization of recovered substrates provides promising results in obtaining wafers suitable for the newly established industry requirements. Al-BSF solar cells fabricated from recycled materials exhibit improved performance, proving the feasibility of reclaiming precious metals and silicon substrates from PV modules. These encouraging first results represent an important step towards cycling PV systems within a circular economy framework, thereby minimizing waste and maximizing resource utilization.
Copyright (c) 2025 Nerea Dasilva-Villanueva, Luis Jaime Caballero, David Fuertes Marrón, Araceli Rodríguez, Eduardo Díez, Jesús Ángel Muñoz Sánchez, Alejandro F. Braña, José Luis Plaza Canga-Argüelles, Enrique Cánovas, Carlos del Cañizo https://creativecommons.org/licenses/by/4.0
Implied J-V Curves Recorded at Elevated Temperatures Using Light Controlled Heating
The carrier lifetime characterization of solar cells is typically performed at room temperature, although the operational temperature of a solar panels can reach 60 °C. We realized a setup for laser controlled photoconductance decay (PCD) measurement at elevated temperatures induced by light. We investigated precursor p-PERC cells from multiple parts of the same ingot using this technique. From the injection level dependent carrier lifetime results the implied current-voltage characteristics are evaluated as well. We observed a relatively small but noticeable increase of the carrier lifetime up to 30% with increasing the temperature from 30°C to 60°C in all samples. Saturation current values obtained using the Kane-Swanson method indicate, that not only the bulk lifetime improves but the surface recombination rate weakens. Temperature coefficient values of the implied cell efficiency are around -0.35 rel%/°C and slightly below which agrees with typical results of electrical tests. However, due to the minor increase of the carrier lifetime, this is still a bit above the value one can obtain theoretically considering purely the known decrease of the open circuit voltage caused by the increased intrinsic charge carrier concentration at higher temperatures.
Copyright (c) 2024 Gergely Havasi, Dávid Krisztián, Ferenc Korsós, Shaoyong Fu https://creativecommons.org/licenses/by/4.0
Understanding the Effect of Grown-in Defects in Silicon on Solar Cell Efficiency
Improving the efficiency of silicon-based solar cells is imperative to maximise harnessing of solar power. The current improvements in efficiency were attained by better manufacturing techniques and purer materials. There is however indirect evidence that the so-called agglomerated grown-in defects in silicon have a direct impact on cell efficiency and if this is the case, the efficiency could be improved by crystal engineering. This study focuses on understanding the defect generation and growth mechanisms in commercial silicon crystals and their impact on cell efficiency. Silicon wafers from different parts of the crystal having a range of oxygen and dopant concentrations and growth profiles, were investigated. These crystals were characterized using various tools and techniques such as Infrared Light Scattering Tomography (LST) to measure the defect density, and Fourier Transform Infrared Spectroscopy (FTIR) to measure the oxygen concentration. Solar cells were then fabricated out of these wafers to measure the performance of the devices. An understanding of why and how such defects impact the yield of different silicon wafers will lead to a thorough understanding of the relationship between the defect types, size and densities and cell efficiency. Moreover, this study will also shed light on the development of crystal recipes or after-crystal procedures to eliminate or minimize these effects on solar cell performance.
Copyright (c) 2024 Jinta Mathew, Bulent Arikan, Sercan Aslan, Ryan Bugeja, Davide La Fata, Jessica Magro, Vahdet Özyahni, Selin Seyrek, Nurhayat Yildirim, Daniele Zingariello, Marija Demicoli, Raşit Turan, Luciano Mule' Stagno https://creativecommons.org/licenses/by/4.0
Understanding Hydrogen Passivation Mechanism in poly-Si Passivating Contacts via SixNy Composition: Insights From Effusion Studies
Tunnel Oxide Passivated Contact (TOPCon) cell performance relies significantly on hydrogen for its passivation of defects. In this paper, we discuss the temperature dependent effusion of hydrogen from the silicon nitride (SixNy) layers deposited on top of poly-Si/SiO2 passivated contacts. Silicon content in SixNywas varied by silane/ammonia flow ratio. FTIR shows significant N-H stretching & bending peaks for nitrogen-rich SixNy layer compared to silicon-rich SixNy layer, and few Si-H bonds compared to silicon-rich SixNy. During effusion, the N-H bonds in N-rich SixNy layer break to provide H2 , NH3 and N2, resulting in stoichiometry change. Negligible effusion of nitrogen occurs for Si-rich SixNylayers. Next, we investigate the mechanism of hydrogen passivation on symmetrical i-poly-Si/SiO2/i-poly-Si structures with different hydrogenating layers namely Si-rich SixNy , Al2O3 and a stack of Al2O3/SixNy, and conclude that a thin 15nm Al2O3 enables the best passivation. We also discuss the possibility of H diffusion in molecular H2 form, most suitable for SiO2 interface passivation, while the atomic hydrogen enables both passivation and de-passivation of interface dangling bonds.
