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Mono- and multicrystalline solar cells have been stressed by potential-induced degradation (PID). Cell pieces with PID-shunts are imaged by SEM using the EBIC technique in plan view as well as after FIB cross-section preparation. A linear shaped signature is found in plan-view EBIC images at every potential-induced shunt position on both mono- and multicrystalline solar cells. Cross-sectional SEM and TEM images reveal stacking faults in a {111} plane. Combined TEM/EDX measurements show that the stacking faults are strongly decorated with sodium. Thus, the electric conductivity of stacking faults is assumed to arise under the influence of sodium ion movement through a high electric field across the SiNx anti-reflective layer, resulting in PID

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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.

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