The global shift towards low-carbon and renewable energy sources, driven by climate concerns associated with fossil fuels, has positioned solar photovoltaics (PV) as a major alternative. With the increasing adoption of PV technologies, it is crucial to study various PV module types. This thesis focuses on the HyET Powerfoil, an amorphous silicon (a-Si) PV module with a polymer encapsulation, offering a lightweight alternative to conventional crystalline silicon (c-Si) PV modules. Due to the new type of polymer encapsulation (TE) and to compare a-Si absorber with its c-Si counterparts, numerous factors must be examined before large-scale outdoor deployment to prevent failure and degradation and assess module reliability.

This research addresses the losses observed in HyET Powerfoil modules, leading to the design of an experiment involving two groups of four modules each to identify and segregate potential degradation at the interfaces. The modules included 2 c-Si glass-encapsulated PV modules, 2 c-Si glass + TE encapsulated modules, 2 HyET modules with glass encapsulation, and 2 HyET Powerfoils. The primary objective was to investigate factors contributing to performance losses especially the short-circuit current (Isc) and soiling compared to traditional glass-encapsulated modules. The study utilized measurements from a monitoring system and a solar simulator, along with regular cleaning. Initial findings indicated significant absorber degradation, with HyET Powerfoils showing a degradation rate of around 17% at the final measurements. Additionally, the TE polymer exhibited substantial losses in transmission due to degradation and soiling.

The thesis also addresses optical degradation in HyET Powerfoil modules, particularly focusing on the TE polymer stack. Using a combination of outdoor exposure tests, WOM ageing, and surface roughness measurements, the study assessed degradation mechanisms. The results indicate that the TE polymer stack experiences significantly higher soiling of around 1% more than glass. This can be attributed to increased surface roughness. Moreover, the adhesive used in the TE polymer stack was identified as a major contributor to optical degradation, leading to increased light scattering of around 5%. These findings suggest that while TE polymers offer certain benefits, their long-term durability under various environmental conditions needs further optimization.

Additionally, an injection-dependent Electroluminescence (EL) predictor was developed to screen for hotspots, based on the IEC 61215 Hotspot Endurance Tests. Defects visible in the EL images were classified into three modes based on defect intensities: Mode A, Mode B, and Mode C. Further testing revealed that only Mode B defects led to hotspot formation due to their localized effects.

In conclusion, while the flexible HyET Powerfoil demonstrates the potential to facilitate high-efficiency modules for lightweight applications, specific areas in the polymer configuration need improvement. This study indicates potential pathways for enhancing the long-term performance of these modules.

This thesis investigates the formation of hotspots in single junction amorphous silicon thin film solar modules through experimental methods. Employing electroluminescence (EL) imaging and infrared (IR) imaging, the study aims at identifying and classifying defects that can be used to predict hotspot formation and assesses the endurance of different sized modules.
To predict hotspot formation on small 30 by 30 cm monolithically interconnected modules, the research first categorises shunts into four different classes based on their severity and localization (Mode A, Mode AB, Mode B and Mode C). Mode A defects are severe and cover a large area, Mode B defects are severe and localized, Mode AB defects are severe and rather localized and Mode C defects are weak and localized. It was found that only shunts that are severe and localized lead to the formation of hotspots (Mode B and rather localized Mode AB). Since no hotspots formed at locations without predictors EL based shunt classification has proven to be an effective predictor with high predictive accuracy for hotspots.
Industrial modules with a dimension of 190cm by 30 cm exhibit similar defect behavior, however the interaction between multiple hotspots within one cell leads to some exceptions. When multiple defects are located within the same cell, the most severe and localized defect forms a strong hotspot, while the other defects either form weaker hotspots or no hotspots at all. Due to a higher current level also Mode C defects can lead to hotspot formation when they are the most severe defect within a cell. Furthermore locations that show defect cluster or current crowding also experience strong hotspot formation. Lastly, shunts that were found to be originating from scribe defects are prone to form strong hotspots.
EL based shunt classification has therefore proven to be a reliable predictor for hotspot formation on modules of different sizes. Furthermore this procedure did not induce any performance losses on the modules. However the EL imaging procedure itself is quite time intensive and therefore not suitable as a quality test that could be implemented at the end of a production line.
Using IR imaging in reverse bias, hotspots can reliably be identified on small and large modules. Due to higher current levels, hotspots can easier be identified on large modules. However high reverse currents can lead to significant damage and loss of performance of the modules. IR imaging in reverse has proven to be a faster alternative for hotspot detection, suitable for production line integration.
The findings contribute to improved defect identification and hotspot prediction techniques, enhancing the reliability of solar module manufacturing and maintenance processes. Future work should focus on refining defect classification and exploring the behaviour of hotspot formation and impacts on reliability in field applications.

