Visual Characterization of Anti-Reflective Coating on Solar Module Glass

Anti-reflection coatings (ARCs) are widely used on PV module glass to increase light transmission. The PV community is increasingly concerned with how long these coatings last in the field and would benefit from a simple method for quantifying performance on fielded modules. In this work, we demonstrate how a straightforward visual inspection of the color of reflected light can identify the presence of an interference-based ARC. By tracking the color shift over time a qualitative measurement of ARC degradation can be made. This method is applicable in full-sun outdoor conditions and only requires a flashlight and a standard RGB camera. We demonstrate how the physics of thin-film coating interference and color theory accurately predict the color the reflected light. This technique could gain widespread use for inspecting PV modules in the field because it is easy to perform and requires no specialized equipment.