Structure, morphology and opto-nonlinear behaviors of Nd:PbI2/FTO thin film system for optoelectronics

Device grade PbI₂ nanostructured thin films were developed by a cost effective sol-gel spin coating method with different (0,1,3 and 5 wt%) Nd doping concentrations on FTO substrates. Films revealed excellent structural, vibrational, electronic structure, and nonlinear optical properties on Nd doping concentrations. X-ray diffraction and vibrational spectroscopy of the specimen demonstrated an excellent crystalline quality and growth along (001) planes. Surface morphological studies of the films showed the compact and uniform distribution of particles throughout the surfaces. Also, the transformation in morphology was noticed from nanorods to nanoparticle by Nd doping content. The transmittance of the films were noticed to be ~ 70-75% in the visible region of the solar spectrum. The bandgap of the films were obtained in the range of 2.36-2.45 eV. Refractive indices n, extinction coefficient k, real and imaginary part of dielectric constant ɛ₁ and ɛ₂ were also analyzed. Third-order nonlinear optical parameters such as third-order nonlinear optical susceptibility χ⁽³⁾ and second-order refractive index n⁽²⁾ were obtained in range 2.10 × 10^-11 - 1.54 × 10^-8 esu and 5.10 × 10^-10 - 9.18 × 10^-8 esu over the plotted energy region.