Copyright (c) 2024 Suchismita Mitra, Dirk Steyn, William Nemeth, Sumit Agarwal, Paul Stradins https://creativecommons.org/licenses/by/4.0
Evolution of Pore Reorganization of Porous Silicon
To obtain a closed and smooth surface of a porous Si layer for an epitaxial growth of a silicon wafer, the porous Si must be reorganized. To understand the reorganization process, the evolution of the pores is investigated in this contribution. The reorganization process is interrupted at different stages and cross-sectional SEM images are taken to evaluate the change in pore size and shape during reorganization. Additionally, the stress is measured using XRD. At the beginning of the reorganization of the pores, the as-etched columnar pores with diameters of about 5 nm become coarser with larger diameters. At temperatures above 900°C, the surface closes and thus becomes smooth. In addition, the form of the pores starts to change from columnar to round with diameters between 55-65 nm. When the highest temperature of 1100°C is reached, the columnar pores have disappeared and the pores are round and faceted. With an additional plateau time of up to 20 min, there is no visible change in pore faceting. The as-etched sample shows tensile stress and the sample annealed at 700°C is nearly unstressed. When the temperature is increased beyond 900°C, the stress is compressive and no further change is visible.
Copyright (c) 2024 Sarah Sanz, Yves Patrick Botchak Mouafi, Giso Hahn, Gabriel Micard, Barbara Terheiden https://creativecommons.org/licenses/by/4.0
Deep-Learning Based Depth-Tracking of Stacking-Faults in Epitaxially Grown Silicon Wafers
Stacking faults in epitaxial silicon wafers are structural defects that can reduce the recombination lifetime of the final solar cells significantly. They are known to originate mostly at the interface between substrate and deposited layer, at contamination particles and atomic steps. This work presents a non-destructive and automated characterization method on full-size wafers to locate stacking faults and determine their layer of origin to identify process-based root causes. A deep learning model and a quantification via geometric defect properties is realized on dark field microscope images, with the potential to be transferred to inline images measured in dark field mode with high-resolution cameras. We achieve detection rates up to 92% for regular wafer surfaces. The depth analysis combines geometric properties of the stacking faults and measured wafer thickness and is applied on full-scale epitaxial wafers. Most stacking faults are confirmed to originate at the interface layer and their number is higher by 1-2 orders of magnitude when deposition occurs on a reorganized porous layer. However, our results also indicate that a non-negligible part of stacking faults has its origin within the epitaxial layer.
Copyright (c) 2024 Theresa Trötschler, Saed Al-Hajjawi, Siddharth Raghavendran, Jonas Haunschild, Matthias Demant, Stefan Rein https://creativecommons.org/licenses/by/4.0
Inline Measurement of Light Beam Induced Current (LBIC) Under High-Injection and Reverse Bias Conditions
Quality control in solar cell production relies on characterization methods that are fast enough to yield information on the properties of each solar cell in less than about one second. Imaging techniques such as electroluminescence (EL) are well established methods revealing spatially resolved quality mappings. Scanning techniques such as light beam induced current (LBIC) are common laboratory methods yielding complementary information but do not meet the speed requirements. In our work, we analyse an inline implementation of the LBIC method which is extended with respect to its measurement parameters, i.e., both the laser power and a solar cell bias-voltage are varied. As these extended conditions differ from conventional LBIC-applications at zero bias and low injection, we compare our inline-LBIC images with EL images and conventional LBIC images by means of an image contrast analysis. We find that our method resembles more the EL imaging as variations in the local series resistance are prominently detected. Thus, the proposed LBIC approach with extended measurement parameter range can yield both local short circuit information and local series resistance information. With our setup, measurement speeds around 700 ms are achieved.
