Interplay between Iodide and Tin Vacancies in CsSnI3 Perovskite Solar Cells

Abstract

Tin-based perovskite materials have the drawbacks of high density of Sn vacancies, structural deformations of SnI6– octahedra, and oxidation of unstable Sn2+ states, resulting in poor chemical stability processed at inert and open atmosphere. In this work, we demonstrate the temperature effects on reduction of Sn vacancies (Vsn) in polymorphic CsSnI3 perovskite solar cells. Evidence of light-induced I– ion diffusion and an interplay between iodide and Sn vacancies were briefly presented. We have observed by X-ray photoelectron spectroscopy that the formation of iodide vacancies (VI) are highly activated at 60 °C, contributing to the reduction of acceptor defects, mainly Sn vacancies (Vsn). The formation of SnO– and SnO2– at high temperature mitigates the Sn–I interaction and eventually increases the trap density at Au/CsSnI3 interfaces. We have observed by time-of-flight secondary ion mass spectrometry that the delocalized I– ions are accumulated near the metal contacts and form AuI– ions which diffuse th...