Vacuum-Deposited Wide-Bandgap Perovskite for All-Perovskite Tandem Solar Cells.

All-perovskite tandem solar cells beckon as lower cost alternatives to conventional single-junction cells. Solution processing has enabled rapid optimization of perovskite solar technologies, but new deposition routes will enable modularity and scalability, facilitating technology adoption. Here, we utilize 4-source vacuum deposition to deposit FA 0.7 Cs 0.3 Pb(I x Br 1- x ) 3 perovskite, where the bandgap is changed through fine control over the halide content. We show how using MeO-2PACz as a hole-transporting material and passivating the perovskite with ethylenediammonium diiodide reduces nonradiative losses, resulting in efficiencies of 17.8% in solar cells based on vacuum-deposited perovskites with a bandgap of 1.76 eV. By similarly passivating a narrow-bandgap FA 0.75 Cs 0.25 Pb 0.5 Sn 0.5 I 3 perovskite and combining it with a subcell of evaporated FA 0.7 Cs 0.3 Pb(I 0.64 Br 0.36 ) 3 , we report a 2-terminal all-perovskite tandem solar cell with champion open circuit voltage and efficiency of 2.06 V and 24.1%, respectively. This dry deposition method enables high reproducibility, opening avenues for modular, scalable multijunction devices even in complex architectures.