The SiliconPV Conference Proceedings cover the proceedings of the international SiliconPV conferences taking place annually.
TIB Open Publishing (Technische Informationsbibliothek (TIB))
Contactless Measurement of Current-Voltage Characteristics of Back-Contact Solar Cells
This study presents the application of a novel contactless method for measuring the current-voltage characteristics to interdigitated back contact (IBC) solar cells, addressing challenges associated with the rear metal contacts. The method involves a comprehensive characterization approach, utilizing reflectance and different photoluminescence measurements including partial illumination and different excitation wavelengths. Conventional contacted flash test measurements serve as a comparison. By implementing a simplified procedure with only two wavelengths for EQE, this technique enables accurate performance characterization without direct contact to the cell, reducing the risk of cell damage and measurement time. Results show a good average agreement with a strong correlation between contactless and traditional methods, particularly for the open-circuit voltage (Bravais-Pearson correlation R = 0.98) and efficiency (R = 0.78), while highlighting some discrepancies in the measurements of the short-circuit current density and the series resistance Rs, which may result from both the contacted and the contactless measurement. The pixel-wise application of the Rs determination offers insights into the lateral distribution of series resistance-induced losses and highlights opportunities for optimizing cell design. This research confirms the efficacy of the adapted contactless method for IBC cell characterization and demonstrates its potential for broader applications, especially in inline measurement processes. Further refinements can enhance the absolute accuracy of the method.
Copyright (c) 2025 Johannes M. Greulich, Cyril Leon, Stefan Rein https://creativecommons.org/licenses/by/4.0
Fused Quartz Crucibles for PV Applications: The Role of Czochralski Process Parameters and Sand Quality on the Bubble Formation and Growth
Monocrystalline silicon ingots are grown in a Czochralski (Cz) furnace by melting high purity silicon feedstock in a fused quartz crucible. As the standard solar cell size is getting larger, silicon ingots manufacturers have increased their demands on crucibles size and properties. Among other factors, the formation of bubbles and their growth affect the crucible`s properties and performance, which in turn are affected by the process parameters. The mechanisms of these bubbles formation and growth are still not well understood. In this study, we investigate the bubble formation and growth in three different types of crucibles before and after use in a Cz process. The crucibles have different sand qualities, -size and -chemistries. The content of hydroxyl (OH) is measured by Fourier Transform Infrared Spectroscopy (FTIR), while bubble size and distribution are measured by X-ray tomography and optical microscopy, respectively. The results indicate that a reduction in OH content correlates with increasing bubble growth. The reference crucible, which has coarse particle size distribution and standard chemistry, has the largest variation in bubble content and the largest average bubble growth for the samples investigated. The crucible with the finest particle size distribution and high purity seems to be the best choice for silicon ingot production as it experiences, on average, the lowest bubble growth in the bubble free (BF) layer. The results also show that the crucible quality (e.g. the manufacturing process and chemistry) affect the bubble content as well as the OH level.
Copyright (c) 2025 Marisa Di Sabatino, Sebastian H. Hansen, Gabriela K. Warden, Bartlomiej A. Gawel, Mari Juel https://creativecommons.org/licenses/by/4.0
Contact Resistance Increase in Ga-Doped Silicon Solar Cells at Current Injection and Elevated Temperature Treatments
PERC solar cells based on Gallium p-type doping were treated at elevated temperatures in the range of 80…160°C and current injection. Current injection is conducted in a current-induced degradation (CID) setup in the dark, measuring voltage while applying a current at 0.06, 0.53 and 1.0 times the short-circuit current – ranging from maximum power point to open-circuit injection conditions. The results of the CID treatment show no significant light and elevated temperature induced degradation (LeTID) behaviour for these Ga-doped PERC cells. PERC cells treated at temperatures above 110°C show an increase in relative voltage during CID starting the earliest at a measurement time of 50 hours. It was found that the voltage increase could be related to increased contact resistance between the front silver metallization and the phosphourus emitter as indicated by comparing electroluminescence imaging before and after CID treatment and confirmed by transfer length method measurements. These measurements on a cut-out stripe showed an increase in contact resistivity and a lateral intensity variation as visible in the post electroluminescence image.
Copyright (c) 2025 Matthias Müller, Mahsa Mohammadi, August Weber, Jonas Kern, Matthias Trempa, Thomas Buck, Johannes Heitmann https://creativecommons.org/licenses/by/4.0
Simulation and Analysis of PECVD Process for Silicon Nitride Deposition Using CFD: Impact of Pressure on Deposition Uniformity
This study presents a computational fluid dynamics (CFD)-based simulation of the plasma-enhanced chemical vapor deposition (PECVD) process utilizing COMSOL Multiphysics. Specifically, the research focuses on the deposition of silicon nitride (SiNx) on silicon wafers, where this layer functions as an anti-reflective coating (ARC) to enhance light absorption. Regardless of the solar technology in question such as passivated emitter and rear contact (PERC), tunnel oxide passivated contact (TOPCon), hetero-junction technology (HJT), or tandem, understanding the deposition of ARC is crucial. This work simulates the multi-physics involved in PECVD process, encompassing fluid flow, plasma reactions, gas-phase reactions, and surface reactions. In this work we successfully demonstrated the modelling of the complex PECVD process capturing various physics like fluid flow, plasma physics, heavy species transports, and plasma, gas-phase, as well as surface reactions, and further validated it experimentally. The model was then used for various parametric studies i.e., effect of input parameters like pressure and temperature on the key output parameter i.e., deposition rate. This research not only demonstrates the capability of simulating intricate solar manufacturing processes like PECVD but also lays the groundwork for future simulation-based optimization of such processes and creating digital-twins as a part of Industry 4.0. This study represents the first documented investigation in the literature to report electron density distribution and transient thin film growth dynamics on silicon wafers within a tubular PECVD chamber.
