Since its first edition in 2008, the Metallization and Interconnection Workshop for Solar Cells (the MIW) has provided a forum for experts in those fields to exchange and discuss. The last 12th edition of MIW workshop took place on 23rd and 24th October 2024 in Chambery, France. In this paper as opening to the special issue of Solar Energy Materials and Solar Cells we summarize the status and new findings that were presented as well as technology survey on emerging trends based on participants' feedback.

Perovskite-silicon triple-junction photovoltaics offer efficiency gains beyond dual-junction devices but at the expense of added complexity1. Here we address two key bottlenecks in perovskite-silicon-based triple-junction solar cells: reduced open-circuit voltage (VOC) in the wide-bandgap (WBG) top cell and limited photocurrent generation in the middle cell1,2. A non-volatile additive, 4-hydroxybenzylamine (HBA), regulates WBG perovskite crystallization and passivates defects, promoting oriented growth and suppressing non-radiative recombination. Together with improved energy-level alignment, this yields VOCs of up to 1.405 V and enhanced stability. To overcome the current limitations in the middle cell, a three-step deposition strategy enables the formation of thick, low-bandgap perovskite absorbers while preserving microstructural integrity and enhancing electron extraction. Also, low-refractive-index SiOx-nanoparticles (SiOx-np) that accumulate in the front valleys of the textured silicon bottom cell act as an optical middle reflector, enhancing light absorption in the middle cell. These advances are then combined in 1-cm2 perovskite-perovskite-silicon devices, achieving a certified efficiency of 30.02%.

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.

Reliable and esthetically pleasing lightweight photovoltaic modules for building integration are expected to grow interest in the consumer market, especially for retrofitting older buildings and storehouses that are not structurally designed to withstand additional dead‐weight. The present work reveals the design of a novel module architecture attaining a total weight <6 kg/m 2 . The approach uses a highly transparent polymeric foil as the front pane and as an encapsulant to maintain optical coupling between the cell and the incident solar radiation, while the mechanical rigidity of module is maintained by the use of a composite backsheet, which consists of a polypropylene‐based honeycomb sandwiched between two layers of fiber reinforced skins. Two polypropylene skin variants were evaluated, with fiber densities of 820 and 660 g/m 2 . For esthetical improvement of the lightweight PV modules, a colored interlayer foil was used. Reliability testing included flexural bending and static mechanical load tests, environmental tests like, damp‐heat, ultraviolet radiation, thermal cycling, and humidity freeze. Several other critical tests, like hail‐impact test and fire‐ignition test, were also performed to check the potential of these architectures for building integration. The fiber density in skins of composite backsheets impacted the performance of modules against mechanical loads.

Predicting the energy output of a bifacial photovoltaic (PV) module is usually not as straightforward as for a monofacial module. The problem usually lies in the estimation of the back-side irradiance which strongly depends on the mounting conditions, tracking or fixed positioning and variable ground albedo. We developed a new direct-diffuse power rating model for predicting the energy yield and performance ratio of bifacial photovoltaic modules (DDPRbifi). The model was validated on 16 bifacial monocrystalline silicon modules of three silicon PV technologies (SHJ, IBC, TopCon) and monitored at four different locations in Europe. The new model shows the best accuracy on all PV modules regardless of the module technology and monitored location. On average, the discrepancy between the simulated and measured performance ratio of the observed modules is around 2 %.

Ultraviolet-induced degradation (UV-ID) of various PV cell types was analyzed under optical UV filters with different cutoff wavelengths. Cell types studied included interdigitated back contact (IBC), passivated emitter and rear totally diffused (PERT), and heterojunction technology (HJT) based on crystalline Si (c-Si), and metal halide perovskite (MHP) cells. Analyzing degradation rates in two distinct regimes proved beneficial for all cell types. We used empirical linearizing functions ln(t) for c-Si technologies and 2 root t for MHP samples where t is time. These were applied to extrapolate UV-induced degradation over the lifetime of PV modules under various levels of optical UV filtering and used to predict the relative economic benefits for PV power plants. Degradation rates for all technologies were generally faster under the long pass optical filters having shorter cutoff wavelengths transmitting more UV irradiation and at elevated temperatures when testing MHP samples in the range between 60 degrees C and 90 degrees C.

