Synthesis, crystal structure, vibrational properties, optical properties and Hirshfeld surface analysis of a new Bi (III) halide complex: (C2H8N)3BiBr6 for optoelectronic devices.

A new organic–inorganic material, dimethylaminium hexabromobismuthate (C₂H₈N)₃BiBr₆ was elaborated by the slow evaporation technique at room temperature. This compound is synthesized and characterized by X-ray diffraction, Raman spectroscopy scattering, Hirshfeld surface analysis, ¹³C NMR spectroscopy, photoluminescence and by UV–Vis spectroscopy. The crystal lattice is formed by discrete [BiBr₆]³⁻ anions surrounded by dimethylaminium cations. Besides, the title compound crystallizes in the space group R 3 ¯ of trigonal system. The unit cell parameters are a = 29.3387(9) Å, b = 29.3387(9) Å and c = 8.4642(3) Å. The Raman and infrared spectra recorded at room temperature were interpreted by analogy with homologous materials. The cohesion of the structure is ensured by a huge network of N–H...Br hydrogen bonds and van der Waals interaction (C–H....Cl). The UV–Vis measurements, performed from 200 to 2400 nm, show a direct and wide optical bandgap evaluated at (2.840 ± 0.005), (2.482 ± 0.004) and (2.805 ± 0.006) eV by different methods. The Urbach energy presents a low value estimated at (182 ± 3) meV confirming the high quality of our compound. In addition, the evolution of the extinction coefficient (k_e) and the refractive index n with the wavelength λ were determined. Furthermore, we have demonstrated that n obeys to Cauchy relation. Other optical parameters such as the skin depth and the optical conductivity were calculated, and all obtained results were discussed. We have demonstrated, in addition, that the energy losses are mainly in the bulk rather than the surface of the studied material. Based on the Wemple–Di-Domenico model, the dispersion parameters E₀ and E_d relative to the (C₂H₈N)₃BiBr₆ sample were calculated. These encouraging results such as the obtained high and direct optical bandgap value prompt us to propose this compound as a basic material for optoelectronic devices. [ABSTRACT FROM AUTHOR]