Development of Testing Methods to Predict Cracking in Photovoltaic Backsheets
Michael Kempe, Trevor Lockman, Joshua Morse
National Renewable Energy Laboratory (NREL), Golden, CO, United States

In recent years there have been some significant failures of photovoltaic backsheets resulting from inadequacies of design that are not detected in current versions of the qualification standards. In some cases, this has resulted in catastrophic failure in less than 5 y of deployment. In this work, we develop a test sample construction and evaluate accelerated exposure conditions necessary to duplicate the cracking field failure of backsheets using a small and manageable coupon. This sample uses a piece of solder wire to put in some controlled topology into the backsheet. Through exposure to different environmental stressors it was found that the application of thermal cycling stresses, after thermal or ultraviolet radiation exposure, is of primary importance to duplicate these failures.