Synthesis, Crystal Structure and Green Luminescence in Zero-Dimensional Tin Halide (C8H14N2)2SnBr6

Organic-inorganic hybrid metal halides with broad-band emission are currently receiving an increasing interest for their unique light emission properties. Here we report a novel lead-free zero-dimensional (0D) tin halide, (C8H14N2)2SnBr6, in which isolated [SnBr6]4- octahedrons are cocrystallized with organic cations, 1,3-bis(aminomethyl)benzene (C8H14N22+). Upon photoexcitation, the bulk crystals exhibit broad-band green emission peaking at 507 nm with a full width at half-maximum (fwhm) of 82 nm (0.395 eV), a Stokes shift of 157 nm (1.09 eV), and a photoluminescence quantum yield (PLQY) of 36 ± 4%. Combined structural analysis and density functional theory (DFT) calculations indicate that the excited state structural distortion of [SnBr6]4- octahedral units account for the formation of this green emission. The relatively small Stokes shift and narrow fwhm of the emission are hence caused by the reduced distortion of [SnBr6]4- octahedrons and rigid molecular structure. The discovery of lead-free (C8H14N2)2SnBr6 and insight into the mechanism of green emission provide an essential platform toward unveiling the relationship between structure and property for 0D metal halide perovskites.