This paper introduces the product–level circularity metric (PLCM) as a practical tool to assess the circularity of integrated photovoltaic (PV) elements. The PLCM, originally proposed by Linder et al., quantifies product circularity by comparing the economic value of reused, recycled, or repurposed components to the total value of the product. By focusing on economic value rather than mass or energy, the PLCM offers actionable insights for manufacturers, designers, and policymakers, highlighting opportunities to enhance resource efficiency, reduce material dependency, and support circular design strategies. To demonstrate its applicability, we adapted the PLCM methodology for PV products and developed an Excel–based tool to facilitate its use. Three illustrative case studies are presented: a building-integrated-PV roof tile with embedded flexible thin-film solar cells, a conventional crystalline-silicon module, and a glass–glass perovskite module. These examples show how components with higher economic value can strongly influence the overall circularity score and how PLCM can guide design–for–circularity decisions. In the perovskite module case, a scenario–based sensitivity analysis further highlights how different assumptions on material recirculation and design choices can meaningfully shift the resulting circularity assessment, offering valuable insights for prospective technology development. While the metric does not account for energy consumption or end–of–life recyclability, it complements existing sustainability indicators such as life cycle assessment (LCA). Used together, PLCM and LCA provide a more holistic view of product sustainability. This paper underscores the PLCM’s potential to advance circular–economy principles in the PV industry and to support transparent, design–oriented evaluation of material choices and product architectures.
This work presents a numerical study of two passive cooling strategies for photovoltaic (PV) modules using recycled materials. The main goal is to limit the performance losses caused by high operating temperatures under real outdoor conditions, which differ significantly from Standard Test Conditions (STC), and to improve the overall electrical efficiency. The analysis is performed using three-dimensional transient simulations in COMSOL Multiphysics, coupling heat transfer and fluid flow in solid and porous domains. In the first configuration, a recycled polyurethane (PU) foam layer saturated with water is applied at the rear of the PV module to enhance heat dissipation through coupled heat and moisture transport within the porous structure, including evaporative cooling effects. The second configuration uses aluminum fins attached to the rear surface of the module, increasing the heat exchange area and strengthening natural convection with ambient air. The results show that the PU foam and aluminum fin systems reduce the average operating temperature by 16.4 °C and 9.8 °C, respectively, compared with the reference module. These reductions translate into relative electrical efficiency improvements of 8.49% and 5.10%, confirming the effectiveness of both passive cooling approaches under the studied conditions.
Partial shading conditions (PSCs) represent a complex and often unavoidable challenge in photovoltaic (PV) systems, leading to reduced maximum power output and causing mismatch losses. PSCs also result in multiple peaks on the power-voltage (P-V) curve, where the maximum power can become trapped at local maxima. Array reconfiguration techniques are therefore essential for improving the efficiency of the system and ensuring optimal power extraction from PV systems. In this study, the conventional Total-Cross-Tied (TCT) and eight advanced methods for static reconfiguration were analyzed. These include: Shape-Do-Ku (SPDK), Ken-Ken (KK), Skyscraper (SS), Jigsaw (JS), Kendoku (KDT), Novel Grecian Reconfiguration (NGR), Novel Ramanujan Reconfiguration (NRR), and Super Magic-Square Reconfiguration (SMR). The performance of the system was assessed under four realistic partial shading scenarios: corner (S-1), half (S-2), tree (S-3), and chimney (S-4). Key performance indicators, including Global Peak Power (GP), Shading Loss (SL), Execution Ratio (ER), Fill Factor (FF), and Power Gain (PE), were used for assessment. The results demonstrate that the NRR and SMR configurations are capable of reliably tracking the GP across different positions on the P-V curve. These methods attain average ER of 74.76% and 74.46%, respectively, with the NRR configuration demonstrating superior overall performance-enhancing the GP by 1.26%-25.03% and FF by 2.41%-49.37%, while reducing SL by 2.47%-77.77% compared to existing reconfiguration techniques. These results highlight the superior effectiveness of the NRR scheme, confirming its robustness and efficiency in optimizing PV array performance under diverse and challenging PSCs.
