Quantitative Optical Determination of Water Content in Solar Modules by Short-Wave Infrared Reflectometry
Rishi E Kumar1, Guillaume von Gastrow1, Joswin Leslie2, Rico Meier2, Mariana I Bertoni2, David P Fenning1
1University of California, San Diego, La Jolla, CA, United States
/2Arizona State University, Tempe, AZ, United States

A short-wave infrared (SWIR) reflectometry method is developed to quantify the water content in solar modules in a non-contact approach. Water content has been implicated as a key factor in many module degradation pathways, including contact corrosion and yellowing. Despite these established issues, to date no robust method for quantitative in situ determination of water content in modules is available. The Water Reflectometry Detection (WaRD) method provides this capability by leveraging the short-wave infrared optical spectrum, in which water exhibits vibrational absorption bands, module components are highly transparent, and solar cell back reflectors are reflective. Here, we describe the operating principle and demonstrate measurement of moisture in encapsulated Al-BSF and PERC architectures over the full range of temperatures and relative humidity relevant to field operation and damp heat testing.