Efficient Perovskite–Cu(In,Ga)Se 2 Tandem Solar Cells Enabled by Coevaporation

We demonstrated perovskite–Cu(In,Ga)Se2 (CIGS) tandem solar cells in which the perovskite top absorber is deposited by coevaporation, enabling highly uniform film formation on rough CIGS bottom cells. In addition, we introduced a compact tin oxide buffer layer on the zinc oxide surface, effectively preventing the detrimental Lewis acid–base reaction with the perovskite. A certified power conversion efficiency of 24.5% (1 cm2 aperture area) is achieved from the resulting monolithic perovskite–CIGS tandems. This work establishes a scalable vacuum-based route for delivering high-efficiency perovskite–CIGS tandem photovoltaics.