Abstract
The main focus of this work is to investigate the degradation behavior of two newly developed encapsulants for photovoltaic applications (thermoplastic polyolefin (TPO) and polyolefin elastomer (POE)), compared to the most widely used Ethylene Vinyl Acetate (EVA) upon exposure to two different artificial ageing tests (with and without ultraviolet (UV) irradiation). Additive composition, optical and thermal properties and chemical structure (investigated by means of Thermal Desorption Gas Chromatography coupled to Mass Spectrometry, UV-Visible-Near Infrared spectroscopy, Differential Scanning Calorimetry, Thermogravimetric Analysis and Fourier Transform-Infrared spectroscopy, respectively) of the analyzed polymers were monitored throughout the exposure to artificial ageing tests. Relevant signs of photo-oxidation were detectable for TPO after the UV test, as well as a depletion of material’s stabilizers. Signs of degradation for EVA and POE were detected when the UV dose applied was equal to 200 kW h m−2. A novel approach is presented to derive information of oxidation induction time/dose from thermogravimetric measurements that correlate well with results obtained by using oxidation indices.
Highlights
Accepted: 11 January 2021Encapsulant materials are key components in photovoltaic (PV) modules because they need to provide and ensure several properties and functions
If during the 1960s and the 1970s the prevailing encapsulant was based on polydimethylsiloxane (PDMS)
Three types of polymer materials commercially available have been chosen in this study: an ultra-fast cure ethylene vinyl acetate (EVA, PHOTOCAP® 15580P from Specialized Technology Resources), a thermoplastic polyolefin (TPO, Icosolar® from Isovoltaic) and a polyolefin elastomer (POE, PO8110 from 3M)
Summary
Encapsulant materials are key components in photovoltaic (PV) modules because they need to provide and ensure several properties and functions. These materials provide optical coupling, give mechanical stability and support, protection to the electrical components from environmental factors and ensure electrical insulation for safety reasons [1]. If during the 1960s and the 1970s the prevailing encapsulant was based on polydimethylsiloxane (PDMS). The transition between the materials used as encapsulants has taken place mainly because of economic considerations as well as relatively proved reliability, rather than to outstanding EVA material properties. Due to their chemical structure, PDMS based materials have less impact on mechanical stress on solar cells than
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