Corrosion, LID and LeTID in Silicon PV Modules and Solution Methods to Improve Reliability

In this paper, some degradation and failure modes of PV modules are discussed. PV module reliability became a topic of extreme importance since manufacturers generally establish tight warranty periods with customers, despite having degradation rates around 0.6–0.7% a year. Special attention is given to corrosion, light-induced degradation (LID), and light and elevated induced degradation (LeTID) due to its frequency and contribution to the overall degradation rate. An overview of the corrosion mechanisms in metal contacts and their interaction with encapsulant and backsheet deterioration are presented. A systematic description of the types of corrosion by-products and their respective expected colors when observed through an optical microscope is presented. The most common techniques to evaluate corrosion are highlighted, as well as some observations and conclusions based on the results from previous studies. As for LID and LeTID, the main variants of concern to the photovoltaic industry are identified along with the mechanisms responsible for the generation of recombination active defects. At last, prevention and correction measures are described in order to minimize economic losses.