Mapping chemical and mechanical property degradation in photovoltaic modules

An understanding of material interactions and degradation pathways in both fielded modules and modules used for accelerated testing is important to understand how photovoltaic (PV) materials affect reliability. As part of the effort to build this understanding, a suite of destructive and non-destructive testing protocols has been developed to compare material performance and reliability under the stresses of different service environments. The characterization approaches to be discussed in this presentation describe our recent experience mapping the physical and chemical changes observed in degraded PV modules. Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) has been shown to provide a unique combination of sensitivity, spatial resolution and quantitation suitable for the study of ion migration pathways in encapsulants after PID (Potential Induced Degradation). Similarly, the depth resolution and sensitivity of imaging depth profiles determined by Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) have expanded our ability to follow chemical changes in cells extracted from modules following PID testing and Damp Heat exposure. As an extension of our ongoing efforts to correlate chemical and physical degradation properties, we have recently added NanoHardness Testing (NHT) of the extracted core to our analysis protocol. NHT has been found to be sufficiently sensitive to detect mechanical property differences in backsheet structures taken from modules after field exposure.