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 FA0.7Cs0.3Pb(IxBr1–x)3perovskite, 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 FA0.75Cs0.25Pb0.5Sn0.5I3perovskite and combining it
with a subcell of evaporated FA0.7Cs0.3Pb(I0.64Br0.36)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.