Copyright (c) 2025 Vinay Prasad, Arun Appadurai https://creativecommons.org/licenses/by/4.0
Numerical Analysis of Metal Poly-Si Contact in TOPCon Solar Cells Through Device Simulations Using Sentaurus TCAD
Tunnel oxide passivated contact (TOPCon) is an emerging technology for highly efficient with excellent passivation photovoltaic (PV) devices. However, a standard TOPCon cell suffers from insufficient efficiency gain and recombination losses due to the presence of a direct metal-crystalline silicon contact. Therefore, bifacial configurations with advanced passivated structures have been considered in this research work. In this work, the performance of bifacial TOPCon device with double-side (DS) TOPCon structures, integrated with poly-Si, is explored and modeled using Sentaurus TCAD software. The reported study develops a framework to obtain state-of-the-art bifacial TOPCon structures with optimized input parameters and considering tunneling structures. The impact of collective front/rear SiNx layer thickness (from 50 to 100 nm) and p+ poly Si thickness (from 20 to 100 nm) on the performance of bifacial-DS TOPCon solar is studied and analyzed for optimized PV performance. This research study reveals that optimizing the p+ poly-Si thickness enhances carrier collection with minimal bulk recombination losses. The PV performance of DS structure indicates that incorporating DS carrier selective contacts increases the PV efficiency. Also, the detailed analysis of bifacial TOPCon structure reveals that suppressing the recombination by incorporating tunneling structures on both sides can be the key strategy to improve PV performance with an optimized efficiency of 26.3%. The reported study set a clear direction for higher PV performance by incorporating a tunneling approach in next-generation c-Si solar cells at low cost.
Copyright (c) 2025 Savita Kashyap, Shiladitya Acharyya, Durga Prasad Khatri, Pradeep Padhamnath, Anil Kottantharayil https://creativecommons.org/licenses/by/4.0
Correlating Structure Loss and Operational Conditions in Czochralski Silicon Ingot Growth Using Machine Learning
This work investigates the relationships between process parameters and the occurrence of structure loss in Czochralski silicon ingots using machine learning. Subsets of features are identified from a dataset of over 14,000 ingots and are used to train random forests to predict structure loss with high accuracy. Multiple rounds of feature importance analysis and refinement are conducted to isolate the process parameters that may have the most significant impact in the occurrence of structure loss. Partial dependence analysis is employed to examine how variations in particular parameters might affect the likelihood of structure loss happening. The results show that the most predictive features of structure loss are primarily recorded late in the process. These features are often influenced by manual interventions or reflect the outcome of structure loss itself. In contrast, early-stage parameters exhibit limited predictive power, suggesting that either early indicators of structure loss are not captured in the available data or that structure loss originates from events occurring later in the growth process. While not predictive in a preventive sense, the model effectively detects deviations from normal operation, thereby demonstrating the value of machine learning for uncovering complex patterns in manufacturing processes data.
Copyright (c) 2025 Alfredo Sanchez Garcia, Rania Hendawi, Hendrik Schön, Marisa Di Sabatino https://creativecommons.org/licenses/by/4.0
Well Intended Contact Failures on Interdigitated Back Contact Solar Cells
The interconnection of the cells that make up a solar panel is a simple step, but it is not unimportant. The panels are made up of cells in series, so that a poorly connected cell can spoil the good performance of the entire panel. Back-contact solar cells have polarity connections on the back, making interconnection critical. In this work contact failures are intendedly induced, solar cells are biased at several conditions and electroluminescence measurements are carried out to detect problems. The results show that even at low amperage, connection faults can be identified by simple image processing. As a conclusion, this detection method could be implemented before encapsulating the panels, avoiding efficiency losses.
