Impact of Interface Layers on Luminescence Imaging of Organic Solar Cells: Discriminating ETL from HTL Defects

Over the last two decades, organic photovoltaic (OPV) devices have seen their efficiency increase, while long-term stability and upscaling have been demonstrated for first-generation modules. Since the maturity level of this technology has now improved, techniques for rapid quality control have become relevant. Imaging techniques such as photo- and electroluminescence have already been used for this purpose. However, defects could only be localized either in the active layer or in interface layers, without being able to distinguish between defects located in the ETL from those within the HTL. Here, we present a simple method to unambiguously discriminate between ETL and HTL defects. Furthermore, we demonstrate the strong impact of HTL thickness on the detected photoluminescence signal. Our approach will help avoid misinterpretations in luminescence experiments and gain an understanding of device failure during processing or aging.