This deliverable summarises progress on developing and applying advanced in-situ luminescent imaging methods to identify loss mechanisms in perovskite/silicon tandem solar cells. The work covers defect screening in tandem devices, continuous monitoring of layer interactions in the perovskite sub-cell, and long-term studies of how defects form and evolve during operation. The results confirm that in-situ luminescent imaging is a powerful tool for tracking degradation pathways, showing that localized defects and interlayer interactions can influence long-term stability, and that electrical operating conditions play an important role in how these mechanisms develop. The methodologies established here provide a framework for evaluating new materials, interfaces, and device designs. Future efforts will apply these techniques to larger-area devices and industrially relevant cell architectures.