Crystallization Control of Blade‐Coated Wide Bandgap FACs‐Based Perovskite

Abstract Transforming perovskite solar cells into commercial production requires advanced scalable deposition technology. However, the deposition of high‐quality perovskite thin films using the blade coating method presents challenges, especially in controlling the nucleation and crystallization of perovskite. In this work, an effective approach is proposed for controlling nucleation and crystallization by simultaneously incorporating two kinds of ionic liquid, namely 1H‐imidazole acetate (IMAc), and 1‐buty‐3‐methylimidazolium tetrafluoroborate (BMIMBF ₄ ), into the precursor solution. This innovative strategy initiates π – π interactions between IM and BMIM cations, thereby enhancing the interaction between cations and the Pb‐I framework. The competitive mechanism of interaction with Pb‐I framework effectively suppresses the formation of unfavorable mesophase, thereby enabling a single crystallization pathway from NMP + PbI ₂ to α‐perovskite. Consequently, this method effectively reduces defects and enhances the crystal quality of α‐perovskite film. Based on this strategy, the power conversion efficiency of the p‐i‐n wide bandgap perovskite device prepared by the blade coating method, is increased to 21.31%, representing one of the highest efficiencies achieved with this technology for 1.68 eV bandgap FACs‐based perovskites. Thus, this approach emerges as a feasible breakthrough strategy that may unleash the full potential of perovskite solar cells.