This study presents a comprehensive Life Cycle Assessment (LCA) comparing HyET Solar's Powerfoil modules to conventional Passivated Emitter Rear Contact (PERC) technology. Through both current and future scenario analyses, utilizing tools like Integrated Assessment Models (IAMs) and Shared Socioeconomic Pathways (SSPs), the research examines key impact categories, including Global Warming Potential (GWP), Terrestrial Acidification, Land Use, and Material Resources.
Current scenario findings reveal that PERC modules exhibit significantly higher environmental impacts across most categories. The GWP of PERC modules is notably high at 50.1 grams CO2-equivalent per kWh, primarily driven by energy-intensive processes in inverter and silicon wafer production. Powerfoil modules, especially the triple-junction architecture, demonstrate reduced impacts with emissions as low as 23.8 grams CO2-equivalent per kWh.
Future scenario findings project even greater environmental benefits for Powerfoil modules by 2050. Efficiency improvements and material optimizations, including the replacement of existing top encapsulant and reducing the carrier foil thickness, could bring down the emissions to 6.2 grams CO2-equivalent per kWh, which is almost 70% lower than PERC modules.
The study also identifies critical hotspots in the Powerfoil modules’ lifecycle, providing a quantitative analysis of environmental impacts after replacing these hotspots in future scenarios. Furthermore, the Global Sensitivity Analysis highlights that module efficiency and solar irradiation are critical factors influencing environmental outcomes. These findings highlight the potential of Powerfoil modules as a more sustainable alternative in photovoltaic technology, with substantial implications for reducing the environmental footprint of energy systems.

Thin-film amorphous Silicon (a-Si) technology has been up and coming in recent years in order to achieve an efficiency comparable to crystalline Silicon (c-Si). Although the technology has existed for quite some time, it has not been researched as much as its crystalline counterpart, especially not in the hotspot reliability sector. The hotspot phenomenon is noticed in field-aged modules commonly due to partial shading or soiling losses. When one of the cells in a string gets partially or fully shaded, the shaded cells are forced to be in reverse bias and dissipate power in the form of heat, causing the formation of hotspots. The hotspots can reach temperatures of beyond 100C. These can lead to the melting of module encapsulants and faster degradation of the module, as well as being a fire hazard because of the elevated temperatures. This thesis was done in collaboration with HyET Solar BV, a company that produces a-Si thin film solar foils. The modules used in this thesis are from HyET Solar BV and we have selected highly degraded modules for the experiments.

This report aims to achieve a couple of things: first, get insight of hotspot formation in a-Si thin-film modules in accordance with the latest International Electrotechnical Comission (IEC) 61215 Certification norms.

Secondly, we have utilized electroluminescence (EL) imaging to classify various defects present in the modules and to evaluate their endurance to hotspot formation. Based on those results, we created a map that shows the probability of hotspot formation from different defects in the degraded modules.

And lastly, we classified the different kinds of hotspots based on factors like shape and location. Also, the possibilities of how these defects originated are explained on the basis of a schematic overview of the interconnection between the cells.

After testing and experimenting, it became apparent that the highly degraded a-Si foils are susceptible to hotspot formation. After light soaking two foils according to the IEC 61215 norms, a couple of hotspots were created in the shaded area. Some of these hotspots could be seen on EL images by defects before they became visible during the visual inspection step. EL imaging is used to characterize different defects that could lead to hotspot formation. These defects are white dots, current crowding and dark regions. The probability map for these defects is as follows: 46.6% of the white dots have turned into hotspots, 16.7% for current crowding and 32% for dark regions. It is suspected that these white dots are a manufacturing process problem; they could be areas of high-impurity contaminants or a sharp point. Current crowding and dark regions are always paired together and depending on which side of the cell they are on, it is suspected that it is a fault in either the P2 or P3 scribes of a cell in the module.