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

Abstract

Abstract The α‐c (α‐FAPbI3) 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‐FAPbI3 ink is developed for the blade‐coating fabrication of phase‐pure α‐FAPbI3 in ambient air free from any additives containing extrinsic ions. The introduction of 2‐imidazolidinone (IMD) to the FAPbI3 precursor inks leads to the formation of intermediate phases that change the phase transition pathway from δ‐FAPbI3 to α‐FAPbI3 by tilting the PbI6 octahedrons with strong coordination to Pb2+. Furthermore, the IMD ligands in the intermediate phase gradually escape from the perovskite film during the annealing, leaving a phase‐pure α‐FAPbI3 film vertically grown with large grains. Consequently, the small‐sized PSCs fabricated with blade‐coated α‐FAPbI3 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‐FAPbI3 PSCs fabricated in the air without non‐native cations or chloride additives, offering a simple and robust fabrication approach of phase‐pure α‐FAPbI3 films for PV application.

Keywords

• 2‐imidazolidinone
• blade‐coating
• perovskite ink
• perovskite modules
• phase‐transition