Microscopy study of snail trail phenomenon on photovoltaic modules

Snail trails on photovoltaic modules are a source of enormous concern to the solar industry as no scientific reports on the mechanisms producing this global phenomenon were previously available. Here, for the first time, we clarify the origin of these snail trails as a product of the formation of silver carbonate nanoparticles which discolor the silver grid. Micropore arrays on the silicon substrate within the snail trail region could accelerate the discoloration by offering reactive compounds via penetration and release. The potential mechanisms of photovoltaic module discoloration are proposed, yielding clues as to how snail trail formation can be mitigated by technical solutions. Aging tests on the discolored modules suggest no significant power degradation or discolored area enlargement after accelerated aging.