Highly Stable Two-Dimensional Tin(II) Iodide Hybrid Organic–Inorganic Perovskite Based on Stilbene Derivative

Hybrid organic–inorganic perovskites have recently emerged as potential disruptive photovoltaic technology. However, the toxicity of lead used in state-of-the-art hybrid perovskites solar cell prevents large-scale commercialization, which calls for lead-free alternatives. Sn-based perovskites have been considered as alternatives but they are limited by rapid oxidation and decomposition in ambient air. Here, an Sn-based two-dimensional hybrid organic–inorganic perovskites [A₂B_{( n -1)}Sn_nI_{(3 n +1)}] (n = 1 and 2) are reported with improved air stability, using bulky stilbene derivatives as the organic cations (2-(4-(3-fluoro)stilbenyl)ethanammonium iodide (FSAI)). The moisture stability of the [(FSA)₂SnI₄] perovskites is attributed to the hydrophobic properties of fluorine-functionalized organic chains (FSA), as well as the strong cohesive bonding in the organic chains provided by H bonds, CH···X type H bonds, weak interlayer F···F interaction, and weak face-to-face type π-π interactions. The photodetector device fabricated on exfoliated single crystal flake of [(FSA)₂SnI₄] exhibits fast and stable photoconductor response.