As global decarbonization accelerates the need for extensive solar photovoltaic deployment, land‐use conflicts have become increasingly pressing. Integrating PV into the built environment emerges as an effective strategy to mitigate these challenges by generating electricity where it is consumed. However, the polymeric encapsulant—a core material in photovoltaic (PV) modules—introduces critical fire safety concerns, particularly in building applications with strict regulatory requirements. This review addresses the issue with a dual approach. First, it presents various solutions to mitigate fire hazards, such as the incorporation of flame retardants, and defines five families of the latter solutions. Despite the central role of the encapsulant in module flammability, little research has focused on the use of flame retardants in photovoltaic modules. Then, a review of the existing standards and testing approaches that can be used for the assessment of building‐integrated photovoltaic fire safety is presented. Based on the findings, a methodology for the evaluation of the fire performance is also proposed, with this framework evaluated at both the material and module levels.

In densely populated or mountainous countries where installation of large-scale solar plants is challenging, photovoltaic (PV) modules in building applications offer a solution by transforming passive surfaces into energy-generating systems. The need for flexible, lightweight, and "invisible" PV modules, with a life-time of over 20 years, comparable performance to the standard modules, and enabled recyclability resulted in various designs on the market. This research focuses on thermoplastic honeycomb sandwich composites (HSCs) with glass fiber-reinforced polymer skins as potential lightweight backsides for PV modules. Through material characterization and damp heat testing, their optical, mechanical, and thermal performance, compatibility with lamination processes, and ability to protect internal components from UV radiation and humidity were evaluated. Results show that proper glass fiber embedment improves mechanical properties and reduces water vapor transmission rates. Semitransparent skins could enable bifacial PV modules but require UV absorbers for long-term stability. HSCs exhibit glass-like thermomechanical behavior but low thermal conductivity, which could affect module temperature regulation. Damp heat exposure caused minor degradation in PP-based materials, while PET materials experienced polymer chain-scission and significant material embrittlement, which indicates the need for improved hydrolysis resistance.

Accurate clear-sky detection (CSD) is essential for reliable data analysis and performance assessments in photovoltaic (PV) systems. However, many advanced machine learning (ML) models function as “black boxes”, limiting their interpretability and trustworthiness. This study presents an interpretable Artificial Intelligence (AI) framework that combines high predictive performance with deep insight into model decision-making. Using a hand-labelled dataset from a fixed-tilt PV system in Golden, Colorado, USA, with 1 min plane-of-array (POA) measurements of global horizontal irradiance (GHI), direct normal irradiance (DNI), and diffuse horizontal irradiance (DHI), a Categorical Boosting (CatBoost) classifier is developed for CSD. The model is iteratively refined through a closed-loop diagnostic process guided by SHapley Additive exPlanations (SHAP). Misclassified instances are analysed using dimensionality reduction via Uniform Manifold Approximation and Projection (UMAP) and clustering, revealing distinct, physically-grounded failure modes such as “cloud enhancement”, where reflected or scattered sunlight temporarily increases irradiance, and “hazy but stable conditions”, where thin atmospheric haze slightly attenuates sunlight without introducing variability. Insights from this analysis inform targeted feature engineering, yielding a refined model with high classification performance quantified by an F1-score of 97.3%, along with substantially reduced false positive (1.99%) and false negative (7.0%) rates, reflecting both overall accuracy and balanced sensitivity to clear-sky and non-clear-sky periods. This interpretable framework improves the reliability of clear-sky filtering for downstream PV applications, including fault detection and diagnosis (FDD) and long-term performance loss rate (PLR) estimation, and provides a transferable methodology for developing trustworthy AI models in energy systems.

As global decarbonisation requires the widespread adoption of solar photovoltaic (PV) electricity, addressing challenges related to land use has become relevant. The conflict between PV installations and other land uses, such as forestry or agriculture, highlights the urgency for alternative solutions. Integrating PV technology into the built environment is a compelling strategy to mitigate these challenges, enabling electricity generation precisely where it is needed. In the context of buildings integrated photovoltaics (BIPV), PV modules serve a dual purpose, functioning both as electricity generators and integral components of the architectural design. Therefore, the architecture requirements — specifically in terms of shape, size, and colour— become relevant for BIPV modules. This paper offers a general overview of the diverse colouring technologies employed for BIPV modules, describing their functioning, challenges, and advantages. An examination of the current landscape of coloured PV products involving considerations of pricing and power output is presented. Additionally, this work addresses the critical topics of reliability and stability in colour solutions, outlining methodologies for quantitative colour characterization. It provides foresight into the potential challenges facing installations in the future and explores the multifaceted social, economic, and environmental implications of this evolving technology.

