LETID in legacy and modern PV modules: accelerated testing and field deployment

The kinetics of light- and elevated temperatureinduced degradation (LETID) in silicon solar cells depend on the precise operating excess carrier density of the device. This dependency causes differences in the way LETID manifests in modern, higher-efficiency devices compared to lower-efficiency, legacy devices that might have been deployed in the field in previous years. In this work we model how different vintages of devices are expected to behave in both accelerated laboratory testing, as well as field deployment. The differing excess carrier densities encountered in various module vintages has implications both for interpreting accelerated test data, as well as identifying, diagnosing, and potentially treating LETID in the field.