Organic–Inorganic Hybrid Tin Halide Single Crystals with Sulfhydryl and Hydroxyl Groups: Formation, Optical Properties, and Stability

Lead (Pb)-free halide hybrid materials have received a great deal of attention because of their potential in optoelectronic applications. However, heteroatom-based amine lead-free tin halide hybrid single crystals have not been well investigated yet. Detailed synthetic processes, growth, crystal structures, and stability of (ACH2CH2NH3)2SnBr6 (A = OH or SH) and (BCH2CH2NH3)2SnI4 (B = I or SH) single crystals were investigated. Interestingly, (IH3NCH2CH2SSCH2CH2NH3)2HPO3 exhibited orange-red photoluminescence (PL) at about 620 nm with an average PL lifetime of about 912 ns. (HSCH2CH2NH3)2SnI4 single crystals exhibited a PL peak at 620 nm with an average PL lifetime of about 0.607 ns. More importantly, (HSCH2CH2NH3)2SnI4 single crystals exhibited reversible red-black color transformations when exposed to a H3PO2 solution and an ambient atmosphere, which was attributed to oxidation from Sn2+ to Sn4+, rather than from I- to I3- (I2). The intriguing characteristics should provide guidance for further optoelectronic applications of these Pb-free halide hybrid materials.