Copyright (c) 2024 Marko Turek, Yuriy Tymyrivskyy, Stephan Hensel, Manuel Meusel https://creativecommons.org/licenses/by/4.0
Characterisation of SiOX / SiNX Surface Passivation Using Time-of-Flight Elastic Recoil Detection Analysis
An accurate description of the distribution of hydrogen at solar cell interfaces is critical for understanding both passivation and degradation phenomena. Time-of-flight elastic recoil detection analysis (ToF-ERDA) has recently been employed to study this hydrogen distribution by providing a one-dimensional (1D) depth profile. In this work, ToF-ERDA was used to investigate the hydrogen profile in a SiOX / SiNX passivating stack. The ability to resolve the interface with the c-Si interface was studied by using polished wafers and thin (20 nm) passivating stacks. This approach, coupled with Monte Carlo ERD (MCERD) modelling, showed that the identification of the interfacial oxide was much more clearly defined compared with previous reports using ToF-ERDA. Annealing the SiOX / SiNX at 450 °C for 5 minutes substantially increased the effective lifetime. However, no noticeable change in the H distribution measured with ToF-ERD was observed. We comment on the difficulty of correlating physical hydrogen measurements with the surface recombination properties.
Copyright (c) 2024 Matthew Wright, Matthew Sharpe, Callum McAleese, Yan Wang, Yifu Shi, Ruy S Bonilla https://creativecommons.org/licenses/by/4.0
Reduction of Scarce Materials in Silicon Heterojunction Solar Cells and Implications on the Performance in the Field
In the first part of this work the potential to save silver for n-type silicon heterojunction solar cells was investigated. Cells were produced with varied frontside screen opening (30-50 µm). The groups were compared for efficiency at different irradiation levels and frontside silver laydown. For five busbar configuration large opening with low series resistance led to the highest efficiency for high irradiation around 1000 W/m² while for low irradiations all cells performed similarly. For busbarless cells lower silver laydown led to similar efficiency with slight advances for narrow screen opening. In summary cell technologies with small busbar-pitch are more tolerant for low-silver metallization. In the second part the impact of the transparent conductive oxide (TCO) was addressed. Silicon Heterojunction cells were produced with either ITO (indium tin oxide) only or an ITO-AZO-ITO (aluminium doped zinc oxide) stack, enabling an ITO reduction of about 50%, leading to a tolerable efficiency-drop of 0.3%. These internal samples were compared to industrial heterojunction-precursors (post ITO) with reference and low silver consumption frontside metallization. For both parts IV measurement showed that series resistance has a strong impact on efficiency but a rather small impact on low light-efficiency. Considering low light conditions TCO-precursor type with differences in passivation have a strong impact. On module level similar irradiation dependence of the efficiency was found and in temperature-dependent IV-measurements a positive impact of high-quality passivation on the temperature coefficients was found while an increase of the series resistance had a negative impact on the temperature dependence.
Copyright (c) 2024 Sebastian Pingel, Ioan Voicu Vulcanean, Timo Wenzel, Winfried Wolke, Vasileios Georgiou-Sarlikiotis, Philipp Schmid, Henning Nagel, Ulli Kräling, Martin Bivour, Anamaria Steinmetz https://creativecommons.org/licenses/by/4.0
TOPCon Solar Cells With Al-Free Ag and Cu Metallization
This work presents an approach to lower the silver consumption of screen printed TOPCon (Tunnel Oxide Passivated Contact) solar cells by reducing and partially replacing the silver by low cost copper metallization paste. On the solar cells front side an adapted process sequence enables the use of a pure Ag paste, which compared to the industrially established AgAl paste offers a better conductivity and respectively requires less laydown to enable similarly low grid resistance. On the solar cells rear side the conductivity of the metal grid is accomplished by a copper paste which is realized within a print-on-print step on top of the Ag contact layer with minimized laydown. A reduction in Ag paste consumption by 40% to less than 9 mg/ Wp without sacrificing conversion efficiency seems achievable and can enable a significant cost reduction for TOPCon solar cells.
