Investigations of Snail-Trail and Associated Microcrack Properities and Behavior in Brazil's Tropical Climate

PV technology reliability and operating lifetime are priority interests for financial investors, developers, ensuring consumer confidence, and research investments. Performance degradation of the PV module is a major concern for technology viability. Cell and module defects and damage can be generated during the manufacturing process, transportation, handling, installation, maintenance, and operating environmental and climate conditions. The relationship between the creation of cell microcracks and the appearance of snail trails or visible discolored regions has been previously studied and reported. This study focuses on installations in the tropical region of Brazil in which high densities of snail trails are observed. This investigation examines further the formation of the snail trails, their microchemistry and origins, and the conditions under which the underlying microcracks can affect the cell and module performances. Specifically, the formation of Ag nanoparticles that react with the presence of oxygen, CO2, and the organic encapsulant is shown to form compounds (Ag2CO3 and AgO2) accounting for the snail-trail discoloration. Over time, bubble formation is observed, starting at the intersection of the microcrack with the Ag fingers then evolving along the snail trail itself. The reversible changes in Pm of the cells and modules is reported under thermal cycling. Direct evidence is presented to show this is due to the opening of the microcracks as the temperature rises above a certain point, and closing or healing of the regions as the temperature returns to near its original state.