Luminescent Imaging of the Reverse Bias Behavior of Perovskite Solar Cells Using ReBEL

Partial shading remains a critical challenge for perovskite photovoltaics, as shaded cells in otherwise illuminated modules operate in reverse bias, which can accelerate degradation. In other solar cell technologies, reverse bias electroluminescence (ReBEL) imaging has been successfully employed to investigate the reverse bias breakdown mechanism. Here, ReBEL imaging is proposed as technique for imaging the local reverse bias current flow on perovskite solar cells. To that end, the ReBEL signal is affirmed to originate from radiative recombination in the absorber layer. ReBEL imaging is compared to established thermal current imaging techniques and reveals superior sensitivity and spatial resolution while showing similar features in the investigated samples. Further experiments reveal a dependence on the reverse bias current: The spatial distribution of the ReBEL signal differs significantly between small and large current injection levels. This could point towards two different breakdown mechanisms. These results show that, despite some open questions, ReBEL imaging could help understand the reverse bias behavior of perovskite solar cells better.