Unraveling the reaction dynamics mechanism and thermodynamic pathway of lead iodide and organic cations in the two-step sequential deposition process

Abstract

The effective reaction of lead iodide (PbI₂) with organic cations determines the quality of perovskite films, particularly at the solid–liquid interface in the two-step process. However, unanswered questions regarding the understanding of the reaction kinetics and the means to improve the perovskite film quality in the two-step process still need to be addressed. Herein, we provide a comprehensive analysis of the crystallization process and mechanism of the two-step method from reaction dynamics and thermodynamics perspectives while systematically summarizing the main developments in achieving efficient and stable PVSCs through the two-step process. Subsequently, we critically assess the effective methods for obtaining high-quality perovskite films by controlling the solid–liquid interfacial reaction between PbI₂ and organic amine salts, covering all aspects, ranging from optimizing microscopic reaction pathways to macroscopically regulating the PbI₂ structure and its existence forms. Finally, we extend the discussion to upcoming future challenges, analyze unresolved issues and opportunities, and propose potential directions to boost the two-step process for a faster commercialization process.