VDE-AR-E 2126-4-100 Anwendungsregel:2021-11

This VDE application guide describes a test method for assessing Light and Elevated Temperature Induced Degradation (LETID) in silicon-based PV modules and cells.
The method is applicable to all silicon (Si)-based PV modules and cells, regardless of whether the bulk material is multicrystalline (mc), Czochralski (Cz) or Float Zone (FZ) silicon. It is particularly relevant for Passivated Emitter and Rear Contact (PERC) cells and modules as they exhibit an increased LeTID sensitivity.
The VDE application guide specifies the requirements for the test setup and the test conditions for the LETID test. Furthermore, it provides guidelines for the analysis, evaluation and documentations of the test results.
The method includes a pre-treatment and dark storage of the solar cells and modules to separate the effects of other types of Light-induced Degradation (LID) from LETID.
The informative annex contains the description of a defect model for the potential root cause of LETID.
The specified test methods can be used to detect LETID sensitivity in solar cells and modules early in the production process. The method can be applied in-process monitoring, for process improvement as well as for quality control.