Stability challenges for the commercialization of perovskite-silicon tandem solar cells

Driven by the growing dominance of balance of system costs in photovoltaic installations, next-generation solar cell technologies must deliver significant increases in power conversion efficiency. Presently, the most promising combination of facile fabrication and power conversion efficiency potential is found in tandem solar cells (TSCs) comprising silicon (Si) bottom cells with wide-bandgap perovskite top cells. However, unsolved issues in perovskite stability have important implications for real-world energy yields, challenging the prospect of widespread commercialization. Here, we present an overview of the current state of the art in stability of perovskite-Si TSCs and elucidate key tandem-specific degradation mechanisms at the cell and module levels. From this perspective, we consider the impact of perovskite phase segregation and strain, the novel challenges faced by perovskite films on textured surfaces and when using TSC-specific electrode designs as well as the exacerbating effects of current matching constraints. We also consider economic factors and determine the lifetime energy yield necessary for perovskite-Si TSCs to compete with single-junction Si solar cells. To conclude, we outline key future research directions to achieve the long-term stability necessary for the successful commercialization of this promising TSC technology.