Copyright (c) 2024 Jan Lossen, Pirmin Preis, Mertcan Comak, Joris Libal, Dominik Rudolph , Jan Hoß, Lejo Joseph Koduvelikulathu https://creativecommons.org/licenses/by/4.0
PECVD SixCy as Barrier Layer Against Aluminum in Solar Cells With poly-Si/SiOx Passivating Contacts
We investigate the barrier properties of phosphorus-doped Si-rich silicon carbide (SixCy) thin films deposited by PECVD against Al/Si alloying in the context of poly-Si/SiOx passivating contacts. The stability of the implied open circuit voltage (iVOC) after firing of single-sided, full area screen-printed Al-contacts increases with carbon content of the barrier layer and depends on the crystallization scheme applied to the samples. Crystallized SixCy layers with an atomic C concentration of about 20 at.% deposited on pre-crystallized poly-Si predominantly show no significant decrease in iVOC values for peak firing temperatures up to 725°C.
Copyright (c) 2024 David Bäurle, Benjamin Gapp, Giso Hahn, Heiko Plagwitz, Barbara Terheiden https://creativecommons.org/licenses/by/4.0
Enhancing Electric Vehicle Autonomy With Solar Energy: A Case Study of the “Takai Urban” in Northern Chile
The global transition towards electromobility presents unique challenges, particularly in regions with limited infrastructure. In Northern Chile, the sparse distribution of charging stations, with distances often exceeding 100 km, complicates the widespread adoption of electric vehicles (EVs). This study investigates the feasibility of enhancing the autonomy of the "Takai Urban", a solar-assisted battery EV through the integration of Zebra IBC solar cells, leveraging the region's high solar irradiance. Initially, the Takai urban EV had a maximum range of 70 km per charge. Through virtual modelling and simulations, which incorporated GPS and meteorological data along a typical 43.3 km route in Antofagasta city, we examined the impact of solar integration on vehicle performance. The simulations indicated that with the strategic placement of high-efficiency solar cells, the vehicle's range could be extended by approximately 48%, achieving a new maximum of 104 km per charge. This approach not only demonstrates the potential for solar-assisted EVs in regions like Northern Chile but also underscores the broader implications for sustainable mobility in similar environments globally. The results highlight the potential for practical enhancements in EV designs using solar technologies, focusing on efficiency improvements and sustainable mobility solutions.
Copyright (c) 2024 Fernando Castro-Gallardo, Jorge Rabanal-Arabach, Sebastián Rodríguez-Romero, Douglas Olivares, Edward Fuentealba https://creativecommons.org/licenses/by/4.0
Patterning by Selective Etching of Poly-Silicon Using a High Etch Rate Single Sided Gaseous Process
This paper presents etching process developments using a single-side gaseous etch process based on the thermal reaction of poly-Silicon and the etching gas (molecular fluorine), that results in a high etching selectivity between layers, and a high etching rate. This work was carried out in the context of the development of solar cell architectures beyond PERC and TOPCon, where more sophisticated etching steps are required in order to accurately pattern poly-silicon layers across the wafer surface.
Copyright (c) 2024 Laurent Clochard, David Young, Mingzhe Yu, Ruy Sebastian Bonilla https://creativecommons.org/licenses/by/4.0
Adapting Solar Cells With Polysilicon Passivated Contacts to Radiation-Rich Environments
In the context of increased space photovoltaic power needs and cost reduction pressures, silicon solar cells spark a new interest for space missions. This is even truer if the cost-effective mass-produced silicon technologies can be adapted to the specific constraints of the space environment. This study successfully demonstrated that cells with polycrystalline silicon-based passivated contacts could be adapted to the main prerequisites for space missions. Indeed, flexible and lightweight alternative polysilicon passivated contacts cells were prepared from gallium-doped substrates, with post-irradiation performances as good as those of conventional (thicker) PERC devices. The influence of the doping level was investigated. Low doping levels mitigate the radiation-induced degradation of the bulk carrier lifetime and therefore of the short-circuit current density, but result in lower open circuit voltages. Furthermore, it was shown that the surface and bulk hydrogenation step investigated in this study does not influence the post-irradiation effective carrier lifetime and its evolution under prolonged illumination in the temperature range 80°C-100°C (at least for the durations investigated here).
