Development and testing of encapsulation concepts for integrated PV modules

Abstract

The global expansion of photovoltaics (PV) is increasingly confronted with limitations in specific geographic contexts, such as densely populated urban centres and mountainous regions, where land availability constrains large-scale field-deployed installations. This has driven the need for integrated PV (IPV) in the built environment. However, conventional glassglass modules are often too heavy or rigid for lightweight infrastructures. Transitioning to glass-free, polymer-based architectures is essential for enabling flexible, lightweight designs, yet this shift fundamentally redefines the requirements for the polymeric stack, which must now provide the structural integrity and environmental protection formerly offered by glass. This thesis establishes a scientific framework for application-specific, glass-free PV designs by characterizing the physical, chemical, and thermomechanical behaviour of polymeric materials. Through five systematic studies, the research investigates diverse pathways, ranging from structural reinforcements to specialized thin-film coatings, and evaluates their performance under accelerated aging and varying processing conditions. The research first addresses the loss of structural rigidity resulting from the removal of the glass layer by evaluating thermoplastic honeycomb sandwich composites (HSCs). Polypropylene-based HSCs were identified as viable glass substitutes due to a coefficient of thermal expansion (CTE) comparable to solar glass, maintaining stable material properties after accelerated aging exposure. In the context of building-integrated steel façades, the study identifies that while adhesion to building elements can be achieved via various bonding approaches, moisture-driven interfacial weakening remains a critical failure mode. The results indicate that further optimization, including the transition toward monolithic backsheets, is necessary to ensure a 25-year service life. For flexible CIGS and thin-film applications, a screening methodology revealed that polyurethane (PU) formulations provide the optimal balance of adhesion and optical clarity. Crucially, the work demonstrates that standard industrial aging tests (e.g., 1000h damp heat) often over-stress these materials, leading to costly over-engineering for shorter-lived consumer products. Finally, an in-depth analysis of encapsulants revealed that manufacturing history and lamination duration significantly impact thermomechanical stability. These findings exposed inconsistent behaviours in co-extruded materials, which led to a systematic characterization of commercially available ethylene vinyl acetate-polyolefin-ethylene vinyl acetate (EPE) encapsulants. This investigation revealed that EPE encapsulants are highly variable in their properties, with ethylene vinyl acetate (EVA) still comprising up to 64% of the volume, thereby challenging the industry assumption that these multi-layer stacks offer inherently enhanced protection compared to single-layer EVA encapsulants.This work proves that glass-free PV is not a "plug-and-play" transition. Success depends on a three-stage integration strategy: fundamental material characterization, lamination process adaptation, and targeted optimization of hydrolysis resistance. By matching the material stack to the specific operational environment rather than relying on generalized industrial labels, this thesis provides the scientific foundation necessary for the next generation of adaptable, high-reliability photovoltaic systems.