Rationally Designed Bilayer Passivation Strategy for High-Performance Vacuum-Processed Perovskite Solar Cells

Vacuum thermal evaporation is a promising scalable fabrication route for perovskite solar cells (PSCs) due to its precise control over film thickness and compatibility with large-scale production. However, unlike solution-based methods, vacuum-processed perovskite films undergo complex solid-state reactions that often cause non-uniform crystallization and a high density of surface defects such as halide vacancies and uncoordinated Pb²⁺ ions. Herein, we report a rationally designed bilayer passivation strategy, termed “Anchor-and-Seal”, to mitigate these surface defects and optimize interfacial energy level alignment. By sequentially applying ethylenediammonium diiodide (EDAI₂) and 4-methoxy-phenethylammonium-iodide (4MeO-PEAI), we effectively passivate defects through strong hydrogen bonding and Lewis base coordination. While EDAI₂ serves as a rigid anchoring agent, the flexible 4MeO-PEAI molecules infiltrate remaining nanometer-scale voids, resulting in broadly uniform passivation and reduced non-exciton recombination. Furthermore, the bilayer passivation induces an upward shift of the Fermi level, thereby enhancing charge extraction. Consequently, vacuum-processed p-i-n PSCs achieve a champion power conversion efficiency of 20.59% with significantly enhanced open-circuit voltage, and exhibit significantly enhanced stability, retaining 94% of their initial efficiency after 1000 h in an inert atmosphere. Notably, a lab-scale mini-module (2.4 cm²) achieves a PCE of 18.46%, demonstrating the scalability and commercial potential of this approach for vacuum-deposited photovoltaics.