Analysis of adhesion characteristics of steel back plates and encapsulants for fire-proof BIPV modules

Abstract

Recently, researchers are actively exploring the use of steel plates as replacements for the backs of building integrated photovoltaic (BIPV) modules to achieve improved workability, reduced weight, and enhanced maintainability. It is crucial to note that the adhesion between steel plates and encapsulants must match the high level observed between conventional backsheets and glass surfaces. In this study, we assessed the adhesion between steel plates and encapsulants and proposed a method to enhance adhesion to the level of existing materials, such as backsheets and glass, by improving the surface of the steel plates and the lamination process. When steel plates were laminated with ethylene vinyl acetate (EVA) encapsulant at 150 °C (as per the preset process), the peel force measured by the 180° peel test was significantly low at 0.045 N/mm. However, it increased nearly 40 times to 1.70 N/mm due to the formation of a structure capable of physical interlocking through surface treatment and an increase in the lamination temperature by 20 °C. Furthermore, we evaluated the adhesion performance of polyolefin elastomer (POE) encapsulant, which demonstrated high adhesion of over 6.0 N/mm, comparable to that between the currently used encapsulants and backsheets. When we examined the surface-treated sample using a confocal microscope and a secondary electron microscope (SEM), the surface-treated sample exhibited a considerably rough surface with a high Rku value of 5 compared to the untreated sample. These modules can maintain high outputs even when exposed to the external environment for extended periods with fire-resistant properties.