A comparative study on optical properties of BiOI, Bi7O9I3 and Bi5O7I materials

This investigation clarifies the optical properties of successive ionic layer adsorption and reaction (SILAR)-prepared BiOI, Bi7O9I3, and Bi5O7I thin films. In our study, after the annealing treatment, BiOI material transforms into Bi7O9I3 and Bi5O7I crystal phase. The crystal structure, morphology and elemental analysis have been confirmed by X-Ray Diffraction (XRD), field emission scanning electron microscope (FESEM), energy dispersive X-ray spectrometer (EDS) analysis. Moreover, we have checked and validified phase transformation and weight loss by thermo-gravimetric (TG) analysis. Here, the comparative optical characterization and assessment of the BiOI and derivatives films have been done by transmittance and reflectance. Meanwhile, with the single-oscillator Wemple-Di Domenico model, the refractive index's dispersion has been presented for BiOI, Bi7O9I3, and Bi5O7I. Interestingly, comparative analysis shows that nonlinear optical behavior becomes lower after phase transformation, confirmed via the second-order reflective index and nonlinear susceptibility estimation. This investigation will open a new window for BiOI based materials to consider it for the nonlinear optical device.