Unraveling the Reaction Dynamic Mechanism and Thermodynamic Pathway of Lead Iodide and Organic Cations in Two-step Sequential Deposition Process

Abstract

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