Raman Spectroscopy as a Possible In-Line Inspection Tool for CIGS Solar Cells in Comparison with Photoluminescence Measurements

Thin film solar cells and in particular Copper Indium Gallium Selenide (CIGS) cells have become increasingly relevant for the renewable energy market due to their high efficiencies, easy installation, high product flexibility, light weight and less labour intensiveness when compared to silicon solar cells. As for today, there are still challenges regarding the manufacturing process though, such as e.g. reproducibility and process tolerance. Therefore, cost-efficient and easily implementable inline process control methods are required that allow for an identification and elimination of non-conformal cells at an early production step. As part of this work, the potential of Raman spectroscopy and photoluminescence imaging as contact-free inline inspection tools are evaluated. The efficiencies and VOC values of two CIGS samples with various individual contacted cells were correlated with results from Raman spectroscopy and photoluminescence imaging. Both methods have proven to have high potential for the realisation of early-stage contact-free inline inspection tools in the manufacturing process of CIGS solar cells.