Evaluation of Moisture Sorption Characteristics of PV Encapsulants and Edge Sealants Using the Dynamic Vapor Sorption Technique

Reliable moisture-diffusion data are vital for assessing photovoltaic (PV) module durability. This work demonstrates dynamic vapor sorption (DVS) as a fast, accurate technique for characterizing the diffusion properties of PV encapsulants and desiccant-filled edge sealants, particularly through direct measurement of the saturation concentration. The measured diffusivity and solubility coefficients for ethylene–vinyl acetate and polyolefin encapsulants agree with published values, while a dual-mode sorption model derived from DVS data predict edge-sealant breakthrough times with a 12% relative error after 8000 h at 85∘C/85% RH. Extended to outdoor climates, the model predicts over 25 years of moisture protection for a 2-cm sealant under tropical conditions. The small sample requirement and automated isotherm generation of DVS, together with its limitations, are discussed, highlighting its value for PV material characterization.