Synthesis, structure, and optical properties of the nanocrystalline bismuth oxyiodide (BiOI) for optoelectronic application

The present work demonstrates the synthesis of bismuth oxyiodide onto FTO substrates (BiOI/FTO) via suc-cessive ionic layer adsorption and reaction technique (SILAR). X-ray diffraction (XRD), Raman spectroscopy, and field emission scanning electron microscopy (FESEM) were used to study influences of deposition cycles on the structural and surface morphology of the BiOI/FTO films, respectively. Moreover, the chemical composition of samples was investigated using the energy dispersive X-ray spectroscopy (EDX)/elements mapping. The results were clarified the purity and nanostructures features of the BiOI thin films. The optical parameters of BiOI/FTO films were measured using the optical transmission spectra T (lambda) and reflectance R (lambda) in the wavelength range of 300-1500 nm. The estimated indirect optical band gap was decreased from 2.06 to 1.79 eV as deposition cycles were increased. The refractive-index at abnormal dispersion region was analyzed and considered in terms of single-oscillator models. Influences of deposition cycles on the optical dielectric constant, loss energy functions, and optical conductivity were estimated and discussed. In addition, nonlinear parameters such as third-order nonlinear susceptibility chi((3)), non-linear refractive index n((2)), and nonlinear absorption coefficient (beta c) were estimated based on semi-empirical relation. So, the distinctive optical parameters for BiOI/FTO were concluded to be promising as an optical system for nonlinear optical devices.