Formamidinium Lead Iodide Perovskite Thin Films Formed by Two-Step Sequential Method: Solvent-Morphology Relationship

Area of Science:

• Materials Science
• Solid State Chemistry
• Optoelectronics

Background:

• Formamidinium lead iodide (FAPbI3) perovskites are promising materials for optoelectronic devices.
• Film quality, particularly grain size and morphology, significantly impacts device performance.
• Solvent properties play a crucial role in controlling the crystallization and morphology of perovskite films.

Purpose of the Study:

• To investigate the correlation between solvent properties and the morphology of FAPbI3 perovskite films.
• To optimize the preparation of high-quality FAPbI3 perovskite films for enhanced optoelectronic applications.
• To identify suitable solvents for achieving larger grain sizes and improved film uniformity.

Main Methods:

• Two-step sequential deposition method for FAPbI3 perovskite film preparation.
• Utilized various solvents for formamidinium iodide (FAI) precursor: isopropanol, n-butanol, and tert-butanol.
• Characterization techniques included X-ray diffraction (XRD), scanning electron microscopy (SEM), absorption spectroscopy, and photoluminescence (PL) spectroscopy.

Main Results:

• All tested solvents facilitated the formation of the desired α-phase FAPbI3 perovskite.
• Film morphology, specifically grain size, was significantly influenced by the choice of solvent.
• Tert-butanol resulted in the largest grain sizes (2-5 µm) and preferred crystallite orientation, while n-butanol showed incomplete conversion indicated by excess PbI2.

Conclusions:

• Solvent properties such as viscosity, electric permittivity, and polarizability correlate with the resulting perovskite film's grain size.
• Tert-butanol is identified as a superior solvent for fabricating large-grained FAPbI3 perovskite films with fewer grain boundaries.
• The findings are crucial for advancing the performance of perovskite-based optoelectronic devices.