Copyright (c) 2024 Nicolas Enjalbert, Romain Cariou, Sébastien Dubois https://creativecommons.org/licenses/by/4.0
RF-Sputtered Ti-Based Dielectric Layers as Al-Diffusion Barrier for Passivating Contacts
We investigate TiNx layers deposited via RF magnetron sputtering on their efficacy as a diffusion barrier layer between Al and tunnel oxide passivated contact layer stacks during contact formation in a fast firing process. We obtain implied open-circuit voltage (iVOC) from photo-conductance decay measurements in order to analyse the diffusion barrier quality for different parameter variations. In particular, we show the impact of both higher peak temperature and increased thermal budget (by decreasing the slope of the temperature ramp) on iVoc during the sintering (“fast firing”) process, leading to passivation quality losses. iVOC losses below 1.5% are shown for peak firing temperatures up to 725°C, with absolute values up to 717 mV after firing. Contact formation at this temperature yields median contact resistivity (ρc) values below 3 mΩcm2 with a sheet resistance (Rsheet) of about 40 Ω/□ for the Ti-based layers.
Copyright (c) 2024 Benjamin Gapp, Heiko Plagwitz, Giso Hahn, Barbara Terheiden https://creativecommons.org/licenses/by/4.0
Pushing Heterojunction Technology Further: Novel Metallization Processes and Architectures
This work provides an overview on the different approaches to make Silicon Hetero-Junction cell (SHJ) production more scalable by investigating alternative metallization processes which can potentially be competitive with the standard Ag-based processes (Ag micro-size). With this purpose, this research aims at introducing the idea of widely using Ag-coated Cu formulations and/or low-Ag deposit solutions involving Ag nanoparticles-based formulations and reactive Ag (also referred as particle free) inks for both rear and front cell depositions on a single (finger and busbars) screen-printing process.
Copyright (c) 2024 Nicola Frasson, Marco Galiazzo https://creativecommons.org/licenses/by/4.0
Inline Mapping of Amorphous Silicon Layer Thickness of Heterojunction Precursors Using Multispectral Imaging
In this paper, we present an inline characterization technique to determine spatially resolved thickness maps of ultra-thin layers on textured silicon substrates. The technique is based on multispectral imaging and optical modelling of discrete spectral reflectance data using rigorous polarization ray tracing and the transfer matrix method. The study demonstrates that quantitative inspection of ultra-thin amorphous silicon (a-Si) layers on textured silicon substrates requires an extension of the standard RGB illumination by two additional LED wavelengths in the near-UV. As the required five images are measured in less than a second, the tool is a suitable candidate for inline applications. The optical modelling requires reflectance-calibrated images which are obtained via linear calibration functions and allows the a-Si thickness to be determined at each pixel. The thin-film thickness can be determined either by a direct modelling of the measured reflectance spectra or by a differential approach using the reflectance spectra before and after coating to eliminate effects from non-idealities due to scattering as well as instrumental errors. The a-Si thickness extracted from the reflection data at the five chosen LED wavelengths shows good quantitative agreement with reference values from spectrally-resolved differential reflectance data. Evaluating a test sample with an intentional a-Si thickness variation, we compared the results from the multispectral thickness map and reference values from spectroscopic ellipsometry. We found good quantitative agreement for a-Si thicknesses above 10 nm and a slight overestimation of about 1.5 nm for thinner layers. Overall, the multispectral approach based on only five different channels proves to allow quantitative thickness maps with reasonable accuracy at inline speed.
Copyright (c) 2024 Saravana Kumar, Christian Diestel, Saed Al-Hajjawi, Jurriaan Schmitz, Marc Hemsendorf, Jonas Haunschild, Stefan J. Rupitsch, Stefan Rein https://creativecommons.org/licenses/by/4.0
Indium Reduction Above 70% in SHJ Solar Cells: Study of the Module Stability
This work focuses on reducing In-based TCO thicknesses to their minimum in SHJ solar cells with the goal to demonstrate the possibility of a drastic reduction of indium consumption in the fabrication process. On the front side, the reduction of the ITO thickness down to 15 nm implies to deposit an additional anti-reflective layer. Three anti-reflective dielectric layers have been studied (SiNx, SiOx and a bilayer SiNx/SiOx) in solar cell and module configurations to maximize the performances and evaluate the module stability under UV exposure. Lower Jsc losses after 120 kWh of UV exposure are measured with the use of thinner ITO layers, in agreement with a lower EQE deterioration in the IR range. The use of SiNx dielectric results in the highest stability under UV and to the best performances after 120 kWh. Following further optimizations of the dielectrics and TCO, the 15 nm of ITO/SiNx option was combined with a thin IMO:H TCO on the rear side. TCO thicknesses down to 30 nm were studied on the rear side resulting in overall indium reduction of 77.2% with very limited efficiency loss at the cell level (below 0.1% absolute after light-soaking). Module reliability of these very low indium content solar cells was studied under UV and damp heat treatments highlighting lower degradations than reference cells for UV and promising results after damp heat test.
