Efficient perovskite/Cu(In,Ga)Se₂ tandem solar cells with a composite intermediate recombination layer

Monolithic perovskite/Cu(In,Ga)Se₂ (CIGS) tandem solar cells offer unique advantages among tandem configurations, including optimal bandgap pairing, all-thin-film architecture, superior radiation hardness, and exceptional stability. Despite their potential, challenges remain in optimizing efficiency and stability, particularly in the intermediate recombination layer (IRL) that connects subcells. This study addresses these challenges by developing a high-performance IRL using a composite structure comprising Al:ZnO/Au/NiO_x/[4-(7H-dibenzo[c,g]carbazol-7-yl)butyl] phosphonic acid (4PADCB). The hybrid NiO_x/4PADCB hole transport layer enhances interface trap passivation, optimizes band alignment, and improves minority carrier extraction, while the ultrathin Au layer significantly boosts the majority carrier recombination rate. With well-engineered subcells, our champion perovskite/CIGS tandem device achieved a record PCE of 28.04% at 0.51 cm² area and 30.71% at 0.15 cm² area (30.1% cross-verified by an external organization), with an exceptional fill factor of 80.9%, alongside outstanding photo- and thermal-stability. This work establishes monolithic perovskite/CIGS tandems as competitive with leading perovskite/Si (34.9%) and perovskite/perovskite (30.1%) technologies, providing a scalable, versatile framework for next-generation photovoltaics.