Newly developed thermoplastic polyolefin encapsulant–A potential candidate for crystalline silicon photovoltaic modules encapsulation

Abstract

Thermoplastic polyolefin (TPO) is a newly developed non-crosslinking material for photovoltaic (PV) module lamination as an alternative to ethylene–vinyl-acetate (EVA) encapsulant. This article assesses its applicability as an encapsulant material. We report the results of various characterization tests for discoloration, optical, and thermal properties degradation before and after the UV accelerated test. To evaluate its weathering stability, the UV-365 acceleration test has been conducted on the glass to glass TPO laminate, with EVA as a benchmark. In 50 days of weatherability tests, the transmittance of EVA significantly reduced while TPO remained almost unchanged. The discoloration of TPO is around nine times slower than that of EVA. The analytical tools like Raman spectroscopy, fluorescent imaging, and spectra have been used to assess the degradation behavior, which indicates a clear difference between EVA and TPO based encapsulant. Thermal properties (glass and melt transitions) of TPO and EVA have been studied through heat-cool-heat cycle testing by differential scanning calorimeter (DSC). This test confirmed that TPO thermal properties remain almost unchanged, whereas EVA shows significant changes after 50 days of UV exposure. In the thermogravimetry analysis (TGA) results, we found that TPO is stable till a significantly higher temperature than EVA. Additionally, the 180° peel adhesion test suggests that TPO has a higher adhesion strength than EVA. This work will help in understanding the applicability of newly developed non-crosslinking TPO as a potential replacement for EVA for the PV modules.