Enhancing Organic‐Inorganic Perovskite Thin Film Crystallization via Vapor‐Solid Reaction by Modifying PbI₂ Precursors films with Pyridinium Trifluoromethanesulfonate

The vapor–solid reaction technique holds potential for producing large‐scale organic–inorganic perovskite films, using a two‐step deposition process. The sucess of perovskite formation heavily relies on the crystallization of lead iodide (PbI 2 ) precursor films. However, the high crystallinity of PbI 2 can hinder organic vapors' diffusion and negatively affecting the solar cells by increasing charge recombination and accelerating degradation. To address this, pyridinium trifluoromethanesulfonate (PTFS) is introduced into the PbI 2 precursor solution to control the nucleation and growth of PbI 2 films. PTFS has been found to effectively suppresses PbI 2 crystallization and enhance the integration of formamidinium ion (FA + ) through hydrogen bonding, facilitating the full transformation of PbI 2 into perovskite. It also minimizes defect formation by interacting with uncoordinated Pb 2+ and FA + ions. These modifications have significantly enhanced power conversion efficiency (PCE), reaching up to 21.19%, and the devices have maintained 93% of their initial performance after 1580 h of exposure to air.