Experimental study of polymers as encapsulating materials for photovoltaic modules

Due to the introduction in the market of new generations of photovoltaic (PV) modules, there is the need to develop improved packaging materials. A reliable encapsulating layer is required to guarantee outdoor operation for more than twenty years, paying attention to factors like protection from weather agents and humidity, promotion of the adhesion between the active layer and the substrate, and electrical isolation. The most popular encapsulant is a thermoplastic polymer called ethylene-vinyl acetate (EVA), which is produced in rolls of extruded thick film. Anyway, another material, poly-vinyl butyral (PVB), seems to be the best choice to satisfy the more demanding mechanical and safety requests in the field of building integrated photovoltaic (BIPV). This is one of the reasons why PVB is nowadays widely used with thin film PV, while EVA is still the standard material for crystalline modules. The success of the qualification campaign of a PV module can strongly depend on the performances of the packaging polymer. Many tests can be done to determine the material properties and predict its behaviour under stress conditions. In this work, we are performing an experimental study to test different formulations of polymers as interlayer materials for PV modules. The mechanical properties are one of our focus. They strongly depend on the temperature and the loading intensity because of the thermoplastic nature of these polymers. They deeply affect the reliability of the modules and determine their application.