Copyright (c) 2025 Yeray Mateos, Dr. Nekane Azkona, Dr. Aloña Otaegi, Dr. Eneko Cereceda, Vanesa Fano, Eneko Ortega, Prof. Dr. Juan Carlos Jimeno https://creativecommons.org/licenses/by/4.0
Performance Comparisons of Bifacial Photovoltaic Modules on Surfaces With Different Albedo Values: PVsyst Simulation Study
The renewable energy sector is continually evolving to meet global energy demands and reduce environmental impacts. In this context, solar energy technologies, particularly photovoltaic (PV) systems, are playing an increasingly significant role in energy production. Photovoltaic module manufacturers and solar power plant investors are especially favoring the production and use of bifacial PV modules. The primary reason for this preference is that bifacial PV modules can capture sunlight on both their front and rear surfaces, offering a higher energy production potential compared to monofacial modules. However, this performance is significantly influenced by environmental factors such as ground albedo (reflectivity coefficient). In this study, the performance of bifacial PV modules on surfaces with different reflectivity coefficients was simulated using PVsyst software. Terrain topography and PV module layout at specified coordinates were modeled using SketchUp. The energy production performance of bifacial modules was examined under various ground albedo conditions, and the results were compared. Simulation results revealed a significant increase in energy production as albedo values increased. These findings demonstrate that the albedo value of the ground where bifacial PV systems are installed is a critical and decisive factor in system performance. The simulation data indicate that as the albedo level increases, both the Performance Ratio (PR) and the annual energy production capacity of the PV systems show a marked improvement. Transitioning from a 5% albedo level to a 70% albedo level resulted in an increase in PR from 85.36% to 93.98%, and in energy production from 1,792 kWh/kWp/year to 1,973 kWh/kWp/year.
Copyright (c) 2025 Nurgül Polat, Meriç Çalışkan Arslan https://creativecommons.org/licenses/by/4.0
Identifying and Mapping Impurity Sources in Deposition-Prone Chemicals for Wafer Surface Wet Processing
Contaminant levels in chemicals used for wet processing are critical to solar cell performance. During wafer immersion in chemical and DI water baths, a thin film forms on the surface, trapping impurities. Also, recycled polysilicon for ingot and wafer manufacturing utilizes similar chemicals for etching, which are again prone to contamination. Contaminants often enter during chemical handling, which is outside the defined boundary of cell and ingot manufacturing area. Despite multiple purification steps, impurities persist even in electronic or photovoltaic grade chemicals. Key chemicals such as HCl, HF, H₂O₂, HNO₃, KOH, and DI water were analysed using ICP-MS to trace elemental impurities, often linked to raw materials (e.g., As and K from fluorspar) or contact with construction materials (e.g., Fe, Mn, and Cr from mild steel piping). Impurities adhering to wafer surfaces, particularly Fe, can reach concentrations up to 10¹¹ atoms/cm², significantly affecting carrier lifetime and cell efficiency. The Landau-Levich equation indicates that higher withdrawal velocities result in thicker films, increasing impurity deposition rates. To mitigate these detrimental effects, impurities must be eliminated at the source, and tolerance limits should be established based on their deposition susceptibility through the liquid film. This study quantifies impurities that may be carried forward in wafer and cell processing, ultimately hindering solar cell functionality. It underscores the necessity of controlling contamination sources in chemical processing to enhance solar cell efficiency and lifetime.
Copyright (c) 2025 Sneha R Iyer, Bhavesh Maru https://creativecommons.org/licenses/by/4.0
Approaches to Reduce the Impact of Edge Recombination in Si Lifetime Samples With Emitter
The injection-dependent effective excess carrier lifetime is an important quantity to describe recombination characteristics in silicon. When measured with the photo-conductance decay technique it is known that for specific sample structures and sizes edge recombination can strongly affect the measured injection-dependent lifetime. Especially in lifetime samples involving an (induced) pn-junction edge recombination can become a dominant effect limiting lifetime towards low injection. We present different approaches to structure samples in order to suppress the detrimental effect of edge recombination on lifetime at low injection.
Copyright (c) 2025 David Bäurle, Axel Herguth, Giso Hahn https://creativecommons.org/licenses/by/4.0
Production-Ready Decomposition of Series Resistance Into Lateral and Fixed Components
The series resistance (Rs) of a solar cell is commonly treated as a constant, but this is a very poor approximation: in modern cells, Rs can vary by a factor of 4 depending on illumination, bias voltage, and temperature. The naïve model leads to incorrect characterization of cell parameters and misattribution of cell losses. Wagner’s linear-response series resistance (LR-Rs) model attempts to treat Rs rigorously but experimental confirmation of the model is limited to EL and PL measurements. In this work we validate the LR-Rs model using IV measurements at multiple light intensities. We find a hyperbolic dependence of Rs on diode current as predicted by Wagner. The LR-Rs model fits the data extraordinarily well, but with a much higher geometric dependency than predicted by Wagner. We show that the model allows us to decompose series resistance into lateral and fixed components. This decomposition is now available in all WAVELABS commercial LED flashers. We illustrate the immediate benefits of this improved model in commissioning of a heterojunction production line.
