Snail Trails: Root Cause Analysis and Test Procedures

The “snail trail” discoloration effect observed at many PV modules after some time in the field was investigated with regard to their microscopic and chemical properties and environmental conditions. We show here the combined results of studies on defect modules after outdoor exposure as well as on mini modules after laboratory DH tests and provide a mechanistic model for the snail trail formation. Finally, we can show that a detailed chemical and physical characterization of encapsulation polymers is a fundamental prerequisite for quality assurance and reliability in solar module production.