Novel coring procedure for Post-Mortem Analysis in CIGS PV Modules

CIGS (CuInGaSe2) solar cells are electronic devices that directly transform sunlight into electricity and fall into the category of thin film photovoltaic devices. Currently, this type of solar cell has reached the record in photovoltaic conversion efficiency of around 23.35%. However, the maturity of a PV technology also requires reliability and long-term stability. There-fore, it is necessary to understand the root cause of the failures of PV systems in the field over the years. An important step towards this goal is to establish a relationship between defects and degradation in commercial solar panels deployed in the field. In this study the main objective is to develop a method to extract and unpack samples from commercial CIGS modules in order to understand degradation mechanisms in field-deployed photovoltaic solar panels. The coring and unpackaging methods were developed to take samples of commercial CIGS modules in the field and analyze them with various lab techniques designed for small scales, including photoluminescence (PL) images, IV measurements, and illuminated lock-in thermography (ILIT). The method, previously developed by the same authors, was applied to investigate potential induced degradation (PID) and partial shading-induced wormlike defects. For PID, the samples that were extracted from the degraded areas of the module showed lower photoluminescence intensity and had significantly lower open-circuit voltage (Voc) and fill factor (FF) values in comparison with reference samples. Upon investigation of the partial-shaded modules, it was observed that the wormlike defects act as local shunts leading to decay of the solar cell properties, as well as an increased sulphur content near the edge of the wormtrails.