Copyright (c) 2024 Adeline Lanterne, Remi Monna, Frédéric Jay, Tristan Gageot, Raphael Cabal, Christine Denis, Benjamin Thiriot https://creativecommons.org/licenses/by/4.0
Cutting Indium Usage by 60% in SHJ-Modules Maintaining High Efficiency
In this work the impact of reducing the Indium consumption for SHJ cells and modules is investigated. Optical simulations show that thinner Indium Tin Oxide (ITO) layers can be used on module level with minor reflection losses while on cell level losses are more severe. For extremely thin ITO layers with a thickness of 7-28 nm on texture a dielectric layer is necessary to maintain / improve the JSC level on both cell and module levels. Results (i) on solar cells (Transfer Length Method - TLM) for lateral resistance and (ii) on shunt structures for vertical electrical resistance showed that there is significant improvement potential if the doping of the layers is adapted parallel to thickness reduction. Solar cell samples with 60% reduced ITO layer thickness on front and rear sides show a similar series resistance level as the 70 nm reference but lower JSC. Optical simulation showed that module integration will recover most of the lost JSC resulting in an expected 0.5%abs. efficiency loss for samples with total (front & rear side) 60% less Indium without adding any process steps. Applying an additional dielectric film enables 80% Indium reduction on the front side with JSC gain on cell level and similar JSC on module level compared to the ITO with reference thickness.
Copyright (c) 2024 Sebastian Pingel, Ioan Voicu Vulcanean, Charlotte Röhnelt, Winfried Wolke, Vasileios Georgiou-Sarlikiotis, Alexander Krieg, Martin Bivour, Anamaria Steinmetz https://creativecommons.org/licenses/by/4.0
Cristobalite Formation in Fused Quartz Crucibles for Czochralski Silicon Production in Different Conditions
Cristobalite is one of the quartz crystalline polymorphs that forms at above 1470 °C in its pure form and above 1000 °C for quartz glass. Its formation during the Czochralski process is therefore inevitable, and is usually controlled by doping the quartz sand with barium or barium-based coatings. The formation of cristobalite can lead to significant structural defects in silicon ingots. In this work, we studied the influence of various materials (graphite, silicon carbide and alumina) on the formation and properties of the cristobalite layer. In our study we investigated glass samples extracted from a commercially produced fused quartz crucible. The samples were heat-treated in different furnaces with different contact materials: alumina, silicon carbide and graphite. The furnace with alumina as contact material was an open-air furnace, while the two others were purged with argon. All of the heat treatment experiments lasted for 3 hours at a temperature of 1500 °C, which is the approximate temperature of the Czochralski process. After the heat treatment, the samples were investigated by light microscopy and X-ray diffraction. The results showed that the contact material is the most determining factor for the cristobalite layer’s thickness and morphology. The enhancement of cristobalite formation is the greatest by using graphite as the contact material, followed by alumina. Results indicate a retardation in phase transformation in comparison to other materials. These findings are an important step to further understanding of the cristobalite formation kinetics in fused quartz crucibles during the Czochralski process.
Copyright (c) 2024 Gabriela Kazimiera Warden, Bartłomiej Adam Gaweł, Mari Juel, Andreas Erbe, Marisa Di Sabatino https://creativecommons.org/licenses/by/4.0
Forecasting Photovoltaic Module Remaining Life-Time Using Accelerated Aging Testing and Modelling on Aged Modules
This work investigates the possibility of predicting the remaining lifetime of a power plant by making accelerated aging testing on monocrystalline silicon cells modules working on a photovoltaic plant for eleven years in France and compares the results with the same testing done on modules from the same batch eleven years ago when they were new. The paper focuses on damp heat results. It is found that the degradation behaviour of the modules exposed outdoor has a similar trend compared to the modules tested eleven years ago when they were new but with a two-to-three-times quicker degradation. Moreover, electroluminescence characterization highlights some degradation differences, especially at the edges of the solar cells. Modelling the lifetime through empirical damp heat model on the used modules predict that degradation may accelerate after 3 to 4 years contrary to what was concluded based on the initial modules testing results eleven years ago: no degradation linked to heat and humidity conditions should have happened before 30 years.
