High‐Sublimation‐Temperature Additives for Efficient Perovskite Solar Cells via Single‐Source Evaporation

ABSTRACT Vacuum‐deposited perovskite solar cells are promising for commercialization due to their low‐temperature processing, solvent‐free fabrication, and precise control over film thickness and uniformity. Deposition via single‐source thermal evaporation offers high deposition rates and excellent reproducibility; however, devices fabricated via the single‐source evaporation of pre‐synthesized perovskite powders lag far behind those produced by alternative methods, such as co‐evaporation or sequential deposition. In this work, we introduce high‐sublimation‐temperature additives (CsBr and CaF 2 ) to address this limitation. By incorporating these additives during the mechanosynthesis of FAPbI 3 powder, we obtain perovskite films with an improved microstructure and optoelectronic quality. Importantly, while the additives modulate the deposition process, they are not incorporated into the final perovskite film. This mechanism differs significantly from traditional additives, which remain in the film to enhance the perovskite quality. Consequently, thin FAPbI 3 solar cells achieve stabilized efficiencies exceeding 18%, similar to those of devices fabricated via co‐evaporation and sequential evaporation processes. Furthermore, the devices exhibit significantly enhanced environmental stability, maintaining over 95% of the initial PCE after 150 days under ambient conditions (∼20% RH, dim light). These findings underscore the substantial potential of additive engineering for single‐source evaporation, enabling the scalable, high‐throughput industrial production of efficient and stable perovskite photovoltaics.