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

Area of Science:

• Materials Science
• Renewable Energy
• Photovoltaics

Background:

• High-efficiency perovskite solar cells (PSCs) often require multiple additives for scalable, air-based fabrication.
• Achieving phase-pure alpha-formamidinium lead iodide (α-FAPbI3) in ambient conditions without extrinsic ions remains a challenge.

Purpose of the Study:

• To develop a simple, additive-free ink for blade-coating phase-pure α-FAPbI3 films in ambient air.
• To investigate the role of 2-imidazolidinone (IMD) in controlling the phase transition and film morphology.
• To demonstrate the performance of PSCs and mini-modules fabricated using this novel approach.

Main Methods:

• Formulation of a novel α-FAPbI3 precursor ink incorporating 2-imidazolidinone (IMD).
• Blade-coating of the ink to form perovskite films in ambient air.
• Annealing process to facilitate the phase transition and removal of IMD ligands.
• Fabrication and characterization of small-sized PSCs and mini-modules.

Main Results:

• Introduction of IMD facilitates a phase transition pathway to pure α-FAPbI3 by altering PbI6 octahedron tilting.
• Gradual escape of IMD during annealing results in vertically grown, large-grained, phase-pure α-FAPbI3 films.
• Small-sized PSCs achieved a maximum efficiency of 23.14%, and mini-modules reached 19.66% efficiency.

Conclusions:

• The developed IMD-containing ink offers a simple and robust method for fabricating phase-pure α-FAPbI3 films in air.
• This approach avoids non-native cations and chloride additives, yielding high-performance PSCs and mini-modules.
• The study presents a promising fabrication strategy for scalable perovskite photovoltaic applications.