Abstract
The reliability of photovoltaic modules is highly influenced by the material properties of the backsheet and encapsulation material. Currently, little attention is paid to the permeation properties of the back-sheet material or to its impact on encapsulation degradation and module reliability. We investigated the interaction of different types of solar encapsulation and back-sheet materials. Therefore, various laminates were made to examine the environmental impact on such materials during the aging processes. One focus of our study lies in oxygen and water vapor permeability of the back-sheet materials. The encapsulants used were an ethylene vinyl acetate (EVA), a TPSE (thermoplastic silicone elastomer), an ionomer, and a PVB (polyvinyl butyral). Back-sheet materials were a TPT (Tedlar-PET-Tedlar) foil, a polyamide (PA) sheet and a polyethylene terephthalate (PET) composite film. Raman spectroscopic and FT-IR/vis-reflectance measurements were carried out before and after different accelerated aging procedures. The water vapor and oxygen permeation properties were measured. A clear correlation between the permeation properties and the observed aging behavior was found. The degradation, especially of the encapsulant, resulted in increased fluorescence background in the Raman spectra. It could be shown that the encapsulation-cell-backsheet system should be optimized in order to minimize the stress on the PV-module components.
Highlights
The performance and reliability of a PV module are highly affected by the degradation behavior of the polymeric components within the module, which are mainly the encapsulant and back-sheet material
Laminates were made from low iron solar glass with four different types of encapsulation material (EVA, a TPSE, an ionomer, and a PVB) and three back sheet materials in a Meier vacuum laminator
The backsheets can be regarded as a resistor delaying atmospheric gas ingress into the PV module
Summary
The performance and reliability of a PV module are highly affected by the degradation behavior of the polymeric components within the module, which are mainly the encapsulant and back-sheet material. Decomposition [6, 10, 11], and degradation of additives such as UV light stabilizers, UV absorbers, and antioxidants [8, 12,13,14] Since these degradation problems have not been solved completely up to now, many new materials have recently been introduced to the PV market which aim for an enhanced reliability and/or lowered manufacturing costs. Permeates, like water vapor and oxygen, are reaction partners in degradation processes inside PV modules The ingress of such gases is governed by the permeation properties of the polymeric back-sheets or encapsulation materials used [3]. It was found that WVTR and OTR were on average higher for the encapsulants than for the back-sheets, and the OTR of PA was two orders of magnitude higher than those of the other back-sheets
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