Copyright (c) 2025 Don Clugston, Bernhard Klöter https://creativecommons.org/licenses/by/4.0
First-Principles Study of Radiation-Induced Defects in Silicon Solar Cells Using Density-Functional Theory Simulation
Displacement damage from high-energy electron and proton irradiation is a critical degradation mechanism in space solar cells, particularly within the Van Allen radiation belts. These energetic particles induce atomic displacements in semiconductor materials, generating lattice defects such as vacancies, di-vacancies, and impurity-related complexes (e.g., BiOi, BiCs and BiHi) that significantly impact the electronic structure of silicon, reducing solar cell efficiency and power output. A fundamental understanding of these defects is critical for designing radiation-resistant photovoltaics. To address this challenge, we employ first-principles Density Functional Theory(DFT) using the SIESTA code with localized orbital basis sets to model the electronic structure of silicon systems with induced defects and impurities. Our study focuses on boron-related defect complexes, including interstitial boron (Bi) and its interactions with oxygen (O) and hydrogen (H), with validation against experimental data and comparative calculations using QUANTUM-ESPRESSO to assess computational robustness. Our simulation identifies key defect energy levels, including BiOi at Ec – 0.23 eV and BiCs at Ev + 0.31 eV, which exhibit strong agreement with experimental data, reinforcing the reliability of our approach. We further analyze the passivating role of interstitial hydrogen (Hi) and its influence on defect neutralization. These findings provide critical insights for defect engineering strategies, enabling optimized doping and thermal processing to mitigate radiation-induced degradation. This research advances the development of next-generation, radiation-tolerant photovoltaics for prolonged space missions by identifying dominant defect configurations and their electronic structure.
Copyright (c) 2025 Oleg Perevozchikov, Victor Perevoztchikov, Aurangzeb Khan, Alex Fedoseyev https://creativecommons.org/licenses/by/4.0
Local Series Resistance: Why the Model of Independent Diodes Fails and How to Understand Silicon Solar Cells in General by the LR-Rs Concept
The theoretical basics of the series resistance behavior of Si solar cells are reviewed and discussed, with an emphasis on the physical understanding of the linear response (LR) concept and the predominant role of experimental results. From this concept, a general fit model for the variation of the lumped series resistance along the I–V curve is derived. Important consequences of general validity for all series resistance determination methods are discussed, showing why the model of independent diodes is inappropriate for Si solar cells.
Copyright (c) 2025 Jan-Martin Wagner, Jürgen Carstensen https://creativecommons.org/licenses/by/4.0
As tunnel oxide passivated contact (TOPCon) cell technology has established itself as the dominant cell technology in global photovoltaic production, this study investigates competing architectures, including TOPCoRE (TOPCon with Rear Emitter), and local TOPCon² (passivated contacts on both sample sides), to identify paths for enhancing power output by improving the cells’ front side. The authors conduct a comprehensive simulation analysis using Quokka3, with input parameters derived from internal measurements and published data. While pointing out the necessary surface parameters to achieve a certain cell efficiency evolution, the sensitivity of the cell concepts to wafer quality, base resistance, and minority carrier lifetime is evaluated. The results indicate that the TOPCoRE concept on p-type wafers can be a strong contender to the standard iTOPCon, reaching 26%+ efficiency, if equally high electrical wafer quality can be achieved. The findings highlight the importance of further optimization paths, with local Front Surface Fields or local front TOPCon layers, demonstrating potential efficiencies of up to 26.5% and more.
Copyright (c) 2025 Nico Wöhrle, Johannes Greulich, Armin Richter, Andreas Wolf, Jochen Rentsch, Stefan Rein https://creativecommons.org/licenses/by/4.0
Numerical Simulation of Flexible Silicon Heterojunction Solar Cell with 27.2% Efficiency
In this article, we numerically demonstrate 27.2% power conversion efficiency in a 15μm-thick, flexible photonic crystal (PhC) silicon heterojunction cell (SHJ). This new class of SHJ cell combines the superior electronic performance of hetero-junction contacts with the wave interference-based light-trapping capability of thin-film silicon PhC, surpassing the traditional Lambertian limit. Through numerical simulations, we show that our flexible PhC-SHJ cell is capable of achieving a short-circuit current density of 44.31mA/cm2 and an open circuit voltage of 756.8mV, paving the way for flexible photovoltaic technology with efficiency beyond 27%.
Copyright (c) 2025 Deep Shikha, Sayak Bhattacharya https://creativecommons.org/licenses/by/4.0
Impact of LeTID in Industrial P- and Sb-Doped n-Type Cz-Si With Melt Recharging
In this study the impact of treatments under illumination at elevated temperatures on the long-term stability of excess carrier lifetime in state-of-the-art melt recharging Czochralski-grown silicon with n-type dopants is investigated. For samples that are treated at elevated temperatures and illumination only, it is found that bulk regeneration dominates until surface related degradation becomes limiting. If an additional light-soaking treatment at room temperature is previously applied, both bulk degradation and regeneration can be observed for P- and Sb-doped Cz-Si. An increase in degradation extent is observed for subsequently pulled ingots which is very similar for both dopant species. It is therefore assumed that the accumulation of impurities in n-type Cz-Si may be involved in an increase of defects that form during treatment at elevated temperatures and illumination. Furthermore, it is shown for Sb-doped material that the applied high temperature processing steps do not have an impact on degradation extent or kinetics.
