Interfacial stability in single- and multi-junction perovskite solar cells

Perovskite photovoltaics offer high efficiencies and low costs, with single- and multi-junction cells showing immense future potential. Yet, their operational stability remains a key bottleneck that is increasingly rooted at interfaces. In this review, we analyze interfaces as metastable chemical microenvironments characterized by high defect densities, steep chemical potential gradients, localized electric fields, and mechanical stress. We establish a unified framework centered on the evolution of interfacial chemistry to compare degradation pathways in single-junction versus tandem cells. From these chemical insights, we distill actionable chemistry-to-function design rules, identify critical gaps in multi-junction interfacial stability, and outline the scalable engineering challenges that must be addressed to bridge laboratory success with commercial reality.