Analysis and insights into snail trail degradation in photovoltaic modules

Abstract

The reliability of photovoltaic (PV) modules is critical in harsh outdoor environments, where they are exposed to various stresses that can cause various degradations. In recent decades, the frequently observed degradation called snail trails in crystalline PV modules, is enormous concern due to less clarity about its effects on PV module reliability and performance. In this work, field-exposed snail trails affected PV modules are examined. Investigation is conducted at both the module and cell levels to uncover associated reliability issues and performance impacts. Examination methods include visual inspection, current–voltage (I-V) characteristics, microscopic imaging, electroluminescence (EL) imaging, and dark-lock-in thermography (DLIT) imaging. Snail trails are found with different degradation modes, where cell breakage and shunt were found as likely occurred degradation along with the presence of bubbles and backsheet degradation. Also, the metallic fingers near to snail trails were found thinner and deteriorated. In EL imaging, characteristics pattern of snail trails was found out as a bright periphery along dark lines. DLIT imaging highlighted elevated temperatures along the snail trail path as a characteristic pattern. Performance losses in the snail trails affected PV modules and cells were attributed to various degradations that observed with snail trails. The findings suggest that the presence of snail trails could serve as an indicator of broader degradation concerns. This work is beneficial to understand the reliability issues and performance losses in snail trails affected PV modules.