Recent advancements in glass-free photovoltaic (PV) module designs have paved the way for lightweight, streamlined structures with versatile designs, all while maintaining high performance and reliability. These innovations are finding broader applications in Integrated Photovoltaics (IPV) domains. Within this context, CSEM has developed specialized encapsulants to ensure the high reliability of lightweight modules. This study will initially introduce newly developed polymeric materials designed to serve as both encapsulants and cover sheets, achieving ultra-low-weight modules with demonstrated weights as low as 700 g/m2. This material stack also holds potential for use in pre-laminates. Additionally, dedicated encapsulants have been formulated, enabling the creation of modules weighing as little as 2 kg/m2, with enhanced hail resistance. For Vehicle-Integrated Photovoltaic (VIPV) modules, which are based on materials with significant differences in coefficients of thermal expansion, further adjustments to the thermo-mechanical properties of the materials, the material stack, and the interconnection design are crucial to enhance module reliability. Simulation tools have been developed to predict the energy yield of curved modules typically used in VIPV. In a second aspect, we demonstrate that these innovative materials can be synergistically combined with highly efficient tunnel back-contact heterojunction (IBC-HJT) solar cell technology. Utilizing SmartWire Contacting Technology and a traditional glass module structure, we achieved a certified record laminate efficiency of 24.7%. The robustness and reliability of this combined approach are presented.

This article reports on the 11th Workshop on Metallization and Interconnection for Crystalline Silicon Solar Cells, which took place in May 2023 in Neuchâtel, Switzerland. An important observation at the workshop was that, while screen printing is still dominating metallization, alternative pastes with increasing Cu content are starting to be implemented in the industry in response to the need to decrease cost and improve sustainability. Compared to previous workshops, interconnection topics were more prevalent in this edition because of the need for interconnection solutions that work at lower temperatures, as is needed for emerging solar cell technologies. Electrically conductive adhesives (ECA) have gained in importance in this respect. Understanding of reliability aspects and insight into proper characterization of ECAs are increasing, yet the challenge is here is to substantially further reduce cost and silver content.

Accurate and reproducible color characterization is essential for colored building integrated photovoltaic products, both for manufacturing quality control and assessing long-term color stability. However, existing characterization techniques struggle to accurately determine color when a surface is behind a transparent layer like a solar PV laminate. In this study, we compare different colorimetric techniques and propose an innovative colorimeter based on a fiber optic spectrometer and large area illumination to address this issue. Samples with varying transparent glass thicknesses and underlying colors are laminated and characterized using a scanner, an integrated sphere spectrometer, a commercial portable colorimeter, and the proposed large area illumination colorimeter. Results show that common scanners produce darker images and inaccurate color determination due to light losses in the glass. As glass thickness increases, reflectance decreases with the integrated sphere spectrometer and portable colorimeter. However, the large area illumination colorimeter exhibits only minimal signal reduction. High reflective foils experience more reflectance reduction with thicker glass than low reflective ones. All devices yield comparable results without the glass layer. The large area illumination colorimeter, compensating for light losses, proves to be a suitable solution for accurately measuring color under glass laminates using reflected light. For example, it reduces the color change from 57 (commercial portable colorimeter) to only 3 for an ivory colored glass laminate. This innovative tool has the potential to improve color characterization in building integrated photovoltaic products, enabling better manufacturing quality control and assessment of long-term color stability.

Electric vehicles (EVs) currently dominate the sales in the automotive market. A big leap in this market can be made by developing a photovoltaic product that can be integrated to an EV, as it can boost the driving range of the EV while reducing the charging frequency. Such vehicle-integrated photovoltaic (VIPV) products are already successfully demonstrated, but they are usually made with glass as a front sheet – making them bulky and limiting their use to the car roofs due to safety reasons. The contemporary focus of the research in the field of VIPV is on developing a product that is lightweight (LW) and easily integrable into the complex shapes of an EV. Therefore, in this work, we present our initial findings on a novel architecture for LW VIPV modules employing polycarbonate (PC) as a front sheet. The mechanical behaviour of the LW module under bending is successfully simulated using finite elements (FE) modelling to predict the fracture of the solar cells, which can then be used as a predictive tool to check the maximal load on the PV body of an EV before cracking the c-Si solar cells. We demonstrate that a change in the temperature of the PC-based LW modules can modify the interspacing between the cells and thus create stress on the connectors. The dog-bone connectors are found to allow almost unconstrained movement of the cells in the module when subjected to variation of temperature. The cell movements may result in mechanical fatigue of the interconnection, which can ultimately result in disconnection of the cells. Initial performance of the dog-bone connectors is investigated by applying mechanical fatigue experiments, which demonstrate that the special geometry of the dog-bone connector could endure a greater number of thermal cycles than a simple prismatic shape would.

