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

Abstract

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 utilise 4-source vacuum deposition to deposit FA0.7Cs0.3Pb(IxBr1-x)3 perovskite, where the bandgap is changed through fine control over the halide content. We show how using MeO-2PACz as hole transporting material and passivating the perovskite with ethylenediammonium diiodide reduces non-radiative losses, resulting in efficiencies of 17.8% in solar cells based on vacuum deposited perovskites with bandgap of 1.76 eV. By similarly passivating a narrow bandgap FA0.75Cs0.25Pb0.5Sn0.5I3 perovskite and combining it with sub-cell 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 multi-junction devices even in complex architectures.