Copyright (c) 2025 Joshua Kamphues, Sarah Marie Warmbold, Juri Miech, Wei Han, Yichun Wang, Axel Herguth, Giso Hahn, Fabian Geml https://creativecommons.org/licenses/by/4.0
Thermally Stable Epiwafers for PV Applications
This work assesses the thermal stability of n-type Epiwafers after a boron diffusion based on the carrier lifetime measurements and photoluminescence images. The Epiwafers show a high bulk quality (iVoc > 735-745 mV) in their initial state after passivation with PECVD SiNx:H films. After a customized thermal budget for boron diffusion, the Epiwafers did not show any significant degradation, suggesting their high thermal stability. In contrast, some n-type Czochralski (nCz) silicon control samples degraded significantly (∆i Voc = -30 mV) due to the formation of ring defects during boron diffusion.
Copyright (c) 2025 Rabin Basnet, Clemens Winter, Nicole Bein, Matthias Heilig, Frank Siebke, Giuliano Vescovi, Daniel Macdonald https://creativecommons.org/licenses/by/4.0
Development of a p-type Silicon Interdigitated Back Contact Solar Cell With Passivated Contacts
P-type interdigitated back contact (pIBC) solar cells represent a promising alternative to the currently dominant Tunnel Oxide Passivated Contact (TOPCon) technology, utilizing the industrially established metallization scheme of Passivated Emitter and Rear Cells (PERC) for the p-type base while incorporating TOPCon metallization for the n-type polycrystalline emitter. In this study, we present the results of optimization efforts aimed at increasing the efficiency pIBC cells manufactured in our lab by minimizing metallization-induced losses. Aluminum pastes with varying silicon content were used, and the firing temperature was adjusted. These modifications resulted in a reduction in the metallization-induced Voc​ loss after aluminum metallization to 5 mV, along with contact resistance values below 1 mΩ.cm². Additionally, reducing the n-polySi thickness led to a decrease in free carrier absorption and an increase in Jsc​. Finally, we achieved non-metallized cell precursors exhibiting iVoc​ values between 730 and 740 mV and a champion solar cell efficiency of 23.3%.
Copyright (c) 2025 Lazhar Rachdi, Marius Meßmer, Mertcan Comak, Jan Lossen, Andreas Wolf, Lejo Joseph Koduvelikulathu https://creativecommons.org/licenses/by/4.0
Observation of an Injection Dependent Lifetime Effect in Highly Hydrogenated Boron Doped Wafers
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.
Copyright (c) 2025 Rune Søndenå, Nicole Aßmann, Frank Mosel, Per-Anders Hansen https://creativecommons.org/licenses/by/4.0
22.2 % All-Aluminum Screen-Printed Silicon Solar Cells
In this work, we present our current development status for all-aluminum screen-printed poly-Si on oxide p-type back junction solar cells. This cell type already features an aluminum front grid which forms locally p+-type layers to collect holes. For the rear side metallization, we use special aluminum-silicon (Al-Si) alloy pastes to locally contact the n+-type poly-Si after opening the dielectric layer by laser ablation. We compare two different glass frits (A and B) and two different concentrations of silicon in the pastes (low and high). Totally, three pastes are used for rear side metallization: (1) Al-Si paste with low Si and glass frit system A, (2) Al-Si paste with low Si and glass frit system B and (3) Al-Si paste with high Si and glass frit system A. The front and rear side of our solar cells were printed and fired separately. The glass frit system B in paste 2, results in reduced shunt resistance of below 5 kΩ∙cm², negatively influencing the open circuit voltage. The high silicon content in paste 3 prevents local shunting in the cells, consequently reducing the series resistance and leading to a fill factor gain of more than 3 %abs compared to the other pastes. Our best Ag-free solar cell shows a power conversion efficiency of 22.2 % with an open circuit voltage of 718 mV and was printed using the high-Si amount paste. In a simulation-based synergistic efficiency gain analysis, we identify the rear side recombination at the contacts and the front grid shading as the two dominant factors.
Copyright (c) 2025 Sebastian Junge, Byungsul Min, Till Brendemühl, Kosuku Tsuji, Marwan Dhamrin, Henning Schulte-Huxel, Verena Mertens, Rolf Brendel https://creativecommons.org/licenses/by/4.0
Low-Loss Singulation of TOPCon Half Solar Cells by TLS and Al2O3 Edge Passivation
This work addresses the separation of tunnel-oxide passivated contact (TOPCon) host solar cells into half solar cells. It demonstrates the feasibility of achieving almost loss-free cell performance after edge passivation by the passivated edge technology (PET). It is shown that edge passivation with aluminum oxide (Al2O3) is also compatible with TOPCon solar cells that have been fabricated with Al-free Ag screen printing paste for the front side finger contacts applying laser-enhanced contact optimization (LECO). The half solar cells, with an edge length of 182 mm x 91 mm, are separated from industrial pseudo-square M10-format TOPCon host solar cells by thermal laser separation (TLS) from the front side. An optimized TLS process results in an efficiency loss of only slightly above 0.1%abs. A high-throughput prototype tool with a capacity of about 16,000 half solar cells per run is used for an Al2O3 layer deposition on the cut edges. Using optimized processes, the PET recovered approximately 85%rel of the cutting losses in pseudo fill factor by applying Al2O3 edge passivation and annealing. Thus, TLS in combination with high-throughput Al2O3 edge passivation is a viable approach for industrial fabrication of highly efficient TOPCon half solar cells, whether LECO and Al-free Ag pastes are applied or not.