Passivating contacts made of polycrystalline silicon (poly-Si) on top of a thin silicon oxide (SiOx) have emerged as a key enabling technology for high-efficiency silicon solar cells, such as tunnel oxide passivated contact (TOPCon) devices. However, achieving high-quality surface passivation with hole selective poly-Si contacts remains challenging, especially on textured silicon. In this work, boron-doped p+-poly-Si contacts were formed on textured silicon surfaces using low pressure chemical vapor deposition (LPCVD) process, followed by ex-situ doping by BCl3 diffusion. Particular attention was paid on engineering more thermally robust oxide layers and controlling the impact of the boron diffusion step on the oxide integrity. A combination of chemical (O3-based) and thermal oxidations, together with a boron diffusion process employing drive-in temperatures between 850 degrees C and 900 degrees C significantly improved the passivation quality and suppressed a central defect pattern seen with thermal oxidation only. Moreover, the impact of the poly-Si thickness on the surface passivation performance was studied. Poly-Si thicknesses ranging from 41 nm to 108 nm on textured samples resulted in comparable single surface emitter saturation current density (J0E) values, indicating a limited influence of the layer thickness within this range. As a result, high and uniform passivation quality was achieved on symmetrical p+-poly-Si textured samples, with a minimum J0E of 20 fA.cm-2 and implied open-circuit voltage (iVOC) values of up to 705 mV.
Cracks in photovoltaic modules can affect power output, but their relevance depends on module architecture and operating conditions. This study examines how crack length and crack number relate to power loss in 230 mono-Si mini-modules spanning full-cell PERC and half-cut TOPCon technologies with busbar counts from 2 to 12, focusing exclusively on cell line cracks that do not lead to electrically isolated cell parts. Electroluminescence images were used to quantify crack characteristics and busbars, while current-voltage measurements at 200 W/m2 and 1000 W/m2 were used to extract series resistance, shunt resistance, and maximum power point. Correlation analysis was then used to assess how crack characteristics relate to electrical performance. The results show that crack length and crack number are not universal predictors of power loss in modern modules. PERC modules exhibit moderate crack-power correlations at low irradiance, but these correlations weaken at 1000 W/m2. TOPCon modules show no meaningful correlation at either irradiance level. The results indicate that crack sensitivity is governed primarily by irradiance, busbar count, and cell architecture, rather than by crack length alone.
Organic-inorganic halide perovskites are naturally unstable when exposed to various environmental conditions, and the presence of lead raises significant ecological concerns. Herein, calcium zirconium oxysulfide, CaZrO3-xSx, a lead-free oxychalcogenide perovskite, is investigated as a potential alternative for optoelectronic and photovoltaic applications. The environmental aging of CaZrO3-xSx thin films was systematically investigated under various external stress conditions, including humidity, temperature, and illumination. Structural and optical investigations indicate that the film retains its crystallinity and remains optically responsive up to 350 degrees C, without detectable degradation or phase transformation. Under high (80%) humidity conditions, the film remains stable for a few days before gradually converting into the oxide phase. The demonstrated environmental and thermal stability of CaZrO3-xSx highlights its potential as a promising, intrinsically stable, and lead-free material for durable photovoltaic and optoelectronic applications.
