Surface Engineering of Perovskite Solar Cells via the Dry-Vacuum Process: Deposition of Lead Halides and Alkylammonium Halides.

Perovskite solar cells (PSCs) have demonstrated remarkably rapid efficiency improvements mainly through spin-coating-based solution processes. While these processes offer numerous advantages, there are also several limitations, prompting research into alternative fabrication methodologies for PSCs. Meanwhile, surface engineering has been identified as one of the most critical factors for enhancing the efficiency and stability of PSCs. For surface passivation, most studies reported to date, especially for n-i-p structures, have relied on solution-based processes. However, these solution processes face challenges in controlling the termination of perovskite surfaces, achieving fine thickness control, and dealing with lead halides that utilize common solvents with perovskites. In this study, we introduce a strategy employing a dry-vacuum deposition process to deposit PbI₂ and PbCl₂ with nanoscale thickness precision on perovskite thin films. This is followed by vacuum deposition of alkyl halides (4-methoxy-phenethylammonium-iodide, MeO-PEAI), which demonstrated improved photostability in devices compared to a typical solution-processed MeO-PEAI surface treatment.