Crystalline Mixed Halide Halobismuthates and Their Induced Second Harmonic Generation

Mixed halide coordination has been widely used to finely tune the properties of inorganic and inorganic–organic hybrid compounds, especially for emerging perovskites materials. Despite the increasing number of reports on preparation methods and the affected functionalities, the peculiar and precise role of the doping halogens in structural regulation of the crystals and the resulting variations on the basic properties remain to be addressed. Here, to shed light into the "black box", a new series of [NH2(CH2CH3)2]3Bi(Cl1–xBrx)6 (x = 0, 0.135, 0.255, 0.385, 0.847, and 1) single crystals were grown from the mixed halide solvents by the temperature lowering method. The correlation between the inclusion amounts of Br in the final crystals with the halide concentrations in the precursors is discussed from different perspectives. The two kinds of halogens share the same position in the mixed halide system, with every crystallographically independent halide site possessing different halogen occupancies. The mixed halide coordination exhibits a regulated effect on the distortion of the anion octahedra. Optical absorption, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and the second harmonic generation (SHG) measurements have confirmed that, with increased Br inclusion, [NH2(CH2CH3)2]3Bi(Cl1–xBrx)6 crystals exhibit a regulated effect on their bandgaps, thermal stabilities, and SHG capacities.