The growing integration of photovoltaic (PV) systems into complex environments—such as rooftops, façades, and vehicles—has introduced new shading patterns and the need for accurate performance modeling under these partial shading conditions. In particular, building-integrated photovoltaics (BIPV) are often subject to thin shadows from nearby building components, vegetation, or infrastructure. These shadings can impact only portions of individual cells, leading to inhomogeneous irradiances that are difficult to capture with conventional simulation tools. A few commercial tools consider the impact of near shading losses on photovoltaic arrays, a well-documented example being PVsyst. PVsyst incorporates a more sophisticated approach using four empirically derived I-V curve templates based on the number of shaded corners per sub-module, but the core logic remains: if at least one corner of a sub-module intersects a shadow, it is treated as electrically shaded. This assumption is valid for large open-rack systems with large shadows. The choice of points to check for shadow intersection could however be improved for thin shadows by considering partial shading at the cell level. This work presents a shadow modeling approach based on vertex projection, and the shadow positions were experimentally validated against photographs of shadows cast on an outdoor BIPV module in Neuchâtel, Switzerland. The near shading simulation is done at the cell level, and several strategies for selecting points to check for shadow intersection are compared to determine the shaded fraction and shading-adjusted plane-of-array irradiance of each cell. This irradiance is calculated by summing the diffuse plane-of-array irradiance and the direct plane-of-array irradiance adjusted for the shaded fraction. Compared with a conservative full-shading baseline, the cell-level model which captures partial cell shading may predict about 2% lower annual irradiance losses for a 25 cm shadow and even more for thinner shadows. At sufficient resolution, the model avoids missing thin shadows entirely—a key limitation of the submodule-level approach. The algorithm scales efficiently at low resolutions, simulating a full year of hourly cell irradiance data in about 17 s for a 40-cell module at 2 × 2 to 5 × 5 points per cell, and about 25 s for 1200 cells at 3 × 3 resolution.
Perovskite solar cells have achieved remarkable power conversion efficiencies, yet their long-term stability remains a critical challenge. Progress in understanding this issue can be supported by combining modelling and characterization of the experimental behaviour obtained during ageing. Degradation studies often rely on post-mortem analysis, which is time-intensive, costly, and requires expertise. Here, we present a modelling framework that provides insights into the underlying mechanisms using simple electrical measurements performed during ageing tests. Drift-diffusion and transfer-matrix simulations of the cell optoelectronic response are combined with a genetic algorithm to reproduce the measured JV characteristics. By tracking the evolution of correlations between electrical parameters (VOC, JSC and FF), simulated mechanisms are compared with experimental data, enabling discrimination between feasible pathways associated with performance improvement during light soaking and light-induced degradation. These mechanisms are simulated by varying material parameters such as charge-carrier mobilities, doping levels, defect concentrations in the absorber and at the perovskite/transport-layer interfaces, and parasitic resistances. Comparison between experiment and simulation distinguishes mechanisms that are consistent with the measured trajectories from those that are not, while highlighting plausible candidates associated with both performance improvement during light soaking and light-induced degradation, thereby providing new insights into perovskite solar cell stability.
Agrivoltaics has been expanding rapidly in France, but its deployment is accompanied by increasing public controversy. France represents a particularly relevant case due to its advanced regulatory framework, making it a useful laboratory for anticipating future conflicts in other countries. Drawing on an original database of 292 agrivoltaic projects, including 65 that have given rise to conflicts, this study analyses the nature and determinants of these oppositions. The results show that installed capacity is a significant factor: large-scale projects are more frequently contested. Conversely, the type of technology does not, overall, influence whether a project becomes contested. A qualitative analysis of 68 documents covering 54 cases of conflict identifies six different categories of conflicts. Most conflicts appear to be multifactorial. The study thus highlights that agrivoltaic controversies extend far beyond the agronomic issues traditionally anticipated and that these dimensions must be integrated into the design strategies governing agrivoltaics.
In recent years, global PV capacity – particularly in the EU – has reached record levels, supporting decarbonization goals but also intensifying market effects such as increasingly frequent negative electricity prices driven by oversupply and limited system flexibility. These conditions pose growing economic challenges for utility-scale PV assets. This study examines the impact of negative price hours on PV performance and assesses the role of battery energy storage systems (BESS) in mitigating these effects, using Germany as a case study. A temporal analysis identifies pronounced seasonal and diurnal patterns, with negative prices peaking in spring and around midday. Under high negative electricity price scenarios, PV systems experience curtailment-related energy losses of up to 10%, while BESS output increases through active participation in day-ahead and intraday markets. Contrary to common assumptions, increasing BESS capacity does not significantly reduce PV curtailment or enhance PV-specific value. Instead, while total system revenues (PV – BESS) rise monotonically with storage size, the gains are driven entirely by BESS revenues. Economically, standalone PV systems exhibit substantial value erosion, whereas hybrid PV-BESS configurations demonstrate greater resilience and higher net present value (NPV) across all scenarios. These findings underscore that the primary value of storage lies in market-based revenue generation rather than curtailment mitigation, highlighting the strategic importance of storage-ready PV designs, either integrated at deployment or retrofitted to preserve asset value in increasingly volatile electricity markets.