Copyright (c) 2025 Elmar Lohmüller, Norbert Kohn, Felix Maischner, Homeira Hashemi, Alexander Göbel, Jonas D. Huyeng, Pierre Saint-Cast, Vivek Beladiya, Saravanan ´Somasundaram, Ralf Preu https://creativecommons.org/licenses/by/4.0
Evaluation of Different Front Surface Passivation Schemes for p-type IBC Solar Cells
In this work, we investigate different front-side passivation approaches for p-type IBC solar cells. We compare a POCl3-diffused and SiNx-passivated front floating emitter (FFE) with an undiffused front surface passivated by a layer stack of aluminum oxide Al2O3 and silicon nitride SiNx, using different technologies for Al2O3 deposition. Further, we investigate a boron-doped front surface field (FSF), realized with different BBr3 diffusion approaches. We achieve promising implied open-circuit voltages iVoc of up to 740 mV with Al2O3/SiNx-passivation, which is a 7 mV increase compared to the reference process using the phosphorus-doped FFE. Further, we fabricated boron-doped FSF samples exhibiting promising recombination parameters of j0 < 6 fA/cm2. The transfer of the Al2O3/SiNx-passivation into pIBC solar cells already reaches peak efficiencies of h = 23.3%, comparable to the FFE.
Copyright (c) 2025 Marius Meßmer, Lazhar Rachdi, Pierre Saint-Cast, Stefan Schmidt, Nico Jung, Jan Lossen, Andreas Wolf https://creativecommons.org/licenses/by/4.0
Maskless Patterning of Laser Activated p+ poly-Si Layers and the Fast Firing Stability of Patterned p+ poly-Si layers
Advanced TOPCon solar cells with local p+ poly-Si/SiO2 passivation stacks under the front metal contacts can be a future replacement for the current TOPCon baseline design. The local p+ poly-Si/SiO2 layers eliminate the metal-induced recombination on the front side, and the local placement of these layers prevents high parasitic absorption losses. Laser activation of p+ poly-Si/SiO2 layers provides an etch stop layer and allows for maskless patterning of these layers in alkaline solution. Patterning in this work refers to removing the poly-Si layer and texturing the substrate in the areas that are not laser-activated. In the laser activation step, the laser processing parameters must be carefully selected to entirely melt and activate the poly-Si layer without damaging the SiO2 layer beneath. Since partially activated poly-Si layers are not fully etch resistant in alkaline solution, patterning step removes the partially activated poly-Si layer and lowers the passivation quality. Even though the fully activated and patterned p+ poly-Si/SiO2 layers show similar passivation quality as non-patterned p+ poly-Si/SiO2 layers before the fast firing step, the fast firing step degrades the passivation quality of the patterned samples. However, an additional re-hydrogenation step in the fast firing furnace can restore the passivation quality of the patterned samples. This fast and industrially feasible re-hydrogenation method ensures a good passivation quality of p+ poly-Si/SiO2 layers in the final fabricated solar cell.
Copyright (c) 2025 Saman Sharbaf Kalaghichi, Jan Hoß, Jonathan Linke, Florian Buchholz, Jan Lossen, Lejo Joseph Koduvelikulathu https://creativecommons.org/licenses/by/4.0
Ultrasonic Tinning of Al Pads for Silver- and Lead-Free Cell Interconnection
Polysilicon on oxide back junction solar cells offer a high efficiency potential with significantly reduced silver consumption by using an aluminum front grid. The cell interconnection typically requires additional silver pads for soldering. Ultrasonic tinning of aluminum generates silver-free tin solder pads which can further decrease the silver consumption. Here, we demonstrate ultrasonic tinning on front side Al pads of polysilicon on oxide back junction solar cells solar cells for a silver-free cell interconnection. We report low damage to the passivation layers with local losses in implied open circuit voltage of 5 mV to 15 mV. On cell level, this results in small open circuit voltage losses of 1 mV to 1.5 mV, or 0.2 %. Single cell mini module fabrication shows moderate cell-to-module losses of 1.3 % to 2 %, reaching up to 20.8 % module efficiency.
