Exploring the Radiation Damage of Vacancy-Ordered Double Perovskites, ((NH₄)_(1-x)FA_x)₂SnBr₆

Degradation studies of the ASnX₃ perovskites to the A₂SnX₆ vacancy-ordered double perovskite form have been well researched, but little is known about how A₂SnX₆ compounds degrade. Herein, a new double perovskite, FA₂SnBr₆ (FA = CH(NH₂)₂), is synthesized and characterized by using X-ray diffraction and X-ray photoelectron spectroscopy. FA₂SnBr₆ is found to crystallize in the P2₁/n monoclinic space group and shows the ability to form single-phase, solid solutions with another double perovskite (NH₄)₂SnBr₆. Solid solutions of ((NH₄)_(1-x)FA_x)₂SnBr₆, where x = 0.03, 0.04, 0.06, and 0.09, are produced, and X-ray radiation damage is investigated to qualitatively and quantitatively uncover degradation mechanisms. Correlation analysis, a new statistical analytical method for X-ray photoelectron spectra, is used to fortify peak fitting models. Comparing shifts in binding energies and relative atomic quantities between two elements constructs phase models from different spectral environments to understand the degradation of these compounds. In each radiation damage experiment, great consideration must be taken to combine the chemistry of the system and the physical process of photoelectron emission with the quantitative phase models formed. Overall, the presence of ammonium in the double perovskite enhances the stability of the compound to X-ray irradiation.