Reproducing the AM1.5G reference spectrum using solar simulators in the laboratory is essential for accurate and transparent reporting of the I–V performance of perovskite-based tandem solar cells, a fast-growing technology approaching commercialization. The International Electrotechnical Commission (IEC) has specified the spectral calibration requirements for tandem devices in IEC 60904-1-1: Photovoltaic devices – Part 1-1: Measurement of current-voltage characteristics of multi-junction photovoltaic devices. However, practical implementation of these standards using multi-LED solar simulators can be challenging. This study shares a method to calibrate multi-LED solar simulators for tandem devices, with code implementation. This method was developed to satisfy the IEC-defined mismatch factor (M) and matching factor (Z) thresholds, which quantify how accurately the solar simulator reproduces the reference spectrum for tandem device measurement. The method is validated on three perovskite–silicon tandem solar cells, all of which achieved |1–M|<5% and |1–Z|<3% for both sub-cells, fulfilling the IEC’s criteria. By sharing this method and code-implementation, this study aims to increase the accessibility of standard-compliant solar simulator calibration.
The soiling of PV modules has been estimated to yield global losses in the solar energy production by 4 to 7%, even considering the cleaning efforts in many solar energy systems. Despite this, soiling measurements are not always available, making models particularly valuable for estimating these losses. However, soiling models currently present two limitations: most of them assume that daily rain accumulations higher than a threshold value can totally clean PV modules and, additionally, that rain will have the same washing effect on all types of soiling, independently of their higher or lower adherent properties. In this work, the HSU model (Coello and Boyle, 2019) is modified to include the two aforementioned effects. The original and modified HSU models are then calibrated for two locations in Africa where observations of long-term soiling losses were available. At the first considered location, the predominant soiling type was mainly washable by rain but showed the partial cleaning effects, while at the second location, despite the frequent and abundant rainfall, the build-up of persistent soiling was observed. The calibrated parameters for the original and modified HSU models were then applied to reanalysis meteorological 2-dimensional input data to estimate the associated soiling losses in Europe for a 20-yr operation without any artificial cleaning. The application of model parameters derived for the African sites for Europe is considered to be valid for the demonstration of the method and delivers exemplary results that might also occur for soiling types found at some European sites. The derived different soiling maps should, however, not be understood as the most likely possible values for European soiling. When considering the exemplary removable soiling type, the original HSU model underestimates on average the European soiling losses by a factor of 4 compared to the estimations of the modified HSU model. When considering the exemplary persistent soiling type, the European soiling losses estimated with the modified HSU model are on average 5.5 times larger than those estimated with the original HSU model. Additionally, the European soiling losses estimated with the modified HSU model considering a persistent soiling type are 2.4 times larger than those considering a removable soiling type, which highlights not only the importance of properly modeling the soiling losses but also of choosing the correct soiling type. The results show that, at least for some soiling types, mechanical cleaning of the PV modules is necessary to avoid high soiling losses even in rainy regions such as Central Europe.
In 2025, global energy transition investments increased by 8% per annum to USD 2,309 billion or 2% of global gross domestic product. Despite a decrease of investments in solar photovoltaics of 11.5%, the newly installed capacity increased by over 15% to reach almost 700 GWp. Globally, the installed solar photovoltaic capacity exceeded 2.95 TWp at the end of 2025. The number of countries installing 1 GWp/year or more has increased by 8 to 44. In 2025, investments in small-scale photovoltaics exceeded investments for large-scale photovoltaic plants by 28%. Levelised costs of electricity for non-tracking solar photovoltaic systems as well as the levelised cost of battery storage decreased again and reached new lows. Countries in emerging economies with grid stability problems and rapidly rising electricity demand for cooling, mainly to combat heat waves, have shown exceptionally high growth rates in new PV installations. Additional demand for renewable electricity and solar photovoltaics is created by a general trend towards electrification of heating, transport, and industry. Market expectations for 2026 are mixed from a shrinking market to a moderate one-digit growth. Needless to mention, neither market expectations are in line with the market growth needed to achieve an annual market of 2.25 TWp by 2030 nor are they on track to realise a 100% renewable energy scenario by 2050.
