Methylammonium‐Free Ink for Blade‐Coating of Pure‐Phase α‐FAPbI3 Perovskite Films in Air

Abstract The α‐c (α‐FAPbI 3 ) has been extensively employed in the fabrication of high‐efficiency perovskite solar cells, yet heavily relied on multiple additives in upscalable fabrication in air. In this work, a simple α‐FAPbI 3 ink is developed for the blade‐coating fabrication of phase‐pure α‐FAPbI 3 in ambient air free from any additives containing extrinsic ions. The introduction of 2‐imidazolidinone (IMD) to the FAPbI 3 precursor inks leads to the formation of intermediate phases that change the phase transition pathway from δ‐FAPbI 3 to α‐FAPbI 3 by tilting the PbI 6 octahedrons with strong coordination to Pb 2+ . Furthermore, the IMD ligands in the intermediate phase gradually escape from the perovskite film during the annealing, leaving a phase‐pure α‐FAPbI 3 film vertically grown with large grains. Consequently, the small‐sized PSCs fabricated with blade‐coated α‐FAPbI 3 film achieve an efficiency of up to 23.14%, and the corresponding mini‐module yields an efficiency of 19.66%. The device performance is among the highest reported for phase‐pure α‐FAPbI 3 PSCs fabricated in the air without non‐native cations or chloride additives, offering a simple and robust fabrication approach of phase‐pure α‐FAPbI 3 films for PV application.