Perovskite/Copper Indium Gallium Selenide Tandem Solar Cells

(CIGS) tandems have emerged as a promising thin-film solution to combine high efficiency with lightweight, flexible, and scalable photovoltaics. This review summarizes advancements in wide-bandgap perovskite design, conformal growth on rough CIGS surfaces, and the challenges of contact formation. We examine the trade-offs between monolithic 2T and mechanically stacked 4T architectures, emphasizing industrial feasibility. Unlike prior reviews, we introduce a "performance-stability-cost" trimetric framework to evaluate technical routes, focusing on critical bottlenecks such as conformal deposition on textured CIGS, indium supply risks, and the mechanical reliability of flexible tandems. Recent progress in interface planarization, passivation, and stability optimization has led to efficiencies surpassing 27%, with considerable potential for flexible commercial applications. The review also explores the integration of these innovations for large-scale manufacturing, offering actionable insights into overcoming current limitations and advancing perovskite/CIGS tandems toward industrial readiness.