Quantitative Determination of Moisture Content in Solar Modules by Short-Wave Infrared Reflectometry

A short-wave infrared (SWIR) reflectometry method is developed to quantify the water content in solar modules in a noncontact 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 standard modules is available. Here, the water reflectometry detection (WaRD) method provides this capability by leveraging the SWIR 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 aluminum back surface field and passivated-emitter rear contact architectures over the full range of temperatures and relative humidity relevant to field operation and damp heat testing.