Copyright (c) 2025 Malte Brinkmann, Henning Schulte-Huxel, Christina Hollemann, Byungsul Min, Sebastian Junge, Rolf Brendel https://creativecommons.org/licenses/by/4.0
An Analysis for Performance of PERC and TOPCon Modules Under low Irradiance Level
In this paper, the performances of PERC and TOPCon photovoltaic (PV) modules under low irradiance levels are investigated. It is found that the specific efficiency of TOPCon module is always larger than that of PERC under low light intensities. Meanwhile, as irradiance decreases, this efficiency advantage for TOPCon module become more obvious. To explain this phenomenon, two key aspects are analyzed. First, the recombination parameters of both modules are calculated. It is found that the recombination parameter of PERC module is larger than that of TOPCon module. However, this difference become smaller with the decreasing irradiance. In addition, the series resistance (Rs) and shunt resistance (Rsh) of both modules, along with the rates of efficiencies change with respect to these resistances, are investigated. It is found that PERC modules exhibit higher Rs and Rsh, while the rates of efficiency change with respect to Rs and Rsh for PERC are lower, compared to TOPCon module. Moreover, as the irradiation decreases, the Rs of PERC increases significantly, and the rate of efficiency change with respect to shunt resistance for TOPCon module is decreased more obviously than that of PERC module. Although we have found the module efficiency is more sensitive to changes in Rsh but less sensitive to Rs, the high series resistance disadvantage and high shunt resistance advantage for PERC module are amplified and suppressed, respectively. These above results provide new insights for the investigation and development of PV modules.
Copyright (c) 2025 Baojie Lv, Wangchun Xi, Wenan Tie, Mingzhe Yu, Xixiang Xu, Hong Yang https://creativecommons.org/licenses/by/4.0
Modelling of Solar Cell Junction Temperature for Crystalline Silicon Photovoltaic Module
Determination of the junction temperature of solar cells is critical for accurately evaluating on-site performance of solar modules. It is difficult to acquire the junction temperature of cells because solar cells are laminated and encapsulated in modules. In this paper, a fine steady-state thermal model is established to directly obtain the junction temperature of cells in the field. The model only needs plane of array (POA) irradiance, backsheet temperature, ambient temperature and wind speed. The junction temperature of the cells obtained from the model is validated by the equivalent cell temperature method in IEC 60904:2021. The results indicate that the model works well in the POA irradiance range of 400-800 W/m2. In addition, the effect of POA irradiance, ambient temperature on temperature difference between junction temperature and backsheet temperature were investigated. It is found that the temperature difference between junction temperature and backsheet temperature is increased with increasing POA irradiance. The required time of modules to reach the thermoequilibrium state is affected by the ambient temperature. The obtained results in this paper provide useful insights into performance evaluation and power generation forecasting of solar modules.
Copyright (c) 2025 Zewen Chen, Yuehua Yang, Haibo Niu, Youzhang Zhu, Xixiang Xu, Mingzhe Yu, Hong Yang https://creativecommons.org/licenses/by/4.0
Reduction of Silver Use in Low-Temperature Interconnection of Solar Cells
New solar cells’ technologies such as silicon heterojunction and tandem solar cells raise new challenges such as temperature-induced degradations, which are problematic for the cells’ interconnection. Electrically Conductive Adhesives (ECAs), usually made of silver particles embedded in a polymeric matrix, seem a promising technology to allow low-temperature interconnection, but raise concern about a high consumption of silver in the manufacture of photovoltaic (PV) panels. In this work, the fabrication of copper-based ECAs is presented as an approach to reduce the silver consumption of the interconnection process. Core-shell copper-silver particles with dendritic shapes that showed resistant to oxidation up to 220°C were used as conductive fillers. Their integration into an acrylate fast-curing matrix was performed in ratios of 59 wt% and 69 wt% fillers, respectively accounting for silver contents of 3.0 wt% and 3.5 wt%. The resulting pastes have resistivities of 3.5 * 10‑3 Ω*cm and 9.0 * 10-4 Ω*cm respectively, globally similar to those of commercial ECAs dedicated to the interconnection of solar cells. Their fast-curing process was measured to occur upon heating at 105°C, and be completed upon heating at 160°C during 20 seconds, enabling high throughputs. First trials of these ECAs into strings of solar cells were made: the stencil-printed patterns had a good quality, but a poor adhesion between the solidified ECAs and the ribbons prevents their further use.
