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

All-perovskite tandemsolar cells beckon as lower costalternativesto conventional single-junction cells. Solution processing has enabledrapid optimization of perovskite solar technologies, but new depositionroutes will enable modularity and scalability, facilitating technologyadoption. Here, we utilize 4-source vacuum deposition to deposit FA(0.7)Cs(0.3)Pb-(I x Br1-x )(3) perovskite, wherethe bandgap is changed through fine control over the halide content.We show how using MeO-2PACz as a hole-transporting material and passivatingthe perovskite with ethylenediammonium diiodide reduces nonradiativelosses, resulting in efficiencies of 17.8% in solar cells based onvacuum-deposited perovskites with a bandgap of 1.76 eV. By similarlypassivating a narrow-bandgap FA(0.75)Cs(0.25)Pb(0.5)Sn(0.5)I(3) perovskite and combining itwith a subcell of evaporated FA(0.7)Cs(0.3)Pb-(I0.64Br0.36)(3), we report a 2-terminalall-perovskite tandem solar cell with champion open circuit voltageand efficiency of 2.06 V and 24.1%, respectively. This dry depositionmethod enables high reproducibility, opening avenues for modular,scalable multijunction devices even in complex architectures.