Sequential Evaporation for Scalable Hybrid Processing of Perovskite/Silicon Tandem Solar Cells

The conformal coating of perovskites on textured silicon for tandem solar cells requires scalable deposition methods, for which hybrid vacuum-solution processing, using an evaporated inorganic scaffold (Pb/Cs halides) followed by solution conversion, is promising. Yet multisource coevaporation of the scaffold, as commonly used for lab-scale devices, is complex and costly to implement at an industrial scale. Here, we investigate sequential single-source evaporation of the inorganic scaffold as an industrially viable alternative. Five sequentially evaporated scaffold stacks were compared to a coevaporated reference. Despite differences in PbI₂ conversion, halide distribution, and morphology, all showed similar single-junction device power conversion efficiencies (∼19%). The best scaffold (a PbI₂/CsBr/PbI₂/CsBr/PbI₂ stack) achieved 28.4% in perovskite/silicon tandems without molecular additives, matching the coevaporated reference (28.3%). This work demonstrates that sequential deposition of the inorganic scaffold offers a scalable route to high-efficiency tandems.