Mechanism analysis of snail trails in photovoltaic modules

The Snail Trail on micro-cracked cell surface of module are frequently founded at PV system over the past few years. Some studies of this discolored phenomena were mainly focused on some abnormal material or minute quantity of elements, however, the detail mechanism are still not clearly disclosed. In this study, the role of encapsulants, cells and lamination conditions were experimentally studied and discussed. One integrated mechanism of Snail Trail formation was proposed and partly verified by some experimental proofs. The migration and reduction reaction of silver ions under currents are believed to be the intrinsic reaction of this phenomena, while the oxidation of nano-size silver particle by the residue peroxide at cracked silver finger were the key reason of color discoloration.