Stability of solution-processed MAPbI3 and FAPbI3 layers.

Area of Science:

• Materials Science
• Solid-State Chemistry
• Photovoltaics

Background:

• Hybrid perovskite materials offer promising photovoltaic properties but suffer from poor operational stability.
• Understanding degradation mechanisms is crucial for their commercial viability.

Purpose of the Study:

• To develop a semi-empirical model for predicting the durability of hybrid perovskite materials.
• To investigate the degradation pathways and factors influencing the stability of MAPbI3 and FAPbI3.
• To explore cation substitution as a strategy for enhancing perovskite stability.

Main Methods:

• In situ degradation measurements under simulated thermal operation conditions.
• Analysis using an Arrhenius-type degradation law.
• Comparative studies under vacuum, nitrogen, and moisture environments.
• Density functional theory calculations for defect generation.

Main Results:

• The degradation of MAPbI3 follows an Arrhenius-type law, predictable by activation energy and pre-exponential factor.
• An intrinsic dynamic proton exchange occurs between organic cations and the inorganic cage, impacting lattice stability.
• Experimental activation energy for degradation in vacuum is 1.54 eV, comparable to DFT calculations.
• Water molecules reduce activation energy in air to 0.96 eV.
• Formamidinium (FA+) substitution for methylammonium (MA+) enhances lattice robustness and material durability.

Conclusions:

• A predictive model for perovskite durability based on degradation kinetics has been established.
• Proton exchange dynamics, independent of water presence, significantly affect perovskite lattice stability.
• Formamidinium-based perovskites demonstrate superior stability, supporting their use in applications if phase stabilization is achieved.