As Europe progresses toward a greener future, the years ahead bring expectations of widespread, large-scale photovoltaic (PV) deployment. Presently, mainstream silicon PV is transitioning away from the passivated emitter rear cell (PERC) architecture towards higher efficiency cell designs: tunnel oxide passivated contact (TOPCon) and silicon heterojunction (SHJ). With net-zero deadlines looming, there is an urgent need for comprehensive sustainability investigations into minimizing the environmental impact of large-scale actions before suffering avoidable consequences. Using life cycle assessment, these three silicon technologies are investigated and compared, finding SHJ to have the lowest global impact, closely followed by TOPCon. Both have lower impacts than PERC for 15 of 16 investigated environmental impact categories, including climate change (−9.9% and −12.1%, respectively), but increased metal use (+29.5% and +13.0%, respectively). A hotspot analysis identifies research opportunities for reducing environmental impacts such as material innovation through substituting silver (metallization) and ethylene vinyl acetate (encapsulant), or, more broadly, improving process efficiency and integrating more renewables into the electricity mix. The environmental impact is further evaluated to consider technological developments and evolving electricity mixes to the year 2034, showing the impacts of SHJ and TOPCon are reduced by >10% for all six identified high-value impact categories. These are then used to model European PV deployment between 2023 and 2034, considering various manufacturing scenarios, which show that this could result in climate change emissions of <0.41 Gt CO2 eq., though implementation of the Net-Zero Industry Act could reduce this to 0.31 Gt CO2 eq. Finally, sensitivity analysis is conducted to investigate uncertainty associated with modeling future impacts, comparing the 2024 and 2025 International Technology Roadmap for Photovoltaics. The sensitivity analysis results provide additional confidence in the findings of the initial comparison and support the conclusion that SHJ technology has, and will continue to have, the lowest environmental impact of the three investigated technologies.
UV-induced degradation (UVID) represents a critical reliability concern for TOPCon-based photovoltaic modules, yet the correlation between laboratory testing and real-world performance remains poorly understood. This study validates indoor UVID testing protocols against outdoor degradation through comprehensive analysis of four module types across five outdoor sites with up to 28 months of field exposure. We demonstrate that post-UV stabilization via brief light soaking is essential for accurate laboratory assessment, effectively reversing dark storage effects that otherwise confound UVID measurements. Comparative analysis reveals a strong relation between indoor testing (following IEC 61215-2:2021 MQT10) and outdoor degradation when proper stabilization is applied, with indoor slightly but consistently overestimating field degradation for TOPCon modules. Notably, while dark storage effects cause significant power loss under laboratory conditions, they do not significantly impact outdoor performance, most likely due to rapid morning stabilization upon light exposure. These findings provide experimental validation for stabilization procedures in testing standards and demonstrate that properly conducted indoor UVID tests can reliably predict long-term outdoor performance, enabling more accurate module reliability assessments for the photovoltaic industry.
