Moisture transport, adhesion, and corrosion protection of PV module packaging materials

We compare the properties of a number of encapsulant and soft backsheet materials that are important for photovoltaic (PV) module packaging. These properties include moisture transport and interfacial adhesion as a function of accelerated exposure to damp heat. Various cleaning and priming methods were studied for improving adhesion to glass and polymer surfaces. Barrier coatings prepared by industry and at NREL have been found to promote adhesion and provide varying levels of moisture-ingress protection. Plasma pre-etch of polyethylene terephthalate (PET) before barrier deposition reduces adhesion strength and moisture barrier properties. Resistance to cracking during lamination and peeling during test are investigated. The relative effectiveness of various combined packaging strategies to protect PV devices has been studied using 80-nm-thick aluminum films deposited onto 10 cm×10 cm glass substrates. Glass/ethylene vinyl acetate (EVA)/aluminized-glass laminate constructions were found to trap harmful compounds that catalyzed moisture-driven corrosion of Al. Constructions with breathable backsheets allow higher rates of moisture ingress, but also allow egress of deleterious substances, thereby reducing corrosion.