Stable organic-inorganic hybrid bismuth-halide: Exploration of crystal-structural, morphological, thermal, spectroscopic and optoelectronic properties

• (C 6 H 5 CH 2 NH 3 ) a Bi b X c was synthesized by a simple hydrothermal method. • Structure and morphology of (C 6 H 5 CH 2 NH 3 ) a Bi b X c were studied. • Optical property and stability of (C 6 H 5 CH 2 NH 3 ) a Bi b X c were investigated. Two kinds of novel organic-inorganic bismuth-halide hybrid monocrystalline compounds (C 6 H 5 CH 2 NH 3 ) 2 BiCl 5 and (C 6 H 5 CH 2 NH 3 )BiI 4 were synthesized and characterized. The crystal structure, intermolecular interaction, morphology, chemical groups and bonds, optical and thermal stability of the samples were systematically investigated through single crystal X-ray diffraction, Hirshfeld surface analysis, SEM, FTIR, TG and UV-vis diffuse reflectance spectra. The results indicated that (C 6 H 5 CH 2 NH 3 ) 2 BiCl 5 and (C 6 H 5 CH 2 NH 3 )BiI 4 crystals displayed a monoclinic system with the space group P21/c and P21/n at room temperature, respectively. These materials showed strong absorption in the ultraviolet and visible light regions, resulting in very low E g , which could be continuously adjustable from 1.67 eV to 3.21 eV by changing the halogen ratio. In addition, these hybrid materials also exhibited good thermal stability. The decomposition temperature of (C 6 H 5 CH 2 NH 3 ) 2 BiCl 5 and (C 6 H 5 CH 2 NH 3 )BiI 4 were 260 °C and 300 °C respectively. Therefore, these organic-inorganic bismuth-halide hybrid compounds have excellent development potential in the field of solar cell research.