Ultrasonic Characterization of Ethylene-Vinyl Acetate in Glass-Glass-Modules

The encapsulant properties, particularly in modules with passivated emitter and rear cells (PERC) and silicon heterojunction (SHJ) configurations, are increasingly pivotal for long-term reliability. Optimal processing conditions for the encapsulant are therefore essential; however, manufacturers often prioritize reduced lamination times to increase throughput, which can lead to incomplete cross-linking and unconsumed reaction starters, potentially resulting in degradation modes such as accelerated aging, cell breakage, delamination, corrosion, and local inhomogeneities. Traditional destructive characterization methods, such as differential scanning calorimetry, Soxhlet extraction, or Shear testing, yield limited insights into the local material properties across the module. Since glass-glass (G–G) modules are gaining a large market share, also due to their bifacial capabilities, preparing samples for traditional characterization techniques has become even more cumbersome and costly. This study proposes a novel nondestructive ultrasonic approach to characterize EVA in G-G modules, extending techniques previously developed for the glass-backsheet configuration. By analyzing frequency-dependent time-of-flight measurements through the samples during lamination, we established a quantitative correlation with the lamination progression. A comparison with results from mechanical shear tests showed the potential of the method for non-destructive evaluation of adhesion strength. Furthermore, the method revealed new insights into the lamination process, including the time-of-flight dynamics during the different stages of lamination. This research, therefore, offers a pathway for in-situ lamination process surveillance and optimization to enhance production yields and reliability, ultimately reducing the levelized cost of energy.