Copyright (c) 2024 Julien Dupuis, Christine Abdel Nour https://creativecommons.org/licenses/by/4.0
Accuracy of PVSyst Simulations in the Reproduction of the Yield Performance of Multicrystalline, Monocrsytalline and Monocasting Modules in Outdoor Conditions
In this study we performed field tests on three small installations consisting of 12 modules each and next to each other, all of them using exactly the same manufacturing technology for cells and modules and employing the same manufacturing equipment and raw materials. The only difference between the systems was the wafer technology used. Two of them were manufactured through the same casting technology (Direct solidification system-DSS) and the same equipment: in one of them we grew mc-Si and in the other one CM-Si (mono casting). In the third system we used traditional Czochralski monocrystalline wafers as technology. Two of the facilities (the DSS based ones) have been closely monitored for three years, and the traditional monocrystalline one for 17 months. For the three installations the performance data is shared and compared with PVsyst simulations and correlated well to each other.
Copyright (c) 2024 Ismael Guerrero, Carlos del Cañizo, Yuanjie Yu https://creativecommons.org/licenses/by/4.0
Evaluation of the Duration of Albedo Measurement Campaigns
Bifacial PV modules are increasingly used in commercial solar PV projects. With the use of the solar energy available at the module’s rear surface, the correct estimation of the albedo during the pre-construction phase of commercial projects becomes more important. The intention of the study is to determine the impact of the duration of a short-term albedo measurement campaign to reduce the uncertainty with respect to satellite albedo, thus providing a ‘beneficial campaign’. Albedo measurements from seven sites in the USA have been used to estimate the impact of 1-day and 7-day measurements (short-term measurements) on the simulated annual electrical energy production. Simulations based on monthly albedo data obtained from a recognised satellite provider have been compared with simulations where the albedo has been corrected based on short-term measurements. The study found that a 1-day campaign is often not beneficial, causing an increase in uncertainty with respect to satellite albedo. Measurement campaigns in winter do not generally reduce the error of the annual electrical energy production simulation, however, a 7-day campaign undertaken in summer appears to often reduce the uncertainty. It should be noted that the climate conditions, ground vegetation and measurement setup of the analysed seven sites in the USA may not be representative for other sites in the rest of the world.
Copyright (c) 2024 Stefan Mau, Adam Sharpe, Christian Gertig, Christophe Campistron, Julia Garcia, Nicolas Chouleur https://creativecommons.org/licenses/by/4.0
Improving the Accuracy of PV Yield Calculation by Exploitation of Real Weather Data
The precision of yield calculation of modern design and simulation software for photovoltaic systems strongly rely, beside the accuracy of the specified module and inverter data, on the quality of the weather data. Since data from weather stations is not available for most locations world-wide this data is calculated by using modern interpolation methods. Beside this, simulation software typically uses historical weather data. In this work the mismatch of yield simulation results based on proprietary data, meaning interpolated or also called synthetical data, and data coming from a weather station in proximity to the installation is evaluated. The simulated data sets are compared to measurement data as obtained by the inverter output and hence give a profound understanding how interpolated data may influence the simulation results. The outcome shows that the quality of the yield simulation, if compared to the measurement data, is increased by a factor of up to four if on-site weather data is used as input for the simulation. The largest source of deviation is irradiation, which varies up to 10% if synthetical and measured irradiation on-site is compared. The second largest sources for simulation mismatches are power calculation and module temperature correction.