Copyright (c) 2025 Nathalie Ronayette, Sonia Sousa Nobre, Sandrine Barthélémy, Olivier Poncelet, Daniel Bellet, Rémi Monna https://creativecommons.org/licenses/by/4.0
2025 marked the 15th edition of the International Conference on Crystalline Silicon Photovoltaics (SiliconPV), hosted in the historic and academically vibrant city of Oxford, UK. Held at the Mathematical Institute (Andrew Wiles Building) at the University of Oxford, this year’s conference brought together over 180 scientists, engineers, and industry experts from more than 30 countries, reaffirming the global relevance and vitality of silicon-based photovoltaic research. A total of 169 abstracts were accepted following rigorous peer review, with 83 oral presentations and 86 posters delivered in onsite. The event was held in conjunction with the nPV Workshop, extending the technical dialogue to the industry section, enhancing collaboration throughout the week. The journey of silicon photovoltaics continues to defy expectations. Once considered a niche energy source, solar power has become a cornerstone of global energy strategies, driven by relentless technological progress, cost reductions, and manufacturing expansion. Single-junction silicon cells and modules now routinely approach their theoretical efficiency limits. Breakthroughs in heterojunction and TOPCon device architectures continue to set new performance records, while perovskite-on-silicon tandem solar cells are now nearing 35% efficiency—a milestone unimaginable just a few years ago. As we push toward the terawatt scale, this rapid innovation brings both opportunities and challenges. The conference theme, “Silicon PV Vision 2/5/10”, encouraged participants to explore what the next 2, 5, and 10 years will bring. Conversations centred not only on cell-level breakthroughs but also on the urgent need for sustainable, circular manufacturing and the development of robust industrial infrastructure capable of supporting exponential deployment. The technical program was organised into five key topic areas: Advances in Industrial Silicon Solar Cells, including novel passivating contacts, back-contact and heterojunction cells, defect engineering, and ultra-thin device architectures; Silicon-Based Tandem Solar Cells, with strong emphasis on perovskite-on-silicon integration, interconnection schemes, and transparent conductive materials; Sustainable Manufacturing, addressing critical issues in silver and indium reduction, kerf-free wafering, circularity, and low-impact materials processing; Characterisation, Modelling, and Simulation, with new insights into interface physics, tandem device behavior, and machine learning-enabled diagnostics; Modules and PV Systems, covering novel interconnection designs, applications in building-integrated and agrivoltaic systems, and reliability under diverse environmental conditions. Throughout the week, Oxford’s historic setting provided an inspiring backdrop for scientific exchange and community-building. In addition to technical sessions, participants enjoyed a vibrant cultural program, including a conference dinner among fossils and dinosaurs with a lively treasure hunt, and informal networking opportunities that sparked new collaborations. We are deeply grateful to the scientific committee, abstract reviewers, session chairs, and all contributors whose work is represented in these proceedings. These proceedings document the state-of-the-art in silicon PV and serve as a valuable reference for the community working to advance solar technology. We hope the innovations and insights captured here will inspire further breakthroughs, helping drive the transformation toward a sustainable, carbon-neutral energy future.
Copyright (c) 2025 Sebastian Bonilla https://creativecommons.org/licenses/by/4.0
Lead Iodide by APCVD for Silicon-Perovskite Tandem Solar Cell Production
Recent advancements in silicon-perovskite tandem devices have shown potential to surpass the Shockley-Queisser efficiency limit for an ideal single junction solar cell of 33.7%. However, high-throughput deposition of perovskite on large areas remains challenging. A promising method for scalable perovskite thin film formation is the two-step deposition process, in which a PbI2 thin film is deposited and converted by exposition to an organic halide source like formamidinium iodide (FAI). The approach in particular addresses the rate limitation for the organic components. Thus, a high-rate deposition of inorganic components such as PbI₂ re-mains the missing piece. One promising high throughput deposition technique is atmospheric pressure chemical vapor deposition (APCVD), that was already successfully demonstrated for the deposition of n- and p-type amorphous silicon as well as transparent conductive oxides. This work demonstrates for the first time the application of an industrial APCVD tool for pro-ducing PbI2 thin films. Stationary deposition shows a Gaussian injector slit deposition profile, while for in-line deposition a PbI2 thin film of 365 nm thickness with a maximum rate of 81.2 ± 12.5 nm/min is achieved. High crystallinity is confirmed through X-ray diffraction (XRD), and subsequent wet chemical conversion with a FAI solution yields >500 nm thick perovskite thin films with a maximum implied open circuit voltage (iVoc ) of 1.133 V.
Copyright (c) 2025 Tom Burgard, Christian Ebert, Heiko Pagwitz, Alexander Pippert, Sven Seren, Giso Hahn, Barbara Terheiden https://creativecommons.org/licenses/by/4.0
Recycling Silicon Kerf Waste and Quartz Pot Scrap for Silicon Production Via Carbothermic Reduction
The rise in photovoltaic (PV) waste across all stages of the PV value chain has created a need for efficient recycling solutions to reintroduce these materials into use. In response, the EU project (ICARUS) is exploring several recycling routes for key waste streams, including silicon kerf, quartz (used crucibles and pot scrap), and graphite (furnace insulation), for silicon production. This paper presents the development of a carbothermic recycling route that uses waste crucibles, pot scrap, and kerf as raw materials for silicon production. Silicon was produced in a pilot-scale submerged arc furnace, and its purity was analyzed using ICP-MS to quantify trace impurities and overall purity. The results showed that the silicon that is produced from waste materials closely matches the characteristics of metallurgical-grade silicon. These findings demonstrate the technical feasibility of waste materials in silicon production, with significant implications for industrial practices, sustainability efforts, and future policies aimed at promoting circular economies in high-demand sectors like silicon production.
Copyright (c) 2025 Birgit Ryningen, Berhane Darsene Dimd, Nagarajan Somi Ganesan, Pål Tetlie, Irene Bragstad, Martin Bellmann, Roar Jensen, Arvid Inge Sørvik, Torfinn Krogstad https://creativecommons.org/licenses/by/4.0