Acetic Acid Production and Glass Transition Concerns with Ethylene-Vinyl Acetate Used in Photovoltaic Devices

Photovoltaic (PV) devices are typically encapsulated using ethylene-vinyl acetate (EVA) to provide mechanical support, electrical isolation, and protection against environmental exposure. Under exposure to water and/or ultraviolet radiation, EVA will decompose to produce acetic acid that will lower the pH and generally increases surface corrosion rates. This enhanced corrosion is demonstrated in this work using aluminum mirrors deposited on glass. EVA also experiences a glass transition, beginning at about -15 °C, making its use questionable in environments below -15 °C. Despite these shortcomings, EVA has proven to be adequate (in terrestrial environments) for encapsulating silicon wafers based PV devices. Thin-film PV technologies, however, are constructed using layers that are only a few microns thick, making them potentially much more sensitive to surface corrosion than are silicon-wafer-based technologies.