The most established key performance indicator for (PV) system performance is the performance ratio (PR) metric, which is the ratio of the actual to the expected specific yield of a PV system. Accurate PR calculations are crucial for the PV systems industry, as errors can potentially lead to hidden underperformance, unfair financial penalties and uncertainty in system value. In systems with high DC:AC ratios, the regular occurrence of inverter clipping causes problems with PR assessment which include masking degradation and increased seasonal variation. A common practice is to exclude clipped data from PR calculations, but this can bias the remaining dataset and masks problems with inverters. In this work, a new improved clipping-corrected PR (CCPR) metric is introduced and evaluated. CCPR takes into account clipping and weather variability, and allows the use of all datapoints during a PV system’s operation. We introduce the new metric and evaluate it for different locations around the world using synthetic data. Different types of clipping ratios and faults of the system are tested, demonstrating that the new PR metric is more robust compared to the current standardized PR metrics, and is not affected by weather conditions. In addition, we show that the new metric is robust against the use of low temporal resolution Typical Meteorological Year data for calculating expected PR, in contrast with standard PR metrics. The widespread adoption and potential standardization of this new metric can lead to more accurate PR assessment for PV systems, reduced contractual risks for companies in the sector and increased in confidence of PV generation by consumers.
This study presents a 15-yr real-field performance and degradation analysis of photovoltaic modules in a Mediterranean climate. Three technologies-polycrystalline silicon (p-Si), monocrystalline silicon, and amorphous silicon-were monitored, with a detailed forensic focus on the most severely degraded p-Si systems. The p-Si modules exhibited an average degradation rate of 2.56%/year, significantly exceeding the manufacturer's warranty. Laboratory flash tests confirmed power losses of -33% to -70% over fifteen years. A multi-method diagnostic approach, integrating electroluminescence, ultraviolet fluorescence, lock-in thermography, and material forensics, identified two primary synergistic degradation pathways. The first involves optical losses from encapsulant yellowing, reducing current uniformly. The second, and more critical, is a severe increase in series resistance caused by interconnect corrosion and delamination, which drastically reduces the fill factor. Microcracks, while widespread, were a secondary factor. The study unequivocally links the degradation to moisture, oxygen, and light exposure, as evidenced by localized protection under a metal-backed nameplate. These findings underscore the critical discrepancy between accelerated testing and field aging, highlighting the necessity of long-term monitoring for accurate lifetime predictions and the development of more durable module materials and designs.
The energy yield of bifacial all-perovskite tandem modules is quantified for a selected outdoor testing location using electro-thermal simulations on cell and module levels combined with a model providing spectral irradiance according to geographical location and time. Cell level modelling is performed using an opto-electronic drift-diffusion-Poisson simulation on the full tandem device under consideration of direct and diffuse front illumination according to the sun position and atmosphere model, and diffuse rear illumination according to the ground albedo. On module level we combine a two-dimensional finite-element large area simulation of the electrodes in an optimized layout for a 100 cm2 monolithically interconnected module with the one-dimensional active area coupling law obtained from the simulated cell level characteristics. Thereby, thermal effects are considered regarding heat generation by light absorption, charge carrier transport and recombination, as well as heat transport through the stack and dissipation at the surface. To reduce the computational cost, operation conditions are binned with respect to limiting photocurrent, ambient temperature, and wind speed. After verification of the validity of the binning approach by comparison with full time-data modelling, it is used to compute the annual energy yield on cell level as a function of ground albedo and top cell band gap, confirming both, a large gain from bifaciality already at moderate albedo and the benefit from lower band gap top cells for high rear irradiation level due to large ground reflectivity. Finally, thermal effects and configuration-dependent cell-to-module losses are quantified via the evaluation of annual energy yield with the full electro-thermal module simulation, using the binned cell-level characteristics as well as the measured ambient temperature and wind speed as input. The results imply that an accurate assessment of upscaling losses is more critical for a reliable quantification of energy yield than consideration of the full temperature dependence.
PV array simulators are devices for PV and PV battery inverter testing. To ensure that these devices operate correctly and can realistically simulate PV modules and PV arrays, a test procedure for the assessment of PV array simulators has been developed and is presented in this paper. This procedure helps testing laboratories to evaluate PV array simulators and leads to more uniform test conditions. Furthermore, it assists developers of such simulators in understanding the requirements, enabling them to optimize and test their devices accordingly. The proposed test series includes three phenomenological observations, in which the interaction between the PV array simulator and a randomly selected PV inverter is tested. Subsequently, three potentially standardisable tests are proposed in which certain properties, such as the accuracy and frequency response of the PV array simulators are tested and evaluated.
