Comparative studies of the structural and optical properties of BiI3 and PbI2 iodide-based semiconductors

ABSTRACT The structural and optical properties of BiI3 and PbI2 powders were compared. The x-ray diffraction results confirm that PbI2 crystallizes in a hexagonal structure, while BiI3 in a rhombohedral structure. The optical band gap Eg was found to be direct at (2.31 eV) for PbI2 and indirect (1.7 eV) for BiI3. Different fundamental optical properties such as refractive index, real and imaginary parts of optical conductivities, dielectric function, and linear susceptibility were determined. The non-linear optical properties were also discussed by deriving the linear and non-linear susceptibilities using Wemple–DiDomenico single-oscillator model. The third-order susceptibility at low absorption region was found to be equal 2.684×10−15 [esu] and 3.685×10−15 [esu], as well as the non-linear refractive index n2, 7.5×10−14 [esu] and 1.07×10−13 [esu] for BiI3 and PbI2 respectively, which evidences their interest in optoelectronic devices.