Eppur si Muove: Proton Diffusion in Halide Perovskite Single Crystals.

Area of Science:

• Materials Science
• Solid-State Physics
• Chemistry

Background:

• Ion diffusion is critical for halide-perovskite (HaP) optoelectronic properties.
• Previous studies assumed halide ions dominated diffusion, overlooking proton contributions.

Purpose of the Study:

• To investigate and quantify proton diffusion in halide-perovskites.
• To challenge the prevailing assumption of halide-dominated ion migration.
• To elucidate the role of water in proton diffusion.

Main Methods:

• Deuterium-hydrogen exchange and migration experiments in MAPbI₃, MAPbBr₃, and FAPbBr₃ single crystals.
• Quantification using D/H NMR, Raman spectroscopy, and elastic recoil detection analysis.
• Confirmation via impedance spectroscopy on HaP solar cells and water concentration modeling.

Main Results:

• Proton diffusion was experimentally proven in halide-perovskites.
• Water presence is essential for proton migration; deuteration is absent without water.
• Proton diffusion significantly contributes to the wide range of reported diffusion coefficients in HaPs.

Conclusions:

• Proton diffusion, influenced by water, is a key factor in HaP properties.
• This finding necessitates a re-evaluation of ion transport mechanisms in halide-perovskites.
• The role of water in HaP performance may be linked to water-dependent proton diffusion.