LID and LETID Evolution of PV Modules during Outdoor Operation and Indoor Tests

We are linking results from module laboratory tests addressing B-O LID and LETID at different test conditions to degradation and recovery behavior under realistic operation conditions in the field. With this thorough comparison, which is unprecedented to our knowledge, we provide valuable data for the validation and further improvement of LETID models. 13 monocrystalline PERC PV modules of the same type are tested according to the experimental schedule shown in Figure 1 which contains test sequences with common LETID test conditions varying in temperature and injected current. The modules are characterized by means of performance measurements at standard test conditions, performance measurements at 200 W/m², electroluminescence measurements and dark IV measurements. On some PV modules, dark IV monitoring is performed in-situ during LID or LETID test intervals to gain more detailed knowledge about the degradation kinetics. The outdoor modules (M02 and M03) have been installed on a two-axis tracker at an outdoor test site in Freiburg, Germany on May 22, 2020, which is going to yield data from two summer periods as well as one winter season at the time of presentation, where significantly different LETID behavior is expected. Furthermore, one of the modules has been thermally insulated on the rear side to show the effect of different operating temperatures. Both modules are operating in MPP. Module temperatures and in-plane-irradiance are monitored.