A reliable and aesthetically pleasing lightweight (LW) photovoltaic (PV) module for building integration is expected to develop a growing interest in the consumer market. However, its application is still limited by old buildings that are not structurally designed to withstand additional dead weight. We present the results of an inter-laboratory investigation within the solar. NET-ERA project “Delight”. The present work has countered this challenge through a novel LW module architecture to attain a total weight of <6 kg/m2. This approach replaces glass at the front with a highly transparent polymer foil to maintain optical coupling between the cell and the incident solar radiation. The mechanical rigidity of the LW PV module is provided by a composite sandwich structure (by adhering a honeycomb (HC) core layer between two fiber-reinforced composite skins) at the back of the module. For the skins and the HC, we have investigated two thermoplastic polymers, polypropylene (PP) and polyethylene terephthalate (PET), and present here the first-hand results of a reliability study done on this novel PV architecture. The investigation includes the effects of accelerated environmental aging, hail-impact tests, peel tests, wet-leakage tests, and fire ignition tests at the module level. Furthermore, the degradation due to the stressors, as mentioned above, is explained by performing fundamental characterization at the material's level using techniques like differential scanning calorimetry. Overall, the modules with PP-HC backsheets performed better than that of the PET-HC based candidates.

Building-integrated photovoltaics (BIPV) are dual purpose, providing both energy and building functions. Aesthetics play a crucial role in the BIPV market, with increasing demand for uniformly colored modules for building skins. Achieving this requires hiding ribbons and metal connections while not compromising durability, and ink coating offers a potential automated solution. This work presents a comparison of three coated metallic ribbons: one commercially pre-coated and two coated with UV-curable-inkjet printing. Glass/backsheet samples with standard or UV-blocking encapsulant were tested through accelerated ageing UV exposure. Results show that the commercially coated ribbons remain stable after 120 kWh/m2 of UV, but the UV-curable-inkjet tested inks show color changes in the encapsulant surrounding metallic interconnects in all cases. Yellowing is attributed to photodegradation of the ink's #1 main component, 2-phenoexyethyl-acrylate. However, PV module performance remains stable despite the color shift, with less than 3% power loss after exposure to 360 kWh/m2 of UV.

The EU crystalline silicon (c-Si) PV manufacturing industry has faced strong foreign competition in the last decade. To strive in this competitive environment and differentiate itself from the competition, the EU c-Si PV manufacturing industry needs to (1) focus on highly performing c-Si PV technologies, (2) include sustainability by design, and (3) develop differentiated PV module designs for a broad range of PV applications to tap into rapidly growing existing and new markets. This is precisely the aim of the 3.5 years long H2020 funded HighLite project, which started in October 2019 under the work program LC-SC3-RES-15-2019: Increase the competitiveness of the EU PV manufacturing industry. To achieve this goal, the HighLite project focuses on bringing two advanced PV module designs and the related manufacturing solutions to higher technology readiness levels (TRL). The first module design aims to combine the benefits of n-type silicon heterojunction (SHJ) cells (high efficiency and bifaciality potential, improved sustainability, rapidly growing supply chain in the EU) with the ones of shingle assembly (higher packing density, improved modularity, and excellent aesthetics). The second module design is based on the assembly of low-cost industrial interdigitated back-contact (IBC) cells cut in half or smaller, which is interesting to improve module efficiencies and increase modularity (key for application in buildings, vehicles, etc.). This contribution provides an overview of the key results achieved so far by the HighLite project partners and discusses their relevance to help raise the EU PV industries' competitiveness. We report on promising high-efficiency industrial cell results (24.1% SHJ cell with a shingle layout and 23.9% IBC cell with passivated contacts), novel approaches for high-throughput laser cutting and edge re-passivation, module designs for BAPV, BIPV, and VIPV applications passing extended testing, and first 1-year outdoor monitoring results compared with benchmark products.

The 10th edition of the Workshop on Metallization and Interconnection for Crystalline Silicon Solar Cells took place in November 2022, as a live event in Genk Belgium, but also including online participants. Despite various safety measures related to the Covid 19 pandemic, the event reached its goals of networking and of knowledge sharing in these technologically important fields. Scientific contributions were presented on various relevant topics including high throughput printing, electroplating, soldering and interconnector bonding. A common theme was the search towards metallization and interconnection solutions for next generation solar cell concepts that drastically reduce the consumption of metals that are limited in supply, notably silver, and are compatible with the extremely high output manufacturing scenarios of the anticipated Terawatt era.