Close-space sublimation as a versatile deposition process for efficient perovskite silicon tandem solar cells

The envisaged breakthrough of perovskite photovoltaic technologies demands rapid advances in scalable and robust high-throughput fabrication methods. Here we present close-space sublimation (CSS) as a vacuum-based, industrially relevant deposition method for the conversion of sublimed PbI$_2$ inorganic scaffolds into high-quality wide-bandgap perovskite absorbers (MAPb(I$_{0.79}$Br$_{0.21}$)$_3$, 1.64 eV), employing a reusable mixed-halide organic source for stable bandgap control. We provide mechanistic insights into the substitution-reaction-limited CSS process and achieve power conversion efficiencies (PCEs) of up to 18.5% for fully vacuum-processed p–i–n single-junction devices. Monolithic integration in tandem solar cells onto planar, nano- and micro-textured silicon bottom cells reveals consistent optoelectronic and morphological properties across all configurations without requiring adjustments of deposition parameters, as corroborated by comprehensive characterization techniques. The resulting perovskite/silicon tandem solar cells reach PCEs up to 24.3%, with minimal variation across the different bottom cells. Our findings highlight the broad process window and versatility of CSS, positioning it as an industry-suitable deposition method for solvent-free high-throughput fabrication.