Variations in Cross-Link Properties of EVA of Un-Aged and Aged PV-Modules

The quality of the lamination process is key to solar module long-term stability and performance. A critical benchmark is the level and homogeneity of cross-linking of the ethylene vinyl acetate (EVA) encapsulant. In order to investigate common issues of the lamination process, a comprehensive study covering a variety of different PV-modules from different manufacturers has been conducted. The degree of EVA cross-linking was analysed by common Soxhlet extraction. In addition, indentation tests were employed which are sensitive to the mechanical properties of EVA, directly correlating to the durability of PV modules. The results reveal the effects of bowing and inhomogeneous temperature distribution during lamination as well an inhomogeneous quality of the EVA foil. Furthermore, the indentation test was used to analyse the mechanical properties of solar modules from different manufacturers before and after outdoor exposure in different regions of the world.