Researchers at Fraunhofer ISE have developed new imaging methods to measure losses in individual sub-cells of multi-junction solar cells, specifically perovskite-silicon tandem and perovskite-perovskite-silicon triple junction devices. The research team detailed the Suns-Voc and Suns-PL imaging methods for tandem cells, and used a combination of luminescence imaging and lock-in thermography for triple-junction cells. These methods provide insights into electric losses, selectivity losses, and resistive losses, making them valuable for quality assurance in production and research settings. Additionally, the effectiveness of these imaging techniques in analyzing the quality of electron and hole transport layers in solar cells is demonstrated, with the potential for application in other tandem and triple junction cell technologies, including III-V compound solar cells for space applications.