Copyright (c) 2024 Andreas Schneider, Matthias Buschmann, Jorge Rabanal-Arabach, Julia Chochollek, Thomas Nierhoff https://creativecommons.org/licenses/by/4.0
Characterization of Electrically Conductive Adhesives to Enable Perovskite-Silicon Tandem Solar Cell Interconnection
The mechanical stability of interconnections in solar modules is crucial for their long-term performance. Electrically conductive adhesives (ECAs) offer a promising solution for the interconnection of perovskite-silicon tandem (PVST) solar cells due to their low-temperature processibility. In this study, the influence of low curing temperatures on the mechanical and electrical properties of ECAs was investigated to assess their suitability for PVST technology. Four commercially available ECAs were characterized, focusing on curing temperatures of 100 °C, 140 °C, and 180 °C. Mechanical characterization through tensile tests and dynamic mechanical analysis (DMA) revealed varying Young’s modulus (E) (stiffness) and glass transition temperatures (TG) among the ECAs. Electrical characterization showed that lower curing temperatures generally led to lower volume resistivity, particularly for ECA C. However, joint resistance values exhibited high standard deviations. Void analysis indicated that void formation had a negligible effect on the mechanical properties of ECAs. Furthermore, the influence of curing degree on mechanical and electrical properties was investigated, highlighting the importance of complete curing for achieving desired properties. Overall, this study provides valuable insights into optimizing the interconnection process for PVST solar cells, essential for enhancing the long-term stability and performance of solar modules
Copyright (c) 2024 Leonhard Böck, Torsten Rößler https://creativecommons.org/licenses/by/4.0
How to Combine SHJ Cell-Edge Passivation and Module Reliability?
The use of cut-cells in most of the current modules is now the norm to maximise the final product performances. But the integration of such new cell configurations also comes with new challenges, especially if small cell size dimensions such as shingle are considered. Indeed, specific edge passivation processes are often used to recover for the cut-cell losses. Alumina Oxide or Polymer deposition are the most studied approaches, with in general promising benefits proven at cell level. However, only few communications after module integration are available, in particular about the impact of these additional layers on final module reliability. We show for example that it is crucial to avoid direct deposition of AlOX over the cell metal pattern in the future interconnection area, as TC (Thermal Cycling) resilience of such modules is clearly degraded. Proper edge localization of the AlOX layer is needed to recover the initial reliability behaviour. To preserve the interconnection quality, three different approaches are investigated: (1) edge localisation of the layer by wafer stacking during deposition (2) introduction of adapted copper plating solutions allowing metal growth through the passivation layer (3) edge passivation process directly applied on final strings just before lamination.
Copyright (c) 2024 Samuel Harrison, Mickael Albaric, Vincent Barth, Benoit Martel, Marco Galiazzo, Nicola Frasson, Agata Lachowicz https://creativecommons.org/licenses/by/4.0
Preface: SiliconPV 2024, the 14th International Conference on Crystalline Silicon Photovoltaics
The SiliconPV 2024 conference brought together nearly 300 scientists and engineers from 27 countries, with 142 abstracts approved by reviewers and presented through 61 oral talks and 71 posters, both onsite and online. 10 submissions were retracted. The conference served as a vibrant platform for exchanging knowledge, sharing ideas, and fostering collaboration among PV experts worldwide. The silicon solar community is witnessing a remarkable period of progress and innovation. Single-junction silicon cells and modules continue to achieve significant advancements, even as they approach the theoretical efficiency limit. In recent months, new benchmarks have been reached for heterojunction and TOPCon devices, with cutting-edge strategies driving further progress. This momentum is even more evident in perovskite-on-silicon tandems, which have now achieved efficiency levels exceeding 34%. Simultaneously, the growth in module production capacities remains robust, positioning the solar manufacturing sector to scale up to the terawatt level – a critical step toward addressing global warming. Bold plans for new gigafactories are taking shape worldwide, highlighting an era of expansion. However, reaching terawatt-scale solar deployment brings its own set of challenges. Beyond manufacturing improvements, the key hurdles lie in ensuring solar technology matures into a fully sustainable industrial sector. These themes – from pioneering concepts in single-junction and tandem cells to sustainable industrial solutions, from advanced silicon materials to high-quality, dependable modules, and from innovative manufacturing techniques to optimizing energy output and costs – were central to the discussions at the SiliconPV 2024 conference held in April, 2024, in Chambéry. We are deeply grateful to the many experts who contributed to reviewing abstracts and full manuscripts, culminating in these valuable proceedings. These proceedings are not just a record of the event; they are a critical resource for the community. By exploring the insights and advancements documented here, we hope you will find inspiration to develop novel technologies that accelerate the energy transition. Together, we can shape a brighter future by ensuring clean and affordable energy is accessible to everyone.
Copyright (c) 2024 Sébastien Dubois https://creativecommons.org/licenses/by/4.0